6.5 to 7.5 metre performance/cruise multihulls

Instead of having the rudder and transom slot in two pieces, (which is what I was intending to do) Jacques suggested epoxying them together to make one unit ... and that is a better solution .. so I've done that - although it looks a little odd. And because the T rudder assembly has not been epoxied together, meaning upper and low units and rudder control systems locked as one assembly, I've been able to separate the two and glue with the boat down low on blocks and not go through the problem of lifting the main hull up high to do the job. If you can follow what I mean.
Also fitted the outrigger horns for the main sheet and traveller system. This is the same setup that Max Purnell had on his Newick 36 Mokihi, a trifoiler that I know well.

 

So basically the slot is still there, but an added fairing to cartridge fills gap back in again? With added fairing being pice you cut out glued back in but onLy against cartridge?


Barry

 

That sounds right. The triangular side view "cheese cut" from transom was filled with foam and lightly glassed, then I cut and glued in two sort of triangular pieces of ply to seal both sides of the slot and to connect to the now half cut away rudder case (like the front end of half a daggerboard case). Next step was to glue the cheese cut to the trailing edge of the upper section of the rudder top section. I'll take some photographs tomorrow to show what I mean; writing doesn't really make it understandable.

 

Gary. Your rudder/board design is exactly as I described it in the AYRS Vol. 79, Rudder design. 1974.

 

There you go OS7, the avant garde of original thinkers. I may have that AYRS copy.
Was going to post the rudder setup but today had to help Jacques with his much modified Farrier. Cut off the long keelson, (jacked up the hull above the mud with just enough room to work under the hull) ground it smooth with belt and rotary sander then glassed it. Looks very smooth and transforms the main hull - but it was not pleasant work. Thanks to science and electric tools though. Imagine using hand tools. Which I have done in the past too. Jacques is rapt - so we sank three bottles each (was it four?) of Leffe to celebrate, me on empty stomach. Will post stuff on the 650 tomorrow. Cheers.

 

Gary is the rudder also pivoting in case you hit something or is it just up and down? I'm thinking with the outside support pin as a hinge and the lower as a break away safety kind of thing maybe.

 

It is only up and down, Rumars, can't pivot. Well, I could make it pivot but would have to cut away a slot in front of the rudder case head - and then make a foam? block to fill the gap. Because as I have it, the pivot point pin is set lower on the retrouse transom. Which would mean making more locking supports required - because a moving/slopping around rudder assembly is very annoying, has to be solid. The inverted T rudder is the cause of this convoluted discussion.
If you had a conventional rudder - then no problems. However a T rudder is a marvelous thing for sailing speed/stern lift/control too - but can be a pain to implement. Meaning you have to live with the fact that you would cause bad damage if you slam into a rock at speed. But as said you have to live with that. If the rudder assembly moves/slops aft to create negative angle of attack on the T lifting section, then massive drag occurs.
However, if designed from scratch and not doing an after-the-problem compromise, (as I sort of am doing) you could design the rudder with pivot pin forward of the top of rudder shaft and having the lock in verical position pin in the same lower place I have it here. This would mean the top pin would be inside the hull (for neatness) or on deck - which would make your connecting tiller controls and bars, protrude higher above deck (which is sort of clumsy in my opinion). However, more than one way to skin a cat. Would like to hear other solutions from you bright boys here. Cheers.

 

Thanks for the info Gary and also for your inspiring thread. I was just thinking maybe it would be easy to do, but I see it's actually more complicated because the angle of attack must be fixed at all times for it to work properly. As you said one has to live with it.

 

Not sure if it would fit you but this setup pivots and can go up and down.
Might inspire though into other contraption.

It's held down by 2 lines with 2x auto-release clam cleats and trapeze handle's on lines to pull tight and fix in cockpit.
There's an aligning pin at the bottom to fix underside when down.
There a second quadrant in the cockpit but could also be steered directly with tiller.

 

Yes, the hinged transom is another alternative; Dick Newick had this on some of his designs ... but they also tend to be complicated and fussy?

 

Yeah, I guess it couldn't hurt to simplify and personally I was not to keen with the double quadrant fuzziness? Although I must say it always worked wonders and pretty straightforward and was very easy controlled when grounded while sailing, that is without experiencing grounding a fancy pansy T inversion naturally.
But I recon the basic setup is sturdy and stable enough.

 

I'm keen to see how this works out I've been weighing up the pros and cons of a hinged transom versus the cutout for ages. I like that the hinged transom can be rigged to spring up when it hits a solid object but the transom slot is a lot simpler to implement.

 

Like I said Owen, apart from the ingenious fuzziness of the double quadrant exactly pivoting in the line of the hinge and corresponding pulleys guiding the wire the basics of the hinged transom worked very well, one could simply avoid these complications though I think.
I would also close the hinging part to avoid the possibility of scooping water in waves.

Simplicity is your friend but is it really simpler to construct a transom slot?
When building the hull one could easily place a double bulkhead and saw when finished.

Guess you're thinking of your formula 40?

 

Superb light weather here in Auckland; went sailing with Jacques on Groucho - better fun than working inside the cramped confines of the 650? Looks like the boat is stationary but was magically sliding along at 4-5 knots, check lee float/foil wake.

 

Yes, being able to go shoal is too useful to ignore, the original (geko) had a deep fixed rudder which would be a real pain to have where I envision storing the boat on its mooring and would prevent me from being able to dry out. Transom slot would be easier to build but a hinged transom is a neat way of doing it too. In truth I'd probably have two different transoms one stock length and one slightly shorter to reduce the boats LoA to avoid some of the more onerous requirements of Cat 1 safety compliance.