Building the Stab for Ted Fancher's Imitation

[Mike Griffin]

I started with all 1" stock as Ted recommends in his article and sanded it down from there.

[Bill Little]

HI Mike,

The stab and elevators were really thick!  All of Ted's planes back then seemed to have this feature.

Mine are foam and I need to sheet them.

Bill

[Brett Buck]

The stab and elevators were really thick!  All of Ted's planes back then seemed to have this feature.

   We don't do that anymore, but the airplane flies great at it is shown, no changes.   If anyone builds it I strongly suggest incorporating the segmented flaps as shown, but if not (and Ted might disagree with me) I would make them the largest of the sizes shown. That will be a hedge against excess weight, and will give a bit more feedback.

    Brett

[Bill Little]

   We don't do that anymore, but the airplane flies great at it is shown, no changes.   If anyone builds it I strongly suggest incorporating the segmented flaps as shown, but if not (and Ted might disagree with me) I would make them the largest of the sizes shown. That will be a hedge against excess weight, and will give a bit more feedback.

    Brett

One of the first things I noticed on Ted's Excitation plans is the thickness of the Stab/Elev.  Just might have to build one for Nostalgia 30!

Bill

[Mike Griffin]

Brett and Bill

I really started to change the stab and elevators as Brett said but this is not the only one I plan to build and I did want to build one exactly as Ted drew it.  I have to say though, the thick stab and elevator are a b**ch to sand down.  I have a cramp from doing it.   

Mike

[Mike Griffin]

Bill you and Brett are correct about the thick stab.  If you click on the "rough in" Picture of the stab in my other post, the hole for the stab is just about 1" thick at the high point.

Mike

[Brett Buck]

Brett and Bill

I really started to change the stab and elevators as Brett said but this is not the only one I plan to build and I did want to build one exactly as Ted drew it.  I have to say though, the thick stab and elevator are a b**ch to sand down.  I have a cramp from doing it. 

   You need coarser sandpaper!  I did a few stabs that way and it took a few minutes at most. Start with 60 grit on a long rigid sanding block and it's maybe  a minute a side.

     Brett

[Bill Little]

Bill you and Brett are correct about the thick stab.  If you click on the "rough in" Picture of the stab in my other post, the hole for the stab is just about 1" thick at the high point.

Mike

HI Mike,

I noticed that as soon as I saw the picture. 

Bill

[Mike Griffin]

Thanks for the tip Brett.  I think the coarsest grit i have is 80. 

Mike

[Ted Fancher]

Thanks for the tip Brett.  I think the coarsest grit i have is 80. 

Mike

I built several airplanes (including the Imitation, the Excitation and the 1982 Walker Cup winning Intimidation) with the very thick stabs and then a bunch, including the Chizler, the Doctor and the Tucker special,  with very thin stabs because I felt stab/elevator configurations were an area of design that had been given short shrift by the fraternity.  The only sentence on the "aerodynamic" task of the tail that I can recall in the press to that date was Bob Gialdini's comment in the Olympic articles stating: "Remember, the tail is a lifting surface ,too and needs to be thick enough to do its job."  Ergo, off I went to experiment!

All of the airplanes involved in both aspects of the experiment had more or less successful careers.  However, in the final analysis my thoughts boiled down to the following,  The tail needs to be thick enough to be rigid, airfoiled, should not be "high" aspect ratio, should be 25% or so of the wing area (for a flapped ship) and it should ideally have a sharp leading edge (as opposed to my preference for reasonably blunt leading edges on the wing).  David Fitz' work and his article "De-tails" were another outgrowth of that experimentation that largely supported those same findings--in addition to his preference for building in some positive incidence in the stab.

IF! somebody chooses to do the thick version stabilizer I think it is important to build the stab in left and right halves which are then glued together with plywood spar joiners or with fibreglass overlays at the joint (like a foam wing).  This allows the use of templates to shape the airfoil so that both sides are identical in all respects...left to right and top to bottom.

Ted

[Ted Fancher]

P.S.  I agree with Brett that building the Imitation with the segmented flaps is worthwhile for someone wanting to understand stunt design better.  There are SIGNIFICANT  (all caps on purpose) differences in response rate and steer-abililty as they go from short to long span (the original plans don't show full span as I'd never been a fan of them for a silly reason, I didn't like the looks of them!)  They also convinced me that most stunt designs utilize much more flap area than necessary and that there are negative results of too much "more" flap then necessary.

I'd be interested to hear Mike and Bill report on their experience playing with the flap size.

Ted

[Randy Cuberly]

P.S.  I agree with Brett that building the Imitation with the segmented flaps is worthwhile for someone wanting to understand stunt design better.  There are SIGNIFICANT  (all caps on purpose) differences in response rate and steer-abililty as they go from short to long span (the original plans don't show full span as I'd never been a fan of them for a silly reason, I didn't like the looks of them!)  They also convinced me that most stunt designs utilize much more flap area than necessary and that there are negative results of too much "more" flap then necessary.

I'd be interested to hear Mike and Bill report on their experience playing with the flap size.

Ted

Hi Ted,
I'm not about to disagree with any of this "stuff" but I would add one caveat on the small flap area idea.  If one tends to build heavy (I usually don't) as I did when I built a Trivial Pursuit many years ago that ended up at 74 oz with a PA61 and pipe (c'mon stop laughing).  I wished many times for more flap area.  As it was final trim used about 15% more flap deflection than elevator to get good corners without risking stalls.
In all honesty it really flew very well with this trim, but in retrospect I think it would have been better with a little more flap area and a little less deflection.
Certainly anyone is free to disagree with this, but I'm preparing to build another "Trivial" now as a take-apart and think I will add a little flap area just in case.  Incidentally, I still think the Trivial pursuit is one of the best looking CL stunters ever conceived.

Randy Cuberly

[proparc]

Certainly anyone is free to disagree with this, but I'm preparing to build another "Trivial" now as a take-apart and think I will add a little flap area just in case. 
Randy Cuberly

It is not something anybody can disagree with. What you need is relative to your circumstances. Identical planes with different weights of say, 64 and 74 oz, will have different lift requirements. You gotta do, what you gotta do!

[Ted Fancher]

Hi Ted,
I'm not about to disagree with any of this "stuff" but I would add one caveat on the small flap area idea.  If one tends to build heavy (I usually don't) as I did when I built a Trivial Pursuit many years ago that ended up at 74 oz with a PA61 and pipe (c'mon stop laughing).  I wished many times for more flap area.  As it was final trim used about 15% more flap deflection than elevator to get good corners without risking stalls.
In all honesty it really flew very well with this trim, but in retrospect I think it would have been better with a little more flap area and a little less deflection.
Certainly anyone is free to disagree with this, but I'm preparing to build another "Trivial" now as a take-apart and think I will add a little flap area just in case.  Incidentally, I still think the Trivial pursuit is one of the best looking CL stunters ever conceived.

Randy Cuberly

No surprise, Randy.  The old original TP is now @ 72 oz and does use more flap than elevator travel, altough the difference is more modest than yours.  I expect that has to do with the density altitude difference between 55 degree, sea level SFO and 100+ degree, 2200MSL or so Tucson.  The original TP, by the way has shorter flaps than later versions with the outboard flap stopping at the start of the wingtip and the inboard the same length as the outboard...thus 1.25 or so inches prior to the tip.

If somebody managed to build a 55 oz TP I expect we'd be hearing a different story yet!

Ted

[Bill Little]

Hey, Ted!!

I have the *OLD* foam cores for the wing and stab/elev.  What I really want to know is do you feel it is advisable to use a circular bellcrank?  I have a couple of brand new ones like you used in the original Imitation.  What say you?

I am pretty sure mine will have an OS .40VF on pipe!

Thanks!
Bill

[Ted Fancher]

Hey, Ted!!

I have the *OLD* foam cores for the wing and stab/elev.  What I really want to know is do you feel it is advisable to use a circular bellcrank?  I have a couple of brand new ones like you used in the original Imitation.  What say you?

I am pretty sure mine will have an OS .40VF on pipe!

Thanks!
Bill

They work just fine, Bill.  If the ones you have were the ones I had built by John Swickwrath, however, I'd replace the bearings.  The two I used a lot  (in the Imitation and the Citation V) both wore out the original bearings and had to be replaced due to wobbling on the shaft and making the airplane hunt.  These were machined from aluminum plate and had lightening cut-outs.  The bar with the pushrod holes was aligned at three degrees from neutral to allow for line sweep although on the circular platform it probably didn't make a bit of difference.

Ted

[Gerald Schamp]

Hi All,

My TP was built with a flat stab, 1/2" thick with 3/8" elevators, plus I added 1/4" to the flap width off the plans and they were full length flaps, outbaord flap was 3/16" wider at tip than inboard. At 69 ounces it flew well I thought, had various engines in it from a PA .51RE, Stalker .61RE and ST .60 all of which had more than enough power for the plane. The plane did not hunt in level flight, had a good corner I thought, and probably flew best with the PA .51RE after Bruce Perry set it up.

Ted has a great design in both the Imitation and TP airplanes, probably IMHO two of the most friendliest designs ever put out along with the Paul Walker Impact. The Imitation was one of the most copied designs in the Northwest during the 80's when ST .46 & .60's were the POC at the time and all were great flyers. IF memory serves me, hard to tell at this age, but Don McClave had one he flew at a Nats on the east coast many years ago, and left it with Dave Midgley who flew it for a couple of years and then it got passed around to many up and coming flyers and the name was affectionately changed to the "MClave". But it was basically an Imitation with a full fuse.

[Bill Little]

They work just fine, Bill.  If the ones you have were the ones I had built by John Swickwrath, however, I'd replace the bearings.  The two I used a lot  (in the Imitation and the Citation V) both wore out the original bearings and had to be replaced due to wobbling on the shaft and making the airplane hunt.  These were machined from aluminum plate and had lightening cut-outs.  The bar with the pushrod holes was aligned at three degrees from neutral to allow for line sweep although on the circular platform it probably didn't make a bit of difference.

Ted

Thanks, Ted.  There is an Imitation up in Huntersville (maybe William Davis??) powered with one of Stan Powell's K&B .40s.  Very, very good flying model.

Bill

[Ted Fancher]

Thanks, Ted.  There is an Imitation up in Huntersville (maybe William Davis??) powered with one of Stan Powell's K&B .40s.  Very, very good flying model.

Bill

OMG!!! Why would a stunt pilot ever settle in "Hunters"ville?  I'd develop a twitch every time I wrote my address.

Ted

[Will Davis]

Bill,

I was the one with the Imitation , very good airplane, it had the thinner flat stab, 1/2 inch foam, tapered elevators, powered by the stan Powell K&b 40.. Something very special about this design, easy to fly, very easy to trim, I never felt it gave up anything being a profile,

Stunt flyer living in Hunters ville  is like having a horse named  "Buck".  might be OK, might not