Wasn't there someone who made an into a trimaran?
I was mulling the far fetched idea of using two paddle boards for amas, or custom pontoons that could double as kayaks. The trampolines would add welcome deck space and it solves the issue of what to do with the dinghy once and for all. There are issues to consider.
In nice weather you'd sail with no ballast. In bad weather you'd fill the tank for added stability. It would be easy to detach the AMA hulls for exploring. Two dinghys, for a couple. Since the boat already sails passably well, even if you lost both AMA hulls, she would not be crippled. File this one under the IX files ;p
Ix
What about getting an old Prindle or something and custom making arms to attach the hulls. Then, by taking the original trampoline tubes with you, then you'd have a speedy cat to sail around instead of a kayak to paddle when you got to your anchorage.
I am just thinking you'll need more length and buoyancy than some kayaks would provide, and (I totally have no idea if this is true, because I can't find two tri designers who agree on this in a 5 minute Google search) would think that you would want an ama length of at least 18 - 20 feet to go with the 26 feet of the Mac.
RGF wrote:Didn't Mad Mike's Mac X have fold out amas/floats of some type?
Although, I think Mad Mike ditched the 50hp engine for something much smaller.
Do you mean for fear of tearing them off?
Mad Mike
Had 2 compressed air ammas that could be deflated when not in use , he also went with 2 10 or 15hp eng so as he always had a back up power unit
The math to determine the proper size of amas is pretty easy:
Displacement of ama x length of aka= torque resistance. Units matter, so if you use lbs. for displacement and feet for aka length you get ft.lbs. of torque resistance to heel.
We know from Macgregor testing that it takes 135 lbs of force at the top of the mast to pull a 26M over to 90 degrees. 135*33 (top of last to center of rotation=33) =4455 ft lbs of torque. So divide 4050 by your proposed aka length to determine the necessary displacement of an ama needed to prevent knockdown.
Now if we assume a 700 lb fully submerged displacement for a 12 foot sit-on-top kayak based on a 350 lb carry capacity at 50 submerged, then you would need a 6.3 foot aka (from center of rotation) to meet this requirement. Also note that the aka has to be rated to withstand deflection of 4455 lbs. at 6' as do the mount points. Anyway thats a short aka so basically any kayak strong enough to withstand the forces will do the job.
So certainly possible. Look at aluminum tube schedule to find a 10' deflection rating > 5000 lbs. which will give plenty of Margin, and use same sized pillow blocks to mount it. Take the tubes all the way across the boat from aka to aka for best mounting strength, and have a pipe bender bend them in a smooth sweep to match your mount point requirements for an above-deck mounting so you don't need to compromise the hull. Mount them aft-of-midline to decrease round-up tendency.
Keep your total beam < 14 so you can pull into slips without disassembling.
I'd have to build amas that could be used as kayaks.
Also I'd want the folding system to be drop dead easy. Or msybe be able to assemble on a beach after launching. No piece could weigh more then 70 pounds. I could lash the cross beams in place using anchor points glassed onto the hull sides. Cross pieces would have to fit along side the boat on the trailer. Amas could be stored on deck. I don't envision this thing to be very wide. AMA hulls would be just six feet away from the boats hull. The boat could even still be used without them.
I want more strength then those engine mounts. I can make it strong enough. The lash on cross beams, made from aluminum truss type beams should be very strong. Probably overkill. Cross cables could give support for fore and aft bending forces such as may happen if you hit a dock with the front of the AMA hull. Lashings would be multiple wraps of dyneema. The lashing points would consist of straps of fiberglass applied from one side, going under the bottom of the boat, to the other. They would end where the hull chine is. That system would be very very strong.
If the boat did wind up inverted. You could remove one of the AMA hulls since it's designed to remove easily for use as a kayak, and let the boat right itself. If you filled the ballast before the storm hit you the boat should be very stable.
Someone else would have to do the math as far as stability without water ballast.
That kayak would not work. 14 feet is the min , and it needs to be built for the task.
Ix
into a trimaran? 
