Sponson construction

[will_myster]

What would be the approporate density of foam for a 7 cell rigger? I would also like to know if i used really dense foam and cut the center out after i glue the balsa and ply on to it then glue the top back on? anybody tried that?

[Paul]

Hello Will,

I wouldn't bother cutting the foam out of the center, the weight is next to nothing and provides flotation. If you want to build it really light make it 100% hollow. Oh, I use pink foam insulation from Dow Corning.

Paul.

[will_myster]

well i can see a small weight gain thats all. Plus what can be lighter that air accept helium. A bit of foam will obviously been in them incase i crash and burn. :D. At the moment i treating my second build of this design more carefully, as it it its vey strong and i want to shed some unneesary weight which is that foam.
my current rigger weighs 150 grams bare. and i want it to me about 135. At the moment im being stingy with the weight thing, so dont tease me. FE weigh enough as it is with out the help of dead weight:cool:

[Paul]

Hello Will,

I just finished a new scale hydro that weighs 105 grams, it's construction is 1/16" balsa covered in 3/4 ounce fiberglass and finishing resin. That includes foam flotation in the sponsons so my suggestion would be to use alternate materials, my boat is solid enough to drive nails with so that should get you thinking.

Paul.

[will_myster]

i must say i 105 is a good weight, when i told the forum of my rigger weighing 150g bare they told me i could be sacrificing strength but. I followed the method of Gary Peruesse and made sure iddint skimp with any thing to with power transfer and disipation. So the motor mount is strong and so is the area that is attached. Flex cable is 1/8" and should be able to handle what i throw at it. At 1050g fully rigged with 7 cells i think i did a reasonable job. I said "i think" :D