Small trimarans under 20'

shipwright;
Trawl through this build blog for some beam socket connection ideas.

http://www.aquidneckcustom.com/blog/?p=148

 

I'm not trying to sway you one way or the other but you might find the following article of interest. It's by the Gougeon brothers who had a strong background in double and triple diagonal type wood/epoxy boat construction and also strip construction. In a project like yours with a short LoA weight is very important it's the difference between a good or a disappointing end result.

https://books.google.com.au/books?i...QgZMAA#v=onepage&q=trimaran adrenalin&f=false

My K25 trimaran project is built in double and triple diagonal mainly as I was attempting to reproduce a similar and historically accurate reproduction. It's reasonably lightweight but I think I could do as well or better in strip plank paulownia with less work and quite possibly a lighter solution. I've opted for wood/epoxy and a few concession to modern techniques in the construction but it's still basically the same idea. If I was starting from a clean sheet and not attempting to reproduce the original style of construction I'd definitely go for a composite strip plank. Probably something along similar lines to Adrenalin with a strip plank and light carbon uni for crossgrain strength.

 

For some reason the full article doesn't come up with my link. If you search on formula 40 trimaran adrenalin you should get the full article.

 

hull planking

Redrueben:Thanks for comments, I have strip planked many hulls, usually you have to glass outside and inside, strip plank would be 10mm plus glass.
diagonal planking 2x3mm ply-glass externally. Built many of our skiffs these were usually 2x1/10" cedar, varnish only in-out. I can still get red cedar ply.
were I to strip plank in timber would use Port Orford Cedar, but have done
successfully using airex foam stripped, hulls very stiff and certainly quick to assemble.
I have a couple of cubic metres of pawlonia in the shed but would be reluctant to strip a high performance hull with it ,it is very carroty,just snaps across the grain as in timber shake. However the die is not yet cast.
Shipwright

 

Planking

Corley thanks for interest: re different forms of planking. I built the first of Crowther Big tri,s Captain Bligh-this was done in double diagonal ply frp outer, this boat was actually prior to Gugeons west system in retrospect she could have been built a lot lighter ,not so much in hull structure but in fitout (fairly spartan) and the great cross wings,.post launch and some racing we went looking for weight,large centreboard origolly on Oregon, was replaced with a westrn red cedar immediate effect. usually if you have done the hydrostatics and allowed sufficient buoyancy to carry projected hull mass
you will not go far wrong. Another aspect of this project is cost as a prototype this is always in the back of your mind.

 

Planking

Corley thanks for interest: re different forms of planking. I built the first of Crowther Big tri,s Captain Bligh-this was done in double diagonal ply frp outer, this boat was actually prior to Gugeons west system in retrospect she could have been built a lot lighter ,not so much in hull structure but in fitout (fairly spartan) and the great cross wings,.post launch and some racing we went looking for weight, large centreboard origonally in Oregon, was replaced with a westrn red cedar immediate effect. usually if you have done the hydrostatics and allowed sufficient buoyancy to carry projected hull mass
you will not go far wrong. Another aspect of this project is cost as a prototype this is always in the back of your mind.
Later I built a prototype 7m fast inboard boat in airex strip planks was quick and effective bulld, the down side was having to glass the inside ,it was still lighter than the polyester production hulls, the important thing is not to have tunnel vision in design ,look at all aspects as every project is different.
Shipwright

 

Do you have a target displacement in mind for your trimaran?

 

Displacement

Corley: around the 450kg.
been investigating costs re ply versus strip plank.
only way I could afford strip planking is if I machine it all myself.
Strip is quicker but as the time is mine not to concerned, from previous boats should take 40-50 hours.
Just came to memory the SLSA Surf boats were all diagonal planked till they went to FRP. Strength and weight were always primary concern, scantlings were usually silver ash.

Shipwright

 

That seems a good target displacement. Looking forward to seeing your project evolve.

Cheers.

 

Fast Tri

Doug Lord: Re fast tri. Hi performance, This is not an impossible scenario
but take my position coming out of a performance cat, at 76 its killing me
so the tri is the next logical step. scenario is 2 adults 2 grandkids who thrive on speed, stores and equipment for overnight camping. Sea conditions in Moreton Bay good day 10-15kn, 1m wave, off day is solid 20kn+ wave to 2m,would not be surprised if they did not leave the beach
The comparative cats 16-18 Hobies great boats but put these loadings on them
and all of a sudden your not looking to bad and I would like to think they would have to keep up with me. The sea is a great leveller ,if you do not design for loads and sea conditions. tripping around the web there are quite a few really hot tri,s that would give a cat a go. one advantage of the tri is it is a fairly stable platform you can put a pretty big sail plan on to suit. Hydro foils have designed and fitted for our power cats for years ,but to fit them to a sail boat in Moreton Bay would be suicide.
Have attached an A-Cad file,3D of main hull. could not get the pdf file to load

Merry Xmas to all Nelson

 

hydrofoil tri

Nelson, I don't know anything about Moreton Bay-why would hydrofoils be suicide on a sailing tri?
Sorry, but I couldn't open the file you attached...
Merry Christmas to you and most everybody on boatdesign!

Ocean going foil configuration on Maserati-similar to my much smaller Fire Arrow design( http://www.boatdesign.net/forums/mu...f-righting-trimaran-test-model-36058-164.html ) :

 

All the sandbanks in Moreton Bay make for interesting sailing hitting one at speed with a float foil would be exciting but the crunch and ensuing repairs less so. I think you are right shipwright stick to your vision keep the boat simple it's easier to design and cater for loads in a main hull daggerboard and rudder.

My only observation (and I know it takes the concept out of this thread) is I'd go a touch longer making the boat even say 23'-25' will improve the motion and give you some more displacement to play with and room for a nice cockpit while maintaining fineness ratios. As you would know most trimarans turn out overweight so it's good to have a bit of displacement to play with.

 

Corley, so the problem with Moreton Bay is widespread very shallow water? You don't need more than 3-4' maximum for a foiler off the foils?

 

Widespread and very mobile sandbanks. Lots of shallow water similar to what they see in the Everglades Challenge.

 

I was trying to find out more about Moreton Bay and I ran across this:

"Sailing on Moreton Bay-Redcliff in Moreton Bay"- if this is real it seems to show a lot of boats in a pretty big area? Is this really Moreton Bay? Wherever this is it appears like a damn good place to sail.....particularly for a 20' or so foiling trimaran designed for it.
Anyway, it looks like plenty of water around Redcliff but the map looks like the sandbanks would be at the other end of the bay?
https://www.google.com/webhp?source...58827455928127,0.25281219769033214&oz=9&qop=1

I found this but it sure doesn't seem to go with the picture or the map showing two clubs at Redcliff and others further down :
Moreton Bay is filled with sandbanks from sand supplied via littoral drift along the coast of Moreton Island. The field of sandbanks extends across the entrance to Moreton Bay and evolved after sea level reached its present position, about 6,500 years ago after the last ice age. Between Tangalooma and Skirmish Point on Bribie Island are the Middle Banks, Central Banks and Western Banks. From north of Moreton Island towards Caloundra are the Yulle Road, Spitfire Bank, and the Salamander Bank, amongst others.
Amity Banks are found just west of Amity Point, while the Moreton Banks lie to the west of the southern tip of Moreton Island. These banks can be hazard for marine navigation because they are constantly changing due to tidal currents.