Formula 40 singlehanded trimaran build log

[Corley]

I thought I'd just set up a thread for my build log of my Kurt Hughes Formula 40 singlehanded trimaran. I've just received the plans and will start making some bits soon. I think my first project will be to build the beams in my workshop. I dont think I'd quite conceptualised how massive the beams are on this boat you need some serious strength for cantilever beams that are 40' wide

http://www.multihulldesigns.com/desi.../f40shtri.html

I'm building my Kraken 25 for now but will start building some bits and pieces for this boat among my other projects I envision around a 3 year build timeframe once I start getting into it. Right now I'm tossing up whether I build the boat by cylinder mold or the endgrain balsa over male form mold system. I'm comfortable with both systems but tempted to build with the engrain balsa method as achieving a consistent hull shape should be easier and potentially a little lighter I like the lack of stringers that the method brings too. The boat has a very confined (and simple) cabin so every bit of internal space helps.

[themanshed]

Have you considered foam core?

[Doug Lord]

Good luck, Corley-looking forward to it!

[Corley]

I had a chat to Kurt about what he did with Geko his formula 40 trimaran Kurts boat has a developed ply skin with a vacuum bagged balsa core a good approach to save having to install stringers and have better panel stiffness and means an easier to fair exterior. As far as weight goes the boat weighs in at 1790kg which is about 10kg lighter than the minimum formula 40 rules so weight wont be an issue as long as I'm careful with how much resin I go throwing around. Kurt has updated his plans to implement carbon uni reinforcement of the beams and other high stress areas. He has also drawn some new and very good looking reverse bow amas which really suit the boat. I certainly considered foam core but I'm happy to go with Kurts recommendations on materials and the cost of foam is a fair bit higher as well. I'm building on a budget so that angle is important.

[cavalier mk2]

Glad you mentioned the balsa addition. Every time someone says tortured ply, cylinder molding, constant camber or double diagonal limits you to one planking thickness I cringe. Core can be vacuum bagged or strip plank added etc....inside or outside the hull for a thicker laminate on the bottom for strength or to increase load carrying. When people get locked into one approach they often miss the possibilities offered by combinations.

[Corley]

Kurt sent me a .dxf file containing the flat plan for the mold segments. These have to be cut with a fair bit of accuracy luckily I have a contact at a laser cutting business that specialises in accurate cutting of patterns out of sheet goods. They also auto nest the cutouts for optimum material efficiency it will probably save me a sheet or two of cdx plywood.

Kurt's modern cylinder mold is a biaxial mold to reduce the amount of fight in the developed plywood segments when doing the final wiring into a hull.

[Samnz]

Originally Posted by Corley

As far as weight goes the boat weighs in at 1790kg

where did that figure come from?

[Corley]

Its actually: Weight: 3,950 lb (1,791.7 kg) from the link I posted. I think Kurt listed his boat at 1790kg maybe he saved a bit of weight somewhere. Thats about the weight you would expect from a formula 40 some were built a little lighter in carbon but there wasnt much advantage so they tended to be 1800kg and less exotic. I recall Gary posting up at one stage most of the tris were about 1900kg. If you have a look at Kurt's blog the boat is being pulled apart for transport to Holland (its demountable).

[dantnz]

What happened to Geko - did it get sold?

[Corley]

It was sold to a fella from Holland I believe. Its been demounted for container transport to Holland where it will be raced and cruised in a very spartan fashion(not much spare payload for cruising junk) the new owner wants to have a crack at the Round Britain race in the future.

[FMS]

Look forward to following this thread.

[Corley]

Build locations are my current interest I've looked at building near Westernport Bay and its actually surprisingly affordable. Yaringa Marina have sheds for building at $550 per month not wide enough to have my boat fully assembled in though. Allcraft Marine have a building shed with a big enough floor area to take my boat fully assembled for $600 a month(sounds like a deal) it has a basic crane and a launching trailer wide enough to take my boat to the water no concrete floor is the only negative I can see and getting my boat out through the narrow Warneet channel, think I'll need a few pusher boats to make it out and a good high tide. The plan is to set a double ended mooring at Hastings in Westernport Bay it's pretty well protected from most winds there.

[Corley]

My business has been flat out and leaving me with little time to work on this project so I've started farming out parts of the job to third parties to construct my approach is to make as many fiddly parts as possible in advance to make the finishing stage of the job shorter and faster.

I've been doing a number of organisational steps towards the construction of the tri. Plans are at the fabricator and construction has begun of the mast step, tiller assembly, chain plates and mast fittings.

I've been in contact with Hart Marine in Mornington and one of their blokes Ben has taken on the job of constructing the daggerboard, daggerboard case and rudder as a home project.

The other work that I'm looking at farming out is construction of the beams I've contacted Julian at Noosa Marine and am forwarding the planset so he can quote up construction of the main and rear beams. So many expensive materials in them that I cant afford any stuff ups so out they go to be made offsite.

[spidennis]

That is a sweet looking boat, and that's some massive beams! ..... and looking forward to seeing the build take shape. pics man, we need pics!

[Corley]

While I'm doing daddy stuff and changing nappys for the new bub I've farmed out some work to a mate of mine Ben. He is building the carbon fibre daggerboard for my formula 40 project. We opted for carbon uni in the end due to lighter weight and similar cost to the equivalent glass uni original (due to less material requirements with the carbon uni). The mold has been constructed and the melamine insert fitted ready for lamination and bagging. In the end we opted for the "short" daggerboard in a half height case. Since the boat is being built for category 1 racing multihull compliance the daggerboard case will be enclosed in a shroud between the top of the case and the underside of the deck. The advantage of the short daggerboard is it allows more adjustment while fitted to the case and we should be able to retract the board by about 1/3rd of it's total length before we pull it up to deck level. Ben is also making the foam sandwich/carbon daggerboard case and a kick up cassette style rudder which pops up through the transom but is immersed under the boat in normal use to Kurt's plan. The rudder being mounted closer to the transom gives some stowage advantages for light gear inside the boat and reduces the amount of steering gear intrusion into the rear compartment. As with any multi we are keeping the weight out of the ends but we will have quite a lot of storage for light but bulky gear in the fore and aft compartments and storage in the floats for light gear, fenders etc. We are looking to make the boat as shoal draft as possible it's always handy to be able to beach and dry out for repairs or just to enjoy a day out on a secluded beach.