Cowl fitting question

lostpilot28 · #1 05-26-2008, 07:06 PM

I've got my lower cowl fitted up and started getting the top one ready for aligning/drilling when I noticed that I had a slight "misalignment" at the front of the upper cowl. It's shifted to the left maybe 1/4" and can be pushed back into position by hand. I'd say your average airplane builder can align them just with your hand...maybe 10 lbs of force (I'm guessing).

If I un-clecoe the rivets on the firewall hinge the front sets into position correctly, but the aft-right side of the upper cowl shifts up and away from the hinge (maybe 1/8"). If I push the aft of the cowl back down to the hinge, the front slides to the left. Doh!

I already have the side of the upper cowl drilled to the hinge, so I can't do much re-aligning. Is this the "preload" that breaks off the hinge eyelets on some RVs?

Any suggestions?

yakdriver · #2 05-26-2008, 10:03 PM

Sonny, Get out the heat gun and heat the area and push it back a little farther than where you want it. Go slow and it will come in. Don

szicree · #3 05-26-2008, 10:38 PM

Whoa! My experience is that heating epoxy does no good and usually seems to just cook things. Polyester, on the other hand, gets really pliable when heated. Unfortunately, all the current cowls are prepreg epoxy.

yakdriver · #4 05-27-2008, 08:53 AM

Epoxy forms very well with heat. Don

szicree · #5 05-27-2008, 09:54 AM

That is surprising to me. I'll clarify my earlier post then. My RV-4 cowl did not soften at all when heated with a heat gun and began to burn instead. Van's has since advised that the current cowls are not reformable with heat. YMMV.

yakdriver · #6 05-27-2008, 10:06 AM

Sonny's cowl is a James cowl that is all layups with no honeycomb. You cannot reform the honycomb portions of the Van's cowl but you can work the edges. I have over 45 years composite experience including building 90% of a Lancair 360. You can do quite a bit of forming epoxys with heat, been there done that a lot. Don

lostpilot28 · #7 05-27-2008, 06:09 PM

Thanks for the replies, Don and Steve. As Don suggested privately, the inlet rings will probably do an ample job of holding the cowl in alignment.

I agree that heat will allow you to work with cured epoxy. Back before I bought my PulsarXP I was looking into a Long-EZ. I did a ton of research and found a couple of examples of where the wings would droop if it sat in the heat on a black tarmac. One report said the tips actually touched the ground and the builder/owner had to remove the wings, lay them inverted on a table and reheat them to straighten them out. But then again, that story could have been slightly exagerated.

szicree · #8 05-27-2008, 08:51 PM

Quote:

Originally Posted by yakdriver

I have over 45 years composite experience including building 90% of a Lancair 360. You can do quite a bit of forming epoxys with heat, been there done that a lot. Don

I'm sorry if I came across as questioning your expertise, cuz I really didn't mean it that way at all. Perhaps my cowl is of a different type of epoxy than the SJ, but it's actually the edge I was trying to reshape. I heated the heck out of it and it did soften the tiniest bit, but not enough to reshape or take a new set. With polyester things get downright noodly, but the edge of my cowl seemed very rigid even when on the verge of burning. I know nothing of composites in general, only what my own experience was with this particular product.

hcccs · #9 05-28-2008, 10:34 AM

When fitting my upper cowl I cut too much of the section that mates with the cowl cheek. What is the best and easiest way of fixing this? A bit of fiberglass cloth on the backside to hold a little wedge to fill up the missing material? Is that good or is there a better way?

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