Working with canopy bows

[mike.smith]

My windscreen is in, but I'll soon be starting on the canopy. I bought the pre-bent canopy bows. Any hints on working with the pre-bent bows, since they don't match up with the fuselage contours? Like how to tweak and bend them and get a good match? I'm hoping I don't need to make a full bending pattern on my workbench.

Thanks,
Mike Smith
Sonex #439

[kmacht]

Mike,

I made a bending jig. I took a block of wood a little thicker than the bow and cut a big outside radius in it. Probably about a 8 or 10" radius. I then screwed a piece of 2x4 about 6" long just far enough away from the radius block to fit the bow in between them. You then put the bow in there and either push or pull it a little to change the radius. I saw the technique on someones sonex website before. It was either Jeff Schultz or Bob Milka. Just be carfull to keep the bow flat against the table when making the adjustments otherwise you get a twist as well as a bend. Also, small changes at the center of the bow has a large affect on the bottom ends of the bow. I found it easiest to start in the center of the bow and work down each side. I tried starting on one side and working my way up and over and it just made the bow a mess. My bows were pretty close but seemed to have two flat spots with no curve towards the bottom. Hope that helps. Good luck.

Keith
#554

[N111YX]

You'll find the plans offer and "X/Y" coordinate pattern to fine-bend the bows (at least they used to). The problem is that it's for an airplane that does not really exist. You want the bows to fit your airplane. I suggest getting two large pieces of paper and, similar to taking a pencil to a penny to create an image, make an "image" of your front windshield and turtledeck arcs. Then, you are at least working with the exact shapes you'll use. I found that the bows can be bent using one's knee when bending in and the floor itself when bending out. I just made my second canopy and the bows took about 30 minutes each of trial and error bending to where I was happy with the shape...:)

[daleandee]

Here is a photo of a simple bending jig made with some scrap pieces of wood:

https://s3.amazonaws.com/expercraft/dal ... 2eca95.jpg

Other ideas presented here work well. There are a lot of ways to skin this cat ...

Dale
N319WF

[mike.smith]

So it sounds like making a jig to match the actual fuselage curves is not necessary. It sounds like the important thing is to have something between which to bend the bows in a flat manner.

Mike

[142YX]

I found that the bows can be bent using one's knee when bending in and the floor itself when bending out. I just made my second canopy and the bows took about 30 minutes each of trial and error bending to where I was happy with the shape...:)

30 min each? wow Kip.. want to come over and do mine for me ;)

I am at this phase.. been struggling with the canopy bows for two days now. I ended up buying this tubing roller from Harbor Freight, thinking it would make the job a bit easier..
http://www.harborfreight.com/tubing-roller-99736.html
and they sell after market dies in all shapes and sizes for the roller here
http://www.swagoffroad.com/Harbor-Freig ... _p_51.html

Its a fine tool for making the initial bend (if you were starting from scratch, with a straight piece of tube), but not the right tool for this job to make the tight tweaks to the bow to get it to conform to the exact shape you need it to be in.

I'll give it another shot trying my knees..

[rizzz]

Check out this entry on Eric Witherspoon's kitlog:
http://www.mykitlog.com/users/display_l ... 473&row=31
seems like an easy set-up to bend/adjust the bows.

[mike.smith]

Hi,

Just finished the canopy frame last night. In the end my knee:
http://www.mykitlog.com/users/display_l ... 0607&row=6

And a couple of 2x4's did just fine:
http://www.mykitlog.com/users/display_l ... 0649&row=5

Mike Smith
#439