"Stiff" paper on rear stab?

[tpwpny]

My Kit 302 (Cessna 170) instructions call for covering the spar securing the base of the rudder and rear stabilizer with stiff paper (and tissue) to cover the corresponding spars. Just wondering - what's the purpose vs just covering with tissue? Added strength or something else? Seems an obscure area to reinforce vs other parts of the fuselage.

[Bill Gaylord]

I can't say for sure with this specific model, but sometimes cardstock is specified as a filler material, used to fabricate the small area of the rear fuselage that is above the stabilizer, on either side of the v-stab (rudder). Personally I'd prefer to use light balsa and sculpt the missing areas, if that were the case. Just did that on a Cub, that specifies running stringers and covering to fabricate a very small area of the upper rear fuse. Much easier to do with sculpted balsa, where the pieces were pre-covered also.

[tago]

Just finished a Beaver that came with the card stock for that purpose and will go with Bill's method next time. Card stock was hard to work with and the result looks much less than good. Wasn't sure I wanted to sandwich the paper between the fuselage & rudder as instructed, but figured it was included and should be used.
Clean balsa glued to clean balsa would make a better joint wouldn't it?

I think tissue would be ok, the idea being you just need to cover the stringers/spars for aerodynamics. The card stock is probably recommended for any fuselage that ends in a pointed taper. Don't really see that it would serve to strengthen the assembly.

Correct me if I'm wrong please.

[tpwpny]

Thanks to you both. Kit 302 doesn't come with the card stock but to me, balsa seems a better filler next time. I used bond paper and covered with tissue. Still not sure if that buys me any extra strength/ support but next time the tapered fuselage is probably worthy of another solution.

[Bill Gaylord]

It's possible the plans spec cardstock for 2 reasons:
1. Kit makers like to avoid calling for sculpted parts, as much as possible.
2. The filler would likely require laminating some of the kit stock wood, for adequate thickness. In that sense, the plans would be calling for a material not supplied with the kit, unless the builder creates it by laminating.

Both are very simple tasks in this case, and worth making out of balsa. As far as weight is concerned, light balsa should easily weigh equal or less, as it can be hogged out once sculpted, leaving just enough area for gluing. Cardstock weighs.