Tip up question

[Kilo Charlie]

I have done lots of reading on here (THANK YOU) and spent some time in the hangar and I want to make sure I am getting this right before I go too far.

I am building the front of the tip up canopy frame and trying to mate it to the fuselage. I understand that F-702 skin lines up with F-771 (the forward most top skin) and also the side skins of the fuselage. I saw people using tape, straps and pixie dust to make this happen (by the way if you have any extra pixie dust please let me know because I am all out). Is it fine to crank down on straps to get it in position and then drill the C-614 splice plate and hope for the best?

I am using wooden blocks to put pressure on the high spots to bring them down.

I just wonder how much spring back is too much? Should it sit in place unaided or its fine to MAKE it fit.

Currently I have the 90-95% solution and I wonder if I can just bend the leading edge of the skin (F-702) down in the 2 places that it is sticking up. The worst is shown here:

it's about 1/16" too high but inline everywhere else.

Also I have debured the frame and skins but NOT dimpled/countersinked yet, should this be done now or after drilling the splice and ribs into place. The plans leave everything undersized so I am assuming things can/should still move a little?

I have also left the angled row of rivets undrilled on the sides of the frame. It sure looks like the skin would create a flat spot instead of the nice radius if I Cleo and install rivets there, I think I may make spacers once everything else is in place. Or is this under the canopy and doesn't matter?

Thanks for any pointers you have,
KC

 

[bruceh]

The two sections (canopy and forward top skin) don't align perfectly. I spent untold hours trying to get them close to no avail. What you have with 1/16" or less is pretty good. You can always fair it out later before painting.

Here is what mine looked like after playing around with it forever.

I even tried to shim up the forward top skin, but there just isn't any way to stretch that top skin over the shims and still get the longeron and side skin holes to line up with the top skin.

 

[lr172]

I would not strap then drill. I would be afraid of what would be there after I took the strap off. I layed out my frame long before I put a skin on it and worked to get it aligned all around. If you have it really nice except one spot, I would say move on and bondo it. It may move around a bit once your get the plexi and gas struts on it. I had two spots that needed bondo (1/32" off maybe). Other than not seeing the rivets, you would have no idea that I did it, even looking from 1 foot away. I don't believe you can get perfection with the canopy. I really struggled with the sides. However, after fairing and paint, you would not know that I didn't hit it perfect, except for the invisible rivets.

Larry

EDIT: I remember riveting the plate on one side and then using clamps on the other side so that I could see how it layed in a self-supporting manner. Once I had it where I liked it, I drilled the other side.

 

[High_Flyer]

Be careful

I've done the strap thing on the F-702...
I drilled the C-614 with the strap in place. After removing the strap my C-702 skin was too low compared to the forward skin and I had to cut srtips of metal to use as shims between the frame and the C-702 skin to get it to be level with the forward skin
So if you do put a starp before drilling make sure you don't stretch it too much.
Alain.

 

[BillL]

I have done lots of reading on here (THANK YOU) and spent some time in the hangar and I want to make sure I am getting this right before I go too far.

I am building the front of the tip up canopy frame and trying to mate it to the fuselage. I understand that F-702 skin lines up with F-771 (the forward most top skin) and also the side skins of the fuselage. I saw people using tape, straps and pixie dust to make this happen (by the way if you have any extra pixie dust please let me know because I am all out). Is it fine to crank down on straps to get it in position and then drill the C-614 splice plate and hope for the best?

I am using wooden blocks to put pressure on the high spots to bring them down.

I just wonder how much spring back is too much? Should it sit in place unaided or its fine to MAKE it fit.

Currently I have the 90-95% solution and I wonder if I can just bend the leading edge of the skin (F-702) down in the 2 places that it is sticking up. The worst is shown here:

it's about 1/16" too high but inline everywhere else.

Also I have debured the frame and skins but NOT dimpled/countersinked yet, should this be done now or after drilling the splice and ribs into place. The plans leave everything undersized so I am assuming things can/should still move a little?

I have also left the angled row of rivets undrilled on the sides of the frame. It sure looks like the skin would create a flat spot instead of the nice radius if I Cleo and install rivets there, I think I may make spacers once everything else is in place. Or is this under the canopy and doesn't matter?

Thanks for any pointers you have,
KC

Definitely do not compress down with great force. Treat this frame like a delicate flower that has to be just so to settle in place.

There is no reason in the world to accept uneven skin match around the top.You just have to step back and think.

Have you drilled the hinges yet? Riveted hinges to the frame? I will guess not.

In order to yield a nice fit to the forward curvature - think of this in sections. 1. The center is controlled by the splice. 2. The sides by bending the frame at the hinge notch. 3. The total "lift" is by the hinge pins.

This begins with the splice, Then hinge pin, then hinge rivets (may swap those), then bending the frame at the hinge notch. Look at it and think - - it will come into focus.

OK - back to your fitting - center section, splice plate. (my first mistake) It is critical that the skin on the canopy frame NOT BE DEFORMED by downward pressure from above. You need to ensure that a straight edge leaves no gap when placed fore-aft over that joint. You may have to jack it up from the bottom to do this as it tends to fold downward with that pressure. If you get this splice in the correct place it will begin a successful domino effect to a nicely fitting frame. No gaps. My lost sleep on this is your gain. More to come as you progress to get it aligned. Keep in mind this is tricky and you will have to mentally conquer it. Do not be complacent at any step.

Oh - and put all the clecos in that front skin.

Edit: Bruces gap in the picture above is due to the hinge being too high. This was a result of the the splice being depressed in the center. It is avoidable. Remember the dominos, then CAN fall your way.

 

[Kilo Charlie]

Sounds like no on using the straps

Sounds like I need to keep working it.

All: Thanks for your lessons learned with drilling and straps.

Bill: Thank you for the explanation on how you got yours to sit flush. I will work from center out and see what I come up with. Just playing with the hinges changed things a bit.

Ok back to work and I'll pass on my dads words of wisdom "When in doubt, get a bigger hammer"

 

[jj_jetmech]

Sounds like I need to keep working it

After hours of fighting the shape between the canopy skin and fwd fuse skin. I made a resin and flox shim between the skin and the canopy frame letting the skin find its natural shape, clecoing an overlapping piece of sheet metal to only the fwd fuse skin.. The end result is near perfect. I also made my own fwd canopy skin and side skirts to eliminate the gaps on the canopy deck and aft roll bar. Vans should have left more material on the canopy skin and skirts..

good luck!

 

[Bugsy]

I wouldn't strap

I strapped it and forced a fit, now I get a click when I open the canopy and in the end I still didn't have a nice fit. I'll fair it out with glass before painting. Canopy alignment is what it is. Good luck

 

[bill v]

should the top skin be riveted?

should the top front skin be riveted before fitting the canopy? the manual seems to indicate this but I hate to rivet this skin until after everything else is done but don't want to fit the canopy and then find out I should have riveted it. the pictures in this thread show you are not riveting this skin do you know this is ok?