Guy Prevost

Guy Prevost

Well Known Member
Howdy,


UPDATE! 2-18-07 DO NOT STRETCH YOUR SEATBACK WELDMENTS! Ken at Van's says that the seatback weldments vary by .030" max and that I should squeeze my fuselage into it. This is the exact opposite of the advice given to me in an email from another person at Van's.

My front seatback weldment is too narrow by about 3/8" of an inch. I could shim it in, but Van's said it is better to stretch it. I've heard about spreading the roll bar, but not the seatback weldment. Anyone out there with any experience or suggestions?

Regards,
Guy
 
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3/8" overall?? Are you sure the cockpit is square and not bowed outward somehow??

If in fact you have to spread the weldment 3/8", that's a lot. I think I might go with a shim on each side.

If you've got time, and if it's truly too narrow, see if Van's will help you with a correct one.

I had to bend my roll bar. But I don't believe the fit (parallel) of the attachment plates would be that critical as with bending the rear seat support to make up 3/8" width.
 
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Hi Guy,

I did have to spread my roll bar, but not my seatback. However, I would suspect the same procedure would work. A foot on one side and pull on the other. If you can't move it that way, try a bottle jack and a couple of pieces of wood.
This advice is worth exactly what you paid for it ;)

Cheers
 
Low Pass said:
3/8" overall?? Are you sure the cockpit is square and not bowed outward somehow??

If in fact you have to spread the weldment 3/8", that's a lot. I think I might go with a shim on each side.
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It's somewhat less than 3/8".

I'm pretty sure the cockpit is square and unbowed. This is a new matched-hole fuselage, so there is no jig. I had to bend the longerons, but they fit perfectly--literally just laid in place. My aft deck is parallel with the longerons at the front of the cockpit within the .1? accuracy of my digital level.

I'll probably try a combination of bending and shiming the seatback weldment.

Guy
 
Measure twice, stretch once.

Might I suggest you get a few measurements before stretching the seatback. If I were at the hangar I would measure mine for you, I'll be out there tomorrow evening. As I understand it, the most important thing is that your canopy rails are parallel, the seat back can affect this. Mine like the others, just slipped right in place perfectly.

I'll try to get those measurements if you like.
 
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RatMan said:
Might I suggest you get a few measurements before stretching the seatback. If I were at the hangar I would measure mine for you, I'll be out there tomorrow evening. As I understand it, the most important thing is that your canopy rails are parallel, the seat back can affect this. Mine like the others, just slipped right in place perfectly.

I'll try to get those measurements if you like.
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Wow! You read my mind! I logged on this morning in order to ask for some cockpit measurements. Specifically the measurements between the weldment mounting plates immediately behind and ahead of the weldment mounting feet. So, I'll take you up on your offer!

Is there anyone else that can supply the same measurements? More information is always better.

I'm trying to figure out whether there is a problem with the weldment, the matched hole fuse, or if I did something wrong. My longerons, etc. appear to be perfect so I'm guessing it's the weldment but would like more information before proceeding.

Thanks in Advance!
Guy
 
Don't stretch your weldment.

It turns out I was given bad advice from Van's. The seatback weldments don't vary by more than .030".

If you run into this, after talking to KEN at Van's to make sure your situation is the same, squeeze the fuselage in to meet the weldment.

Guy
 
Hi Guy,

Finally got out to the hangar today (work has been getting in the way of building my airplane). It dawned on me today that page 8-23 states you will probably have to flex the fuse in or out to get the fit perfect. Don't know if you are building a QB or not so you may have skipped this page.

Anyway, for those that might be interested in the future, my seat back weldment measures roughly 26 11/16 at the widest part of the front flange and 25 13/16 at the rearmost flange. These measurements are from the outermost face of the flange.
 
RatMan said:
Hi Guy,

Finally got out to the hangar today (work has been getting in the way of building my airplane). It dawned on me today that page 8-23 states you will probably have to flex the fuse in or out to get the fit perfect. Don't know if you are building a QB or not so you may have skipped this page.
Click to expand...


I wish the new manual (matched hole) had that tidbit of info. It would have saved me some greif!

Guy
 
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