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Wing and Stabilizer arrangement for aerobatics

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Wing and Stabilizer arrangement for aerobatics

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Old 01-21-2002, 01:06 PM
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Mike James
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Default Wing and Stabilizer arrangement for aerobatics

I've been doing a lot of research on both Pattern and IMAC designs, and in comparing notes, find 3 basic arrangements, on planes with typical Pattern dimensions...

The most popular one seems to be to have the wing about one inch below the thrust line, with the stab on the thrust line. The second most popular seems to be to have both the wing and stab on the same line, but slightly below the thrust line. The third most popular seems to be to have the wing and stab on the same line, right on the thrust line.

I'm hoping that someone here (Ollie or Paul?) may be able to shed some light on why this is so, and benefits/drawbacks of each.

THANKS!
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Old 01-21-2002, 04:11 PM
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Default Wing and Stabilizer arrangement for aerobatics

personaly i think it has more to do with looks, access, and engine/pipe arangement. i think the drag of the wing lower than the engine has sommit to do with 'on the thrust line' arangement to cancle that out. anymore than that i dont know
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Old 01-21-2002, 04:43 PM
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Default Pattern Aircraft Alignment

I think the general idea is to have the thrust vector equal and opposite (aligned) to the total drag vector so that there is less pitch change when the throttle is advancing or retarding. The presence of a draggy landing gear would require that the wing be mounted a bit higher. A streamlined gear or retractable gear would allow the wing to be mounted a bit lower.
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Old 01-23-2002, 08:49 AM
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Default Wing/Stab setup

Thanks Ollie! Any other opinions?
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Old 01-24-2002, 03:56 AM
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Default Thrust line

i think it all depends on what performance you're looking for. i do know that having the wing and stabs on the thrust line you can get better rolls without coupling and hovering/TR's are alittle easier, because if the stab is slightly higher than the wing (CAP 232) you need to hover with the plane leaning toward the canopy rather than straight up so the stab and wing are in-line. Also have heard that moving the stab up away from the thrust line will increase sensitvity of the elevator.

rob o'
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Old 01-24-2002, 05:11 AM
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Default Performance

I'm hoping to find out more from all of you. I suppose the "ultimate" performance would be "symmetrical in every axis with no coupling".

My first instinct would be to put both the wing and stab on the thrust line, since so many maneuvers are done inverted, and we want the same response. I would think that with most pattern-proportioned ships, the stab wouldn't be affected by the downwash from the wing. BUT... There are so many good designs (i.e. "Summit" series, vs. "PTX Vector" vs "Angel's Shadow", vs. ZN Line products) with different setups that all apparently work.

If any of you know the forces involved, (some aerodynamic, some related to mass forces, as Ollie stated) or have done your own research, please share some info with me!

Thanks again, everybody.
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Old 02-10-2002, 01:31 AM
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Default Update: New place for Design discussion

As some of you are probably aware, the Administrator has kindly added "Design, CAD, and 3D" to the "Scratchbuilding" forum.

So, for questions and discussions of things like the "Aerobatics Setup" question above, as well as a variety of conceptual ideas, come on over and join us in "Scratchbuilding".

See you there!
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Old 02-15-2002, 10:17 PM
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Default Wing and Stabilizer arrangement for aerobatics

I would avoid placing the stab directly in line with the chord line of a symmetrical section wing. This seemed to cause a peculiar pitch instability in level flight, which I think was caused by interaction of the vortex generated by the wing with the horizontal stab. I fixed the problem by giving the wing about 1/2 degree positive incidence, and never again placed the stab on the same line. Had the same problem many years ago with a control line speed model.
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Old 02-19-2002, 01:53 AM
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Default Wing and Stabilizer arrangement for aerobatics

Wing and stab in line? Dunno....works for the Edge. Not peculiar at all.
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Old 02-19-2002, 02:20 AM
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Default Wing and Stabilizer arrangement for aerobatics

I built many U/C models with wing and stab in line, and only had problems with pitch stability in a couple of them, and in one R/C pattern model. I think the problem arises when the alignment just happens to be perfect, so the stagnation zone behind the wing hits the stab directly on its leading edge stagnation point, and may thus tend to be develop an unstable attachment to the stab, where random gust effects may attach the flow to either the underside or topside of the stab in a rather indeterminate manner, resulting in peculiar pitch excursions. I think the evidence for this is that a change of wing incidence as small as 1/2 degree corrected the problem completely for me. The fact that no full-scale Edge has reported any problem may be due to renolds number effects. In general, full scale designers tend to avoid having wind and stab directly in line, and I think the fact that such alignments usually work is due to small building errors that inadvertedly place the stab just a little above or below the wing chord line.
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Old 02-19-2002, 04:24 AM
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Default Wing and Stabilizer arrangement for aerobatics

I just dug out the Edge 540 drawing from the factory brochure, and the horizontal stab appears to be about inches above the wing chordline. I would be surprised to see any full scale designer place the wing and stab directly in line.
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Old 02-19-2002, 04:45 AM
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Mike James
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Default The original question

Hello everyody, and thanks for your input so far. Let me be a little more precise about my original question. I'm aware of the textbook "stab in the downwash" issues, but that doesn't seem to be a factor when we're talking about these long tail moment Pattern planes. What I am trying to determine is:

Suppose you had 3 identical models, with typical Pattern proportions. One has the wing and stab both on the thrust line. One has the wing and stab on the same line, but a bit below the thrust line. The third one has the stab on the thrust line, and the wing a bit below that. What would be the differences in performance? (All 3 of the above types have been championship winning setups, so what (besides "fashion") causes designers to selct one over the other?

I've asked this question on various forums, have written to the NSRCA, and have personally written to several "name" Pattern flyers, over the last year. So far I have not received even ONE definitive response. This leads me to believe that most designers don't really know, and are just experimenting until they get what they want. Any expert Pattern designers care to jump in here? I would sincerely appreciate it.

Thanks!
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Old 02-19-2002, 05:22 AM
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Default Wing and Stabilizer arrangement for aerobatics

I don't think that there would be any significant differences, Mike, as long as the wing and stab are not directly in line, which can cause problems. Incidentally, I meant to say that the full scale Edge 540 appears to place the horizontal stab about 6" above the wing chord line, but finger trouble interfered. The trouble that I experienced with wing and stab directly in line reared its ugly head in the form of uncommanded pitch excursions from level flight, at random intervals, equivalent to sudden application of about 10% elevator deflection. Putting the horizontal stab as little as 1/4 inch above or below the wing chordline, I think, will probably prevent this from happening.
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Old 02-19-2002, 10:26 PM
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Default Re: The original question

Originally posted by mikejames0
Hello everyody, and thanks for your input so far. Let me be a little more precise about my original question. I'm aware of the textbook "stab in the downwash" issues, but that doesn't seem to be a factor when we're talking about these long tail moment Pattern planes. What I am trying to determine is:

Suppose you had 3 identical models, with typical Pattern proportions. One has the wing and stab both on the thrust line. One has the wing and stab on the same line, but a bit below the thrust line. The third one has the stab on the thrust line, and the wing a bit below that. What would be the differences in performance? (All 3 of the above types have been championship winning setups, so what (besides "fashion") causes designers to selct one over the other?

I've asked this question on various forums, have written to the NSRCA, and have personally written to several "name" Pattern flyers, over the last year. So far I have not received even ONE definitive response. This leads me to believe that most designers don't really know, and are just experimenting until they get what they want. Any expert Pattern designers care to jump in here? I would sincerely appreciate it.

Thanks!

Mike

I spoke with Chip Hyde in Ireland at the worlds about some airplane design questions. Mainly what I got from him is that he feels that a lower wing design (unlike the Vector which is mid wing) will roll better than a mid wing design. As far as stab placement I think you need to look at the incidences that you want to carry. A 0-0 setup prefers a closer wing-stab arrangement and a + + setup requires the wing stab to be further apart, this is just what I have found from looking at different designs. I wouldnt get too concerned with the placement of the wing stab, go with something that is roughly conventional and looks good. From there the correct wing area, stab area, fuse side area and placement of the high point, airfoil, and WEIGHT are the most important design factors, with the weight being the greatest importance. With the new schedules you need a very light plane. In Ireland there were not a lot of planes over that 10.25 lb mark. Anyways I am not a designer, I just fly em and tell ya whats wrong with them!!
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Old 02-20-2002, 02:45 AM
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Default Thanks!

Hi Chad, and thanks for the effort. And thanks to Chip Hyde of course, too. This is actually the most specific answer I've had so far.

I suppose what confuses me about "higher vs. lower" in these discussions is that about 50 percent of the Pattern manuevers are still flown inverted, and so that makes me wonder about these design decisions. After all, a low-wing design is a high-wing design, when inverted, right?

Anyway, unless more readers here post something I haven't seen before, I'm proceeding with my original plan, which is to mount the horizontal stabilizer on the thrust line, and the wing about one wing thickness lower than that.

An image of the design is attached. Thanks again for taking the time to help.
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Old 02-20-2002, 03:36 AM
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Default Wing and Stabilizer arrangement for aerobatics

Well, with the wing areas and weights of modern pattern ships what they are it really doesnt take much to fly inverted, on that same note the planes are soooo stable anyways I dont think it really matters where the wing is for inverted flight. I think from your picture that you have it in about the right location, I would try it out, it is simple to move around later for "experimentation". I have also talked to guys like Hebert about adjusting the stab to remove knife edge mixing, what I got on that was essentially, it makes little to no noticable change in knife edge mixing if you move the stab up or down. That tells me that this is really an insensitive part of the design. Some designs like the Typhoon have the stab very low (like 1" below the thrust line) and seem to do quite well. So my suggestion is to put it where you think it looks good, fly the crap out of it, and determine what thrust/incidence work best for that placement of wing/stab. Now on the Vector (which I did all the initial testing of) has a wing/stab arrangement that looks similar to yours. It has a downthrust of aobut 1.5 degrees, with 0-0 on the wing/stab. Some of the lower wing designs have 0.5 degrees down with a little positive on the wing. When my Evolis's arrive (soon I hope I am dying here) I can see if I can accurately measure the downthrust etc etc for ya, then you have a top end machines notes to compare with!! Later
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Old 02-20-2002, 03:55 AM
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Default Information

Cool, Chad,

I first saw the Vector on Dez's page, and thought it looked like a good one. Simple and clean.

Starting about 10 years ago, I used the approach of collecting all the measurements I could get from all the Pattern sitesand publications I could find, and then "averaged" them in a spreadsheet. I definitely see the "cookie cutter" approach, with most improvements being in minor cosmetic differences, more exotic ($$) materials, better engines, and better manufacturing methods. (like ZN Line or "Angel's Shadow")

Looks like the "real" aspects of these designs hasn't changed too much, and I suppose that's to be expected, given the flight parameters.

ANY information that you or other aerobatic flyers and designers would be willing to share with me would be great. I'll collect it, test any "new" concepts I find on my new ship this summer, and let you know if I can really prove by experiment that one way is better than another.
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Old 03-01-2002, 11:14 PM
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Default Wing and Stabilizer arrangement for aerobatics

If you take a look at the jet on your Pic on your user name...... you will see how we do our latest aerobatic project. I like to call it a t-tail. It is however not really a t-tail as it (the stab) is not quite to the top of the fin. The wing is on the thrust line with 1 degree positive and the horizontal stab is 0 degree from the datum line. These are some really stable....... yet aerobatic planes that will perform like crazy...... yet almost land themselves. If I knew how to download a pic... I would send you one of the plane in the bones........ ready to cover. It is the third in this series of experimentals we have built. The first suffered a catrastophic failure of the crystal on the third flight. The second is still providing very good service........ and the third we changed up a bit to see what would come of it..... ie ( about a 20% airfoil that is not quite symetrical.... with just a bit of a flat area to give a little extra lift). Hope this is what you are talking about...... if not I appologize. Tex
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Old 03-02-2002, 01:57 AM
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Default Wing and Stabilizer arrangement for aerobatics

Originally posted by Tex Pilot
If I knew how to download a pic... I would send you one of the plane in the bones........ ready to cover.
Just click the "Post Reply" button instead of replying with the "Quick Reply" at the bottom of the page. Then when you are there look for the "attach file" box and thats it.
Cheers,
Grant

P.S. The tail configuration you were describing is know as cruciform.
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Old 03-02-2002, 03:02 AM
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Default At Last

Hi TexPilot,

I would love to see some photos and/or data on your aerobatic plane. Andy Lennon has been claiming the virtues of "T-Tails" on aerobatic planes for years, and claims no adverse coupling effects. The one thing these would lack, for hardcore performers, is the lack of prop blast over the horizontal stabilizer, which some guys like to have.

If you aren't able to post photos here, perhaps you'd consider emailing me? (Just click the "Email" button here, or email me at drumer@alaska.com)

Thanks!
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Old 03-02-2002, 03:53 AM
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Default Wing and Stabilizer arrangement for aerobatics

T tails have a bad reputation for slow recovery from spins and other deep stall maneuvers. and handling will be very different, upright from inverted. I would avoid T tail for aerobatics. In deep stall, the horizontal tail may be completely blanketed by turbulent, slow air spilling off wing, and recovery from spin may be very slow or even impossible.
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Old 03-02-2002, 10:42 AM
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Default Aerobatics

So... I shouldn't lomcevak the King Air?

This is interesting to me. There must be an issue like this, or Pattern planes would have T-Tails. I just like creative designs, and love hearing the "why" part of these discussions.

Anyone else have input on this?
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Old 03-02-2002, 07:24 PM
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Default Wing and Stabilizer arrangement for aerobatics

T-tails can be blanketed by the mail wing. They are also harder to make strong because you have less surface to attach them to at the top of the fin.
Cheers,
Grant
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Old 03-03-2002, 09:13 PM
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Default Wing and Stabilizer arrangement for aerobatics

Thank you for the info Cadet. Here is the t-tail...... as I call them. I have found that they actually are cruciform....? (sp). We have no problem whatsoever with this design. My friend that is teaching me scratch building tech...... is the one to origionally design this I believe. If anyone has any thing to add........ please feel free. We just drew this one up on freezer paper....... and built it. The plane came partly from a pic I had in my mind. Thanks, and I hope you enjoy the pic. Also..... the tail wire braceing will add to the strength. Tex
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Old 03-03-2002, 09:42 PM
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Default Wing and Stabilizer arrangement for aerobatics

Hi MikeJames. I tried to e-mail at the address you gave and could not get through. Here is another view of the (cruciform) tail plane. I guess I am calling it *Somethin Else* Thanks, Tex
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