IowaRV9Dreamer

IowaRV9Dreamer

Well Known Member
My tribulations with the slider canopy frame continue. As of now:
  • The shape of the square tubes matches the shape of the fuselage side.
  • The square tubes are 1/16" inset from the outer edge of the fuselage side per plans.
  • The shape of the front round tube matches the shape of the roll bar.
  • The height of the front round tube is 3/8" above the rollbar per plans.
  • The shape of the rear round tubes matches the shape of the aft fuselage.

The problem is that the canopy frame has a twist to it - when mounted on the plane the aft side of the right square tube is about 1/4" lower than the front side - in other words it is not parallel to the longeron. The left side square tube is parallel to the longeron.

The resultant twist is making it so the rear round tubes cannot both be in the correct place relative to the aft fuselage. If I temporarily take out the twist on the plane with clamps - the canopy frame is PERFECT!

So what I need to do is take some twist out of the canopy frame. So far I've been clamping it to my work bench and using a piece of conduit as a lever to twist it.... with no result other than a bent conduit.

I think my next attempt will be an 8' 2x4 and two people to generate the twist.

I don't want to bend the rear bows - since they seem to be the right shape now.

Has anyone else had to untwist their canopy frame? If so, how did you accomplish it? Never has 1/4" seemed so far :(
 
Sounds like you're on the right track, just go easy. You really need that twist taken out in my opinion. Bad thing with getting one thing right it messes another up but press on, you will get it.

How did you repair your side bow? Hopefully you were able to weld it.
 
square tube was welded

Thanks Kelley - it is frustrating to be so close, and yet so far (1/4 inch!).

Steve Ciha welded the square tube perfectly. It hadn't broken (just cracked) and now it is as good as new.

I'm just wondering how to fixture the thing and apply the correct pressure to get it to twist (and not kink).
 
I had a worse twist and was afraid I would break the welds if I twisted the frame too much. I ended up mounting the delrin anchor blocks, using it to hold the canopy frame in place at the rear with the rail properly aligned, and then drilling the plexi into the frame. Thus, the plexi holds the side rail in place in the proper position. It places a little bit of force on the plexi, but not much.
 
IowaRV9Dreamer said:
Thanks Kelley - it is frustrating to be so close, and yet so far (1/4 inch!).

Steve Ciha welded the square tube perfectly. It hadn't broken (just cracked) and now it is as good as new.

I'm just wondering how to fixture the thing and apply the correct pressure to get it to twist (and not kink).
Click to expand...

Two people- then stand the thing up on the front hoop and clamp it securely (very securely, bolt it down if necessary) to the table. Helps to set it up so you can take some measurements in advance, to get a sense of how much bending you have accomplished. We did the latter with my frame by placing the bottoms of the front hoop at the edge of the table. We then used a long straight edge and a level held vertically to indicate off the edge of the table to the prongs for the plastic blocks. Sounds complicated, but it wasn't. Then gave it a two-man twist. Worked perfectly, though the amount you have to twist beyond what seems reasonable may feel scary at first.
 
The frame doesn't sound twisted to me. From your description, you need to shorten the right aft canopy bow about 1/4" about where it is welded to the square tube. You'll have to trig it out for the exact amount.
Or try shimming up the left (opposite corner) front bow 1/16" and see how things look.
 
Dave, I was fighting mine like yours until I measured and found that one of the square tubes was welded 3/8 inch lower than the other side, it made it appear that the frame was twisted. Since I was going to go with a dark grey powder coat color anyway, I carefully cut and re-welded the tube. It was alot better after that. Take some measurements to make sure you don't have the same issue. Like I mentioned in the other post, your canopy will spread the frame apart, take that into account.
John.
 
So long as the canopy slides forward and aft nicely, and so long as it is not so low or high in the back that you won't be able to get the pin secured in the delrin block, does it really matter if the square tube is perfectly parallel to the longerons?
 
alpinelakespilot2000 said:
So long as the canopy slides forward and aft nicely, and so long as it is not so low or high in the back that you won't be able to get the pin secured in the delrin block, does it really matter if the square tube is perfectly parallel to the longerons?
Click to expand...
It isn't that the square tubes aren't parallel , it is that the twist is causing the right rear bow to not match up with the aft fuselage. Because of the twist, I can't get both left & right aft bows to the same height relative to the aft fuselage. If there was no twist it would work perfectly.

I agree that the square tubes being parallel isn't that important, but with my frame it is a convenient place to measure the twist.
 
IowaRV9Dreamer said:
It isn't that the square tubes aren't parallel , it is that the twist is causing the right rear bow to not match up with the aft fuselage. Because of the twist, I can't get both left & right aft bows to the same height relative to the aft fuselage. If there was no twist it would work perfectly.

I agree that the square tubes being parallel isn't that important, but with my frame it is a convenient place to measure the twist.
Click to expand...
Ah, got it, I think.

Have you tried a conduit bender yet? This will allow you add any additional bend you might need without disrupting the geometry of the frame elsewhere.

Further, not sure that this is part of your problem, but I had an issue right up near the top aft center where the left aft bow was lower than the right aft bow. Some nylon washers between the plexi and frame on the low side solved that issue. Not sure that you have that issue, but mention it just to note that shims can be used if necessary to get the plexi exactly where you want it, which is what is most critical.

Good luck.
 
alpinelakespilot2000 said:
... I had an issue right up near the top aft center where the left aft bow was lower than the right aft bow...
Click to expand...

That seems to be a recurring theme. Mine was like that, and since I did my canopy I've seen at least 2 others the same way. Shims worked for me, too (though they are buried in Sika now).

It really is easier with the thing firmly clamped and a couple of guys heaving ho. Just be sure to have refreshing beverages as a suitable bribe :)
 
Middle of the night thought

Shim the same side front corner not the opposite front corner of the frame. You won't notice one canopy skirt is 1/8" higher than the other but your eye will see a slanted skirt.
 
Steve said:
Shim the same side front corner not the opposite front corner of the frame.
Click to expand...
Thanks Steve - I was playing around with shims yesterday. Shimming the opposite side made it worse, but like you say shimming the same side made it better.

The problem was to get enough twist, I had to add a full 1/4" to the front corner, and then the front bow was pretty obviously not aligned to the roll bar.

I'm going to get some clamps, a helper, and a beverage bribe as described above. I'll take a picture of the twisting process.
 
Last edited:
twist and shout

I have a love hate relationship swith my bow so take this for what its worth.

Stand the frame on the floor on the front bow (on cardboard or something to prevent sratching). Step on it on each side where the square tubes are welded to the front bow. Grab the rear bow as far apart as possible and start twisting the way you want to go. Work you way into it. To check progress look from the sides to see if the two square tubes are parallel. Another way to eyeball it is to sight from directly behind and see if the aft bow is symetric with the front bow.

Warning, this may change your aft bow shape, so you may need to tweak that again. After an unknown number of itterations it will either come in, or your tolerance for misalignment will increase:D
 
Canopy frame now untwisted

Well, my canopy frame now fits quite well. The twist has been removed, and all without bending any of the curved tubes. I thought I'd post my story in case someone else needs to untwist their canopy frame.

When I took the canopy frame out of the box, the curve of all the round tubes (front and back) matched the fuselage and roll bar perfectly. I had a little mishap with one of the square tubes (ahem) which was rewelded.

But the big problem with my frame was twist - the right rear corner of the frame was a full 1/4" lower than the left rear corner. This twist was causing the right aft bow to fit badly against the fuselage.

Thanks to A&P (and future RV builder I'm sure) Colin Reed for helping supply both brawns and brain - because with the following precision operation we were able to twist the canopy into submission.


It is a little hard to see in the picture, but the front of the frame is clamped rigidly to the edge of the EAA workbench. The entire frame sticks off the bench. An eight foot 2x4 and two airplane fanatics supply the needed twist. One pushes down, one pulls up.

When the right side of the bench starts lifting off the floor :eek:, get a kid to sit on it.

When you are putting so much twist into the frame that you are sure it will snap :eek: :eek:, keep going.

Finally, when the edge of the benchtop (3/4" MDF) starts to delaminate :eek: :eek: :eek:, you will have reached the correct point. :cool: I'm not sure how much twist we had to put into this, but it was a lot, like 10 inches on a side or more. That steel is tough stuff.

Now the shape of the rear bows matches the shape of the rear fuselage within a 1/32 or two. I will have to use thicker spacers on the right side between the frame and the plexi to make it come out perfect, but thats OK as I'm going to use Sika.

After much grief this came out great. The canopy frame slides perfectly on the rollers and track. Now I'm actually looking forward to the scary plastic part.

Thanks to all for your help.
 
Congratulations!

Toldya :cool:

It's quite the education in materials to learn just how much you can abuse something like that and wind up with a good result, isn't it? And truly one of those cases (as I learned myself, the hard way) where two can do a much better, and quicker, job than one. I tend to work solo a lot, so that was a good lesson for me, when I did more with a friend in 45 minutes than I managed to accomplish in 20 hours, alone.

On to the next step!
 
Congrats!

This is why I spent the $ and bought a new Miller Tig welder, so I can fix problems such as this and to my total amazement I can still weld after 15 years. I guess some things just never go away! Congrats on your fix and glade you are over the hurdle. Will sure be glad when I?m to that stage! Mean while back to the VS. Cheers!
 
Slider Progress

IowaRV9Dreamer said:
Now I'm actually looking forward to the scary plastic part.
Click to expand...

Dave: Please keep us posted on your progress...and especially how you do the SIKA...I hope to start on my slider this August and am also planning on going the SIKA route...

Doug Lomheim
OK City, OK
90116
 
No problem - I posted my "big cut" section in the Tips forum. When I get the spacers figured out, and the canopy trimmed, and the frame painted, then I'll be ready for the Sika!
 
Hey Dave. Ron here in Oregon 9A QB. Just putting the seatbelt bracket in the floor. I happened on your rack twisting and looks like iam headed that way too! Thanks to all for the info. Say what is SIKA???? Thanks Ron
 
Hi Ron - do a search on SIKA - it is a brand of adhesive designed to hold windows into boats. Lots of builders are using it to bond the canopys on.
 
You must log in or register to reply here.