Design Considerations for a Saito 72 Gol

Having recently acquired this engine after previously sniveling about my folded wing incident, I thought I might ask a few questions of the Saito users and other four stroke gurus. I noted while attending the Nats that Steve Moons french design flew quite well although differently and the thin high aspect wing really handled the loading quite well. Also noted Gordys plane to be a peach with what appeared to be a more scale like, possibly smallish tail surfaces but was steady as rock in the corners. Brads plane was comfortably conventional stunt and flew very well also. Any advice would be appreciated. Any thoughts on wing considerations for this powerplant, moments etc.

Also would like a little break-in tutorial as I wish no damage on this pretty new motor.

Thanks

John,

On break in, just follow the directions that come with it. They have worked pretty well for me. As Dirt pointed out to me last weekend, it's amazing the amount of abuse these engines will take.

On planes, hey, your choice. I think the Berringer planes are overgrown combat planes. But they sure fly nice. Alan Resinger's Sukhoi, now sadly departed, really flew well and looked quite nice in the air.

LAST EDITED ON Jul-22-03 AT 12:00 PM (CDT)
 
>John,
>
>On break in, just follow the directions that come with it.
>They have worked pretty well for me. As Dirt pointed out to
>me last weekend, it's amazing the amount of abuse these
>engines will take.

I agree with that. I break in the engine as described in the instructions (with the carb). I then set the engine at about 9500 RPM with a 12" prop using the carb and let it run most of a gallon. I use whatever stunt fuel I have laying around for most of the break in (oh, the horror!) and then switch to YS 20/20 fuel when the manifold is installed. I see no need to put expensive fuel out the exhaust stack during the super rich break in. Also, a little castor for break in seems to work well.

I have simply abused my 4 strokes, whether I wanted to or not. The original engines I had were abused on purpose by switching fuels, nitro, props, RPM, venturis, and tanks. I eventually sold them to very happy customers who loved them. The engine that I ran in the last two Nationals has been actually run so lean in one run that there was zero smoke coming out, and there have been several runs with tremendous vibration. As far as I can tell the engine still performs at almost the same level as it did last year, even after all the abuse.

As far as airplanes and design, I really feel it is just like all airplanes and designs. There will be some things you see that you like and some things that you see that you don't. You commented that my airplane at the NAts looked nose heavy, well it's not. I measured it the other day and it is 6-5/8" from the trailing edge which is actually 3/8" more aft of Paul Walker's 4 stroke Impacts. What you were seeing is the effect of the large propellor I run. I have spoken to Paul and he agreed that my prop while perfectly fine for 99% of the stunt community will not corner at the Top 20 level. Hey, live and learn...

Even Brian Eather echoed these comments and said that while fine for Europe, here in the US there is a premium on hard corners and I would need to reduce my prop resitance. If you want to see hard corners, get a tape of the NW regionals and watch the new P-51. I am now on the PW prop program!

I actually did the calculations for measuring the nose moment for the Saito 72. It came out that a standard 10" nose would be reduced to 8.75" for the CG location shown on the plans to not change from the original 2 stroke location. I myself have found that there is no need for the CG to be as far back as a 2 stroke, and Paul has echoed these findings.

The calcs:

For a typical 2-cycle stunt nose, we assume the ever-popular 10 inches from the leading edge. ST 60 = 13 oz with muffler (we will omit pads for the sake of this discussion). We will assume the CG of the engine is 2" back from the spinner backplate. We will also assume a spinner and prop weight of 1.5 oz.

Now let’s use a little algebra to find the EQUIVALENT nose length for a Saito 72 to equal the moment of the ST 60. We will assume the Saito 72 weighs 17.2 oz with muffler. The spinner and prop weighs 2.8 oz (I use a 2 ½” spinner and 14” wood prop). We will assume the CG of the engine is 2" back from the spinner backplate. We will assume a center of lift 3 inches back from the leading edge of the wing (for example). This assumed number would bring the airplane into perfect balance. So, the total moment for the engine would be the following:

NL= the unknown ideal nose length

(20 oz ) x (NL-2” + 3”) = 20 oz (NL + 1) = (20 NL oz inch + 20 oz inch) = total moment caused by the engine at nose length NL.

Now we will calculate the weight of the tank and the fuel. We will assume 4.5 oz of fuel (some claim far less), utilizing a Sullivan 6-oz clunk tank of 4” in length. Just for fun, we will assume that the front of the fuel tank has to be 5.25” back from the spinner backplate to clear the engine (this is actually true). We will assume that the fuel tank weighs 1.5 oz.

The moment of the fuel tank with fuel in terms of the unknown nose length NL=

(4.5 oz + 1.5 oz) x ((NL– (5.25” + 2”) +3”) = 6 oz (NL-4.25”) = (6(NL) oz inch – 25.5 oz inch)

The moment of the fuel alone = (4.5) x (NL-4.25) = (4.5NL oz inch –19.125 oz inch)

Setting the moment equation for the Saito moment equal to 221.25 oz*inch and solving for NL =

221.25 = (20NL +20) + (6NL –25.5)
221.25 = 26NL – 5.5
NL = 8.72” (Not that short really)

I would suggest a TBolt wing, 8.75" nose and 18.5" tail moment and use Doug Moon's tail. That was the configuration of the Furias and it was a bad mother. You will have to notch the front of the wing a little to keep the distance from the firewall to the spinner the same as say a 9.5" nose. That is what Doug, Bob, Mike, and I do.

BTW, for the Dr. Jekyll to have the EXACT same CG as the OS VF Impact, the wing would move forward 5/8" which would make the nose moment 8.75". Pretty cool huh?

Although, I am busy making props now, I am certain that a CG shift is not necessary.

>I would suggest a TBolt wing, 8.75" nose and 18.5" tail
>moment and use Doug Moon's tail. That was the configuration
>of the Furias and it was a bad mother. You will have to
>notch the front of the wing.

Thanks for the compliment Brad.

>
>BTW, for the Dr. Jekyll to have the EXACT same CG as the OS
>VF Impact, the wing would move forward 5/8" which would make
>the nose moment 8.75". Pretty cool huh? I am busy making
>props now, I am certain that a CG shift is not necessary.

72 Design.....hmmmmmmmmmmm......can I weigh in on this?? I dont know but here goes....

Well John you need to know what you are after first. Get an old 60 sized model and stuff it in there. It can really help out in what your goals will be and what type of design to go after. It is deffinently a different feel for sure!

If you want a very light even feel like you get with the 2s planes on 12" props then the nose on your plane will have to be pretty short. You cant get into adding a bunch of tail weight to offset the engine should it be nose heavy due to the MOI thing/barbell effect, blah blah blah. Brad will argue this with me to no end... However take a 72 and a 2.5" spinner and a carbon prop and it weighs 19-20 oz. That is 1/3 of the models overall weight in the first 3 inches of the airframe. That is something to consider. Another thing I have noticed about the 72 planes that I have seen...not that many. While still having the CG pretty close to normal they appear to have a nose heavy turn. Large prop causing the turn to be dampened along with 1/3 of the overall weight in the first three inches of the plane. The elevator is working hard to move that much weight. Just the other day I weighed my PA with a header only and a prop and spinner and it was 5.5oz lighter than the 72 with all the same rigging, yet they both are in the same confines. There is a lot less required of the elevator in that situation. Brad is right the Furias is a was a Bad Mother...BUT only after a MASSIVE CG shift! I removed 3oz of weight from the nose but kept the same monster prop and it became a real nice plane to fly and it was very accurate. Best of both worlds. Huge prop creating a very stable flight path but an aft cg for easy light handle loading and accurate crisp corners, not blinding but crisp very repeatable corners. This was the model I was going to go to the FAI with and I believe it was very top twenty worthy.

If I build another 72 plane...and I just might...I would really shorten the nose to take advantge of the ability of the motor to turn monster props. If I have to take the props down to 12" in diameter what am I gaining? My 65s already trun a good 12" 4 blade or a good 13" 3 blade. Why make the change?

Al Rabe has a BBQB that has a 7.5" nose and a 21" tail...I think. That plane flys real good and has a good stunt looking corner(tail around the front look). Check with him to get the full numbers on that plane.

Brad listed the numbers of 8.75 and 18.5. That is a very good ballpark number IMHO. I had the Furias at 8.75 and 17.75 and it(nose) was to long for that tail. It(tail) needed another 2" in my opinion. Or the nose shorter. I used the T-Bolt wing(best wing in the world) and 26% tail section with Stablets.

IMHO one should take full advantage of the motors ability to spin very large 2blade props. Design it to have a way aft CG on purpose and use the length of the prop to keep it stable and let the aft CG give it a very light unloaded handle. Just think how much a normally heavy loaded handle would have sucked in that nasty Friday wind.

>If I build another 72 plane...and I just might...I would
>really shorten the nose to take advantge of the ability of
>the motor to turn monster props. If I have to take the
>props down to 12" in diameter what am I gaining? My 65s
>already trun a good 12" 4 blade or a good 13" 3 blade. Why
>make the change?

Al would agree with that. We spoke on that very thing the other day. More prop stability allows the CG to go back further.

LAST EDITED ON Jul-22-03 AT 01:13 PM (CDT)
 
One other thing about design. The 72 is a big motor so give it a big airplane. Mine had a 3" wide fuse with a large amount of side area.(But it was still small compared to Al's plane) A large verticle stab and a Rabe Rudder. The T-Bolt wing with flaps that put it at 710sqr inches and tips that put the span at 62" I would NOT go smaller for sure. With the 72 in there the weight was 66oz all up ready for fuel. With the 56 is was 63oz. I would still try for the magic 60oz all up weight(hard to hit with a bigger model but it keeps you on your toes). Wing loading is wing loading right. Excessive weight just creates a trap when trimming it out.

Yes it carries half the fuel load but it isnt anything you have any control over so I wouldnt worry to much about it when designing your model.

One of the best things you can do is shoehorn that thing into a model and get a first hand feel for what you are dealing with. Then go off others EXPERIENCES and make some decisions from there. You will need to know what "Feel" you are after when designing your model.

On Break-in. When I broke in the 56 that turned out to be a real good one I followed the instructions during the first 20 minutes of its life it never revved above 4000. Then I started with the throttle slightly up for a few secs then back down. Then up some more then back down. Paying close attention to the color of the blowby coming from the case. As it got clearer and clearer I leaned the needle more and more never leaving the RPM in one place for more than 2 minutes. At 45-55minutes run time I was at a full setting per the flight instructions and going full throttle to idle with the perscribed 12" prop. I would constantly change the RPM. After 1 hour I switched to the 14" prop for just 3 tanks(8oz). Full throttle to idle many times. Many times I would leave it at 3/4 or 1/2 throttle for several minutes and then full and then idle. I had it all over the place. Yes the big prop got it hot. This motor turned out to be the best one I have seen so far. It went from the stand to the plane with the 14" prop and from the first flight it was flying great patterns. No fly-in time on this one. I think the 14" prop load at the end really loosend things up and got it ready to go.

>>I would suggest a TBolt wing, 8.75" nose and 18.5" tail
>>moment and use Doug Moon's tail. That was the configuration
>>of the Furias and it was a bad mother. You will have to
>>notch the front of the wing.
>
>Thanks for the compliment Brad.

Loved my TBolt wing but did find that it needed more tip weight than other wings I have used and the span is pretty healthy. Wondering if it might be just as good at the nominal/conventional 60 inch span.I have made no hard decisions here but did feel that with the short time I had on the last Chevelle, while it was particularly stable and a cutter it did give what seemed to be false readings concerning level flight ie sometimes it appeared to light on tip weight, others it seems not enough. Trim tab adjustments were tried but with no real improvemnet as none was truly necessary and that wing would really fight any tab type trimming.
>
>>
>>BTW, for the Dr. Jekyll to have the EXACT same CG as the OS
>>VF Impact, the wing would move forward 5/8" which would make
>>the nose moment 8.75". Pretty cool huh? I am busy making
>>props now, I am certain that a CG shift is not necessary.
>
>72 Design.....hmmmmmmmmmmm......can I weigh in on this?? I
>dont know but here goes....
>
>Well John you need to know what you are after first. Get an
>old 60 sized model and stuff it in there. It can really
>help out in what your goals will be and what type of design
>to go after. It is deffinently a different feel for sure!

Well, I have some definite ideas that I am sure are not far off of yours because I was very pleased with the plane I had that was quite similar to your current bird. However, I love my Chevelles but just can not stomach another one. Need some variety of shape and style so am massaging some semi scale ideas into another original that will go back a generation and become a Bel Air!
>
>If you want a very light even feel like you get with the 2s
>planes on 12" props then the nose on your plane will have to
>be pretty short. You cant get into adding a bunch of tail
>weight to offset the engine should it be nose heavy due to
>the MOI thing/barbell effect, blah blah blah. Brad will
>argue this with me to no end... However take a 72 and a
>2.5" spinner and a carbon prop and it weighs 19-20 oz. That
>is 1/3 of the models overall weight in the first 3 inches of
>the airframe. That is something to consider. Another thing
>I have noticed about the 72 planes that I have seen...not
>that many. While still having the CG pretty close to normal
>they appear to have a nose heavy turn. Large prop causing
>the turn to be dampened along with 1/3 of the overall weight
>in the first three inches of the plane. The elevator is
>working hard to move that much weight. Just the other day I
>weighed my PA with a header only and a prop and spinner and
>it was 5.5oz lighter than the 72 with all the same rigging,
>yet they both are in the same confines. There is a lot less
>required of the elevator in that situation. Brad is right
>the Furias is a was a Bad Mother...BUT only after a MASSIVE
>CG shift! I removed 3oz of weight from the nose but kept
>the same monster prop and it became a real nice plane to fly
>and it was very accurate. Best of both worlds. Huge prop
>creating a very stable flight path but an aft cg for easy
>light handle loading and accurate crisp corners, not
>blinding but crisp very repeatable corners. This was the
>model I was going to go to the FAI with and I believe it was
>very top twenty worthy.

So whats did you guys find to be the max RPM range you could run on this beast without running past the optimum revs/ torque curve
I would be willing to run a little less diameter on three blades to get the corners where they need to be but dont want the engine to run out of piss and vinegar in the verts and overhead stuff. Seems that yopu could over prop this thing to where vertical stuff might suffer.I dont know that... just my experience elsewhere. I loved my piped stuff when it was working but when it gets really windy everybody flies faster one way or another. I have no qualms with 5.0 lap times as maneuver speed is the only thing that can get dicey really dicey with severe winds provided you keep some lap speed going. Truly wish there had been a 72 in the air last Friday so we had something to evaluate.
>
>If I build another 72 plane...and I just might...I would
>really shorten the nose to take advantge of the ability of
>the motor to turn monster props. If I have to take the
>props down to 12" in diameter what am I gaining? My 65s
>already trun a good 12" 4 blade or a good 13" 3 blade. Why
>make the change?

Stability... just my opinion... while no small issue can be a real pain in the butt when trying to run the CG to far aft. Big prop might cure some of this I am sure but I have tried a to far aft on a PA and it mnakes for a funny flying airplane. I certainly want no arm yanker at every corner but have noted that those with far aft CG.. entry point on rounds is forward of the actual maneuver position such that the plane pitches from a point on the level plane at handle input and then settles into the rounds behind that entry point. It doesnt seem to get scored down but should. Certainly seems that Gordons plane on a smidge less diameter had really nice corner. I kind of get the feeling and its only a hunch that Al's short nose, long tail and big prop work well with the particular wing planform he uses since the high point of the wing is aft also. Just a thought.
>
>Al Rabe has a BBQB that has a 7.5" nose and a 21" tail...I
>think. That plane flys real good and has a good stunt
>looking corner(tail around the front look). Check with him
>to get the full numbers on that plane.

That may be exactly what I do!
>
>Brad listed the numbers of 8.75 and 18.5. That is a very
>good ballpark number IMHO. I had the Furias at 8.75 and
>17.75 and it(nose) was to long for that tail. It(tail)
>needed another 2" in my opinion. Or the nose shorter. I
>used the T-Bolt wing(best wing in the world) and 26% tail
>section with Stablets.

I liked mine also. Debating what to do here as you may have read farther up.
>
>IMHO one should take full advantage of the motors ability to
>spin very large 2blade props. Design it to have a way aft
>CG on purpose and use the length of the prop to keep it
>stable and let the aft CG give it a very light unloaded
>handle. Just think how much a normally heavy loaded handle
>would have sucked in that nasty Friday wind.

My guess is that all handles were loaded. Those men were working it!
Thanks to you and Brad and Randy for your input.

>>I would suggest a TBolt wing, 8.75" nose and 18.5" tail
>>moment and use Doug Moon's tail. That was the configuration
>>of the Furias and it was a bad mother. You will have to
>>notch the front of the wing.

Why would you want to build something that was bad?

>
>As far as airplanes and design, I really feel it is just
>like all airplanes and designs. There will be some things
>you see that you like and some things that you see that you
>don't. You commented that my airplane at the NAts looked
>nose heavy, well it's not. I measured it the other day and
>it is 6-5/8" from the trailing edge which is actually 3/8"
>more aft of Paul Walker's 4 stroke Impacts. What you were
>seeing is the effect of the large propellor I run. I have
>spoken to Paul and he agreed that my prop while perfectly
>fine for 99% of the stunt community will not corner at the
>Top 20 level. Hey, live and learn...

In the other post about this corner thing I was simply commenting based on past observations of your flying style. Glad you came up with some calcs that proved your CG location was what you wanted but sorry to hear that the prop you worked with Brian on proved to be a damper. So what are you doing in terms of prop. I noted that Gordys three blade 13 1/2 x 4/8 pitch seems to haul the mail at good revs with plenty of corner. Are you going to something like this?

>Even Brian Eather echoed these comments and said that while
>fine for Europe, here in the US there is a premium on hard
>corners and I would need to reduce my prop resitance. If
>you want to see hard corners, get a tape of the NW regionals
>and watch the new P-51. I am now on the PW prop program!

Lemme in as after the last couple years in frustration I am in no mood to reinvent what already is working!
>
>
>I actually did the calculations for measuring the nose
>moment for the Saito 72. It came out that a standard 10"
>nose would be reduced to 8.75" for the CG location shown on
>the plans to not change from the original 2 stroke location.
> I myself have found that there is no need for the CG to be
>as far back as a 2 stroke, and Paul has echoed these
>findings.
>
>The calcs:
>
> For a typical 2-cycle stunt nose, we assume the
>ever-popular 10 inches from the leading edge. ST 60 = 13 oz
>with muffler (we will omit pads for the sake of this
>discussion). We will assume the CG of the engine is 2" back
>from the spinner backplate. We will also assume a spinner
>and prop weight of 1.5 oz.
>
>Now let’s use a little algebra to find the EQUIVALENT nose
>length for a Saito 72 to equal the moment of the ST 60. We
>will assume the Saito 72 weighs 17.2 oz with muffler. The
>spinner and prop weighs 2.8 oz (I use a 2 ½” spinner and
>14” wood prop). We will assume the CG of the engine is 2"
>back from the spinner backplate. We will assume a center of
>lift 3 inches back from the leading edge of the wing (for
>example). This assumed number would bring the airplane into
>perfect balance. So, the total moment for the engine would
>be the following:
>
>NL= the unknown ideal nose length
>
>(20 oz ) x (NL-2” + 3”) = 20 oz (NL + 1) = (20 NL oz
>inch + 20 oz inch) = total moment caused by the engine at
>nose length NL.
>
>Now we will calculate the weight of the tank and the fuel.
>We will assume 4.5 oz of fuel (some claim far less),
>utilizing a Sullivan 6-oz clunk tank of 4” in length.
>Just for fun, we will assume that the front of the fuel tank
>has to be 5.25” back from the spinner backplate to clear
>the engine (this is actually true). We will assume that the
>fuel tank weighs 1.5 oz.
>
>The moment of the fuel tank with fuel in terms of the
>unknown nose length NL=
>
>(4.5 oz + 1.5 oz) x ((NL– (5.25” + 2”) +3”) = 6 oz
>(NL-4.25”) = (6(NL) oz inch – 25.5 oz inch)
>
>The moment of the fuel alone = (4.5) x (NL-4.25) = (4.5NL oz
>inch –19.125 oz inch)
>
>Setting the moment equation for the Saito moment equal to
>221.25 oz*inch and solving for NL =
>
>221.25 = (20NL +20) + (6NL –25.5)
>221.25 = 26NL – 5.5
>NL = 8.72” (Not that short really)
>
>I would suggest a TBolt wing, 8.75" nose and 18.5" tail
>moment and use Doug Moon's tail. That was the configuration
>of the Furias and it was a bad mother. You will have to
>notch the front of the wing a little to keep the distance
>from the firewall to the spinner the same as say a 9.5"
>nose. That is what Doug, Bob, Mike, and I do.
>
>BTW, for the Dr. Jekyll to have the EXACT same CG as the OS
>VF Impact, the wing would move forward 5/8" which would make
>the nose moment 8.75". Pretty cool huh?
>
>Although, I am busy making props now, I am certain that a CG
>shift is not necessary.

Thanks for the calcs....already have this drawn up with an 8.75" nose and 18" tail moment but having folded my wing I am a bit leary of shoving my tank back into the wing. I know this should and will work fine but confess some apprehension.( No Bob this is no reflection of my love for the method and wing in particular)

>Thanks for the calcs....already have this drawn up with an
>8.75" nose and 18" tail moment but having folded my wing I
>am a bit leary of shoving my tank back into the wing. I know
>this should and will work fine but confess some
>apprehension.( No Bob this is no reflection of my love for
>the method and wing in particular)

John,

You are in luck. It uses a 6oz tank so cutting into the wing will probably not be needed.

LAST EDITED ON Jul-22-03 AT 01:47 PM (CDT)
 
Hmmm well I havent pulled the Carb off and fitted the manifold I bought from Steve yet but by my drawings here the tank needs to be shoved into the wing about an inch and a quarter to have any play room at all.

Thanks again!

John,

This was a good thread about all the stuff I went through with my 72 plane.

http://clstunt.com/cgi-bin/dcforum/dcboard.cgi?az=show_thread&om=4388&forum=DCForumID1&viewmode=all

Thanks...followed this thread from the moment you posted and did re-read. To bad it bit the big one before you had a chance to run it in competition.

>Hmmm well I havent pulled the Carb off and fitted the
>manifold I bought from Steve yet but by my drawings here the
>tank needs to be shoved into the wing about an inch and a
>quarter to have any play room at all.
>
>Thanks again!

What kind of tank are you talking about? The Sullivan 6oz clunk tank is pretty short. The standard Metal Uni-flow tanks just dont seem to work in the 4s setup. Cant really explain why but it tested out that way.

John,

I build 6 os metal uni-flow tanks for my airplanes. They are typically 1 1/2" deep, 2 1/2" wide and 3" long. The runs seem no different from the plastic uni-flow tanks.

Al,

I thought you were running a clunk in your metal tanks that you make?

LAST EDITED ON Jul-22-03 AT 06:01 PM (CDT)
 
doug,

You are right, of course, I am running clunk tanks with the dimensions as described. Calling my tanks uni-flow amount to a 67 year mind fart. They are clunk tanks running on an atmospheric vent which runs to a point midway from front to back and top to bottom on the inboard side of the tank. I am very pleased with my runs and wouldn't hesitate to run deeper tanks if necessary. My latest tank for "Snaggletooth 2" is 3 1/2" long, 1 1/2" deep, and 2 7/16" wide to fit in a narrower fuselage. It calculates out to 7.188 oz. "Snaggletooth 2" is a redesign of the original "Snaggletooth" to update the construction and incorporate a .65 2 stroke with a removable tank. Moments and areas are the same as original.

>John,
>
>I build 6 os metal uni-flow tanks for my airplanes. They
>are typically 1 1/2" deep, 2 1/2" wide and 3" long. The
>runs seem no different from the plastic uni-flow tanks.
>
>Al

Thanks Al...Reinhard builds a nice tank around here but I have grown fond of plastic and the ability to see where my plumbing is flopping around. May get him to build me one though.

LAST EDITED ON Jul-22-03 AT 06:00 PM (CDT)
 
John,

My tank is basically a box with all parallel sides. Couldn't get much easier to build. No wedges, no baffles, just a floppy ole piece of tubbing and a home made weight.

LAST EDITED ON Jul-22-03 AT 04:40 PM (CDT)
 
>>Hmmm well I havent pulled the Carb off and fitted the
>>manifold I bought from Steve yet but by my drawings here the
>>tank needs to be shoved into the wing about an inch and a
>>quarter to have any play room at all.
>>
>>Thanks again!
>
>What kind of tank are you talking about? The Sullivan 6oz
>clunk tank is pretty short. The standard Metal Uni-flow
>tanks just dont seem to work in the 4s setup. Cant really
>explain why but it tested out that way.

Sullivan six oz is four inches and the Saito from the hub to back of the carb is four. You do need some room for tubing! Right?

LAST EDITED ON Jul-22-03 AT 06:33 PM (CDT)
 
>Thanks for the calcs....already have this drawn up with an
>8.75" nose and 18" tail moment but having folded my wing I
>am a bit leary of shoving my tank back into the wing. I know
>this should and will work fine but confess some
>apprehension.( No Bob this is no reflection of my love for
>the method and wing in particular)

I've found this thread to be an interesting discussion, so interesting that I pulled up the CAD file for Gordan's Tony to check out some of the specs.

Yes, the tail is a bit smaller than what we've been seeing lately, but as we've seen, the plane doesn't seem to be suffering from any lack of elevator authority.

The wing area, including flaps, is 743 sq. inches. this is measured right through the fuselage. The stab area is 21+% with an area of 160.7 sq inches.

The flap hingeeline is angled forward so the flap area wouldn't be compromised. With a straight flap hingeline, the flaps were really skinny towards the tips, so Gordy had me sweep the trailing edge forward, he based this on the performance of his Colossus. It does have slightly more forward sweep than the Colossus though.

The fuselage, at it's widest point is 4.063 inches wide. Very close to scale.

The calculated, not necessarily where Gordy has it, CG, (25% at MAC)is located 7.06 inches forward of the hingeline at the root next to the fuse side. The root chord next to the fuse is 11.96 inches to the hingeline.

The nose legnth, back of the prop to the leading edge of the wing root chord, is 9.132 inches.

The tail moment, hinge line to hinge line, is 18.943 inches.

The more important numbers as I see it, would be when you measure to the CG. The nose moment to the calculated CG is 12.87". The tail moment from the calculated CG to the stab hinge line is 26.406.

Many of these numbers may have varied slightly, but should be close as Gordan had me extended the fuse side slightly on the pattern sheet to account for the bend along the legnth, so the distance wouldn't be shorter as it would have been if we just used the side view of the plan.

Though there's certainly room for additional design improvement, it did pretty well for the first prototype off the plans. Interestingly, Gordan has only had to add 1/2 oz of weight to the tail. He's looking at a lighter spinner, (3" dia.) that should make the plane balance out where he wants it to, without the additional tail weight.

What this tells me is that the moments derived for the prototype are pretty close to optimum for a Saito .72 powered stunter.

Gordy may jump in here, but if not, these numbers come right from the CAD files for the design. Furthermore, I'm pretty certain Gordy is running the CG further aft than we calculated.

Hope this helps with the discussion.

I'm wondering why everything is spinning around?

>>Thanks for the calcs....already have this drawn up with an
>>8.75" nose and 18" tail moment but having folded my wing I
>>am a bit leary of shoving my tank back into the wing. I know
>>this should and will work fine but confess some
>>apprehension.( No Bob this is no reflection of my love for
>>the method and wing in particular)
>
>I've found this thread to be an interesting discussion, so
>interesting that I pulled up the CAD file for Gordan's Tony
>to check out some of the specs.
>
>Yes, the tail is a bit smaller than what we've been seeing
>lately, but as we've seen, the plane doesn't seem to be
>suffering from any lack of elevator authority.
>
>The wing area, including flaps, is 743 sq. inches. this is
>measured right through the fuselage. The stab area is 21+%
>with an area of 160.7 sq inches.
>
>The flap hingeeline is angled forward so the flap area
>wouldn't be compromised. With a straight flap hingeline, the
>flaps were really skinny towards the tips, so Gordy had me
>sweep the trailing edge forward, he based this on the
>performance of his Colossus. It does have slightly more
>forward sweep than the Colossus though.
>
>The fuselage, at it's widest point is 4.063 inches wide.
>Very close to scale.
>
>The calculated, not necessarily where Gordy has it, CG, (25%
>at MAC)is located 7.06 inches forward of the hingeline at
>the root next to the fuse side. The root chord next to the
>fuse is 11.96 inches to the hingeline.
>
>The nose legnth, back of the prop to the leading edge of the
>wing root chord, is 9.132 inches.
>
>The tail moment, hinge line to hinge line, is 18.943 inches.
>
>The more important numbers as I see it, would be when you
>measure to the CG. The nose moment to the calculated CG is
>12.87". The tail moment from the calculated CG to the stab
>hinge line is 26.406.
>
>Many of these numbers may have varied slightly, but should
>be close as Gordan had me extended the fuse side slightly on
>the pattern sheet to account for the bend along the legnth,
>so the distance wouldn't be shorter as it would have been if
>we just used the side view of the plan.
>
>Though there's certainly room for additional design
>improvement, it did pretty well for the first prototype off
>the plans. Interestingly, Gordan has only had to add 1/2 oz
>of weight to the tail. He's looking at a lighter spinner,
>(3" dia.) that should make the plane balance out where he
>wants it to, without the additional tail weight.
>
>What this tells me is that the moments derived for the
>prototype are pretty close to optimum for a Saito .72
>powered stunter.
>
>Gordy may jump in here, but if not, these numbers come right
>from the CAD files for the design. Furthermore, I'm pretty
>certain Gordy is running the CG further aft than we
>calculated.
>
>Hope this helps with the discussion.

Thanks John,

After looking over my layout(very basic at this point) I recall that I mentioned earlier that I had the nose moment at 8.5 but actually it is 7.5 from the LE and 10.5 from the CG with a root cord of a Noblerish (has to be a word) 10 inches. So CG at 30% for the moment (calibrated eyeball or WAG) and my planned barrel fuse may contribute a little to nose weight as I want a solid mount for the big shaker. Still planning an 18" tail moment but may adjust as necessary before serious construction begins. Need prop and spinner weight and must make scale like fuse mounted gear and that will be a project.

May be bugging folks with carbon and pre preg epoxy experience in on this before to long. Oh Howard.....Howard????

Thanks guys

I have a standard layout that I will continue to use (see attached picture). This allows enough room for the Sullivan 6 oz clunk tank, and the Saito 72 with manifold installed. In the future I will simply notch the front of the wing to move the wing cutout. I too was leary to do the wing notching, but not anymore. It is simply no big deal to do and has zero effect on the strength of the wing. In fact, I bet you could argue it is stronger since the front of the wing is now attached to plywood around a boxed edge (firewall and doublers form a box in the front) instead of just being held by the fuselage sides and a small glueing at the firewall.

Doug is convinced that the short nose with the big prop is the way to go. I am not inclined to argue, as I will most likely move the wing forward in Dr. J just to see the difference between it and Mr. Hyde (that was the whole purpose of the two anyway). All that said though, it appears that PW is NOT doing that. He appears to be leaps ahead of the game in the corner respect. Since the CG is somewhat fixed on the Mr. Hyde I will test the PW props and engine run and we can compare notes. Running these engines is really not rocket science and by the time your new 'rplane is done there will be several good Eather and Bolly props to choose from. The engine setup with the UHP manifold, clunk tank, and YS fuel will still be the same (I predict) and will be the setup for a while.

BTW I use a 2 1/2 spinner made by Maxx products, but they do not make a 3 blade. It weighs 1.8 oz which is the same as a plastic spinner. Since I cannot get Randy Smith insterested in making larger spinners I suppose I will continue to look for alternatives. My engine weighs 17.2 oz and the Moon pads weigh .9 oz. I suppose I would shorten the nose more instead of trying for lighter components. If these lighter components materialize great, if not no heartbreak.

Moving the wing forward...This is a cool thing! Not only do you get a shorter nose but you get a stronger tail!

>I have a standard layout that I will continue to use (see
>attached picture). This allows enough room for the Sullivan
>6 oz clunk tank, and the Saito 72 with manifold installed.
>In the future I will simply notch the front of the wing to
>move the wing cutout. I too was leary to do the wing
>notching, but not anymore. It is simply no big deal to do
>and has zero effect on the strength of the wing. In fact, I
>bet you could argue it is stronger since the front of the
>wing is now attached to plywood around a boxed edge
>(firewall and doublers form a box in the front) instead of
>just being held by the fuselage sides and a small glueing at
>the firewall.
>
>Doug is convinced that the short nose with the big prop is
>the way to go. I am not inclined to argue, as I will most
>likely move the wing forward in Dr. J just to see the
>difference between it and Mr. Hyde (that was the whole
>purpose of the two anyway). All that said though, it
>appears that PW is NOT doing that. He appears to be leaps
>ahead of the game in the corner respect. Since the CG is
>somewhat fixed on the Mr. Hyde I will test the PW props and
>engine run and we can compare notes. Running these engines
>is really not rocket science and by the time your new
>'rplane is done there will be several good Eather and Bolly
>props to choose from. The engine setup with the UHP
>manifold, clunk tank, and YS fuel will still be the same (I
>predict) and will be the setup for a while.
>
>BTW I use a 2 1/2 spinner made by Maxx products, but they do
>not make a 3 blade. It weighs 1.8 oz which is the same as a
>plastic spinner. Since I cannot get Randy Smith insterested
>in making larger spinners I suppose I will continue to look
>for alternatives. My engine weighs 17.2 oz and the Moon
>pads weigh .9 oz. I suppose I would shorten the nose more
>instead of trying for lighter components. If these lighter
>components materialize great, if not no heartbreak.

Thanks again.....after several serious hours of drawing last night we have a semi scale Laird Turner Meteor of Cleveland Air Races fame flown by the flambouyant Col. Roscoe Turner. The profile is pretty close but needs a little tweeking tonight and then will start on the bulkhead views. Radial nose is just under 5 1/2" in diameter and have the engine plate set up to be adjustable so that CG can be moved forward or back as needed up to 3/4 of an inch and the cowl forward or back a little also. The prop on the scale plane was far from close to the cowl so this will not look uncharacteristic of the real thing should it be necessary to protrude a little. Also the entire tail and stab section will be removeable so once I reach the mock up stage I can shift the tail moment a little before settling on final placement but tentatively 18" now.

I will most likely settle on a 13 1/2 three blade Bolly as I assume Paul and Brad and Gordy are and then go larger or shorter/pitch as trim and performance are settled out. Total fuse length is just 39" but there is some girth here. Once bulkheads are drawn and cut I will start whittling blue foam for the fuse buck.

>I will most likely settle on a 13 1/2 three blade Bolly as I
>assume Paul and Brad and Gordy are and then go larger or
>shorter/pitch as trim and performance are settled out.

Paul said 13".

I am making a 13.25 and a 13" at 5 pitch all the way out per Master Walker's pitch.

The Eather prop is a totally different animal. It is about twice as wide at the tips and therefore requires less pitch (about 4.5 to 4.25) to acheive the same RPM and speed.

Brian and I are cooresponding about the new versions he is developing.

>Thanks again.....after several serious hours of drawing last
>night we have a semi scale Laird Turner Meteor of Cleveland
>Air Races fame flown by the flambouyant Col. Roscoe Turner.

Do you have a picture?

>
>
>Do you have a picture?

I will have soon. Didnt have a chance to clean everything up on my drawing yet but have plenty of documentation thanks to the Smithsonian where the real plane resides now and also a bunch from Allan Brickhaus. I will shoot some film soon. This is a monumental task when scaling up from pictures. Massaging a scale look into a stunt ship will certainly require more engineering than the usual box crutch fuse assy and of course making it light enough will be a concern.

The Meteor has a radial cowl, barrel fuse and stringers back past the wing and canopy assy. The plan is to mold shell halves such as described by Al but will probably use blue foam instead of plaster. Once the first set of shells from 1/16th are molded a second set will be molded over these but only extending back past the wing to the canopy assy. Carbon veil will line the inside of the shells. Then, stringers of 1/16 basswood will be run back to the tail feathers. It will be covered to look like a regular rag type construction.

Havent laid out the bulkhead views yet but have all the documentation for this as well so I am not totally flying blind here.

The wing plan at this point is Geobolt minus a few inches but am considering getting a carbon fiber version of this through Jose Modesto. Cut a foamer and sheet including tips and send it to him. He sends you back four shell halves with " bullet proof" tips etc. ready to be joined and ready for paint at price and weight that is certainly competitive. What sold me was when he took his demo and kept banging it on the trunk with mo damage to the wing half. He can give you more details.

Tail feathers will be large at 25 to 28% but scale shape.

???? What seems to be the appropriate tank shimming etc. for the 72. I know it will vary from model to model but want to leave enough room and still be able to get my gear placement settled on.

The 13/5 constant pitch sounds simple enough and I can boil and twist
as necessary. Keep me posted on your findings. Havent put the motor on the stand yet but figure I have plenty of time for that. Do you have any experience with this Golden Knight hemi version of the 72? I have heard it was good. I will follow break in as per instructions and all of you fellas experience.

John Sunderland

>???? What seems to be the appropriate tank shimming etc. for
>the 72. I know it will vary from model to model but want to
>leave enough room and still be able to get my gear placement
>settled on.

Almost exactly 3/32" off the beams, plus or minus a business card or two. It is shown in the pic.

>The 13/5 constant pitch sounds simple enough and I can boil
>and twist
>as necessary. Keep me posted on your findings. Havent put
>the motor on the stand yet but figure I have plenty of time
>for that. Do you have any experience with this Golden Knight
>hemi version of the 72? I have heard it was good. I will
>follow break in as per instructions and all of you fellas
>experience.

All big Saitos are hemis. The Black Knight is just a black version of ours. I would like some of those gold valve covers.

>>
>>
>>Do you have a picture?
>
>I will have soon. Didnt have a chance to clean everything up
>on my drawing yet but have plenty of documentation thanks to
>the Smithsonian where the real plane resides now and also a
>bunch from Allan Brickhaus. I will shoot some film soon.
>This is a monumental task when scaling up from pictures.
>Massaging a scale look into a stunt ship will certainly
>require more engineering than the usual box crutch fuse assy
>and of course making it light enough will be a concern.
>
>The Meteor has a radial cowl, barrel fuse and stringers back
>past the wing and canopy assy. The plan is to mold shell
>halves such as described by Al but will probably use blue
>foam instead of plaster. Once the first set of shells from
>1/16th are molded a second set will be molded over these but
>only extending back past the wing to the canopy assy. Carbon
>veil will line the inside of the shells. Then, stringers of
>1/16 basswood will be run back to the tail feathers. It will
>be covered to look like a regular rag type construction.
>
>Havent laid out the bulkhead views yet but have all the
>documentation for this as well so I am not totally flying
>blind here.
>
>The wing plan at this point is Geobolt minus a few inches
>but am considering getting a carbon fiber version of this
>through Jose Modesto. Cut a foamer and sheet including tips
>and send it to him. He sends you back four shell halves with
>" bullet proof" tips etc. ready to be joined and ready for
>paint at price and weight that is certainly competitive.
>What sold me was when he took his demo and kept banging it
>on the trunk with mo damage to the wing half. He can give
>you more details.
>
>Tail feathers will be large at 25 to 28% but scale shape.
>
Snip
>John Sunderland

John, your plane sounds familiar. I'm attaching a drawing of one I drew up a few years ago. Originally for the Stalker .61RE, but now considering it for the .72. Nose is too long for the 4 stroker, but would only be needing an inch or so removed. My insperation was a French stunter published in FM back in '72 I believe, called the Scepter.

Take a look at the way the fuse is constructed. It uses an inner fuse with the outer built over it. Enough spacing to make it similar to a stressed skin design. Gordy's Tony uses a variation of this same technique. The nose on the Tony is very strong, but light.

I'll be interested to see yours when you get it where you want it. BTW, love your Chevelle.

3f20340a407b3b22.jpg

I'm wondering why everything is spinning around?

>>>
>>>
>>>Do you have a picture?
>>
>>I will have soon. Didnt have a chance to clean everything up
>>on my drawing yet but have plenty of documentation thanks to
>>the Smithsonian where the real plane resides now and also a
>>bunch from Allan Brickhaus. I will shoot some film soon.
>>This is a monumental task when scaling up from pictures.
>>Massaging a scale look into a stunt ship will certainly
>>require more engineering than the usual box crutch fuse assy
>>and of course making it light enough will be a concern.
>>
>>The Meteor has a radial cowl, barrel fuse and stringers back
>>past the wing and canopy assy. The plan is to mold shell
>>halves such as described by Al but will probably use blue
>>foam instead of plaster. Once the first set of shells from
>>1/16th are molded a second set will be molded over these but
>>only extending back past the wing to the canopy assy. Carbon
>>veil will line the inside of the shells. Then, stringers of
>>1/16 basswood will be run back to the tail feathers. It will
>>be covered to look like a regular rag type construction.
>>
>>Havent laid out the bulkhead views yet but have all the
>>documentation for this as well so I am not totally flying
>>blind here.
>>
>>The wing plan at this point is Geobolt minus a few inches
>>but am considering getting a carbon fiber version of this
>>through Jose Modesto. Cut a foamer and sheet including tips
>>and send it to him. He sends you back four shell halves with
>>" bullet proof" tips etc. ready to be joined and ready for
>>paint at price and weight that is certainly competitive.
>>What sold me was when he took his demo and kept banging it
>>on the trunk with mo damage to the wing half. He can give
>>you more details.
>>
>>Tail feathers will be large at 25 to 28% but scale shape.
>>
>Snip
>>John Sunderland
>
>John, your plane sounds familiar. I'm attaching a drawing of
>one I drew up a few years ago. Originally for the Stalker
>.61RE, but now considering it for the .72. Nose is too long
>for the 4 stroker, but would only be needing an inch or so
>removed. My insperation was a French stunter published in FM
>back in '72 I believe, called the Scepter.
>
>Take a look at the way the fuse is constructed. It uses an
>inner fuse with the outer built over it. Enough spacing to
>make it similar to a stressed skin design. Gordy's Tony uses
>a variation of this same technique. The nose on the Tony is
>very strong, but light.
>
>I'll be interested to see yours when you get it where you
>want it. BTW, love your Chevelle.
>
>3f20340a407b3b22.jpg

Thanks John and that is a very pretty design you have there!!! Would love to see that in its completed state! Very nice.

>Thanks John and that is a very pretty design you have
>there!!! Would love to see that in its completed state! Very
>nice.

Thanks John. One of these days I'll build it. I need to decide now what power I'll use. The main reason for posting it was to show you the method I used for the fuse. It's not the only way to go, but it works good for me.

Don't ya just love those open cockpits though?

I'm wondering why everything is spinning around?

>
>
>Thanks John. One of these days I'll build it. I need to
>decide now what power I'll use. The main reason for posting
>it was to show you the method I used for the fuse. It's not
>the only way to go, but it works good for me.
>
>Don't ya just love those open cockpits though?

Cant seem to get away from them! Just looks to cool and barstormer-ish! Yes on your construction method. Jeff Kemp had a similar type construction on his Gee Bee.

That's awesome.

Godzilla wrote:

>BTW I use a 2 1/2 spinner made by Maxx products, but they do
>not make a 3 blade. It weighs 1.8 oz which is the same as a
>plastic spinner. Since I cannot get Randy Smith insterested
>in making larger spinners I suppose I will continue to look
>for alternatives.

You might check with Windy. He says he will have his own line of spinners out "in the Fall", and in some larger sizes.
Sammy

LAST EDITED ON Jul-23-03 AT 08:32 PM (CDT)
 
I would like to confirm Brads breakin procedures. I broke mine in according to the manual that came with it. Pretty much as Brad describes. I used 10% 24% half and half fuel for the breakin.

I had about an hour and a half on the bench when I sent it with Gordy to the Nats as a backup engine. Gordy told me that it was loaned to Steve when his engine lost it's bearings.

I was pleased to hear that the engine performed well mounted in a plane. I was concerned as I didn't remember getting the revs Gordy was getting with his. I suppose the difference is in the fixed venturii and manifold. This has convinced me that if you're serious about stunt with a 4 stroker, then you need to get rid of the carb.

I'm wondering why everything is spinning around?

>I was pleased to hear that the engine performed well mounted
>in a plane. I was concerned as I didn't remember getting the
>revs Gordy was getting with his. I suppose the difference is
>in the fixed venturii and manifold.

I would suggest checking that engine. Something was not quite right. Maybe the valves are too tight. It was really down on power.

PLease let me know.

Thanks for the heads up Brad. I'll be over at Gordans tomorrow. we'll check it out.

I'm wondering why everything is spinning around?

LAST EDITED ON Jul-25-03 AT 04:42 AM (CDT)
 
Nice drawing! Now I know why all these 4 stroke powered planes look like Dick Tracy, with that square chin. I wonder if there's any way around it. I suppose, if one were to go the semi-scale route, one could go with the Hawker Typhoon.. or one of the prototype Merlin Mustangs (they put the intercooler radiator in the chin, so it was also sharp chinned).

LAST EDITED ON Jul-29-03 AT 00:54 AM (CDT)
 
Just spent a long evening figuring out the construction technique vs. weight issues while truing up nose design and longerons etc. I truly think it will be a competitive stunt ship albeit the fact that a 1:1 flap/elevator ratio may be truly in order here. I just perused a really nice set of foam cores I have sitting here and a single panel weighs just under 2 1/2 oz sans sheeting and glue etc but it looks pretty darn good considering the fuse is going to be weight concern here. Any thoughts?

So whats the best weight saver where glue is concerned on a foamer these days? This will be fully sheeted and with a ply spar and a glassed cloth center section as I expect a few extra oz. on just over 670 sq. Any predictions or concerns for weight I should be aware of?

Any predictions or concerns
>for weight I should be aware of?

PLANE SQ IN SQ FT OZ LOADING
Todd Lee Mustang 700 4.86 52 10.70
Geiseke WC Nobler 560 3.89 42 10.80
Contrada Satona 600 4.17 48 11.52
Berringer Sportster 650 4.51 52 11.52
Moon Billy Bear Nats 720 5.00 58 11.60
Saturn WC Hunt 650 4.51 58 12.85
Walker WC Impact 685 4.76 65 13.66
Trivial Pursuit Nats 650 4.51 66 14.62
Patternmaster Baron Nats 750 5.21 80 15.36
Rabe BBQB 650 4.51 72 15.95

This is my worksheet for the Mr. Hyde. I am right at 63 oz with about 1 oz of tipweight.