Cowl / fuselage interface - help please?

Having attached the cowl hinge to the firewall, today I inserted the cowl half of the hinge. See here I then realised the reason why, in all RV except the -4, the upper part of the firewall slopes forward. My hinge assumes the cowl is a cylinder, not a cone. (I hope that is clear!)

Question - how have other -4 builders handled this issue? I can probably borrow a shrinker. Would this solve it? Ideas please.

Thanks.

I remembered this topic from my old mid-1990's RV6 plan book, which has both types of firewalls, and just re-read the instructions. For the straight firewall, it suggested shrinking, fluting, or notching the forward hinge half.

At least your on the right track. BTW, my 6A had the angled firewall, so I have no firsthand experience.

L.Adamson

Firewall cowl hinge

L - thanks for the advice. It is a shame VANS did not leave/put that bit of info in the -4 build book. Never mind. I did in fact try fluting a spare bit of hinge the other day, but the hinge was far to heavy grade for my fluting pliers.

I will try to borrow a shrinker. Failing that I guess it is notching.

Thanks again.

If you're talking about the upper part of the hing, and not the sides, you need to file the edges of the hinge eyes, to that they're taperd. (Sort of like the way gears mesh). Then use a smaller diameter piano wire when you attach the cowl to the firewall. This smaller diameter wire is included in the kit.

This may or may not be what you were referring to...

Jeff

And no, the cowl is not fun, and it's about to get less fun. Enjoy.
MUCH worse than the canopy or tanks, IMHO

IMPORTANT: When you attach the cowl side hing half to the cowl, be sure to rough up the surface of the hing, and drill numerous holes in addition to the rivet holes, and while riveting the half to the cowl, use some resin/flox to embed the hinge half. I don't have any rivets showing through the paint from the parts working. I had some serious vibration issues (another story) during the first 40 hours and the hinge half is still firmly attached. This issue was addressed many times over the years, and it was established that riveting only was insufficient for the beating the cowl takes, especially during start-up, shut down and taxiing. It's messy and a lot of additional work, but you can tell who did it and who didn't.

Jeff

Hi Steve!
If you have added a shim between the firewall-side hinge and the firewall (to get more 'playroom'), the solution is simple. Just put a shim between the cowlside hinge and cowl and shape that shim to zero at the forward side. Additionally (this helps most!) cut each half of the cowlside hinge two times, so that you have 6 pieces of hinge to rivet to the upper cowl. That worked great for me. The overall shape of the cowl/firewall joint makes it rather impossible to get away with unmodified hinges. If I would have had the opportunity to give away one part, it would have been the cowl....

Shrinker

Thanks again for all the replies. A friend with a shrinker tried it on the hinge and says it works really well, so I will start down that route. Thanks again.