22 - 24 trimaran

[oldsailor7]

Thanks Gary. Thats the one I was talking about. A very pretty example.

Lock had the ability to design cabin tops which are pleasing to the eye ---as seen in that one. Lots of other designers seem to have great difficulty with this feature, including amateur builders who try to "Improve" the design for greater headroom or other reasons.

[bruceb]

I see lots of good ideas on the yellow one. Thanks! I have a 36' rotating mast that works well on mine and I think extending the amas would be a good first step. I was already working on new foils. Any other ideas would be welcome, I am in the US and there are just a few 24s still sailing that I have found. Bruce

[jamez]

Hi there PM. Here are the pictures of the big-rigged B24. The rig has since been modifed to cant to windward and the forestay moved forward.

While looking for these pics I came across pics of a 26' tri that had its main hull based on an old surfboat. This one of the nicest such conversions I've seen. if you look at the floats they seem to be very similar to B24 in shape.

[Gary Baigent]

Miranda is the ex-Capricorn - not as I had it Gulf Chariot. I think Gulf Chariot is now Sam Tucker's over rigged, mean, green machine seen above.

[Gary Baigent]

apologies, I had it right the first time - Miranda= Gulf Chariot and Sam's Greenie = Capricorn

[bruceb]

Any idea how the foils in the amas effect tacking? I am sure they are more efficient, but I would hate to lose the Buc's ease of handing. Losing the centerboard trunk would be great- it leaks. (it is 32 years old)

[Gary Baigent]

Tacks just fine, even easier than with the original single main hull board. The stretched Buccaneer with its way better underhung and balanced rudder design also improves helming. In fact before the modifications, tacking with Miranda was terrible with savage weather helm - in that you had to hold the helm over with one leg (or got someone else in the cockpit to do so) while you sheeted in the headsail and main on the new tack - otherwise if you didn't keep pressure there, it would immediately centre with the boat twisting up head to wind ..... that doesn't happen anymore. Another plus is that the foils make the boat track better, less twitchy, and even though they are set at a fairly shallow angle, there is still considerable lift generated - which keeps the leeward float up. Jpeg of Miranda and Flash Harry

[oldsailor7]

Originally Posted by Gary Baigent

In fact before the modifications, tacking with Miranda was terrible with savage weather helm - in that you had to hold the helm over with one leg (or got someone else in the cockpit to do so) while you sheeted in the headsail and main on the new tack - otherwise if you didn't keep pressure there, it would immediately centre with the boat twisting up head to wind .....

I find that curious, because my B24 was light on the tiller and tacked on a dime. I suggest the excessive weather helm was caused by the mast being raked too far aft.
However I agree about the rudder-- and the plans I have show an alternate balanced spade rudder, which was subsequently made standard on the B28.

[bruceb]

I really appreciate the information. I know I have gotten off track on the thread but thanks. The buc 24 is the most fun sailing I have had in a long time. It is wooden, but mine is 32 years old, been in the water most of it, and really has had very few problems. I am an old former boat dealer in the southern US and I have had just as many problems with old glass boats, and they are a lot harder to repair. The build time for a 24 is about 500-700 hrs, and about twice that for all the glass designs I have seen. I am just going to keep up-dating my boat, it is fun and much less expensive. I am planing on replacing my rudder also. The previous owner has hung the rudder on a sloping transom and it tries to over-steer when you push it off center. The boat is nicely balanced though, I have a taller rig with a shorter (9.5feet) boom that probably helps. Gary, what sort of foil profiles did you use?

[Gary Baigent]

A break from US elections, go Obama.
Miranda is not my boat (owned by Malcolm Cheadle, had it for a couple of decades) but I had some influence in the changes. The angled foils are just larger versions of those on 6x6 metre Flash Harry: float dagger asymmetric foils which are relatively small (305 x 39mm chord to thickness and based on NACA65-412 and only a metre long overall with 300mm bury through the floats) - because I wanted a boat that would lift off only in stronger winds (12-14 knots) and in lighter conditions the foils, being small, would not drag too much. The float foils are set at 40 degrees and at 3 degrees angle of attack and they slope forward a few degrees to try and halt cavitation when passing through waves, The rudder blade is 250 x 32mm and based on NACA 64012, rudder draws 700mm below waterline.
On Miranda the foils are set at zero angle of attack - there is no inverted T section on the rudder - it is a foil stabilized tri, not a flyer. If you want her exact foil measurements I can post them later.
Old sailor, you can see in the jpeg that Miranda's rig is dead vertical, no aft rake - the tri is not quite floating in the image, sitting on its cradle.

[bruceb]

The US has made a start towards recovery- I hope we can stay on track. Enough politics, lets build fast boats. Gary, I would like to see the foil details. Light air performance is really important on the US east coast and on the lake I race on, (saillanier.com) so low drag and good pointing is more important than top speed. We rarely get enough wind to "fly" except in storms. Also, how far forward did the transom re-fairing start. Our lake is really low due to a major drought so I am working on my boat this winter. My first project is trying to make it fold/disassemble easier.
I think I like making sawdust.

[Gary Baigent]

Bruce
Those dimensions for Flash Harry's foil would be fine for your tri, just make the foil longer to suit your float depths - if you make them too long, you can easily shorten them. The important thing is to lay plenty of unidirectional carbon through the hard spot area (where the foils exit their cases).
The hull extension fairing on Miranda required plenty of foam because the stern extension began a little aft of the deepest rocker point on the main hull (which is a little aft of a midships) - foam was just epoxied on in blocks, then faired with long boards and later glassed, filled and faired yet again. The rudder was shifted further aft and setup like a daggerboard in its case - so it can be easily removed. Miranda has a shorter second rudder for sailing in shallow water.
You can see in the jpeg the angle of the foil with the boat horizontal - but the B24 has quite an angle of dihedral when sailing with the windward float quite high and the boat leaning over so the leeward foil works at a greater angle, approx 25 degrees - a compromise between lifting and still providing lateral stability. Miranda is a high pointing boat.

[bruceb]

Thanks Gary. How does the crew feel about adjusting them under sail? It looks like the board leading edge is just aft of the crossbeam. Would you change anything, or is that about right? I think I am going ahead with putting the boards in the floats this winter. Are the floats extended forward any?

[Gary Baigent]

You can leave both foils down because the tip area of the windward one just skims the water surface, only fractional drag - but in light weather it is no problem to lift the windward one. If you are going to tack, yes, get the windward one down first, The foil position in the float needs to be a little ahead of the hull balance point, you want the forward part of the float to be lifted, not the after sections - otherwise you'll stick the nose in. Miranda has aft extensions on the floats, none forward.

[oldsailor7]

Originally Posted by bruceb

Thanks Gary. How does the crew feel about adjusting them under sail?

I had my first Trimaran with outboard daggers in the floats in 1964.

Never again.

Fine in flat water and fair weather, but dangerous on a filthy black night, with the rain lashing, the waves crashing and the wind howling.

Do you really fancy going right out to the outboard edge of the craft in such conditions. But if you dont, the risk of severe strucural damage is high.

Classic example is Groupama 3.

Bin there --done that.