OK, anyone ever heard of.............

LAST EDITED ON Feb-09-04 AT 01:14 PM (CDT)
 
the Impact????? I have a profile that I built several years back which is a scaled down Impact. I called it the Impulse. (I built it on an "Impulse") It really does fly well with an OS 40FP, etc., and I am now considering using a built up fuselage and an OS 25VF/pipe. It came out at about a 48" wing span. Very similar in size to the Prowler, but with an Impact airfoil.
Any ideas about this?
I guess this isn't very interesting, huh?
Must be REALLY BORING.........
Thanks
Bill <><

Well, in theory it should work. It sounds like nobody else has tried a mini-Impact. Does the VF 25 weigh any more than the FP 40?

You guys build so fast you may as well try it and see what happens. If nothing else you will have data to report next time this subject comes along.

LAST EDITED ON Feb-09-04 AT 11:17 AM (CDT)
 
The 25VF is lighter than the 40VF, but I will have to weigh them both tonight for exact weights. 25 is in a much smaller case.

On the profile (approx. 80% of original size), I used 1/4" sheet stab/elev. Am thinking about doing a built up tail. I will have the profile at the next contest.

I should be able to build a "built up" one lighter overall.

Thanks,
Bill <><

depending on powertrain weight you could just make a 3/8 stab 1/4 elevator out of sheet. 3/32 sides. All you need is a wing core, or a call to the laser cutter. How big is the pipe compared to a 40 size pipe? will it fit in the fuselage ok?

Just thinking of relevant questions until the experts chip in...

Thanks Steve,

Don't think the "experts" are gonna chip in...... just doesn't seem exciting or controversial enough.

Or I have been black balled and we are the only two that don't know about it.

The pipe is proportionally smaller, and I was thinking of a core/outline type of tail feathers. Mike Starrett's Eliminator was a good 25VF ship, but I felt the Impulse would be a good starting point, especially since Howard, Paul, Brett, et al, have flown/are flying the full size version.

Alas.....................

Thanks,
Bill <><

>Thanks Steve,
>
>Don't think the "experts" are gonna chip in...... just
>doesn't seem exciting or controversial enough.
>
>Or I have been black balled and we are the only two that
>don't know about it.
>
>The pipe is proportionally smaller, and I was thinking of a
>core/outline type of tail feathers. Mike Starrett's
>Eliminator was a good 25VF ship, but I felt the Impulse
>would be a good starting point, especially since Howard,
>Paul, Brett, et al, have flown/are flying the full size
>version.
>
>Alas.....................

Geez, Bill- start a post with "has anyone heard of an Impact" and then ask for random thoughts about a full-fuse version of a model we have never heard of ("Impulse"), and we are blackballing you because we didn't answer fast enough?

Plenty has been written about the Impact and how various people think it flies. Scaled down versions may or may not fly the same, since I have never seen one and generally scaling doesn't mean it flies like the original.

LAST EDITED ON Feb-09-04 AT 04:37 PM (CDT)
 
Thank you for responding Brett,
I changed the title of the original post after over 155 views and one response from a friend. Waited quite a while longer and editied in the sarcasm, etc., so that maybe that would at least elicit another response. All the while several well knowns replied to other posts.
I know I am not a well known "name". See my disclaimer. However, I have always heard of the experts sharing knowledge, and I just wanted to benefit some from the sharing. Unfortunately I do not live in an area where there is any participation nearby. Club field is over 100 miles away; over two hours on back roads.
I ask a question that is valid, and the post has to be changed to where it strikes a nerve to get a response from someone who COULD shed a BUNCH of light on the subject. Think about it.
There are opinions on every design aspect here from proposed 61 powered biplanes (which I really hope Bob can pull off) to 15 size Sig Akromasters.
So, how DOES scaling down an airplane affect it's performance? Do the moments need changing? Tail area? Flap area? Fuselage side area?
All things that you can expound upon, along with others. What information do I need to supply? I know the Impact is so very well known that many know the figures of it by heart. Mine is 80% that size.
BTW: I asked for your opinion in my reply to the "tanks" posting regarding rosin core solder. Just want to know the pluses of using it. I can use any solder, and I wanted to know if it flows better, tins better is more resistant to vibration, etc.
Thanks you,
Bill <><

LAST EDITED ON Feb-09-04 AT 05:08 PM (CDT)
 
>I ask a question that is valid

But your 1st post didn't really ask much of a question
("any ideas about this?")

>So, how DOES scaling down an airplane affect it's
>performance? Do the moments need changing? Tail area? Flap
>area? Fuselage side area?

Much better. Though I'd think you'd do better to focus more.
It's hard to answer such a shotgun-blast of questions.

Not that I can answer any of them

Bill, you asked a question about something that nobody seems to have tried so it's unlikely that you would get much response. Most people are probably waiting for you to do it and tell us.
I've been scaling down designs since about 1950 and it doesn't really make that much difference. I usually make an exact scale model, construction too, because I think that way. They were all stunt models and they all flew like stunt models. I've just completed a 60% Box Car Chief to go with my 60% Barnstormer. The BCC is electric powered (shock-horror!).
Do use resin/rosin cored solder, it works really well on tinplate.

Hi Preston and Dave,
You guys are right. I am not an expert in this field. But, in the areas where I do have expertise I am not used to having to go into minutiae about a subject, the others have a feel for what is being asked. If you ask "what do you think" about a sunject, they have the expertise to answer what they think. It was simply an error on my part to assume (there's that word! LOL!!) that the "ones in the know" here would "know" what to answer. They always seem to. (present company excluded)
I might just go ahead and see what happens, maybe not.
Thanks again,
Bill <><

Disclaimer: I am neither a NATS Champion (yet), professional engine reworker, engine producer, column writer, Hobby Shop owner, *rockeet* scientist, nor otherwise. Just an old Advanced flier. More true now than ever.

Bill,

I just remembered that I asked this exact question to Paul Walker:

How would a reduced Impact fly"

He answered me:

"I don't know."

If PW don't know, how do you espect the rest of the gang to know?

Bill, for what its worth, the Patternmaster series has lent itself well to various scaledowns, all the way to the little Time Machine 40, as we all know. Randy Smith now has small (SV-25?) as well as large jobs now. I imagine the Impact would work the same way, within reason. Differences that might make the finished product untenable to a top 20 flier are not likely to be so noticeable to you or me. Like I said in the earlier note, you are in a good position tyo find out, because if the finished product turns out to be a dud for some reason, you will not have lost as much time as somebody like me that takes forever to build one lousy airplane.

One scaling isue that might come up is that a 48 inch wing plane may be more sensitive to being proportionally overweight than a larger one. Might be best to keep the finish light on this experiment.

At the rate you guys build, I expect to see the finished product at Marietta!

Steve,
Well I was thinking along those lines, too!
As for Marietta, I have a QBK Ares, Monterrous Mustang, and Vulcan to finish first. Aaron might have his Satana done by then. I have also just about completed the hanger rash repair on the Geo Juno!
Well there goes the stick with one design theory!! LOL!!!
But I have a good time, and for only gettting a few dozen flights a year, I do ok.
Bill <><

>Bill, for what its worth, the Patternmaster series has lent
>itself well to various scaledowns, all the way to the little
>Time Machine 40, as we all know. Randy Smith now has small
>(SV-25?) as well as large jobs now. I imagine the Impact
>would work the same way, within reason. Differences that
>might make the finished product untenable to a top 20 flier
>are not likely to be so noticeable to you or me.

I didn't say it wouldn't work. I said it (or attempted to say) that the characteristics might not scale down. A smaller scale-down of an Impact will probably fly fine. But having flown a big one doesn't necessarily tell you much about a small one.

Maybe they are at work or out of town.I am sure its nothing personal.
I enjoy reading your stuff but I am a newbie .What the heck do I know?

leon99:+

LAST EDITED ON Feb-10-04 AT 01:17 AM (CDT)
 
>So, how DOES scaling down an airplane affect it's
>performance? Do the moments need changing? Tail area? Flap
>area? Fuselage side area?

Some things scale well (airfoils and the like). Other things don't scale at all. A smaller airplane with everything else the same turns about the same radius corner, since that's limited by the pilot, not the airplane. So the pitch *rate* is the same, and therefore the tail moment probably doesn't want to be proportionally shorter. If you make the tail proportionally longer, then you either need to scale down the tail more to keep the TVC the same, or leave it the scale size and win dup with *more* TVC. Either one is probably OK - but it's not the same as the full-size model anymore. Furthermore, the lengths scale proportionally, the weight scales with the cube of the linear dimensions (except the engine and ancillary parts that comprise maybe 30% of the total weight). The torques scale with the linear dimensions, but the inertias scale with the square of the linear dimensions, and given the cubically-reduced weight, the natural frequencies go up drastically. And on and on...

Point being, the "scaling rules" will get you in the ballpark, but I wouldn't expect that a simple scale-down would necessarily get you the same characteristics as a full-scale model. I'm sure a straight scale-down of an Impact will result in a good-flying model, but the comparison to the real thing may well be only cosmetic.

Brett

p.s. By the way, I'm sorry I snapped at you earlier, but really, we all have lives to lead, and you were posting complaints about no response roughly 4 hours after the initial post. No offense, but participation here is voluntary, and I reserve the right to respond only to those posts that interest me. Particularly when someone uses his .SIG line to mock my "expertise".

Bill.

Why do't you start with the ELIMINATOR?

It's a simple, very intelligent and proven design.

It's a cinch to build.

Just watch out for the rib emplates, they are wrong in the FM planjs.

GBY,

I think its time for somebody to design "The Emasculator".....!!

Hey Buddy,
Got that one covered.
Bill <><

Hi Ion,
I have flown this 80% Impact as a profile with several engines, and as a profile it flies pretty good. William Davis (from the "Carolina Gang") told me once to build a full fuselage version of it. (This was after winning at a contest my second time out) I never did, but I have an OS 25VF just sitting here w/Pipe, etc., and it seemed like a good idea.
I never really liked the looks of the Eliminator, or I would have built it a long time ago...
Maybe I will just go with a Perroquet. I know how that flies with a 25VF and pipe.
Thanks,
Bill <><

>the Impact?????

Heard of the Impact? Most of us have, but now what?

>I have a profile that I built several years
>back which is a scaled down Impact. I called it the
>Impulse. (I built it on an "Impulse") It really does fly
>well with an OS 40FP, etc., and I am now considering using a
>built up fuselage and an OS 25VF/pipe. It came out at about
>a 48" wing span. Very similar in size to the Prowler, but
>with an Impact airfoil.
>Any ideas about this?

OK, you said the scaled down profile "really does fly well". If so, the full fuselage version should fly well, also. Now, as to the 25VF/pipe, I don't think there is too much experience here in using this set-up. I have never seen one, much less built or flown one. Since the top guys generally fly pipe ships with 40-65 size engines, that is where the greatest amount of experience lies. There are several people who have flown the smaller size ships, and I guess you would need to call on them. However, a lot is going to depend on how you had the 40 FP set up and how you set up the 25 pipe. A good 40 FP set up should definitely have more thrust. So a lot will depend on what you were using when you run your comparisons.

I held back in answering your question for the same reason I would guess that a lot of others did. I don't know the answer to your question. If it is something that you want to do, then you will probably just have to try it. Just don't expect the scaled down version to fly as well as the "full-size" ship. If it did, there would be a lot more people building that size plane with that size engine. They don't build the bigger planes and use the bigger engines without reason.

Still, if properly set up, built light enough, and all the rest, it should give a good account of itself. Is that the answer you are looking for?

Thanks Leonard,
Well it wasn't "exactly" the answer I was looking for, but it does give some confidence that it wouldn't be a total waste of time! LOL!!
Really,Thanks!
Bill <><

Bob Hunt, as I recall, has used a .25VF. You might ask him. He could tell you what to use for pipe and prop. If it's like the .40VF, it is sensitive to prop variation.

While I won't attempt to speak for anyone else, I just gotta share with this little corner of the world that the next time Bill has a question about some esoteric subject, I'm gonna just jump all over it.

Unless, of course, I miss his deadline, which appears to form a rather narrow window of opportunity.

Bill, I think PW gave the best answer to your question, this coming via Ion.

LAST EDITED ON Feb-10-04 AT 02:59 PM (CDT)
 
Stop it Mr Dirt, you're killing me!
I promise to convey my intentions in a much better manner if I ask another question.
Bill <><

Bill, I've posted things that nobody responded too.

I've posted things that some people responded too.

and

I've posted things that I wish nobody would have responded too, and would you all please STOP already!

Ya pays yo money and takes yo chances.

Wouldn't a shrunk Impact be a "Compact"?

Or if the wings are not straight, it will be a Limpact

I think a shrunken Impact would be a "Divot." This due to the fact that when the tail on my first Impact broke off and flitted away, the resulting crash didn't have much impact, but the reduced-size model did make a nice divot in the grass field from which I was flying.

Okay, it's weak. But it's also a lot better than "Compact."

snip

>Okay, it's weak. But it's also a lot better than "Compact."
>
>Dan

Yeah sure, and now your "Divot Dan"

I kind of like that better than Dirty Dan!