Brodak 40 prop findings

So...
Last week, as per recommendation from members of this forum, I tried APC 10.5x4.5 prop. I flew ~10 flights with it just to get a feel for the plane. Last night, after 4 flights I switched back to modified APC 12x4 to see the difference. The following are the findings.

Test platform:
a) Semi-lame pilot. Please keep that in mind while reading. I may have not been looking for what I was supposed to.
b) Fuel is SIG 20% oil(50/50). I mixed 1 gallon of 5% and 1 gallon of 10% to get 7.5% nitro.
c) Highly modified SIG Banshee(41oz dry). CG is 1/4" in front of wingspar. No rudder or engine offset.
d) Brodak 40 motor with Brodak tongue muffler. The motor was broken-in with ten 2min runs and 4min cool down in between. It has about 40 flights since break-in.
e) 4.5 oz uniflow profile tank(Brodak), cut down to 4.1 oz capacity.
f) 64ft eyelet to eyelet .015 lines.
g) Prop A = APC 10.5x4.5 blanaced
e) Prop B = APC 12x4 cut down to 11x4 and balanced.

Findings:
1) Fuel usage: Prop A = 3 3/4oz for full pattern plus 10 laps. Prop B = 4oz for full pattern plus 6 laps. The engine cuts out cleaner with Prop B.
2) Prop B = 5.2 sec/lap. Prop A = 5.1-5.2 sec/lap.
3) With Prop A, the motor takes a little bit longer to come back from 2 cycle. Prop B needs 1/8 needle turn counterclock wise. Weird...
4) Level flight is much easier with Prop B.
5) On round maneuvers, both props feel fine.
6) On squares/triangles, Prop A does not accellerate as well going up but it does speed up more going down.
7) Pulling over the top at the end of a clover-leaf into the wind with Prop A, the lines go slack. Prop B manages to speed up enough to keep lines tight.
8) In the wind, Prop B slows down into the wind a lot more than Prop A.

Summary:
Prop B feels much better on B40. I've flown Prop A on OS 40FP and it is probably the BEST prop for that motor. My guess is Brodak 40 doesn't turn enough RPMs to keep Prop A in its 'sweet' spot.

I'd appreciate any comments as I am not sure I looked at the right parameters.

>So...
>Last week, as per recommendation from members of this forum,
>I tried APC 10.5x4.5 prop. I flew ~10 flights with it just
>to get a feel for the plane. Last night, after 4 flights I
>switched back to modified APC 12x4 to see the difference.
>The following are the findings.

>
>I'd appreciate any comments as I am not sure I looked at the
>right parameters.

Wow. Interesting results.

I own examples of both engines. My FP 40/clones want to wind up much faster than the Brodak. With a .285 venturi and a ST NVA, it seems to like the APC 12.25 x 3.75 trimmed back to either 12" or 11.75". Launch at a wet two cycle. Sometimes an additional head gasket is necessary to keep the run smooth. Some folks like to run an 11 x 4 or and 11.5 x 4 with this engine stock. The engine will speed up in flight but for the most part will hold the same speed. The secret to keeping it from running away seems to be launching while in a slow two cycle with a low pitched prop.

Question - is your FP 40 stock?

My Brodak, on the other hand, doesn't really want to wind up like the stock FP, so I tend to go with a little more pitch to keep my lap speed about right. Your modified 11 x 4 sounds interesting. I would also be interested to see how an APC 11 x 5 compares and works for you. The 11 x 5 right now is my prop of choice for the older OS Max-H 40s and the Brodak 40. The Brodak/YO 11-5 (with a little thinning and shaping work) works even better, but they were hard to get as of a few months ago.

>run smooth. Some folks like to run an 11 x 4 or and 11.5 x
>4 with this engine stock.

I haven't spent much time testing with FP yet. Other pilots here suggested 11.5x4 on FP as well. I was concentrating on my Banshee/B40 setup for the upcoming contest in NJ. I'll play with my FP once I'm back from Palisades Park.

>Question - is your FP 40 stock?

Bone stock. It doesn't seem to be running away with 10.5x4.5 but I can't be sure 100% until I get enough flying time on it.

>Your modified 11 x 4
>sounds interesting. I would also be interested to see how
>an APC 11 x 5 compares and works for you.

12x4 prop doesn't have typical 'APC shape'. I think that's the reason it works so well. I'll see if I can get my hands on 11x5 to give it a try.

>12x4 prop doesn't have typical 'APC shape'. I think
>that's the reason it works so well. I'll see if I can get my
>hands on 11x5 to give it a try.

Steve;

Actually, I did think of it and considered mentioning it, but my observations with cut down props are purely subjective.

George Aldrich marketed a series of props just before his untimely death. These props were much fatter towards the tip than most other props. I asked him the rationale behind the design, and his response was improved line tension. I thought that interesting as I'd perceived the same years ago when I used to take an 11-6, trim it to 10-6, then then round and thin the tip but keep the larger area. GMA's theory was this effect was more prevelant for the lower RPM engines and not those that are designed to run faster.

At the same time, if you look at the CF prop blades from Bolly and others, these propellers appear to have less area per blade, yet they seem generate high thrust as well and are the prop(s) of choice for top flyers. However, I see more of these blades used high RPM engines.

Again, purely subjective. I wish someone who is smart on props would chime in here. For most of us, props are probably the greatest mystery for CL. We can see and fix warps, cure vibration problems, adjust tank height, etc. But determining just how a blade works and what shape/diameter/pitch of blade is the best for a given engine/plane is almost black magic.

You might have somethere there. I recall seeing pictures of 3 planes from this one european team. Their blades did not have any taper towards the tip at all. The width of the blade stayed the same for the last 2/3 of its lenght. I wonder why...

Steven,

Good report, I would guess the difference in level flight is the 11-4 probably weighs more and adds a tad more nose weight. I haven't tried your prop yet but after reading this I sure will.

I have been real happy with the 10.5 x 4.5 and am not seeing the wind up you are describing. I am also not getting the fuel mileage you reported and I am using less nitro (5%). I also have tons of overhead tension even pulling out of the hour glass. This is real interesting and as soon as I can I will pick up a 12-4 and report back.

> I am also not getting the
>fuel mileage you reported and I am using less nitro (5%).
What kind of mileage are you seeing? What kind of weather are you flying in?

>This is real interesting and as soon as I can I
>will pick up a 12-4 and report back.
Please do! I would love to see how others are doing with this prop.

Typical Oklahoma summer 90+ deg with 80+ humidity. I have a 4 ounce tank in the Omnium and it takes every bit of it to get through the pattern. Sometimes if I get off a little lean I have 10 to 15 laps after the pattern but usually only 5 or 6. Jim P. in Ok City is also reporting better fuel mileage than I am getting. Heck I don't understand it..

I have another B-40 in my Noblearf and will be flying it this weekend if the rain gets out of here before the weekend is over. I also put a 4 ounce tank in it so will be interesting to see how the two engines compare on power and fuel mileage.

My mileage improved. I started out having to fill the tank(4.1 oz) with 5% nitro fuel. Now I am comfortable putting in 4 oz of 7.5% nitro fuel and I expect it to run through entire pattern no problem with about 6-10 laps after that.

>Typical Oklahoma summer 90+ deg with 80+ humidity. I have a 4 ounce >tank in the Omnium and it takes every bit of it to get through the >pattern. Sometimes if I get off a little lean I have 10 to 15 laps >after the pattern but usually only 5 or 6. Jim P. in Ok City is >also reporting better fuel mileage than I am getting. Heck I don't >understand it..

The latest Oriental is flying at 41-42 oz with the first B 40 I obtained which is perhaps more broken in than the second. Weather mostly pretty similar. I went up to 10/22 fuel and mileage dropped quite a bit but 4 oz does it all with a slight reserve, even in a steady 4 stroking run.

What's the deal on the 10.5 X 4.5? A new prop or ??.

>
>What's the deal on the 10.5 X 4.5? A new prop or ??.

Hi Jim,

This prop is what I found worked the best for me after trying several others, APC 10-5, Rev-Up 10-6 EW, 10-6W, and a couple others I don't remember.

I found a couple of APC 12-4's yesterday and have cut one down and mounted it on the Omnium. If the rain will get out of here I will fly it this weekend and see how it compares to the 10.5 x 4.5

One item that may be of interest.. I used a plastic 1 3/4 inch spinner on the Nobler ARF and was barely able to get it cut out enough for the 10.5 x 4.5. The 12-4 has a larger hub and I don't think there is enough meat in the 1 3/4 inch spinner to be able to use it. There was barely enough with the 2" spinner on the Omnium.

The Noblearf with B-40 is ready for it's maiden flights and I am starting with the 10.5 x 4.5. It is almost 5 ounces lighter than the Omnium so might not be a good comparison. I will report what I find after I get a few flights in.

Hmm? This must be a new offering from APC, don't recall ever seeing one listed but I'll try to come up with one to try also.
I'm still stuck on the 10-5 APC which performs very well but a little experimenting never hurts.
Guess you did not make it to the Dallas contest. Perhaps this is just as well as it looks like the weather there is pretty much like it is here with off and on rain all day, maybe more tomorrow.
We sure need the moisture but the timing is not the best.

>Hmm? This must be a new offering from APC, don't recall ever seeing one listed
>but I'll try to come up with one to try also. I'm still stuck on the 10-5 APC
>which performs very well, but a little experimenting never hurts.

>Guess you did not make it to the Dallas contest. Perhaps this is just as well as
>it looks like the weather there is pretty much like it is here with off and on
>rain all day, maybe more tomorrow. We sure need the moisture but the timing is
>not the best.

Jeff is working today, when the odds for the scattered showers are only 1 in 5 here. For tomorrow, the chances for rain go up to 60% - I hope it's afternoon stuff as is typical here this time of year.

According to the Weather Channel's web site, Dallas' chances for rain today are the same as ours are. Tomorrow, they will be better off there, with "only" a 40% chance of rain.

I've been meaning to confirm something at Jason's Oklahoma web site, or with you. I have no impediments to a trip to Tulsa at the end of next month, other than a tight budget, but there may be a conflict in mid-October. Houston is having a contest the weekend of the 11th and 12th:

"OCT 10-12--Houston, TX (A) Houston Combat Classic. Site: Scobee Memorial Field, George Bush Park, Houston, Texas. Events: 328, 330 (JSO) 1/2A Combat on Friday, Oct 10, triple elim withcash prizes and awards. Triple Elimination Fast Combat on Saturday and Sunday, $1,000 cash (permitting entries) and awards. Shutoffs required in fast. CD:
Richard Stubblefield, 1922 Thousand Pines, Kingwood, TX 77339 Day Phone: 713-223-1496 Eve Phone: 281-358-3522 Sponsor: PropTwisters of Houston #3022."

Jeff needs me in his pit for him that weekend. And I'm pretty sure that's the same weekend you picked for your fall fun fest in OKC, isn't it? If so, doggone!

.
Kiwi

">What's the deal on the 10.5 X 4.5? A new prop or ??."

No, this isn't a new prop. It's just that a lot of LHS and the big mailorder places don't carry anywhere close to all the APC lineup. Get thyself to the APC website http://www.apcprop.com and look at the difference. Some of these props look like the 10-5/11-4/11-5, etc, but others look much more like daggers, the 12-4 and 12-5 being in that group. You'd never think they'd work for stunt, but they do. Mysterious. I don't understand why there are at least two different designs, but if they work, I'm not going to kick. Steve

>">What's the deal on the 10.5 X 4.5? A new prop or ??."
>
>No, this isn't a new prop. It's just that a lot of LHS and
>the big mailorder places don't carry anywhere close to all
>the APC lineup. Get thyself to the APC website
>http://www.apcprop.com and look at the difference. Some of
>these props look like the 10-5/11-4/11-5, etc, but others

Steve;

I think the question was if APC is making a prop with a 4.5 pitch, 10.5 inches in diameter. From what I can see they don't. Bolly might make this in their Clubman series.

>I think the question was if APC is making a prop with a 4.5
>pitch, 10.5 inches in diameter. From what I can see they
>don't.

Check the APC website again. Look under (of all things) "free flight props".

I found the size, but could not get their site to put anything into the shopping cart.
Steve

Just look at "Prop List". http://www.apcprop.com/html/prop_list.htm They're in order by diameter, not segregated by application. The 10.5 x 4.5 is #LP10545 $3.95. Somebody recommended it for Fox .35's, of all things. It used to be possible to order from the "prop list", but now it's not possible. I just emailed apc and whined about that. The new catagorized system bites. Also suggested a 9 x 3 and an 11.5 x 3.5, and that they should just catagorize props by electric/gas. Don't fall for those "Slow Flyer" props, they're for electric or steam engines or something. Write them! Steve

PS: Just tried the online store, and it worked up to wanting my name and credit card info.

In answer to Bob Kruger's post asking for prop help I might be able to help. The root and the tip are the biggest drag producing areas of a prop. A 4 blade with narrow blades will have a similar blade loading to a fat 2 blade. The 4 blade will have the higher static thrust every time, but (there's always a but) that is not what we all want. A wide tip will produce more and more drag as RPM increases which will limit the speed of the prop. The narrow 4 blade work great on pipe models because the pipe is limiting the RPM. I would suggest trying different props until you find "that sweet spot" of RPM and airspeed.
Andrew Raney

Interesting discovery yesterday..

I flew my Nobler ARF for the first time. Brodak 40 with APC 10.5 X 4.5 same setup I have had such great luck with on the Omnium. Wind was not bad 5 to 7 mph but it was still raining off and on. One little problem... On the Nobler I get wind-up really bad and have no line tension overhead. Part of the overhead tension I am sure is trim and part of it may be related to the prop.

The only thing I can think of is that the Oriental wing in the Omnium is a straight wing with the same thickness the entire span. The Nobler is a double tapered wing which starts out about the same thickness as the Oriental at the root but ends up about half that thickness at the tip. If my thinking is correct this means the Omnium has quite a bit more drag built into the wing than a Nobler. The Nobler wing isn't slowing it down so this ended up not being a good prop choice for a B-40 in a Nobler.

You just really never know what may work and it can be different depending on many variables. Sometimes I get amazed at just how complicated finding the right engine/prop combination can be.

2nd sesion with the Nobler/Brodak 40 this afternoon, most of the trim issues have been worked out and the plane flyes great. I ended up with a Rev-up 12-5 cut down to 11 inches. This proved to be the best prop for the B-40 in this plane.

I also tried the APC 12-4 cut down on the Omnium and didn't like it as well as the APC 10.5 x 4.5. I noticed wind up with the 12-4 which I don't get with the 10.5 (on this airplane)...

So it looks like any of the three I have played with will work depending on the airplane. The APC 10.5 x 4.5 is my choice for the Omnium. (Oriental wing in a 43 ounce airplane) The Rev-up 12-5 cut down to 11 is my choice for the 39 ounce Noblearf.. And Steve has had good results with the cut down 12-4

It's just plain magic

I'm a beginner compared to most members here but I am realizing one thing: there is no magic bullet when it comes to control line flying. I am still curious though if anyone has tried my prop on their B40 ship.