Multiple Magic

[IanHB]

Dick, Thank you for your concern on the success of my TRIMARAN I thought it would be better to post the data here so as to help others with there understanding of the design criteria. The dimensions, all in metric are: Length 1.2m, Beam 1.2m,
Weight 2280 grams, Mast height 2040 mm, Total sail area .8 sq m, Daggerboard depth 320 mm, Rudder size
190x50 mm, Gyatt drum winch, max hull beam 130 mm, max float beam 100 mm. Yes I have photos which I will attempt to post shortly.

[MultiFast Is MultiFun]

Ian -

there certainly doesn't seem too much, if anything out of the normal sizes/specifications for a Mini40/F-48 multihull from what I can see based strictly on the physical dimensions provided. For some of us up here in the U.S. who are "metrically challenged", I have converted the metric to US and maybe someone else can take a look and let you know.

Length 1.2m, = 47.24”

Beam 1.2m, = 47.24”

Weight 2280 grams, = 5.02 lbs

Mast height 2040 mm, = 88”

Total sail area .8 sq m, = 1240 sq. in

Daggerboard depth 320 mm, = 12.5 “

Rudder size 190x50 mm, = 7.4” x 1.96” (14 ½ sq. in)

Gyatt drum winch,

max hull beam 130 mm, = 5”

max float beam 100 mm. = 3.9”

The sail area is actually a bit under maximum, but should not account for problems you indicated. Rudder area is "normal" - but perhaps a touch undersize - but again, not enough to make it a concern. Location of mast relative to daggerboard might be a key, and the maximum beam of the hull and floats may also be a key if their width extends much below the waterline. On the other hand, the Mini40 design FREIGHT TRAIN has a teardrop shape and is almost 6.5 inches wide right at/below the water line.

Tacking slower and in a big arc, rather than tight and small arc.
Easing mainsheet during tack, and sheeting back in slower.
Carrying enough speed into a tack.

Those are my first thoughts about taking problems.

Even though the boat will sit below it's waterline, add some internal weight if you can - wrench, pliers, etc. just to see if added weight (mass) will help pull her through the tack. For right now, those are my only suggestions I can think of - plus a lot more "stick time".

Does the bow go down when beginning a tack, or does it raise up into the air? Secondly, do you have weather helm? If a lot of weather helm, you can try reducing it a bit, and see if it helps. With a lot of helm, the boat will have a tendency to come up into the wind and just "park" there - meaning backing up and then going forward is the only way to tack. Again, it might be the speed and amount of sheeting of the main - too early is worse, as it will tend to stall out. Whereas leaving the sheets a bit out, and heading off, then sheeting in slowly while heading up to desired course should also help.

Let me know if any of these help. Also, any others who care to post suggestions, please feel free.

EDIT: Added
Ian, the following from one of my U.K. contacts:

Just a few words on the problems with tacking. Most people suffer from this problem in the early stages of learning how to sail a model multihull. I know I have been there and got several medals and watched the fleet sail by.

I suggest that you move the jib further forward and make sure that the leech is not too tight. The slot with be about 10 to 12 degrees to allow that main to work correctly.

Seldom is the rudder area size the problem, more often then not it is the main foil that is incorrect or in the wrong position.

[peter]

ian
Slow tacking can be caused by a number of things.
try the ideas below one at a time to see which one works

the throw of the rudder
a wide arc suggests that there isn't enough throw on the rudder, incease this then try again.
is the rudder transom hung or underslung?

when you are just starting to tack, does the luff of the main back fill before the jib?
If this is the case, either sheet the main in more or open the slot by easing the jib out

a good starting point for slot setting is to have the main just off the centre line to leeward and the slot at half the jib height should be around 50-60 mm measured from the mast.

does the boat "hobby horse", rock back and forth while sailing?

If it does move the mast back (if possible)

have you got the centreboard positioned at or just behind the rocker of the boat?

is the mast just infront of the leading edge of the centreboard?

Lots of questions some answers already there. Remember try one thing at a time.
More information along the lines of the above will benefit us to help you out more.

try to fix one problem at a time, there are several more things to try but the above mentioned ones are most likely what is causing your problem.
Peter

[IanHB]

nz.msnusers.com/SharedPicturesIanHB

This will hopefully be a link to a photo album site which I have just created. It contains some pictures of my Tri.

It will be interesting to see if my Geekness has improved?

YES, It worked for me at least.

[peter]

Ian
Your boat looks really good by the photos. Thank you for posting them. If you are still having the same problems with tacking etc. The things I see in the photos is that

the percentage difference between main and jib seems to large, and the draft of the main seems to far forward. What this will do is when you try to tack the main is preventing the jib pushing the bow through the wind.

The centreboard looks like it's backwards.

Swing rigs were tried over here and after testing and adjusting and testing again for weeks the conclusion was that they worked in the breeze strength they were designed for and nothing else. We found that conventional rigs were far and away easier to handle and far less troublesome.

Also the mast to centreboard alignment seems a bit close, try (if possible) moving the mast forward about 10-25 mm, it may help without building new sails.

Hope this offers some assistance if the problem is still there.

As I said before the boat looks really good and is a credit to you.

Peter

[IanHB]

Thank you for the valuable input Peter. Also the kind words. I cannot take credit for the construction which was done by Milton Bloomfield of Christchurch, New Zealand. I swapped a 10 rater for the trimaran about six years ago and have only just got my act together to get it in the water. Too many projects.
Milton`s company " dynamic composites" makes tillers for Lasers.

[MultiFast Is MultiFun]

Ian -
nice photos - nice boat ! Thanks for posting.

For Peter: Some of the older style boards were actually designed to look like they were backwards. Kind of depends on the foils shape and maximum width which "should" indicate forward part of board.

Back to IAN: How does the boat set on the water, relative to main hull and floats? In still water, does it tend to flop back and forth between floats, or are all three in the water at the same time?

Reason I ask, is in the photo the following jumped out at me ......

The main hull has a great deal of rocker in it (keel curve from bow to stern) while the floats look very long and fairly flat bottomed (relatively speaking).

This would infer that if both floats are in the water at the same time, especially when tacking, you are pusing two long straight hulls through an arc sideways. Is there any way to temporarily bend the cross arms up to assure you have only main and one float to worry about when tacking? Maybe a cross wire that can be tightened when the beams are depressed - much like a hunting bow. That may be difficult to do given it appears to be all carbon. I guess my first reaction was "no float rocker compared to main hull" as seen in the side view with truck in the background. Short of doing a test by adding some shaped foam under the floats (which may not work if floats are already in the water) it might raise the main hull slightly and give more rocker to the floats. Add using tape and see if it makes any difference if you build up the float hulls in the middle and forwards. For some reason, the floats just appeared too flat, and flat usually makes tacking an added burden, while too much rocker makes a multihull "hobbyhorse" and pitch in waves and chop.

Just some thoughts, along with what Peter has already suggested. Also looks like great place to sail !

Dick

[IanHB]

;D Thank you for all your support guys.
I must tell you that this tri does not have a major tacking problem and I apologise if that is the impression I gave.
Sure I had a few hairy ones on the first times out, but after your advice on the different technique needed to drive these craft I should become better at all the skills needed to sail a multi skillfully.
My main problems were caused by being cocky and trying to carry to much rag for the conditions.
No problems in the light but the gusts became quite exciting.
I think from your input that I need to look at the amas, their section, forward floatation, rocker and angles.
They do float clear of the water when the opposing unit is on the surface, so that appears to be OK.
I know that tripping over the leeward ama is the major challenge with trimarans.
Putting up a sensible rig for the conditions might be the first step to maximum fun and minimum heartache.
The most important thing as you both suggested is time on the water.
THANKS AGAIN!

[MultiFast Is MultiFun]

Glad you updated us on the tacking (non-issue) !

I was getting close to running out of ideas.