carcraze

Hi all

I need some advice on sheeting some foam parts. I am getting ready to sheet the flying surfaces and I am trying to figure out if I am doing something wrong here. I have sheeted the belly pan which came out warped. The ends were warped up, while this was not too big of a deal as I manged to pull it all in when I mounted to the aircraft. I then did the turtle deck which warped the other way. This is worse as this deck is removable and since it is mounted to a light ply mount I can not pull it in. I have had to add balsa strips to the under side and will block sand it out to get a flush fit.
I do all of the sheeting with poly glue in the shucks on a flat surface and weighted. All of the sheeting is edge glued prior to glueing due to the heavy curves. The foam parts were all flat prior to the sheeting.

Any advice would be appreciated.
Thanks
Mat

BBW Walt

My Feedback: (11)

When I sheet the decks I cut a piece of 3/4 particle board the shape of the piece being sheeted. With the piece in the shuck, upside down, glue applied, the particle board piece fits inside the sheeting sticking up that will later be flush sanded. I then set patio blocks on end on top of the particle board to get even pressure on the part. I usually take pieces of 3/8ths square stock 3inches or so long and shove the excess towards the piece and pin it down. This keeps the sheeting from splaying away from the deck as the glue expands. Im assuming polyurethane is the adhesive you are using. I have never had a warped piece unless the part was cut warped with the shuck. I do the wings with the same principle. Make sure your bench will support the weight with out taking a set. Hope this helps, Walt

carcraze

That is close to my method.
Yes it is poly glue, these are 3 piece shucks as the decks are hollowed. After laying in the sheeting and then the foam to be sheeted and then the core I weighted everything down. I used 2x3 along the length of the core shuck and weighted that. I then went back and using long straight edges clamped along the outside length at the top to pull the sheeting in to keep it from bowing out away from the piece to be sheeted while the poly expanded.
Hopefully if I do both sides of the flying surfaces at once and maybe get some flat pine to weight on top of they will turn out straight.

Mat

BBW Walt

My Feedback: (11)

When you do the wings its better to have a piece of stiff plywood or particle board cut the same size as the parameter of the shuck. It needs to be one piece so the weight is compressed evenly over the entire panel. If you do this with at least 150lbs on a flat bench, both sides at the same time, you will end up with a perfectly straight wing. On the 40% planes I use close to 300lbs on each wing. I lay up one wing, top and bottom at a time. I somewhere have some photos of this set-up. If I can find them I will post it. Milk jugs filled with water works well for weight. I use patio blocks. Walt

carcraze

Good information Walt. This is a 42%, I doubt my bench will handle the weight. I thought I would check the ceramic floor for flatness in my back room. If it is flat I will do the weight there.
Thanks for the information.
Mat