22 - 24 trimaran

[jamez]

Thanks for the link to that blog OS7. Very interesting site.

Bruce, the beams are basically a 4 mm ply box glassed over. I've emailed the URL of this thread to the owner, so there may be some more specific info soon.

here is an old clip of the boat back when it was first re-launched. You can get a good idea of the beams without the nets in the way.

http://www.youtube.com/watch?v=Z-lgC4WBk6Y

 

[bruceb]

The Green Death Trap?? Was that from anticipation or experience? (Or the crew's opinion) Very good details in the video, it answers several of my questions. Has there ever been a direct comparison between Miranda and Capricorn? Bruce

 

[Samnz]

The Green Death Trap?? Was that from anticipation or experience? (Or the crew's opinion) Very good details in the video, it answers several of my questions. Has there ever been a direct comparison between Miranda and Capricorn? Bruce

I own the green death trap (Capricorn), they called it that because I started racing it before I got tramps and the boom was very sharp....

and everytime I raced the rudder or mast broke!

There has been no direct comparision between the two most modified Auckland based Bucc 24s as the owner of the Miranda stopped racing before I started, however it is a general agreement that my taller canting rig and new sails would give the (non foiled) Capricorn a significant speed advantage except maybe in over 20 knots on a 2 sail reach when the Mirandas foils and added waterline could give it a slight edge.

Gary speaks about bucc 24s transom needing modification... this in only a problem at around 7 to 9 knots boat speed as below that it is at hull speed and above that is is flying clear, or at least planing.

The crew and helmsman always sit on the float near the chainplates except downwind in over 15 knots breeze.

The beams were going to be 4mm box but we thought they might break so we added another layer of 4mm ply top and bottom so its now 8mm with 4mm sides, with one layer of 10oz glass boatcloth. Forward beam is about 200mm by 200mm aft one 200mm by 100mm. They seem pretty stiff, a lot stiffer than the original (horrible) configuration, allthough there is no ability to fold this wasnt nessary for me anyhow. I would be happy to supply cut files and the attachment details for these beams.

In the last clip there was a lot of bow down on port gybe even when not fully powered up, we figured out this was caused by the outboard bracket fairing hitting the water, it got ripped of in the last race!

http://www.youtube.com/watch?v=jc2HGfIAAz4

 

[oldsailor7]

Great Video.

There don't appear to be any changes to the basic B 24 configuration except the beams, prodder and taller rig.

Admittedly the ride gets bumpy at 18 kts, but lets face it, 18 kts in a small multihull is frightenly fast.

Lock designed the B24 with a waterline L:B ratio of 8:1, low by modern standards. However that was his trade off between carrying capacity and wetted surface. This gives very good light wind performance without having to worry too much about the weight of the crew. After all Lock designed this tri as a fast cruiser, not an all out racing boat. It just turned out to be an inexpensive all rounder.

Very light cats, (like Richards Woods "Gwahir" for instance) can use an L:B ratio of 15:1 , which enables smoother high speeds and also good light wind performance providing the crew and equipment weight is kept down to a minimum. This boat was designed purely for sailing in the late "Micro Multihull" racing class, and thus had limited appeal.

For those who want to do it, lenghtening the stern section is best done during construction by simply sloping the transom back by two feet, flattening out the buttocks, and using the alternate spade rudder. It's not necessary to stretch it out to 28 ft as in "Miranda". Don't forget that added structure also adds more weight and wetted surface. There is a trade off here. As Mr Cessna said ---"Simplicate and add less weight".

 

[oldsailor7]

In that last video it was very noticeable how the bow threw up water all over the front of the boat at speed in waves.

On my B24 I ran a perforated plywood deck from the ends of the side walkway, forward to the base of the bow pulpit. This did not affect the performance of the boat ---but made it a whole lot drier, and safer to work on the foredeck. A simple mod.

 

[bruceb]

Samnz, thanks for joining in. Crew always seem to have a lack of appreciation of a "testing" program. After the first brisk sail on my boat, my son asked if we could add some extra flotation. I am interested in the ply beams, particularly on how they are attached to the hull and floats. I think you have "tested" the system well enough by now to trust them. How big of a rig are you sailing with now? Bruce

 

[Samnz]

In that last video it was very noticeable how the bow threw up water all over the front of the boat at speed in waves.

On my B24 I ran a perforated plywood deck from the ends of the side walkway, forward to the base of the bow pulpit. This did not affect the performance of the boat ---but made it a whole lot drier, and safer to work on the foredeck. A simple mod.

Its an interesting idea, I have just added some zigzagged cord to a bit of plastic coated dynex to give the crew some feeling of safety and stop the jib falling in the water so much.

I would be worried the perforated ply would get smashed off, unless it was quite heavy?

The other thing is when you buried the main hull bow up to the mast step did it catch the water on the way up?

 

[Samnz]

Samnz, thanks for joining in. Crew always seem to have a lack of appreciation of a "testing" program. After the first brisk sail on my boat, my son asked if we could add some extra flotation. I am interested in the ply beams, particularly on how they are attached to the hull and floats. I think you have "tested" the system well enough by now to trust them. How big of a rig are you sailing with now? Bruce

The ply beams are attached to the floats with a double bias glass tape the the deck of the float and then some 10 oz glass boat cloth overlapping about 150mm the whole way around the join. Then 3 layers of unidirectional carbon on each side of the float like a clamp.

They are attached to the main hull with a heavily reinforced flange bolted fore and aft through the original hardwood beam mounts, then db glass tape around each join, deak to beam, cabin to beam, bunktop to beam, etc.

The Aft beam has been moved aft so the front edge connects to the aft edge of the original beam mounts to give more space in the cockpit and more crew weight aft when pushing hard off the wind, as is the forward beam moved forward to give me a 2m long bunk inside.

The latest mast is 10.7m from the maststep, total of 11.9m airdraft. Im not sure if you'd want to go much bigger, the square head main is awesome for depowering in big gusts upwind but does send the bow down rather quick downwind if your not carefull!

 

[oldsailor7]

The other thing is when you buried the main hull bow up to the mast step did it catch the water on the way up?

LOL. !!! I never did bury my mast step. But then I didn't have a 35 ft mast with a squaretop sail on it.

On the other hand I configured the boat to sail on the Atlantic in the area to the west of the Gulf Stream, en route to Bermuda. I had sailed there before and it can be very rough.
The deck was ply of the same thickness as the cabin side walkways supported by two longerons and pierced with a pattern of 2" holes to relieve any water pressure on top of them. I had similar decking on the stern, on either side of the transom hatch.

Two wires to the bow, supporting a fabric mesh would do the same job.

I'll see if I can find a photo of mine.

 

[tatoski]

Thanks Oldsailor7. I really appreciate it. I've sent you a PM.

 

[tatoski]

Thanks Oldsailor7. I really appreciate it. I've sent you a PM.

Actually I couldn't yet. I read the item on Private Messaging and it is required that I should have 5 posts or more before PM will become available to me. Anyway this is my third already. Two more. Thanks

Tatoski

 

[oldsailor7]

Tatoski.
Can you get marine plywood in the Phillipines. Gaboon if possible. If you can get Samba Magogany 3 ply, that is light and OK in 1/4". What about a suitable epoxy. WEST system Epoxy may be available in your neck of the woods. If not you may have to import Bote-Cote epoxy from Australia. The correct type of epoxy suitable for boatbuilding is very important.

 

[tatoski]

Marine Ply and Epoxy

Tatoski.
Can you get marine plywood in the Phillipines. Gaboon if possible. If you can get Samba Magogany 3 ply, that is light and OK in 1/4". What about a suitable epoxy. WEST system Epoxy may be available in your neck of the woods. If not you may have to import Bote-Cote epoxy from Australia. The correct type of epoxy suitable for boatbuilding is very important.

Oldsailor,

No problem with marine plywood and epoxy. I've built a few boats using Lauan plywood. The 1/4" has 3 ply only and has thin veneers and not so good middle ply but at least void free. Epoxy is no problem too. The local Farrier builder plant that I have visited is using local epoxy. I'll try to get the same stuff

 

[tatoski]

Oldsailor,

One question, what kind of mast does the buc24 use? Aluminum masts here are quite hard to source. Is wood a possible alternative? Thanks

tatoski

 

[oldsailor7]

Oldsailor,

One question, what kind of mast does the buc24 use? Aluminum masts here are quite hard to source. Is wood a possible alternative? Thanks

tatoski

The plans show stock round section 6061T6 alloy tubing. Available just about anywhere.