I understand nobody give much about what I say or about my maths but here goes anyway :

The aluminium masts and beams used on the F16 (Halve of which I designed) use 1.6 mm to 2 mm thick walls. Only Bimare has used 3 mm thick walls on the beams at one time; John Pierce used 4 mm on his Dolphinstrikerless Stealth which was a predecessor to the F16 (but not full F16 compliant) at the time.

My point, 3 mm thick (aluminium walls) is NOT a good rule of thumb for F16's; it overestimates the parts used in real life by 50 to 85 %; overestimating the associated weights accordingly.

I have yet to see a 1.6 mm thick wall on a carbon mainbeam. In my experience with stunt kites I found that carbon beams are relative easy to break when point loaded, especially when the loading is perpendicular to the carbon fibres. This happens at several points along the mainbeam (bolts, transition from hull to overspan, mast step). Basically the glue matrix cracks up allowing movement of the fibres which then break one by one to finally break to whole element there locally. The thinner the walls the easier it was to break carbon tubes that way. We used to reinforce the tips of the carbon tubes for this reason. I strongly suspect that the underlaying layer of timber layer will go some way of improving this.



Density of extruded aluminium is 2710 kg/m^3 (for 6061-T6)
Density of carbon laminate is what ? 1850 kg/m^3 (from top of my head)
Density of Gaboon ply is what ? 650 kg/m^3 (from top of my head)

This means you may not have a carbon wall thicker then 145% of the alu wallthickness if the criterium is to arrive at equal weight of less. Going from 2 mm alu wall to 3 mm carbon wall is an increase of 150% for example.

With respect to ply : 417% increase in wallthickness will do the trick. Therefor a 6mm thick middle layer of this ply (as adviced by J.R. Watson) will weight the same a 1.45 mm thick aluminium wall already (= 90% of 1.6 mm thick walled alu mast section). So here to you need to cut down if any significant weight savings are to be achieved.




Only if the mainbeam is dolphinstriker less; otherwise it would seriously consider making both beams the same. 450 kg of mainsheet pull in the middle of the rearbeam is alot of loading as well.

It seems from the experience I have that the rule of thumbs supplied here by J.R. Watson are too crude to be of much use to an F16. Although they may well be accurate for larger vessels like yachts and Tornado's (don't they use 3 mm thick alu beams Rolf ?). Mind you F18 masts use 1.6 mm wallthickness on the masts as well. Tornado alu masts use 2 mm wallthickness and the A-cat carbon mast I have a cut-off from, uses 1.2 to 2.0 mm thick walls (pure carbon) depending on where you measure it. This is an Australian composites mast and was used by Gary on Altered when that boat was still a mk5 Boyer A-cat.

I hope this info helps.

Wouter