Started the Couger

Sloper

Well-Known Member
Goodaye all

Broke my golden rule today.
One project at a time.

Purchased a Genuine LJ GTR Torana, its in bits but the bodywork is done.

New double carport built, l will be shuffling a few cars around to put the Couger fuselage in the carport while l get a start on the wings.

The Couger take's priority.

l will collect a few missing bits on the GTR in the meantime.
Bonnet, boot lid and front seats, would be interested in any bits and pieces.


regards Bruce
 

bexrbetter

Well-Known Member
After I did my wing spars, in hindsight I believe I could have made my life a lot easier, more accurate and added strength to the assembly with just a simple change.

I found lining up of the angle on the spar sheet a bit of a pain and I wasn't completely satisfied with the result and believe that the simple addition of a little extra width with 90 degree folds is a very suitable solution and easy to accomplish - do need to get to a sheetmetal shop to do the folds for you though.

The result will be a much straighter spar and better looking wing as well as an increase in strength, not to mention a much easier process as the new folds serve as an alignment jig.

I hope the pictures will be enough explanation, the additional material is red in colour wing mod 1.jpg ...

wing mod.jpg

wing mod 2.jpg
 
That's interesting. Which way was it not straight? The only thing I noticed doing the spar was that the rivets expanded one side of the angle and not the other which gave it a slight sweep back/forward. Only about 10mm though.
P6210091.JPG P7100100.JPG
 

bexrbetter

Well-Known Member
That's interesting. Which way was it not straight?
Not straight enough for my dead eye and just a lot of work to get it straight - relative to if you had that folded edge there acting as a jig.

It's just a thought/suggestion, and the way that I would do it if ever again.

Please be aware that is in now way a comment on the current design or build method, merely an alternative technique.

Here's another method for doing all those holes literally anywhere on the build including curved surfaces, go buy some perforated aluminium sheet with 3mm holes and cut some strips off it (if you can't actually buy an offcut), drill a hole in each end relative to your workpiece, pop a rivet/cleco in each end and drill out all your holes at your selected intervals (I use a nikko pen to mark my holes first). Remove and clean up, rivet away.

No measuring, line scribing or centre punching required, super even spacings and super straight is the result. Just a photoshop to give you the idea, of course the idea here is bent over a curved surface ....

plot.jpg
 
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pylon500

Well-Known Member
Hey Bex,
Not sure how thick the web sheets are (0.032"?), but folding a sheet that long will probably bow anyway, unless you can get it done in a very heavy/strong, vertical press brake.
The bowing in the normal construction (without flanges) is a function of setting the rivets.
In the act of riveting, you always try to have the rivet head on the thinner side (if materials of uneven thickness), and try to get the rivets 'down' as quickly as possible (bigger hammer, heavier gun), this will minimise stretching of the thinner material which can cause bowing.
Also, when setting rivets, avoid starting at one end and riveting along in a line, you'll end up with a banana !!
Along something like the spar, I would set a rivet about every foot or so, then go back and put one in between each, then probably do it again before going along and filling all other rivets.
The important thing is to be able to set each rivet with as close to the same pressure/force as all others.
The best sign of this is all the tails being identical.
The Metal Basher.
 

bexrbetter

Well-Known Member
Hey Bex,
Not sure how thick the web sheets are (0.032"?), but folding a sheet that long will probably bow anyway, unless you can get it done in a very heavy/strong, vertical press brake.
.
Yuh, as I mentioned, get to a sheetmetal shop.

Yes, 0.8mm and just over a 2.5M length fold.
 
Here's another method for doing all those holes literally anywhere on the build including curved surfaces, go buy some perforated aluminium sheet with 3mm holes and cut some strips off it (if you can't actually buy an offcut), drill a hole in each end relative to your workpiece, pop a rivet/cleco in each end and drill out all your holes at your selected intervals (I use a nikko pen to mark my holes first). Remove and clean up, rivet away.
Yes I made lots of these type of jigs too. Mine are mostly straight. I didn't make a curved one, good idea!
 

bexrbetter

Well-Known Member
Yes I made lots of these type of jigs too. Mine are mostly straight. I didn't make a curved one, good idea!
Mine aren't curved, merely some 1 meter long by 50mm wide (roughly) by 2mm thick, 40% perforated aluminium offcuts that are flexible enough to be used in most situations.

Great thing about the typical perforated pattern is it allows you to do perfect double rows and other offset or fancy patterns as required ...

plot 2.jpg
 

kgwilson

Well-Known Member
The spar did end up with a curve in it when I made mine as per Garrys plan but it wasn't too bad. The solid rivets do stretch the material which is why you don't just start from one end & install them in line. As Garry said as soon as you fold the D-box over the spar and pull the whole assembly tight with ropes or in my case with ratchet straps (1 on each rib) it straightens out so well that I could not detect any deviation sighting straight down the spar. Worked for me.
 

Garry Morgan

Morgan range of aircraft
Thats Right Kev.
It only makes work for your self for something doesn't matter. A straight edge wont work as the riveting will have some stretch in it and you cant avoid some bending. when the D box sheet it pulled on it is all removed ???????????? If holes are not straight so what, it wont effect anything. If building an aircraft was so important and require so much skill most would crash.
 

bexrbetter

Well-Known Member
The spar did end up with a curve in it when I made mine as per Garrys plan but it wasn't too bad.
I am not talking about the curve in that plane, which is as suggested, insignificant, I am referring to the upper and lower wing surfaces as in standing at the wing tip and looking along the surface towards the wing root, the "waviness" that's why the folds I suggested above, to obtain a straighter edge/flatter surface ...

wave.jpg
 
I found the ribs sticking up above the spar needed filing off. Sikaflex in the ones that were too low. Jigs/spaces were needed where the ribs were going to go to get the spar to have the right height at that point. A folded web would make it easier.
 
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