Hi,
i need some advice on how to make a tunnel hole for inserting a 1.5 mm carbon rod in a sheeted foamcore stab.

Just heating up a metal rod with open flame does not appear to be a great solution, as the wire would cool quickly and i would have to insert the wire several times making the hole larger at the beginning...

is there another simple way to do it without making/ buying sophisticated and expensive hardware?

Thanks for any tips!

How thick is the stab?

I know a guy who cuts slots for half-length ribs that contain holes for the tube. Then a slot for the tube, then (with the tube in place) epoxies the ribs into the foam. When cured, he fills in around the tube.

Might work for you. Good luck,
Dave Olson

Hi Mike, it's a "shaped" stab so it varies from about 1/2 " to 3/4".

It has been arched from prolonged storage. I've straitened it since, but it does have a bit of memory in it, thus the need for these carbon braces.

I want to drill through the rounded balsa tip and use hot straight wire for the inside styro, than gorilla glue the rod in.

Ok, if you're going through the balsa tip it'll be a piece of cake.

Drill a 1/16" hole through the tip. Assuming that the tip is about 3/8" to 1/2" wide, the hole will be long enough to act as a guide.

Just heat the rod and push it through as quickly as it will let you. You may need to repeat it a second or even third time, but as long as you move quickly you won't open it up too much - and since you plan to use Gorilla Glue, it will expand to fill any gaps.

Also, once the wire stops, pull it out quickly before the foam cools and glues it in place.

After you have the hole ready, put a few drops of water in it and run the wire in and out a few times to moisten the hole (Gorilla glue needs moisture to work).

An alternate method would be to cut the end of the wire with a cutting pliers - this will make a sharp end on the wire. Then put the wire in a drill and drill it into the foam.

Also, you could take a piece of 4-40 all thread rod work it back and forth like a file to bore a hole

Just a comment though,
IMO 1.5mm cf seams useless to me in the middle of 1/2"- 3/4" foam, the foam will flex around that small piece. I'd cut a 1/8" slot in the bottom and glue in a ply brace,

good luck

Good point

Job done!

Thanks 4 your comments, I went with 2.5mm rods and drilled 2 holes just underneath the balsa skin on opposite sides (not in the middle). Thus made sort of cf spars. It is straight now[8D]

Cheers,
V.