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l-21 from a pa-18a

Beaverpilot

Registered User
Manitoba Canada
Well I went and bought a Supercub project, now what?
It is plans built from wag with all the superstructure of a 18a the welder was a aircraft structural instructor (for welding) and copied his supercub along with the Northland drawings. The project was stalled for several years due to partners becoming ill and passing on. So it sat in a garage for 15 years. Present day. There are some changes I would like to incorporate to my new baby. I really like the l-21 style and would like to go this route. My concern is cutting out the c windows and replacing the turtle deck and stringers. Pros and cons anyone? I also want to extend the rear baggage and flip the dogleg. Does one need to have it in a jig or can this be done without one. I'm all ears my other concern is cutting out the old dogleg do you need to grind out all the old material? I'm adding in the tube that goes crosswise by the yolk mount as per the Northland dwgs.
It has both wings complete one new and one used along with the parts to build a new wing. Several flaps and ailerons. A box plus of instruments. A lower time 0-235 mothballed,
Wheels brakes struts and the list goes on and on.
I consider myself really fortunate to find this project and evermore so that this resource is available.
Thanks everyone,
John from Canada.
 
Good on ya and good luck John!!

You'll find a lot of good info here on the SC site...at least a billion years of experience to draw from.
 
I like the L21 glass as well. You can buy the channel from Univair in 6 foot pieces. Haven't noticed the frame moving when installing the inverted dog leg. You can make a fixture out of a sheet of aluminum off the dogleg that is there, cut it out and then invert the jig and fit your tubes.
 
I like the L21 glass as well. You can buy the channel from Univair in 6 foot pieces. Haven't noticed the frame moving when installing the inverted dog leg. You can make a fixture out of a sheet of aluminum off the dogleg that is there, cut it out and then invert the jig and fit your tubes.
not really sure what you meant here, with the jig.
 
We laid a piece of aluminum up against the dog leg and then riveted some angles to it to locate the tubes. After we cut the dog leg out we inverted the jig and used it to fit the tubes for the inverted dog leg.
 
Steve,

I am putting in L21ish windows without the extended sky light on my plane and found and ordered the 1/4" track from Univair. I haven't received the track yet but I believe there is no way it can go on there without some backing or support. What do you use or suggest? I'm thinking an angle frame bent out of 0.032 CM with the track tack welded to the angle. The gaps between structural members are up to 18" or so.
 
Steve,
what was the part number for the channel?? Is it the same as the rear windows or the standard 3/8 piper channel?
 
I received the 1/4" track and the rubber gasket material from Univair and it will work just fine with the Lexan I'm planning to use. Still wondering if there is a proven way attach the track to the fuselage? I can make a frame to attach it to, but it looks like the frame must be welded to the the tube and the track attached to the frame after the fabric is completed...maybe with machine screws thru nut plates.

Is there "standard" way to attach the window frame?
 
I received the 1/4" track and the rubber gasket material from Univair and it will work just fine with the Lexan I'm planning to use. Still wondering if there is a proven way attach the track to the fuselage? I can make a frame to attach it to, but it looks like the frame must be welded to the the tube and the track attached to the frame after the fabric is completed...maybe with machine screws thru nut plates.

Is there "standard" way to attach the window frame?

The only way I have seen it done is being brazed or tac welded.
I just got my project home tonight around an hour ago.
Now the sorting and organizing starts. I have another shipment of parts coming this weekend.
 
Piper drawing 12204 has the channels for the L-21 rear windows. 12204-2 (The lower rear window channel) does not have a flange and it appears from the section view that it is tack welded to the tube. 12204-3, -4, -5, (the turtle deck frame) all have a flange on the side of the channel and could be tacked, pk screwed or otherwise fastened per your choice.
 
RHL,

Thanks for the info. I pretty much constructed mine as you mentioned except I made the forward track rigid since it is attached to my front window frame and will not need to be wrapped with fabric. The other 3 sides are done with tabs that will be bolted on and covered with a painted piece of alum trim. I'm happy with the way it turned out.

I put a pic of the way it will go together on my Lowrider LSA page if anyone is interested.
 
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