Cowl fit?

[RVG8tor]

I am at the stage of setting the top cowl to the spinner, I already made sure the top and bottom form a nice 13" circle centered on the inlets.

I measured the center of the aft part of the cowl but when I try to set that at the center of the fuselage it makes the gap on the left side between the spinner and cowl larger than on the right. If I just let the cowl move to match the spinner on the left and right the center line of the aft part of the cowl is off from the center of the fuselage. It looks like I have plenty to trim, so no issue there.

So what is more important having the aft part of the cowl centered on the plane of making the gap around the spinner even? The spinner face is canted slightly due to the engine mounting so I am inclined to mate the spinner face and just take what I get on the aft fit.

Thanks for any help!

[jthocker]

Here's what has worked for me Mike. Find a piece of plywood 3/16" thick and maybe 6"x 14", and slide that between the cowl and the spinner back plate. Push the cowl up tight to this plywood piece, trapping the wood between the cowl and spinner backplate. This will set your spinner gap. This is assuming we are working with just the top cowl. Then at the aft side make the distance the cowl side overlaps the top skin the same on both sides. Don't worry about the centerline. Just center the front of the cowl on the spinner, and make the overhang on the sides equal and you will be good to go. Then trim the aft edge, drill a few #40 holes in the firewall hinge, clecoe the cowl to the hinge.
Then clecoe the bottom cowl to the top at the spinner, use some strong duct tape to pull the aft side of the bottom cowl up tight to the fuselage, letting the top cowl overlap. Trim the aft edge of the bottom cowl, then drill a few holes in the side hinges and clecoe in place.
Good luck!

[RVG8tor]

Originally Posted by jthocker

Here's what has worked for me Mike. Find a piece of plywood 3/16" thick and maybe 6"x 14", and slide that between the cowl and the spinner back plate. Push the cowl up tight to this plywood piece, trapping the wood between the cowl and spinner backplate. This will set your spinner gap. This is assuming we are working with just the top cowl. Then at the aft side make the distance the cowl side overlaps the top skin the same on both sides. Don't worry about the centerline. Just center the front of the cowl on the spinner, and make the overhang on the sides equal and you will be good to go. Then trim the aft edge, drill a few #40 holes in the firewall hinge, clecoe the cowl to the hinge.
Then clecoe the bottom cowl to the top at the spinner, use some strong duct tape to pull the aft side of the bottom cowl up tight to the fuselage, letting the top cowl overlap. Trim the aft edge of the bottom cowl, then drill a few holes in the side hinges and clecoe in place.
Good luck!

Jon,

Thanks for the tips, I eventually go to the same place. My overhang after cutting and fitting which took hours (mm at a time) is about 1/16 different from the two sides so I will take that. I will use the reminder of your tips to work the bottom cowl. Of course I built the "A" model so I will have that to contend with. I have cursed not doing the tail wheel many times through this build!!

Cheers

[robertahegy]

Sometimes getting the cowl lined up and getting an even space behind the spinner is not possible due to the irregularity of the cowl mold. You can lay in some cloth and resin in the inside of the part of the cowl that is too close and maybe lay on some cloth and reesin on the part too far away. Then you can sand the area to create the nice smooth gap you want. That's what I did. Few builders have ever gotten a good fit without doing some kind of "bodywork" on their cowls. Go for the good alignment first and then correct the gap behind the spinner once the cowl is properly fit to the airplane. My cowl had a huge underbite before correcting it.

Roberta