Twiggy MKIII

So, Here is a good question for the group. The twiggy MkII accomplishes its intended goal quite well: speed, low tech build, and minimal, but adequate room for overnight racing.

What would the Twiggy MKIII look like? How could one modernize the existing design while maintaining it's original goals?

Would it look more like a 30' Idec? A chined, wave piercing hull with the rig as far aft as possible, or would it look more like the Kurt Hughes racing plywood trimaran design.

The other design to consider is Adagio, Meade Gougeon's 40+ year old trimaran that's rated equally to the highly modified F31, Cheekie Monkey, which last I heard is now for sale.... again.

The things all of these faster plywood trimaran designs have in common are the lower freeboard, wider platform, and exceptional design talent...

So, if one wanted to attempt a modern, plywood racing trimaran design, would it simply tuwn out looking like a 30' IDEC, or would be more like the Twiggy MKIII?



Thoughts?

 

It's amazing how many people(designers included) that seem to ignore the benefits of square or over square beam on trimarans, particularly on small under twenty tri's. Crowther is certainly one of the greatest multihull designers. Thanks for this Raps!
One thing I'm sure a MKIII should have these days is ama lifting foils and maybe a rudder T-foil.

 

Flat top the main, canting mast, curved daggerboard foils in both amas, better wavepiercing ama shape, and a bit wider beam. That's all that comes to mind. I would lean heavily toward the 30' IDEC trimaran idea.

 

One thing I had thought of with the twiggy design was to raise the fore deck so you do not have as much of a down ward step when moving forward. As well as more forward bouancy considering they would pitchpole.

Or has the change in the sailing approach over come that now.

 

Ama foils have certainly proven to reduce the incidence of pitchpole or ama burying in the boats that use them.

 

The Twiggy Mk2 plans call for a rotating 8"x5" aluminum mast.
Like the Mod70 trimarans I think a Twiggy Mk3 should have a rotating wing mast of larger section, along with the square top main.
Maybe 12"x5" or even 18"x8".
This would improve the performance too.
I think Bill Bullimore's Twiggy Mk2 "Wingover" had such a wing mast.

 

Ian Johnston shortened the mast on his Twiggy and found the boats handling much improved. When I chatted to him about my F40 trimaran project he reckoned it was worth moving heaven and earth to try and get a carbon mast even if it wasn't a rotating section.

 

Don't know why you blokes are talking about IDEC as a reference to a wide beamed boat ... because the Irens designs are narrow in overall beam, compared to the ORMA and MOD70 designs.
Twiggy M3 is near square already. You could make it square or oversquare but to continue modernising the design, would require foils in the floats, T on the rudder ... and a lightweight wing mast.

 

As I am sure some of you will know I have written about my Twiggy experiences here voluminously. I loved my boat, for her flaws as well as her sweet traits. Going square has real problems. I interviewed Irens about Sodebo and B and Q which were built nearby. As Gary says he did not make them square as square boats are a little strange in their stability characteristics - you really do not want a boat more stable sideways than fore and aft.

One of my main gripes with the Twiggy was the small rudder volume (area x distance) between centreboard and rudder. It gave the boat strange handling at times so although I think the boat is a great design I would start afresh rather than base a design on the Twiggy.

As for the rotating stick - they always seem to be heavier than an equivalent fixed stick and this kills them for me.

cheers

Phil

 

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Phil, do you think the use of a foil on the daggerboard along with a T-foil rudder and possibly an UptiP foil on each ama would improve the characteristics of a square or over-square tri? Particularly in reference to under 30' coastal and sheltered water tri's....?

 

Doug in my limited experience it seems that going square is fine for most conditions as you can usually sail with the apparent wind on the beam somewhere by tacking downwind. There are some high wind situations where you need to be able to run square and if you bear away with lots of reserve stability onto a run with little reserve then that is tricky - at least it was for me. I ended up never sailing the boat as hard as it could be sailed (if I kept the apparent forward) because there was always the possibility I needed to run square.

I would be more interested in a large rudder T foil and foils on the ama I once drew but never built. If you put foils up the front then if they go negative (at the bottom of a wave) you can pitchpole. My idea was to make an ama mounted T foil which pivoted. Instead of a forward mounted wand to control orientation it would just have a trailing arm with a trim tab to constantly keep it at a positive angle of attack. I thought the trailing arm could be somewhat flexible so that AOA lessened at greater speeds. You still run the problem though of what happens at the bottom of a wave when you are delivering the boat, or cooking dinner, or jogging along slowly and plow into the wave ahead. You still low down need lots of volume up front, smaller decks than the Twiggy had and maybe the T foil down back.

The biggest wave I ever had on the Twiggy was about 100miles off Brisbane. We hit the continental shelf on the way back from an aborted trip to Fiji. We were on a broad reach with the jib up and a large wave leaned us over and she rounded up - with no main up (in about 22knots solid). She leaned over so far that my friend sitting on the windward side of the cockpit fell onto my head (I was on the leeward side). The wave crest made some white water getting through the leeward net and we headed off again on the next wave after I got back on heading. I never broached her any other time.

cheers

Phil

 

Thanks for your thoughts, Phil. I'll be starting to test The Fire Arrow test model again in April or May this time in stronger wind. She uses a lifting foil on the daggerboard, a rudder T-foil and two ama foils(one used at a time) and is oversquare. Seems very stable in pitch when on foils but if she is overpowered off the foils she'll want to try to pitchpole. At least she did that once.......
edit-One main advantage of a properly designed version of this configuration is that the main hull would fly in a 5 mph(4.4knots) breeze. Another is that the rudder T-foil working with the daggerboard lifting foil would give the boat tremendous pitch control authority.

 

So, would a scaled down 1/4" ply 30' IDEC be a faster design than the Hughes Tomcat 30?

The Tomcat is supposed to be 1800lbs, with a 375 sq' main 175 sq' jib and a 675 sq' chute. AMA displacement of 4,340 lbs and an overall beam of 28' That's a lot of righting moment, low free board and an draft of 8'10" with the board all the way down.

Setting aside the potential foil modifications for a moment, the initial design certainly looks fast on paper. Why don't we see more hot rods like this around?

 

The later Crowther Hemlock design Hasta La Vista is like a more modern supercharged Twiggy a little longer at 35'. It's a nice boat that felt like it could have done with a bit more sail area in light conditions and had a high top end. I'd have float rudders on it for a bit more control when it pulled the main hull out in a breeze which it does quite easily.

Lock seemed to have consolidated quite a lot of his thoughts about float shapes at that point as Hasta has quite different floats with more volume down low apparently they are about 150% of displacement which looks about right with the eyeball. They had taken the diesel out of her when I saw the boat in Port Lincoln and was floating high on her lines and looking good. She felt lovely at that point with the quick motion that comes with a light boat as you walked around her deck you could feel the weight shift.

Boats like B&Q and IDEC/Sodebo had a different underlying design concept they were like lengthened ORMA's and based around what was believed to be the maximum manageable sail area while lengthening the hulls for better longitudinal stability which explains the relatively narrow beam. It's a more sea kindly approach which isn't as "stiff" as an ORMA and hence more forgiving offshore. They do lack a bit of power versus the more beamy Ultimes though.

The KHSD Tomcat 30 is a pretty good looking tilt at the same concept personally I'd like something a bit longer maybe around the 35' mark as a minimum. I see all of threads on really short trimarans and am always thinking it's good to build in more length while trying to keep hull volumes, freeboard and hence weight under control. The low weight helps keep the structural challenges manageable so it's a symbiotic relationship between the design factors.

 

I realized in my post I didn't really address your question I think the answer lies in the low accommodation and payload that tri's of this type offer. It takes a special buyer to forgive the relative lack of space for the sailing qualities. I sailed back to Melbourne on the cat behind Hasta in the photos it was a very comfortable thing with lots of space onboard but altogether pretty stodgy by comparison despite the racing sails and equipment.

That to my mind is the rub performance tri's are rather selfish boats. Even in quite large sizes I don't really see them as much more than a boat for a couple or a small family for charter or syndication which is one of the engine rooms of production multihull sales they would be a tough sell. As an example Hasta is 35' you could probably have a couple and their kids onboard without a mutiny but on a cat of the same length you could take two families in comfort and privacy.

If you scaled down IDEC you would reduce the length more than the beam which would put you back towards more Tomcat like dimensions. Relatively speaking a Tomcat style design kept light would be a better solution imo from a performance perspective.