Kerdyn Green Foam - trimaran / multipurpose

If performance is high on your criteria I vividly remember John Goodman's GIS with Mic Storer on board flying by me some years ago when the GIS was a recent design.

 

Thanks - yes there is Youtuber called Boat Rambler who build a GIS, and it certainly seems to move quickly. A couple of videos from the Texas 200 s also show them doing very well, and someone who owned one called Gir has posted a bit. For something that looks simple it seems very well designed and swift. Pretty boat too. I gather a touch twitchy - i.e. needs constant attention if you single hand her, but with some ballast she is bit more 'normal'. I read one chap put some sand bags in until he got used to her.But that is what sailing dinghies is about - a boat that needs TLC is typically why one sails small.

But one boat at a time for now Hoping to have some clear days in December (I am Cape Town based) on leave to finish foam and fairing on the main hull, and get rub rails installed for stiffness so I can glass and flip it into rope cradle. I was going to say 'her' but I gather sailing canoes should be called 'him'.

On Boat Rambler - he has some nice Lateen rigged traditional Portuguese boats which are interesting. Quite a fun channel if you have time.

Back to the Kerdyn - I did some tests with expoxy to see how it butt joins. It advertises strong adhesion. Certainly looks that way - couldn't brake it at the joint. And in flex the Kerdyn kept its rounding uniform. I did V the join for extra surface area bite, and only went 80% in as I will be doing this on the boat and then do the last 20% when I flip it.

 

Gir's the boat that passed me some years ago.
I use Gorilla glue for butt joints in pet foam, wouldn't use it anywhere else but ok for something that's going to be skinned on both sides.
It shouldn't be an issue with the Kerdyn you're using but the Gurit Gpet I used to build QB apparently was extruded in ~ 2.25" strips joined together leaving parallel hard spots in the foam. It didn't affect the build particularly but over time the lines print through the thin skin of glass I used.

 

Thanks - I can see I am going to have the same, there are some hard spots in the foam you can see in the pictures from the extrusion. What glass oz did you use out of curiosity?

 

8.9 oz tooling cloth, my favorite discount glass supplier had some on sale at a very reasonable price and I took it instead of using 12 oz biaxial. A big mistake on my part, the tooling cloth works well when vacuum bagged but is almost impossible to wet out properly by hand. Initial desire to save some money and weight lost in the hassle of extra work and mess but the boat is light.

My old eyes missed the lines in your foam, I assumed it was like the previous gpet foam I'd used that was homogenous.

 

Thanks I am using 400 grams for the first time. Looks quite thick and intimidating so will see how it lays up. Fairing compound has not worked great on the foam - S 600 - too thick. But used cabosil and microfibre which works well. Tests done on bonding have gone well. The foam will break before the join, which bodes well. Not had too much time to work on it, but I have carved out Vs at the joins for bonding and this has worked well. I expect fairing will be some trial and error in terms of finding a nice spreadable and easy sand mixture. So far the process has been quicker than anticipated. The foam doesn't like UV sun too much (which is a surprise given it is all recycled bottles which seem happy to live an eternity as litter), so need to get cracking and glass. Hope it was an excellent Christmas Skip. Sounds like you have done a fair amount of sailing. Texas 200 on the bucket list, would like to here more but this probably not the thread for it. Either way greetings from a mild weathered Cape Town.

 

I'm surprised also that the pet based foam is not sun tolerant, I'll set out some scrap and and see what happens over the winter. I consider myself a newbe sailor, have done thousands of miles paddling but was infected with the proa virus later in life and have only done a few hundred miles in same, split between trials and four expedition adventures so far. I envy your weather at the moment, seven inches of fresh snow is melting at the moment and next week the temperatures not expected to get above freezing all week ;-(

The tales of my adventures are here.
Texas200 https://texas200.com/2009
Texas200 https://texas200.com/2024
Proa File | QB and the Texas 200 https://proafile.com/multihull-boats/article/qb-and-the-texas-200

 

We've got a Hobie Bravo, which has furl reefing. Obviously the sail shape is not that great when reefed, but overall it's a great system in terms of convenience. It has a squaretop with vertical battens and although it's not a racing rig, it has pretty good gust response, pace and handling IF the boom is used.

Our Bravo has the optional boom and it's vastly better than sailing it boomless. Boomless sailing seems terrible to me. Upwind the mainsheet has to handle the compression load that the boom normally takes up, so the mainsheet load becomes much higher. It is then very hard to pull the mainsheet on hard enough to get the sail properly flat, so you normally end up with a much deeper and much less efficient sail.

Then, when you ease the mainsheet in a gust, the clew moves forward and makes the sail deeper, not flatter. The lack of good response when dumping the sheet could capsize you quite easily. Downwind the sail obviously tends to collapse. On reaches it becomes excessively deep, with huge amounts of "return" at the leach and associated weather helm.

Perhaps most importantly, when you come out of a tack with eased mainsheet, the sail's normal deep shape means that the "return" on the leach catches the wind well before the luff has any power (because of the very deep shape) and therefore makes the boat hard to bear away. The boom is of course critical to having a vang, which provides a wonderful twist control.

I learned these things after the Hobie's gooseneck broke when I was pulling the boom up too high when furling the sail. The chance to sail the same boat and rig in both modes made it a pretty good test. The Nacra cats use boomless mains, but they sail very different downwind angles and have fully-battened mains which means the battens hold the sail flat and take many of the loads of the boom.

In lugs the yard does some of the jobs of the boom so my remarks don't apply to them.

A boom can be incredibly simple and light - the gooseneck can be just a plastic rowlock (which is the system I may put on the Hobie) but makes an incredible improvement in my experience. I'd go for a decent-sized section because cheaper unstayed squaretop rigs offer good gust response but can twist off too much without a decent vang - something like an old-style Laser vang would work well.

So for what it's worth I'd vote five stars for the vertical furling squaretop rig with boom, and two stars or less for the same rig without a boom.

 

Thanks very much for the input CT, appreciate it.