Pee Wee Pal

[Jim Robinson]

I've always enjoyed reading about vintage models, but up until just a few nights ago I'd never expected I'd be building one. I ran across a set of plans for the "Pee Wee Pal" and decided that this old-time free-flight model needed to be built. The original design, by Walter Musciano, was published in Model Airplane News, Feb 1958. The model was a scaled down version of the authors larger designs typical of the era, and was designed specifically for the new Cox Pee Wee .020 that had recently been introduced. An interesting note in the author's accompanying construction article cautions builders to limit engine run by running the engine on the ground for a predetermined amount of time prior to launching "if the builder does not relish cross-country chases to retreive his model".

I do have an operational .020 engine, and am tempted to build this little bird as-per plans, but I'd have to drive a long way to find a spot large enough to turn it loose. Consequently, my version will be 3 channel R/C and IPS powered. At original size, wing span is 33" and area is a rather smallish 140 squares. The model is quite sturdily built compared to today's parkflyers, so it's bound to be a bit heavy. I'm a little concerned that it may not be much of a park flyer. I've got some super-light 1/8" sheet for the forward fuse sides, and I've been weighing, sawing, and stripping balsa for 3 days now, so maybe I'll be OK. Also using Kokam 340s. Hoping to come in at 7 oz. AUW or less, and wing loading will be 7.2 oz./sq. ft. if I can reach that goal.

I finished the wing last night except I still need to saw it into 4 pieces and glue it back together with the polyhedral. Here's a question: Should I reduce the amount of di/polyhedral since it will now be R/C? Plans call for a total of 4" under each tip, which seems a bit much to me even for a rudder/elevator 3 ch model. I was actually thinking about eliminating the polyhedral altogether and building in about 2 1/2" of dihedral only. What do you think? Any suggestions?


Here's a few pictures. The 3rd picture is one I found on the web and shows the finished model.








Jim

[tim hooper]

Jim,

Just for appearance' sake alone, I'd add the polyhedral. Mind you, it'll interesting doing so now, after you've built the wings as one panel!

tim

[vintage1]

That will fly fine on IPS. 3s Kokams good on 'A' (5.33:1) ratio box and 7x6 prop or 2s Kokam on 2 (3.5:1) ratio box and 7x6.

Have fun with the rudder linkage.

Also make sure pack can get well forward - not a very long nose on that. CG issues etc.

[Jim Robinson]

Thanks for the replies. Yeah, I had a struggle with how to build the wing. Plans say to assemble spar first and begin gluing ribs in place. I figured there was no way I'd possibly get a straight wing that way unless I built a jig with the polyhedral already built into it, and constructed the wing in the jig. Too much effort for a plane that likely won't fly great anyway, so I decided to build it flat and cut it apart later. Also much easier to sand LE and fwd sheeting to shape while wing is a (flat) unit.

Am not looking forwarg to rudder linkage, but I think I will build a crank into the horizontal, as it is an approximately 3/8" thick lifting section. I thought about going with a pull-pull system, but decided I'm not man enough for that kind of fiddling.

Plan is to mount all onboard gear as far fwd as possible, but I think the short nose moment is a bit deceptive when you factor in the lifting stab.

OK, wing is going "under the knife" next. Will report back.

Jim

[Ian Easton]

Me personally; I would build it with all the polyhedral as shown on the plan. It will be a bit sensitive, but easy to fly. I can fly my big Cherub converted to RC with just trims alone. One thing I would have done differently on this one though, would have been to eliminate the LE sheeting on the wing and the stab.
It certainy is a cute one.
Rudders shouldn't be too much trouble. A bellcrank in the middle with a link to each one should work. You might actually get away with controlling just one rudder.

Ian

[California Condor]

Originally Posted by Jim Robinson

Thanks for the replies. Yeah, I had a struggle with how to build the wing. Plans say to assemble spar first and begin gluing ribs in place. I figured there was no way I'd possibly get a straight wing that way unless I built a jig with the polyhedral already built into it, and constructed the wing in the jig. Too much effort for a plane that likely won't fly great anyway, so I decided to build it flat and cut it apart later. Also much easier to sand LE and fwd sheeting to shape while wing is a (flat) unit.

Am not looking forwarg to rudder linkage, but I think I will build a crank into the horizontal, as it is an approximately 3/8" thick lifting section. I thought about going with a pull-pull system, but decided I'm not man enough for that kind of fiddling.

Plan is to mount all onboard gear as far fwd as possible, but I think the short nose moment is a bit deceptive when you factor in the lifting stab.

OK, wing is going "under the knife" next. Will report back.

Jim

I used a "pull" (not pull-pull) system one this one. Kevlar thread routed through small teflon tubes (the kind used for thin CA application) to pull the rudders out against a small torsion spring.
The model is a 1942 "Pusher Persuit" for the SAM SOS event. It is powerd with a LPS "B" 4.8 motor/gear and an APC 7x5 E prop. I will be flying at the SAM Champs next week.

[Jim Robinson]

Thanks for your reply, Ian. Actually the sheeted leading edge is one of the things that attracted me to this one. You see, I have a bunch of Balsa Products "LW tissue" ( similar or identical to litespan) laying around, and while I love the look of a model covered with this stuff, frankly I haven't had much luck with using it on lightweight structures. I was actually looking for a model with a bit heavier construction than the typical parkflyers/slowflyers to use some of this stuff up on. Incidentally, only the top surface is sheeted.

Thanks for the suggestion, Condor. I had been actually been toying with the idea of using a rubber band to return the rudders, but I like the sound of your torsion spring a lot better. I may re-think using this system to save a little weight. That's a unique model you have there, did you do a thread on it? What is the covering on the wings?

I have the polyhedral issue licked:
I built some sanding jigs to sand the bevel onto the ends of the wing panels. They were fairly easy and quick and did a great job. Naturally I had to build 2 jigs because the 2 joints weren't the same angle, but these are certainly the cleanest wing joints I've ever produced. I didn't even bother with blocking up the tips when I attached them (of course I checked this out with a ruler before I let the CA fly). I simply CA'ed the stubs together while holding the panels in alignment, and the actual dihedral/polyhedral measurements all came out within 1/16". I don't think I've ever come that close in the past when I did block the wingtips up!

Here's some pics, I think I'll tackle the fuselage next.

How's this for a tight fitting joint?!

Jim

[vintage1]

I am coming more and more to the idea that jigs don't take as long to make as trying to get things right without them does

Fabulous carpentry.

There are some build threads that you just know will result in a successful aeroplane - and this is one of them.

I can't hack Litespan on ultra lightweight structurs - you need to pull it pretty hard to get it tight - That structure looks perfect for it.

Very warmest congratulations on a little work of art.

[Jim Robinson]

Thanks for the kind words, Vintage. An unexpected interuption brought progress to a screeching halt this eve, but I'm back on it now. Shall return...

Jim

[clipclop]

Vintage1,
Your right about the jigs and time, the results are better too , the better the jig the better the result.
I allways jig wings to sand the joint , I think the end alignment and added strength alone make it worthwhile, and as you say is useually quicker in the end .
Jim,
Construction is looking great , dosent look like you will need much filler on it .
Stewart

[Ian Easton]

That's really nice - now I have to start thinking seriously about jigs too.

[Jim Robinson]

Thanks for all the compliments, everybody. Stewart, too late for the filler! I should have checked out my rib patterns a little closer, the 3 outboard tip ribs were all a little too high under the sheeting. I managed to sand completely through the sheeting in a couple spots on the right tip panel. Scabbed a doubler onto the back side of the sheeting in those spots and then gobbed the topside up with balsa filler. Yuk! It looks like crap, but I guess I'll have to live with it. I can maybe paint something onto the covering there so the filler doesn't show through. Maybe a checkerboard band or something.

I've made a little progress toward a fuselage in the past couple days. Had to widen the fuselage about 1/2" so the Kokams could lay flat on the back side of the firewall. I laminated 3 layers of 1/32" balsa for the firewall instead of using the 3/32" birch ply called for in the plans. Motor stick stops flush with the back of the firewall to accomodate battery pack. Firewall glues to fuselage sides with about 2 1/2° downthrust, but no right thrust. I sanded 3° of right thrust into the horizontal motor stick gussets before gluing them in place. Motor's endbell (capacitor) clears the firewall by about 1/8", but it still sticks out too far forward and looks a little odd. Not too bad, I can live with it. Wish I'd checked that out before I printed the patterns for the fuselage sides. I could have easily extended the "cheeks" forward a little for appearance's sake. Oh well, now that I think about it, everything about this airplane looks a little odd .

Thought I was pretty smart laminating the balsa firewall until I remembered that I have to attach the single-wheel landing gear to it . Hmmmm... Think I'll sandwich the landing gear between 2 peices of 1/32" ply with some 1/16" sheet filler and attach the whole thing as a unit, full width, across the lower front face of the firewall. I made some really cute little 3/32" tri-stock to reinforce the joints all the way around.

So far the fuselage weighs 10 gm. and the wing 22 gm. I still have some work to do on both, so those figures will go up. Can anyone with some experience venture a guess what my finished weight might be based on these figures? So far I'm at about 1 1/8 oz. How am I doing? I know my GymSwallow wing weighed 18 gm. in this state, but that's really not "apples to apples".

Here's some pics:








Later,
Jim

[vintage1]

I'll have a stab at 6-7oz covered with LIPOS and radio in.

steady performer on 2 cells, contest duration type performace on 3....

[harrier81]

Hi, i would like to see a picture of your finished model, i decided to build my own pee wee because i have a cox 0.20 without plane... so here is one pic of the fuse...

Where are other pee wee pal builders????

[BobHH]

Well, mine has an old World Engines single channel radio in it finally. Sorry but did not get a picture yet with the rudder linkage. Covered in tissue and dope.

Bob Harris