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Looking for advice for a clipped wing Cub

KingAirNeal

Registered User
So, a little over 20 years ago I restored a 1946 J-3 with aluminum spars and a back seat with a metal back and plywood seat. We had modified the 65hp engine to a 75hp.

I loved that bird.

I have done a Champ and a few others since, and now that I am finally flying for a major, in a couple of years I would like to build another plane.

So, I decided I want to do a Clipped wing Cub. Experimental.

Wants

Rear seat PIC
O-200 power. With electric start, not opposed to hand propping, just don't want to anymore. Too many eyes watching.
Exposed cylinders, J-3 style, if an O-200 can do that.
No flaps
Metal spars
Heavy struts, big forks
Do NOT want a left side door, but a supercub style left side sliding windows
Rear seat like my old one, which I think is PA-11 style right?
Balanced controls if y'all think it would be better
No inverted system
Wing tanks, 12 gals each should do it?
Smoke tank (where the old fuel tank was maybe?)


Basic, gentlemen's aerobatics (no negative) Sunday fun toy.

Thinking a Javron tubing kit (yes I can weld, and actually want to do it)

Does Javron do wings without flaps?

Thoughts?



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That should be a fun plane, A fresh modded O-200 will bring a big smile to a Clipped wing. Pretty close to double the power from what you had and will rev higher when wanted to.

I would include the "Riblet" series of airfoils as a consideration.
Any of the wings can be done without flaps very easily if you are assembling them which I expect since you are clipping.

I have always thought the front seat should be mounted with quick release mounting so as to be removable for for solo flights. Stow it behind you.
 
Regarding an open cowl O-200, the majority of Legend Cub S-LSA are that way, including mine. No issues other than its tough to get the oil temp up above 140 F in cold weather. No issues in hot weather. Mine has metal eyebrows made by Legend. I think they make them from Carbon Fiber now.

Also, the Legend has two 11 gallon wing tanks and no header and can be solo from either seat. Now that I think about it, you might want to look at the Legend kit which can be bought at the component level. They use heavy forks, PA 11 struts, metal spars and no flaps. They might even mod the wings for you.

That kit can be certified Experimental Amateur Built at 1600 gross.

Rich
 
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Yes, Javron can and will do a wing without flaps. Would also probably do a clipped one.

Give em a call, its free (the call that is)

Bill
 
Regarding an open cowl O-200, the majority of Legend Cub S-LSA are that way, including mine. No issues other than its tough to get the oil temp up above 140 F in cold weather. No issues in hot weather. Mine has metal eyebrows made by Legend. I think they make them from Carbon Fiber now.

Also, the Legend has two 11 gallon wing tanks and no header and can be solo from either seat. Now that I think about it, you might want to look at the Legend kit which can be bought at the component level. They use heavy forks, PA 11 struts, metal spars and no flaps. They might even mod the wings for you.

That kit can be certified Experimental Amateur Built at 1600 gross.

Rich

I will look into that, thanks!!! No issues in Las Vegas about cold temps for the oil.


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If you going to do a metal spar clip wing I would suggest beefing up the compression supports in the top of the spar at the strut attach point. Also something not often thot about is raising the lower door hinge 7/8". I've done this to several clip wings with and without a field approval. Its easier on an experimental as you just have to raise the fuselage member at the door opening and adjust diagonal members to fit. Nothing is needed to be added, just a dimension change. Even better is to use square tubing in door bottom and fuselage door frame area along with a strip hinge. Makes a nice, clean install and gets rid of that chopped out area in top of door that is drafty, weak and always breaks.

If you might be interested in an airfoil change, I know where you can find T type truss braced ribs, similar to what Dakota Cub and others have but with 23012 (Taylorcraft, Helio) or 2412 (Cessna) airfoils made to fit Piper spars on the 31" centers. A lot less trimming as you need with the USA 35Bs speed changes
 
Here is what I would do - nay, what I did: go find a good Decathlon for around forty grand in good shape. Fly the socks off of it - it is much better suited for mild aero than a clip cub without an inverted system, and probably half the cost. Then restore your Piper to its original configuration, saving even more money, and in the end you willl have two valuable airplanes. My spouse actually likes the Dec, and will endure slow rolls. And best of all, when I want to go somewhere, I go at 120 knots instead of 85 mph.
 
Here is what I would do - nay, what I did: go find a good Decathlon for around forty grand in good shape. Fly the socks off of it - it is much better suited for mild aero than a clip cub without an inverted system, and probably half the cost. Then restore your Piper to its original configuration, saving even more money, and in the end you willl have two valuable airplanes. My spouse actually likes the Dec, and will endure slow rolls. And best of all, when I want to go somewhere, I go at 120 knots instead of 85 mph.

I have flown and owned a Super D. Good airplane. Loved it. Just not what I am looking for.


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If you going to do a metal spar clip wing I would suggest beefing up the compression supports in the top of the spar at the strut attach point. Also something not often thot about is raising the lower door hinge 7/8". I've done this to several clip wings with and without a field approval. Its easier on an experimental as you just have to raise the fuselage member at the door opening and adjust diagonal members to fit. Nothing is needed to be added, just a dimension change. Even better is to use square tubing in door bottom and fuselage door frame area along with a strip hinge. Makes a nice, clean install and gets rid of that chopped out area in top of door that is drafty, weak and always breaks.

If you might be interested in an airfoil change, I know where you can find T type truss braced ribs, similar to what Dakota Cub and others have but with 23012 (Taylorcraft, Helio) or 2412 (Cessna) airfoils made to fit Piper spars on the 31" centers. A lot less trimming as you need with the USA 35Bs speed changes

I have read about the piano hinge to the door trick, and planned on the square tubes and doing just that.

How would you beef the compression supports? Thicker material?

And I am interested in the Tcraft airfoil section. How do you think that would change how it flies? Will it still feel like the classic clipped Cub?




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I've got a cuby project that I thought about building the same way - but with L-4 greenhouse
 
"If you might be interested in an airfoil change, I know where you can find T type truss braced ribs, similar to what Dakota Cub and others have but with 23012 (Taylorcraft, Helio) or 2412 (Cessna) airfoils made to fit Piper spars on the 31" centers. A lot less trimming as you need with the USA 35Bs speed changes"

Could you post this information for us? I would like to have this in my back pocket for something in the future...
 
If you might be interested in an airfoil change, I know where you can find T type truss braced ribs, similar to what Dakota Cub and others have but with 23012 (Taylorcraft, Helio) or 2412 (Cessna) airfoils made to fit Piper spars on the 31" centers. A lot less trimming as you need with the USA 35Bs speed changes

Do share! :) Dito on the strut attach support, very good point for a clipped wing.
 
King Air...... Here's a pic of that strip hinge mod. It was on a certificated Cub so had to add the material for the field approval. I would relocate the horizontal tube below the door if I were building an experimental. Raise it up 7/8" gets rid of that weak, drafty cut out normally required for the lower door to clear the lift struts.

I would prefer wood for spars for a clip wing but if you go with the aluminum several suppliers have the reinforcements that go across the strut attach fitting area of the front and rear spars ........ in different styles. .. Dakotas are nice. As for airfoils .......... I would go with the 2412 ( would actually have to be at 14 - 15 percent to fit the Piper spars) because its a proven section (Cessna) and would not require a wing incidence change. The 23012 T Craft section really needs about 1.5 - 1.8 degrees of added incidence to work well. Either section should work well, should stall a little faster and go a little faster without all the trimming required for the high lift USA35B. But even a stock clip wing is not really a "Cub" anymore ................ not as much fun cruising around with the door open............or maybe I'm just too old! Was originally no starter and 75HP. Try not to get too much weight up front, starter, alternator and battery really start to make it less of a clip wing. .......... If this was a certificated Cub I wouldn't even consider cutting good spars to make a clip wing. Either use some salvageable spars damaged at to root end or build with new wood. But if you are going metal, make the fuselage/wing attach like a Super Cub then find some TriPacer wings..........IMHO Options are endless with experimental!

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Why not build single piece door hinged at the top with the bottom horizontal tube in the original place. I've done the geometry and it clears the strut. Moving the bottom tube up just makes it harder to climb into. There are pictures on this site of single piece doors.

Building wings with a Cessna airfoil is a foray into the unknown. If you opt for this please let us know how it works out!

The CWC's with Taylorcraft airfoils have all been specialist aerobatic machines. My experience with that airfoil is it won't leap off the ground like a Cub….

Andrew.
 
Why not build single piece door hinged at the top with the bottom horizontal tube in the original place. I've done the geometry and it clears the strut. Moving the bottom tube up just makes it harder to climb into. There are pictures on this site of single piece doors.

Building wings with a Cessna airfoil is a foray into the unknown. If you opt for this please let us know how it works out!

The CWC's with Taylorcraft airfoils have all been specialist aerobatic machines. My experience with that airfoil is it won't leap off the ground like a Cub….

Andrew.

Andrew

Hinging the door at the top of the existing longer would be marginal at best IMHO. I'm trying to see how you fiigure it........ These are a couple of the pics I use in the field approval....... moving the hinge point as you suggest would mean moving it down approx. 3/16 and in 3/16. I used the 7/8" dimension as it was the dimension specified in the STC to cut the door. I'm old and the 7/8" isn't really noticeable but it is a reality ....... door opening is reduced. Lower red center is where you propose?


Piper J3 Lower Door OriginalX.jpgPiper J3 Lower Door HingeX.jpg

A foray into the unknown?? Foray......... That might be the name of my new airplane(s). Been wondering what to call it since the name "Super Pacer" is pretty well used up! It has the 2415. Like you said its mostly for the aerobatic types and they worked out pretty well.............. that's what King Air is looking for, and how this whole thread started. The clip wing Cub with a 2415 section isn't going to leap off the ground like stock wing with the USA53B. It does have 35+ square feet of wing missing:smile:
 

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Im not looking for a super hard core acro bird. I still want it to have the classic clipped wing cub "feel". I am concerned changing the airfoil will make it fly so different I wont like it. The personality is important to me, not necessarily the performance.

I love the door info, that is perfect. When I get with Javron to cut my fuselage tubing kit, I am sure they can incorporate that for me with a simple click of a mouse.

I also assume if raising the tube 7/8" and going to a square tube, the lower tube on the door goes square and is raised as well, thus making the lower door section and therefore the opening, just that little bit shorter right?

And still curious why you would prefer a wood spar over aluminum? I know the engineering behind why old growth spruce is the superior material, but I was under the impression the new stuff kinda sucks...

Not interested in a single piece door. I always liked flying with the door closed and top open. My J-3 had a super cub style left side sliding window. Loved sticking my throttle arm out the side, just like when I was towing gliders in the PA-18...

Gotta remember, Im not looking for speed. Im looking for fun. I fly at .78 Mach all the time. Not in a hurry when its playtime.


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I plan on no official electrical system. No alternator/generator, and probably just a small PC680 style battery with a lightweight pull type starter.

I would prefer to flip it Armstrong style, but we cant get away with that kind of behavior like we did 30 years ago... The old left foot in front of the tire and starting from behind trick... also, where this would be hangared, I am afraid in this day an age some one would see me hand propping and get triggered into running off to a safe space or summin...


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Ha, I use the old "left foot behind the gear leg" method. ....... Nothing wrong with aluminum spars, you just have to beef them up in the strut attach area. Being experimental you are not tied to the original Piper dimensions, you can go up on spar size.......... metal or wood.

Here's a pic of the hinge points from the field approval package...... in 3 little different configurations feds wouldn't go for just adding a sheet metal channel over existing 7/8 tube (thot it would blow off at mach .04). If I were to modify an existing frame this is the way I would go to raise the hinge line. Just a .032 sheet channel formed to fit and a MS20257P3 or P4 hinge. Use a 1/2 x .035 square on the bottom of the door. If you did this with the wing/struts in place you could lower it as much as possible...... "custom fit". The 7/8 was just the number as designated in the STC for the door cut out. I'm sure by moving the hinge point up and in and with a little "fitting" that dimension could be shortened. Might be a better way to go, if you replaced the top tube with a 7/8 square you would be locking in to the hinge height. Keep it like the print and add the channel?

If I were to build a CWC today.......... , EAB, I would use the 2412 type section. Nothing really to lose. You already clipped it so STOL isn't what you're after. A 100+ HP engine on a 800 pound airframe would be a descent performer. We just happen to be tooling up right now for a 63", 2413.5 section, truss braced, T section type rib for 31" spar centers.

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I have seen pictures of a few different experimental Cubs with single piece doors. That is what I'm going to try before I decide I don't like it. I can understand if you don't want one though.

Andrew.
 
Douglass fir for wing spars. About 1/3 the cost of sitka spruce, 20% heavier but 20% stronger. Metal fatigues but wood has memory. All the hipo acro mounts use wood spars for good reason. The 23012 Taylorcraft airfoil will give good results if you increase the AOI. Same thing I'm doing right now. If you need numbers I will have to consult my notes in the shop, my memory is not to be trusted. Regards, Dana LaBounty
 
Douglass fir for wing spars. About 1/3 the cost of sitka spruce, 20% heavier but 20% stronger. Metal fatigues but wood has memory. All the hipo acro mounts use wood spars for good reason. The 23012 Taylorcraft airfoil will give good results if you increase the AOI. Same thing I'm doing right now. If you need numbers I will have to consult my notes in the shop, my memory is not to be trusted. Regards, Dana LaBounty

Dana

The chord line of the "drooped nose" 23012 makes it necessary to raise AOI by about 1.2ish degrees to bring it into the same parameters of the USA35B if my memory is correct ............for the speeds and weights of the SC type. I investigated the 2412/2415 sections and decided to go with that section as the C of L was nearly the same as the USA 35B and I could make the wing changes with out the fuselage modifications for wing attach.
 
You should do well with either of those airfoils. I have but a small engine, A65F with NFS 8:1 pistons and O-200 cam. Should be a strong 80hp. As such I'm keeping the gross wt. light and just sticking the wings on the stock PA-18 structure. That's still a couple degrees positive from the J-3 so it should fly more or less O.K.
 
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