DOH! I shouldn't have dimpled the firewall!

[ArVeeNiner]

Hi:

So I'm getting very close to installing the last skin. This is the skin above the instrument panel. In my haste to get all the preps completed I noticed that I hadn't dimple the holes located on the tabs on the top edge of the firewall so I dimpled them. Then I realized (of course after the dimpling was done) that I think I hadn't dimpled them for a reason. I'm thinking that they weren't dimpled to make the installation of the cowl hinge easier during match drilling.

Is this true? If so, should I try to "un-dimple" these holes? Should I just leave them be? I'm thinking leave them be and build on.

[Vlad]

Kelly do not worry you did everything right. You can perfectly fit and (back)drill hinges or strips on dimpled holes.

[Brantel]

No worries, build on, don't undimple them. No problem fitting the hinges and cowl with them dimpled.

[Rick6a]

Originally Posted by ArVeeNiner

........ the holes located on the tabs on the top edge of the firewall so I dimpled them......should I try to "un-dimple" these holes? Should I just leave them be? I'm thinking leave them be and build on.

Kelly,

Call Van's. You are sure to get conflicting advice on an open forum. Personally, I would not hesitate to simply undimple those holes. There is going to be a stack up of material with the SS firewall tabs located in the middle of the stackup. You want the upper cowl hinge half to lie perfectly flat against those tabs and you may even have to slightly radius the edge of the hinge half to better nest against the firewall without riding. If undimpling is generally considered bad practice, riveting that upper cowl hinge half and subsequently causing it to ride under a series of dimpled holes is a far worse alternative. I suppose you "could" machine countersink the hinge half to accept the dimples but I am not sure it is thick enough. Call Van's and let us know what they say.

[Brantel]

Countersink the hinges, works great, plenty of meat to work with. More meat in them hinges than in that top skin.

[Dave Cole]

The hinges are much thicker than either the top skin or the firewall, neither of which are thick enough to countersink.

I would dimple the thin parts and countersink the hinge.

[pierre smith]

Camloks instead, around the top rear cowl and the two bottom sides (next to the air exit) of the bottom cowl....why? Because Van calls for a .090" hinge pin wire at the top in a .125" hinge, which leaves a .035" gap between the eyes and the pin, allowing cowl motion and grey "smoke: behind the cowl, not to mention the difficulty of inserting/removing the cowl pins and the same difficulty on the bottom.

Hinge pins work well joining the two halves along the left and right and vertically to locate to lower cowl.

All it takes to install camloks is a zig-zag piece of .062" rivetted to the underside of those firewall flanges. Space them 4" apart and use three per side on the bottom.

Regards,

[ArVeeNiner]

Originally Posted by pierre smith

Camloks instead, around the top rear cowl and the two bottom sides (next to the air exit) of the bottom cowl....why? Because Van calls for a .090" hinge pin wire at the top in a .125" hinge, which leaves a .035" gap between the eyes and the pin, allowing cowl motion and grey "smoke: behind the cowl, not to mention the difficulty of inserting/removing the cowl pins and the same difficulty on the bottom.

Hinge pins work well joining the two halves along the left and right and vertically to locate to lower cowl.

All it takes to install camloks is a zig-zag piece of .062" rivetted to the underside of those firewall flanges. Space them 4" apart and use three per side on the bottom.

Regards,

Pierre:

Do you have any pictures of the zig zag piece? Is this something I make or purchase?

Thanks

[dpansier]

Originally Posted by ArVeeNiner

Pierre:

Do you have any pictures of the zig zag piece? Is this something I make or purchase?

Thanks

http://www.milspecproducts.com/RVLancInstr.pdf