TX18+10%. Change of material thickness for ribs

[Vundu]

Hi guys.
Busy installing the stringers on my Build. Running low on 3/8ply for the ribs but have lots of 1/4 and 400gsm glass. (I would have to import ply which is a pain).

I have adjusted the ribs placement from 1005mm to 830mm so adding 2 in the build.

My question is: is it safe to substitute the 3/8 ply for the stringers with 1/4? If so but the safety is marginal, should I change the glassing schedule to compersate?

Any advise welcome, thanks.

[OneWayTraffic]

By ribs I'm not sure if you mean stringers (bow to stern) or frames (port to starboard.)

In either case I would laminate your 6mm plywood to make 12mm or 18mm whatever the requirement is. That seems stronger for the weight than adding a lot of glass. Since you are building an upscaled boat I would not reduce the scantlings anywhere under any circumstances. The plans have some margin of safety but you are already eating into that with the scale up.

[Vundu]

Thanks onewaytraffic. I do mean frames. I agree the +10% is already adding alot of potential force, that's one of the reasons I added 2 frames to reduce spacing. Plans call for Approximately 920mm spacing, add 10% is over 1000mm. I reduced to Approximately 830mm.

[Jaysen]

Double up the thinner ply. Stronger and lighter.

[TomW1]

If you have enough double up the 1/4" then you would not have to glass the frames just coat them with epoxy which I believe is what the plans call for.

Tom

[Vundu]

Thanks for the advice. Greatly appreciated! I will go ahead as you have all suggested.