1.   Triangulating the moment in the lw portion of the beams would reduce their section considerably.    We use a 60mm thick wall stainless tube as the compression brace on the 18m proa.  That means if they do not have the desired clearance of around 1m then they will not add much drag when ploughing through waves.  

The height of the stubs should be reviewed as well.  Mast beams and rudders have the big loads so you need to look at how these are resolved through the hull, beams and bearings.

2.  I do not agree with all that is stated on the wave piercing bow link.  None of the bow profiles shown would be my preferred.  My preference is  large waterplane at the bow, flat bottom with rocker, low stem and peaked deck.  A fine stem reduces the volume of attached flow and consequent spray, which could be further reduced by a spray rail.  

Under static conditions the longitudinal metacentric height is as important as reserve buoyancy in avoiding pitchpole - this condition is when the boat is almost stopped then gets large, rapid increase in sail drive, forcing the bow down.  KMl is a function of waterplane shape and overall length.  At speed other factors as I previously described help avoid pitchpole by providing net dynamic lift.

I do a lot of experimenting with pedal boats.  The linked video clip shows the latest V16-62 hull:

The hull is 6.2m long and weighs 5.3kg.  Some of the weight saving is achieved by reducing freeboard.  If it had a round bottom and flat deck it could be easily driven deeper into waves even under pedal power - I know from comparative testing.  With the flat bottom, large forward waterplane, mild rocker and peaked deck it rises easily when driven into a wave despite the low reserve buoyancy.  

You cannot achieve the same extreme reduction in reserve buoyancy with a sailing boat because the CoE is much higher than a pedal boat but the same factors apply.   This aspect is worth detailed analysis to see how much reserve is actually required and what weight can be reduced.

3.  Yes - Foam will add weight!

4.  I have asked Nol Twight (Campaen) if I can post photos of the rudder mount as it gives an appreciation of the forces involved.  Rob said he has devised similar system for the new boats so there might be some sketches of that.

The hydraulic steering was implemented with orbital motors/pumps in a closed circuit. The ones used weighed 7kg each - 4 are required.  They can carry the wheel and do not need a gearbox although we retained the existing gearbox to keep circuit pressure low thereby allowing low cost fittings.  The hydraulic pipe only needs to be 10OD and you would need some hoses to get the flexibility across the moving joints.  

In my view the steering system needs continuous rotation with unidirectional rudders.  There is no point in aiming for a fast boat using high drag rudder sections.  Cavitation becomes an issue above 20kts so the rudders need careful attention with that in mind.  

5.  The bury is the depth of the stub or mast inside the hull assuming a bearing at the deck and a bearing at the bottom.  A revised example assuming pod and windward hull now total 1000kg (10kN) and the beam length is 6m.  The righting moment is 60kNm.  If the bury is 1m then the force in the top and bottom mounting is 60kN.  If the bury is 2m the force is 30kN.  The stub needs to be strong enough not to crush at the loading points under those loads.

If your beam is 200mm deep then the opposing forces in the top and the bottom faces of the beam to produce a moment of 30kNm are 150kN if the moment is shared equally through the beams.   It needs to be a very strong section not to crush under those forces.

If the hull avoids hatches between the connection of the two beams then the stress associated with 30kNm is trivial if a triaxial cloth is used.  Rough calculation is that 200gsm triaxial cloth would give a safety margin for that torque for the hull dimension being considered.   It could be even less with increased hull section area between the masts.

Another aspect on this is that the span efficiency of the sails can be increased if they sweep the deck.

Rick

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