Twiggy trimaran

Does anyone have the plans for the centreboard/daggerboard for the Lock Crowther Twiggy trimaran? Any info much appreciated.

 

There was a thread I started earlier in the year enquiring into the twiggy trimaran. I think it went to about 4 pages long, I cannot remeber what the title was. it may be fund under my name as starting it.

The thread was Twiggy Drawings back in april, and was 2 pages.

 

I had one built about 15 years ago. It was a cedar board and had no real glass reinforcing just 10 OZ or so sheathing cloth. Typical NACA 0012 section. Not hard to make it you want to do one. I would make some changes - make the top snug in the case so the board doesn't wobble in the case - it always makes some noise which is a pain when sleeping. Also chop the bottom of the board off and then glue it back on. I almost wrecked my case hitting a rock. A friend called Glen almost sank his main hull because his board went through the case.

If I can help get back to me

Cheers

Phil

 

Thanks for the response Warwick and Catsketcher. Read your thread Warwick and helpful although not what I was after. Catsketcher your knowledge of the twiggy may be of more benefit. I need to know the layout of the up/downhaul blocks, lines cleats etc. for the daggerboard. If you have any drawings or memories of said layout it would be much appreciated. Original board lost in qld floods with boat on hard.

 

There is a Twiggy on the lake nearby. I can see if I can get a pic for you. I will check my Twiggy plans to see if I have the board.

IIRC the downhaul grooves are about 30 % aft (about where the section is widest). Lock didn't call for a pulley at the base of the grooves - just a piece of bent copper for the rope to run through from one side to another. Epoxy this in place. Flare out the ends and clean them up so they don't rough up the rope.

Thje designed board was a constant section all the way through. This is not bad but you may like to make the top part square. This gives a far greater area at the back of the board if you hit something. It also stops as much turbulence at the case slot when fully down.

You can pretty much work out the dimensions yourself. Check out the case - IIRC the section is either a NACA 0012 or 0015. It doesn't really matter. Leave a small amount of clearance in the case so it doesn't wobble too much and go from there.

The height of the board is determined by the boom and hull bottom distance. If you raise the boom ( I did to help fit a dodger in) you could have a longer board. That may help the boat stay easier to steer in tricky conditions - a bigger rudder would be nice too - or get it further aft on an extension. A friends Twiggy handled better than mine with its rudder extension.

Pricing the cedar is hard. It could get pretty pricey quickly. Cedar is lovely to work with but you may need quite a lot of quarter sawn 100x50 or larger. Ring around a few mills. I found a place that would let me look through a few planks to get the nicest ones. Building a board is some of the nicest facets of boatbuilding.

The glass was just sheathing cloth. Nowadays boards aren't built this way. The timber is usually just a core with a heavier glass layup.

Will check in the shed tomorrow for the plans

cheers

Phil

 

Hello,
I have a Mk 2 Twiggy with a fixed rudder and find that it does not want to turn at low speed, I can help with daggerboard numbers but need help with the rudder. I am on Lake Macquarie, moored at Wangi.

 

Catsketcher, any photos would be a great help. If you have the daggerboard plans it would be even better. I have the plans for the hulls and crossbeams(MK1) but no daggerboard, so fingers crossed. 3timesbetter, I have to make a new rudder as well, but mine is a lifting/pivot rudder. What exactly are you looking for?

 

Twiggy steering can be affected by sail balance, if the main is sheeted on more than the headsail weather helm can make steering difficult. Better to view rudder as a trim tab and steer with sail trim. Properly set up the boat should hunt wind shifts going to windward while pointing as high as an Etchell.

 

Some shots of the rudder and CB plans that I have. The section is nothing special but I have not got the full drawing.

3 times better - As Roger says you should sail a Twiggy as though the rudder follows the boat and gives it a fine tune. You steer a Twiggy with the mainsheet - on for up and off BEFORE you start to bear away. A Twiggy in a breeze will not bear away unless you ease first. It makes you sail better.

As for low speed manouvring it's pretty simple - get fast. When cruising our Twiggy I used to see the look of concern at anchorages when people would see me after pulling up the anchor. I would floor the engine and when the boat got up to about 5 knots I would then cut the motor and steer. Some poor mono sailor would see me aiming at them and get wider eyes until I cut the throttle and turned. Trying to steer at low speeds is very tricky. This has to do with the Twiggy's short distance between rudder and CB and its very high rotational inertia. So learn how to judge 30ft widths and then go through them with speed enough to steer. In a breeze this can be about twice as fast (or more) than a mono.

I would love to have a sail on your boat so give me a call on 0438 732441 and I can come around. We did meet when your boat was at Oyster Cove and I went to have a look at my old neglected boat.

Tribalance - Photos of plans attached. Get back if you need higher res.

cheers

Phil

 

Catsketcher, thanks for the plans. The one with the rudder foil should be a great help. Any chance of photos of the daggerboard system from the twiggy re up/downhaul as previously mentioned? Thanks again in anticipation.

 

I have experienced the boat hunting the wind, it does a better job than me, you can actually abandon the steering position and do other things, until the wind strength changes significantly. The original rudder was broken off the boat and was hastily replaced prior to hand over by the previous owner and looks to be about a 24% section. I have done some drawings to replace it with a 12% section.
Any one who wants to come for a ride is more than welcome. 0426245955.
As to gunning the motor then steering, I moved the outboard onto the center-line about 0.6m behind the rudder shaft and it is better, not good but better. Nothing compares with twin motors on a cat for putting it where you want.

 

Tribalance

No photos unfortunately in the file. Roger or 3 times may be able to take a few for you.

cheers

Phil

 

Daggerboard, et al

I am going down to the boat to do some work on the rudder quadrant, in shallow water, soon.
If you are really desperate I can give you dimensions and supply some photos of the daggerboard. My boat has a couple of ropes attached to the 'board and we find it will not stay completely down, but it doesn't have to,anyway. You can lift it with one hand until it hits the boom and you can stand on it and put it flush with the floor. The top is chamfered fore and aft and the tie down rope slips off, I am going to put an eye on the top of the board.
It handles nicely, we can beat windspeed to windward up to about 8 knots and then I suppose the windage takes over, but we can do 11 upwind in 15, easily.
Off the wind we only hace to tack [gybe] 30 degrees off DDW put put the apparent on the beam.
I have a 500 sqft screacher I want to use but would need an absolutely quiet day to need it.

 

Regarding the centerboard; on the port side of the centreboard case opening (on the cockpit sole) and immediately adjacent to the routed channel of the board fix a ss saddle. On the starboard side fix a cam cleat. On the top of the board fix another cam cleat and a saddle. Be liberal with the epoxy.

Raise the board (using the saddle on the top of the board) and pass a rope through the opening of the board and tie it to the saddle allowing about 600mm tail. Fully depress the board and stop the tail in the cam cleat on the top of the board. To raise the board pull on the starboard line and when at max jam it in the cleat on the starboard side of the cb opening.

You can also adjust height of the board with the tail but I find at speed the loads too high.

Next time I have a camera I will take some pics.

 

Twiggy daggerboard dwg

Here is the daggerboard dwg, part of sheet 4 (attached).
The design section measures 21 3/4" from leading to trailing edge.
The thickness at the widest point is 3 1/16" .
The widest point is located at 7 1/2" from the leading edge (or about 33%).
The leading edge has a radius of 3/8" .
The trailing edge radius is 1/16" .
(all these dimensions are before glassing)

Lock calls for 4 layers of 5 oz cloth and epoxy.
Of course, it would be a good idea to check the dimension of your daggerboard trunk to be sure the design section will fit.....