Positioning of hulls

How does one determine the proper camber and placement of the outriggers (am i using the correct term here??) fore to aft and top to bottom? Are there any formulas to follow or is it a matter of testing it in the water before a final fit?

Also, what guidelines can you offer regarding the depth of the outrigger hulls? If they draft too much you’ll never be able to ride on only two hulls - is there such thing as too little?? If so, how would one determine this?

…more to come i’m sure! :slight_smile:

Usually answered by the designer of the plans - ie: Cross sections, displacment, and angle of hulls compared to vertical, also depends on three hulls or two, since the main hull of a trimaran will usually (usually) support most of the hull weight until really pushed. Once the main hull (or windward hull is free of water, the leeward float/hull must be able to absorb all of the weight of the boat and retain enough buoyancy to keep from submerging.

Most trimaran plans I have seen have the floats angled anywhere from 3 to 10 degrees. If floats are high off the water, then more angle, if close to the water (when unloaded as windward hull) then less angle is needed.

Again, it is related to the displacement you have designed into the entire boat - so there really is no magic number to answer your question - sorry.

Partly why I recommend building from established and proven plans - otherwise if a home design prototype - you may hit - or miss with buoyancy.

Yeah, i figured it wouldn’t be that easy… so in the design process it’s (simply) a matter of trial and error, experience and solid knowledge of nautical design?? :slight_smile:

I’d like to produce a boat that looks something like the Brossard trimaran or the IDEC tri. I found some great pictures of the Brossard tri and there is a strong resemblance between it’s main hull and those of the one pictured under the 2 Meter Boats section of your photos. I was thinking of combining something like that with floats from one of the more commonly available plan boats - any specific recommendations?

Also i have one (more) question regarding building technique. It’s sort of a variation on how you did your MultiOne. I was thinking of doing the following: Cut out my hull cross sections from bulsa and glue them between blocks of foam (every 2" or 4" depending on the plans and final size.) Then roughly cut them down to profile with a hot wire cutter. The final sanding/faring would be done bringing the foam just down to the balsa bulkheads. Cutting out 2 sets would assure symmetrical hulls and would provide structural stability. (yes i also would have to align them fore to aft, likely with a dowel or something running down the center through a hole drilled in each bulkhead.) Would this add too much weight? Is there no reason to have that much structure? OR, OR is this an acceptable way to build? :slight_smile:

I would then plan on glassing the whole thing.

Would it be valuable to cut out the centers of the foam and bulkheads (like the supports in plane wings) in order to lighten them some? If so i’d need to figure out another way to align them length-wise…