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Old May 31, 2009, 12:15 AM
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SUPER CHEETAH Restoration

A new resto project underway! Super Cheetahs are one of the most enjoyable and un-nerving planes to slope, i had to find another and another and...These planes in my opinion are under rated in todays slope arena. Those of you out there that actively flew, built and combated these sturdy planes know what im talking about. Short of an all out centerpunch in the wing or obliteration of the tail feathers by another Cheetah, these planes are pretty much indestructable and will rule the sky in the war. I hope more of these get resurrected and enjoyed even when we know they are "butt ugly" as quoted by its creators, Bob and Larry Pettyjohn.

This one will be for my son so we can go combat with real planes. No foamies allowed, hahaha. We hope you enjoy the trip down memory lane and get excited finding and flying one of the greatest slope planes of all time! If you have stowed away your SC machine because you think its just too ugly or just not up to par with your current tastes, dig it out and breath new life in it. Or send it to me, i'll be glad to rebuild for you or add to my collection.

As Larry demonstrates in the photo below...Batter up!...EJ
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Old May 31, 2009, 12:21 AM
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WING STRIPPED:

Been at it 3 evenings now stripping the old dried out cardboard wing skins. You may wonder why i put myself through the torture, just get another set of cores, they're cheap. Its the builder and restorer in me, its what i do - check out my website. Its quite a bit of work and looking at the small craters all over the foam core is disturbing. But, we will get this restoration done up and you wont even notice any performance or durability issues. This is the thin E374 version so it ought to fly pretty savy like my greenie.

The tail feathers are ready to touch up and re-skin with 1/16" balsa. Ailerons and elevator surfaces are stripped and ready to be adjusted to their mating subtrails. Im going to widen the ailerons to 1-3/4" and we will hinge from the center using cloth hinges. Lots of guys dont like'em. I do, have never had a failure and you dont have to mess up the monocoat when doing maint.

The fuse is in excellent shape! Till later...EJ
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Old May 31, 2009, 12:44 AM
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NEW FIN:

Fab'ed up a new vertical fin the old s'cool way. Made up a pair of 1/4" balsa symetrical airfoil sanding formers and lightly epoxied them on top and bottom of fin foam core. I made the core longer so it can be fit as needed later. Sand, sand, sand the styro until it got fully shaped down to the sanding forms. I used a 12" sanding block to maintain uniformity. Once happy with shape i cut loose the formers to make ready for skinning with 1/16" balsa skin.

Once skinned and trimmed, new 1/4" balsa cap and leading edge are epoxied on, final sanded and contoured ready for monokote. Remember those formers i cut loose? When you do yours keep them for next time you need to make another fin. Will save a lot of hassle. Be sure and file away a copy of the total fin shape you traced for next time. Maybe make a few extra for those knarly combat sessions!

Some technical:

Top former major airfoil thickness dim = 0.475".
Bottom = 0.650".

Add skins and you end up with 0.600" top, 0.775" bottom.

EJ
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Old May 31, 2009, 01:02 AM
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WING SKINNED:

Now its starting to look like a flying machine...Used 1/16" balsa sheeting by joining two 4" x 36" sheets using white glue. Cut each skin close to wing planform with leaving about a 1/2" all the way around for extra measure. 3M Super 77 aerosol contact cement was used to apply the skins. I have done over a dozen models with this stuff without a hitch. The key is do it in warm weather, keep it light and let set for 3mins before mating the surfaces. Coat BOTH surfaces or you will have delamination problems.

Once set up for awhile (6 hours) with weight applied in the saddles, the excess balsa skin is trimmed and sanded flush all the way around. Prepared the raw leading edge surface very carefully so it becomes flat and not rounded using a hand planer instead of a sanding block to make flat as possible. Mixed up some 30min epoxy and coated both the leading edge and the wing panel surfaces. Taped up and let set for 2 hours.

I use half round x 1/2" pine moulding for tough leading edges. makes for a nice wing cutter in combat, hahaha! De-taped the LE's and began to make some serious chips. Takes about an hour each panel to get a good Phillips Entry contour. The planer is a lifesaver followed up with a 12" long block sander and 220 grit.

Next is glassing the center section. I use a 2-1/2" wide piece of 1.5oz with a 3' wide piece of .5oz S glass on top. Z-Poxy was used as the adhesive because i like the way its flexible and not prone to cracking. Little tough to sand down but if you let it cure overnite it responds well. After BOTH sides are glassed up, the edges of the glass seam to balsa is filled and sanded with light spackle. Yes, monokote will adhere to the spackle as long as you have a 400 finish and the right iron heat.

Finally, the wing tips are capped with 1/4" hard balsa and sanded flush all the way around. Lots of sanding and chipmaking in this business huh? The ailerons are 1-3/4" wide for great roll rate even at low speeds. They will also serve as flaperons to slow this bad boy down into the LZ. Trailing edges are sanded to 1/32" to keep things clean and minimal drag. Ends of surfaces are beveled to eliminate neusence denting on landings.

A general inspection for straight and true lines and detailed with 400 grit all over make the wing ready for monokote!
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Old May 31, 2009, 01:10 AM
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Ready for MONOKOTE:

We are heading into the home stretch getting this bird ready to fly. All the parts are finished ready for monokote. The ailerons were found to be too thin in relation to the finished wing sub-trailing edge, about 0.100". Leaving in this condition would have caused too much enduced drag on the wing. So i went ahead and skinned the bottom surface of the ailerons with 1/16" balsa sheet, sanded and blended to a clean trailing edge. All fixed now.

Individual part weight figures:

Vertical fin = 0.8 oz
Horizontal stab/elevator = 1.7 oz
Wing & ailerons = 23 oz
Fuselage = 9.5 oz

EJ
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Old May 31, 2009, 01:23 AM
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Here is a photo of the Pettyjohns and the Super Cheetah article courtesy of Slope Soaring News, Nov 1988 issue. I have recently contacted Larry and briefly discussed some history and building tips. Larry is doing fine in SoCal and wants to get a new kit in the box for old times sake just to have. He sold the company a dozen years ago to somebody in New Mexico. I am trying to find that contact as of this writing. If anybody out there knows where Super Cheetahs are being sold or collecting dust, i would appreciate a notice.
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Old May 31, 2009, 01:45 AM
UAV = RC right?
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Super Cheeta reserection

Hweeler

Your posts have given me the bug to bring my SC back to life! It was my first aleron plane and I chose it for a couple of reasons. One being durable and the other, combat!
Anyhow I live in So Cal as well and desire to start flying more these days as time permits. Mine is very heavy in flight trim but with the lift at Cajon on a medium day it would be epic to fly probably!
As it sits now I would just have to put the electronics back into it and ballance it.
I would be intrested in a new faster airfoil for it due to the one I got with the kit was the slower more lift wing I think.
Let me know if you can aid with that ok.

Cheers
KR
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Old May 31, 2009, 02:44 AM
Mmmm...balsa dust!
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I still have the fuselage for the regular Cheetah tucked away in the garage. It's gone through a few wings over the years including one that had music wire embedded in the leading edge (used to fly with some guys who played rough). From the photos it looks like the Super Cheetah has a nicer platform for the stab.

My wife and I are planning some travels and I figured the old Cheetah 'fuse with a new foam wing would make a great traveling airplane. I could either fly it or use it to beat back bears raiding the campsite.

Doug
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Old May 31, 2009, 02:57 AM
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Ahh, the memories...Here's my Super Cheetah. This one has a balsa tail and 1/32" ply covered full span wing. Unfortunately, the radio is pre-1991 ready so it would be a crime to fly.
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Old May 31, 2009, 04:40 PM
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Quote:
Originally Posted by vintagemxr
I still have the fuselage for the regular Cheetah tucked away in the garage. It's gone through a few wings over the years including one that had music wire embedded in the leading edge (used to fly with some guys who played rough). From the photos it looks like the Super Cheetah has a nicer platform for the stab.

My wife and I are planning some travels and I figured the old Cheetah 'fuse with a new foam wing would make a great traveling airplane. I could either fly it or use it to beat back bears raiding the campsite.

Doug
Doug,
Do you race vintage motocross down there in Dave's AVDRA series? By your username we may have another interest.

EJ
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Old May 31, 2009, 04:43 PM
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Originally Posted by 1000MPH
Ahh, the memories...Here's my Super Cheetah. This one has a balsa tail and 1/32" ply covered full span wing. Unfortunately, the radio is pre-1991 ready so it would be a crime to fly.
Looks great! What do you mean a crime? Heck the more vintage the better in my opinion. If it works, dont fix it. Lets see it fly 1000mph, or at least a 100 mph, hahaha...

EJ
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Old Jun 01, 2009, 12:54 AM
Mmmm...balsa dust!
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Originally Posted by hweeler
Doug,
Do you race vintage motocross down there in Dave's AVDRA series? By your username we may have another interest.

EJ
EJ,

I raced mx and desert in the early '70s and then a bit in the formative years of AVDRA about 1996 or so. Bultaco 250 Pursang. Great fun with Dave and the gang but too hard on the 'ol body. Every time I'd crash I'd lay there for a while and look around to see if I was in Heaven or the heat meant I was still alive and in Arizona. About that time I started using the vintagemxr moniker with my new Hotmail account and it just sort of stuck. Two constants in my life: motorcycles and model airplanes.

Doug
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Old Jun 01, 2009, 03:15 AM
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Originally Posted by vintagemxr
EJ,

I raced mx and desert in the early '70s and then a bit in the formative years of AVDRA about 1996 or so. Bultaco 250 Pursang. Great fun with Dave and the gang but too hard on the 'ol body. Every time I'd crash I'd lay there for a while and look around to see if I was in Heaven or the heat meant I was still alive and in Arizona. About that time I started using the vintagemxr moniker with my new Hotmail account and it just sort of stuck. Two constants in my life: motorcycles and model airplanes.

Doug
Very cool Doug! Boydstun is a great guy isnt he? Puts on some great races with our club CALVMX. I too have your sickness with bikes and sailplanes. Charlie Richardson of CR High Performance is another guy i do business with, im sure you know of him? I build CZ's and when i need HiPerf parts and services he's my go to guy. Another great sailplane buff and pilot. Its been two years since i badly broke my leg while racing my KTM495 monster. Just on the trail now but have a 250 CZ for the track. What is it about sailplanes and motocross? I was talking with Bob Martin the other day and he as well is an old MXer and sailplane modeling legend. Raced Montesa Capras. We actually raced together in the early 70's at Deadmans Point in Apple Valley!

These Cheetahs are somethin huh? I've been out of it for some time and i went to the hill today and my friends let me try out their Acacia and a F3B Eagle. Was a lot of fun zooming around those Cadillacs. Then i was flying the Cheetah and got a bad radio hit. Nosed in at about 75ft into a tree. Wing popped off with a little leading edge damage and the fuse and feathers was undamaged. I tell you my flying partner and I just love the Cheetahs over all that we've flown. Butt ugly, cheap and reliable but they are real survivors and a blast to fly! There is another one coming in tomm with a dbl taper RG-14 obechi skinned wing and another set of stock cores.

Take care...EJ
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Old Jun 02, 2009, 01:39 AM
Mmmm...balsa dust!
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Casa Grande, AZ
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Quote:
Originally Posted by hweeler
Very cool Doug! Boydstun is a great guy isnt he? Puts on some great races with our club CALVMX. I too have your sickness with bikes and sailplanes. Charlie Richardson of CR High Performance is another guy i do business with, im sure you know of him? I build CZ's and when i need HiPerf parts and services he's my go to guy. Another great sailplane buff and pilot. Its been two years since i badly broke my leg while racing my KTM495 monster. Just on the trail now but have a 250 CZ for the track. What is it about sailplanes and motocross? I was talking with Bob Martin the other day and he as well is an old MXer and sailplane modeling legend. Raced Montesa Capras. We actually raced together in the early 70's at Deadmans Point in Apple Valley!

These Cheetahs are somethin huh? I've been out of it for some time and i went to the hill today and my friends let me try out their Acacia and a F3B Eagle. Was a lot of fun zooming around those Cadillacs. Then i was flying the Cheetah and got a bad radio hit. Nosed in at about 75ft into a tree. Wing popped off with a little leading edge damage and the fuse and feathers was undamaged. I tell you my flying partner and I just love the Cheetahs over all that we've flown. Butt ugly, cheap and reliable but they are real survivors and a blast to fly! There is another one coming in tomm with a dbl taper RG-14 obechi skinned wing and another set of stock cores.

Take care...EJ
EJ, I agree, Dave B. is a great guy. I think few people are as nuts about vintage dirt bikes as Dave is. He's a man of strong opinions too. I did some web page stuff for him about 1998 or so. I think he still uses some of the copy I wrote then on his current web site.

'Fraid I don't know Charlie Richardson. Some years now since I fiddled with vintage bikes and names have kind of slipped away. Did some photo work and web stuff for Rick Doughty of Vintage Iron back about 2000 - 2001. That was pretty much my last contact with the vintage dirtbike scene except for what I see at vintage bike shows:

http://rides.webshots.com/album/569528999BPizDr

Cheetah story for you: I was flying at the "Microwave Towers" site east of Phoenix about 1987. I launched my Cheetah with my new 7 channel Futaba Rx in it because my 4 channel unit had croaked. As soon as the glider left my hand and headed out into some nice steady lift I had the really sick feeling that only comes when you realize you forgot to turn on the radio in the airplane. I watched the Cheetah and my new Rx and servos head west towards Phoenix. Nice and trim, flew straight and level very well all by itself. About 200 or 300 yards out I saw the Cheetah slowly begin to turn with the wind until it was coming straight back at the hill. Zipped along right smartly downwind in about 15 - 20 mph wind. The Cheetah impacted in the rocks and brush about 30 ft below the launch point. I hiked down, straightened out the wing, switched on the Rx this time, and re-launched. Flew the rest of the afternoon.

Doug
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Old Jun 02, 2009, 02:34 AM
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Cheetah story for you: I was flying at the "Microwave Towers" site east of Phoenix about 1987. I launched my Cheetah with my new 7 channel Futaba Rx in it because my 4 channel unit had croaked. As soon as the glider left my hand and headed out into some nice steady lift I had the really sick feeling that only comes when you realize you forgot to turn on the radio in the airplane. I watched the Cheetah and my new Rx and servos head west towards Phoenix. Nice and trim, flew straight and level very well all by itself. About 200 or 300 yards out I saw the Cheetah slowly begin to turn with the wind until it was coming straight back at the hill. Zipped along right smartly downwind in about 15 - 20 mph wind. The Cheetah impacted in the rocks and brush about 30 ft below the launch point. I hiked down, straightened out the wing, switched on the Rx this time, and re-launched. Flew the rest of the afternoon.

Doug
Doug,
Now thats a sales pitch story for the Super Cheetah if i ever heard one -Amazing!

Very nice VMX bike pics. I especially like the CZ and the CCM thumper. beautiful machine. I had a deal ready to build one this year until the guy backed out when his property dropped like a rock!

Charlie Richardson is the CR of CR High Performace Sailplanes back in the 90's. He had some great kits including the Turbo, Renegade, Contender, Fun-1, Climax and others. He sold the business and opened CR High Performance Products building, racing and supplying everything CZ. he's a top national expert 250 class rider. His 250's are the fastest in the country.

http:///www.crhighperformance.com

Back to Cheetahs. The Obechi skinned RG-14 wing panels (2 piece) and airframe came in today. They look like 7% thick. I think i will build a sloper out of those and build the Cheetah with stock thin E374 wing.

Take care...Eric
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