F-421 and panel tilt

[FinnFlyer]

Trying to fit F-421 (forward top skin). I'm having a hard time figuring out whether to cut rear edge of F-421 in a shallow circle to make it fit to the 7 degree slant (1" over 7 7/8") per dwg 26.

Per dwg 41 it looks like the slant is only 2 - 3 degrees (3/8" over 7 7/8").

Per dwg 27 it looks like top of F-421 is at 90 degree to rear side of F-421 and F-421 rear edge does not need to be cut.

If I do cut F-421 then the F-421A strip won't lay quite flat and I'll have to cut forward canopy skin to match the cut F-421.

If I don't cut then I'll have to let forward tip of canopy and its fairing overlap F-421 (extend past forward canopy skin) a bit and bend the forward square bow of canopy frame back a bit.

https://drive.google.com/file/d/17iW...ew?usp=sharing

I hope there's still some RV-4 builders looking here.

Finn

[Lufthans]

Hi Finn,

Sorry, not a builder. If you want, I can measure the tilt of my panel. I believe however that it is simply 90 degrees to the forward part of the top longerons (which themselves of course slope downward somewhat, so maybe this is where the conflicting numbers for the slant are coming from?).

Check this image, and especially note the bent square tube on our canopy frame. This tube sits very close to the panel. The piece that is sticking out forward of that is actually on top of the rim of the panel and is equally wide all along the square tube. I think that alone should give enough clues as to where to place the panel.



Check the row of screws on the forward lid, and how this is parallel to the forward lip of the canopy frame:



These screws go in the forward rim of the panel.

Hope this helps and good luck,

Hans

[FinnFlyer]

Thank you Hans.

Actually the slope of the longerons are about 3 degrees (1 5/8" over 28 9/16") according to plans.

From your second picture I see that your canopy forward fairing do extend out over the forward skin (out over the screws holding the skin to the panel).

And in the October issue of Kitplanes page 14 I see what looks like an RV-4 with open canopy that also have a rounded forward canopy fairing.

So maybe a 3 degree panel is not uncommon and I should not cut F-421 and instead bend back the square canopy frame tube a bit.

Finn

[F1Boss]

The top skin is a rectangle. So, the top if the firewall leans fwd a bit too.

If you want to make your plane to updated specs, you can add 1 3/4" wide.032 strips along the fwd fuselage to allow for a butt joint between the side skins and the top cover skin. Looks and seals a lot better that way, and no long row of holes in your fwd longerons!

Pics available if you send me a PM with your email.

[FinnFlyer]

Thanks Mark!

So don't trim the rear edge of F-421?

As far as I can see, I do need to trim it at the firewall and along sides.

Seems that per plans the firewall is vertical.

https://drive.google.com/file/d/16AG...ew?usp=sharing

https://drive.google.com/file/d/1e04...ew?usp=sharing

Finn

P.S. I'm sorry but can't figure out how to make pictures show up in postings.

[Lufthans]

I can see how these drawings can be confusing, yes.

Just to confirm that the panel is in fact perpendicular to the forward top longerons.... (just came back from the airport)

Hans

[F1Boss]

Originally Posted by FinnFlyer

Thanks Mark!

So don't trim the rear edge of F-421?

As far as I can see, I do need to trim it at the firewall and along sides.

Seems that per plans the firewall is vertical.

Finn

P.S. I'm sorry but can't figure out how to make pictures show up in postings.

It is far easier to cut the cowling to match the 421 skin if the 421 has a straight edge. In fact, if you tilt the upper cowling to 90deg from the fwd longerons, both cuts are straight. Easy to fit that way, and your attach hinge will also be straight if you build it that way.

If you make the upper firewall vertical, both the cowl and the 421 skin will have a curve where they meet. Not easy to get right! AND dang near impossible to get the attach hinge right.

I use doublers and nutplates in my builds - but those are Rockets, and just a bit different.

I also like to push the Easy Button!

[AX-O]

Something to think about.

If had t do it again, my panel would end up tilted. Using the standard design places some information on my screens not easy to see. The perfect way would be to make the panel perpendicular to our line of sight when we look down at the center of the panel.

Trying to figure out how to retro that now but it is not easy. I should have done it from the begining.

[FinnFlyer]

Originally Posted by F1Boss

If you make the upper firewall vertical, both the cowl and the 421 skin will have a curve where they meet. Not easy to get right! AND dang near impossible to get the attach hinge right.

I use doublers and nutplates in my builds - but those are Rockets, and just a bit different.

I also like to push the Easy Button!

In my case that would mean tilting the firewall top forward 1", probably too much. So I have both trimming of forward F-421 edge and cowling to look forward to

If my forward fuse side skins weren't already riveted to longerons I would definitely go with the strips with rivnuts. For one thing, one could space the screws evenly without having to fit them in between the bolts and rivets.

Finn

[FinnFlyer]

Originally Posted by AX-O

Something to think about.

If had t do it again, my panel would end up tilted. Using the standard design places some information on my screens not easy to see. The perfect way would be to make the panel perpendicular to our line of sight when we look down at the center of the panel.

Trying to figure out how to retro that now but it is not easy. I should have done it from the begining.

Right. Hard to retrofit. In addition to what's behind your panel, you'll also have to consider the canopy 3/4" square bow that would then hide more of the panel and who wants to redo the canopy frame, skins and fairing.

Have you considered tilting your screens?

Finn