Brine Shrimp Catamaran

[Kelldog]

Hello Everyone,
I just purchased a Catamaran that was designed by Thomas Firth Jones. I would ask him the questions that I have but he is no longer with us. So the next source is this forum as I know there are many knowledgeable people here who may answer a few questions. The design is a 23.4 Brine Shrimp. The one I just acquired was built in 2000 by Shelby Craghead. I am not sure if he is around now.

Question 1; I would like to lengthen the hulls by 3 feet to 27.4 feet. Where would be the place to insert the 3 feet? The section just before the aft beam? The section forward of the forward beam? Or, right in the middle of the hull/cabin.

Question 2; Mast height per design is 27 feet long. (I have the plans that came with the boat.) Would I need a taller mast? (I think so)

I have known of this boat since 2005 and Have seen it for sale over the years. It has lived a few lives. I have read Mr. Jones books and he is respected in the multihull community for his contributions to the affordable multihull self-build genre. I look forward to any feedback on my questions. I know this is not the "norm".

Thank you,
Kelly

[Cavalier MK2]

Extend it right in the middle, see how it sails. I'd think about a mizzen rather than a re rig.

[Kelldog]

Thank you for the input Cavalier!
I do prefer a sloop rig though.

[44'cruisingcat]

The middle is probably the most difficult way to extend, you'd need to remove the rig, and buy longer shrouds, possibly lengthen the boom, or alter mainsheet attachment, etc etc etc... Everything would need to be very strong too, to handle all the structural loads.
Simplest is to lengthen the transoms, but only of real benefit if the transoms are well immersed with the boat normally loaded.

[Kelldog]

Thanks 44' cruisingcat,

I forgot to mention in my original post that this boat is on a trailer and fold ups. I will be storing it for awhile to work on it. I know that if I add to the middle section I would have to have more sail area, more rigging, etc. When the time comes I'll be prepared for that. The boat weighs 1,200 lbs with a payload of 1500 lbs. I imagine a hull lengthening would add to those numbers as well.

[Cavalier MK2]

Structurally it is the easiest way to add meaningful load length and blend it in with the lines. A 4 foot transom extension on a 23' boat isn't going to help much. Brine Shrimp isn't far from a Wharram and when James lengthens a design on request the middle section is where it goes.

[44'cruisingcat]

Makes sense. But it is a lot easier to add to the middle at the design stage than it is to an existing boat.

[Kelldog]

Easier indeed! My inspiration is derived from a youtube video by a couple who added 5 feet to their Wood's Catamaran. It looked like a huge undertaking but they were very successful. I know it can be done.

[Kelldog]

Well, I have my little cat unfolded an parked in my parking area. Heh heh.. looks like a mini boat yard! I am starting a dagger board case repair at the bottom of the hull. small leak. The hull opening is 1 1/8 wide and roughly 18 long. I need to sand or grind up into the case to get it ready for epoxy/glass repair. Not easy to get up in there at least 4+ inches to take the bottom paint off down to the existing glass or wood

Any ideas?

I did use a grinder to try and get some paint off.. not that effective. I've attached a couple of pics of the boat

[Cherod]

a grinder with a sanding disc on top of the grinding stone ( better to use a cutting stone ) with appropriate ( polishing ) retaining centre nut will remove most things, paint included,,, ( tip, lift regularly to prevent clogging )

[Cavalier MK2]

Couple quick ideas are to use adhesive paper on a flush cutting saw blade, one of those multi tools you can get at harbor freight cheap.

Second idea is similar using a reciprocating saw with a dead blade at the right length covered with the adhesive paper.

Third idea also involves that course grit paper but on a disc sander.

[catsketcher]

Getting power tools into the slot is going to be hard.

I would try a blade. Something like a long chisel, scrape it down to remove the bottom paint. Maybe a hooked scraper would be better.

Then when some paint is off I would go to 40 grit paper on a stick. For
tough jobs I often use 7inch (180mm) sanding discs. Screw onto a stick and put on your dust masks. Eventually you will get there. If you can do some from up top that would be much better - longer stick needed.

Good if someone could be up top making stick go up and down whilst you are underneath just applying pressure to the sides down low.

cheers

Phil

[Cavalier MK2]

The idea Phil is to use the blade or disc of the power tool in the slot not jam the tool in there itself. He wanted to clear off the bottom 4-5 inches, not the whole thing. I've done this before and it works. One advantage of doing it by hand is you are unlikely to take off more than you want. The downside is the time it will take you to get off something close to what you want but it can be good exercise.

[Kelldog]

Another question. I am about to purchase epoxy and supplies. I am considering Raka Epoxy or Aeromarine Epoxy 1.5 gl kit. I prefer not to use west systems. I know there's a lot of threads on which epoxy is better.

The idea is I will roll on epoxy about 4-6 inches up into the sanded daggerboard case and then apply and roll on the cloth and wet out with more epoxy. I have done epoxy/fiberglass work before but not in a confined space like this.

[Cavalier MK2]

The whole inside of the trunk should be covered with glass already. If it isn't you have a challenge. Just covering the joining area with another layer for the leak is straight forward. Foam brush on a stick comes to mind, other coats before it is all the way hard to skip sanding between coats. Phil's thoughts for finish sanding. And Finally,

Making sure the board now has enough clearance.