Included here are pictures of the hard point for the control horn. There are two ways to do this conventional and with expanding foam, I prefer the expanding foam but most people do not have the experience to do it. So I’ll describe it first than do the conventional which is what I will use on this plane. My reason for using the conventional method on this plane is that the TE of the flaps have a gap between the top and bottom sheeting instead of being glued together. If the foam gets between the TE and the covering it will bubble out. So the pictures of this are from Bills plane which is a H9 ARF P-51D.

The two part foam is available from tower I’ve inclused a picture of it. I cut and glue in the ply (and use marine ply, not lt. Ply), marking the covering side for where the ply is. When the flap is all buttoned up drill two ¼ in holes in the flap end cap bay to fill with foam. One hole is a fill hole one is a pressure relief, never pour into the pressure relief hole. If you plug both holes the pressure will blow the flap apart so it is good to practice first or get someone with experience to help you. Anyway as the compartment fills the foam will start to come out of both quarter in. holes. Leave it and let it harden, the next day the overflow will cut right off easy.

The conventional method is to put the ply down then put balsa between it and the top flap sheeting not much is needed, I used scrap from around the shop I believe it is 3/32. When putting the ply in you have to know where the hinges are going because if one is going in the same bay as the control horn the ply has to be pushed back to allow the hinge block to glue directly to the bottom sheeting. I’ll explain why it is ok to put the hard point so far aft later when it is time to hook up the linkage.

Using an X-acto knife and razors I shaped the wing TE cap and flap LE cap to fit into place. A final sanding was used to make sure it fits correctly. The end cap needs to fit with just enough force to hold it in place while the wing is held LE up and TE down, or the flap held TE up and LE down. If you tap it while in that configuration the end cap should be loose enough to dislodge or drop out. The purpose here is simple; if it fits tightly it will deform the sheeting and ruining the seam between the flap and wing. It must be inside of the top and bottom sheeting, no part of the end cap can extend forward of the LE of the sheeting of the flap or aft of the wing TE. Also when removed the open end of the flap spread ( this is the end closest to the root) this is typical of thin wood like I have here (not the case with the H9 and Kyosho). When you look at the flap end caps notice that there is a gap to the sheeting, this is the only area I plan to squeeze the wood to CA it. Accepting there will be some miss match there.

Joe