On Sat, 11 Jun 2016 02:14:42 -0700 (PDT), wrote:

On Tuesday, January 30, 1996 at 12:00:00 AM UTC-8, Scott Vose wrote:
Has anyone thought about converting a Macgregor 25 sail boat to a Tri
hull? I wonder if you could buy a old Hobie 16 or Hobie 18 and modify the
Macgregor to attach the Hobie hulls to each side. Removable for trailering
would be nice.
Would this work? Would the performance improve to something like a F24?

The reason I am thinking of this is that I have a old (1972) Venture ( a
Macgregor) in need of work. I think it might be fun to try out.

Scott Elde

You absolutely can build a trike as described. All the ratios being batted about by the armchairs is just hot air. The MacGregor 26 uses water ballast in the bilges for righting moment under sail but it motors with these tanks dry. With twin 60hp outboard motors, the boat will easily hydroplane and exceed speeds of 20 knots. So, skip the water ballast and the motors by adding an ama (outrigger hull) on each side.

Leave the daggerboard just the way it is. It extends over four feet into the water so you will get plenty of lift off of it while beating windward. Pull up the board for runs and reaching.

The actual design you will need is pretty important. Each ama probably needs to be over 100% of the boat's displacement for safety considerations. Digging in the lee ama in heavy wind is a once-in-a-lifetime experience. But, the physics of keeping its nose out of the water ain't all that tough.

You're going to need really good aka design though. Maybe fasten horizontal tabernacles that allow you to pull out the akas for transport on a trailer or traditional monohull sailing? I would not want to bore through the freeboard unless absolutely necessary. Check out the Corsair designs for some ideas. Now, if you lose the lee ama under sail you're gonna have a story that you will NEVER forget.

Sure, it's not going to be as fast as a production trimaran - but it would be one hell of a lot of fun to sail. I'll bet you that the main hull will plane quite easily on a broad reach.

For what ever it is forth I saw a tri built by a guy that specializes
in building Wharram Cats and like the Wharrams it was just tied
together. http://wharram.com/site/gallery A modification of this
scheme might work to hold the outboard hulls in place temporarily to
see how the design will work.

--
Cheers,

Bruce