Mini 40

[Martyn]

Hi all

Some friends and I are going to build some Mini 40 Tri's. The design that we have decided on is the Ghost Train.

I have had a few question in the back of my mind about these boats that I thought someone here may like to comment on.

We are thinking of some foils on the floats much like the ORMA 60's to try to create some extra lift. These would be curved under the floats just like the full size boats. Any comments?

Is it necessary to fit rudders to the floats if the main hull is going to be clear of the water much of the time(hopefully)?

Does anyone have a good way of attaching the cross beams to both the main hull and the floats? I know it will make transport difficult but I am considering building the boat with the beams fixed.

The boats will be built of Carbon, does anyone know what sort of layup should be used? I know that Marbleheads are built from 1 layer of 4oz carbon and 1 layer of light glass , is this enough, or would 2 layers of carbon be needed in some of the high load areas ie. around the beams etc.

[F-48]

Hi Martyn -

First off - a wise choice of building plans. It is a well proven design, and it looks good too. To my knowledge, quite a few have been built and raced in Europe, England, Australia and New Zealand. Here in the US, they are a bit scarce, although I have sold a few plans so some may just be slow building.

The curved foils may work but may also introduce you to a lot of design and engineering work. Having the right amount of curve to lift, but not "fly" the boat seems to be the question. Unless you go to something like the "foiler" from Microsail, that senses the water level and adjusts it's height above the water, I think (just speculation) that the small area may not be that helpful.

Peter Birch from Australia may have insigt as I think a fe of his guys have tried the smaller, non-adjustable foils. If he doesn't respond, email him using provided link. If you use the foiler setup, keep in mind to make them easily removeable for light air days, and also be reminded of issues if you sail in ponds that have weeds.

A rudder under each float would be helpful if you intend to spend time up on one hull - but linkage may be an issue. Do a Google on "Ackermann" which is an issue when steering with wheels (rudders) wide apart, since each has a different arc during a turn.

If you are going with fixed beams, you can just glass them into or onto the deck. It will be a mighty big platform to transport, however. Better to glass in some aluminum or stainless small drilled and threaded piece and then use machine screws to hold cross beams in place. That way you can easily disassemble for transport or storage.

A Marblehead schedule for carbon and glass is sufficient. I would add a second layer internally for any cross beam (or other) attachment points, around the daggerboard trunk and rudder. Other than that, the glass (or carbon) is merely to keep the water out!

Hope this helps -other s may add to the comments too.

Post photos as you build - everyone likes to see a new boat take shape. Good luck.

By the way - where are you and friends located (country-wise)?

[Martyn B]

Thanks for the info.

One more question regarding the foil on the bottom of the rudder. How neccasary is it, and would it be worth making it adjustable via the remote? I think I have come up with a way of doing this, but is it a waste of time?

We are currently in Spain, for the next two years anyway, and will then be returning to Australia and NZ.

[Dick Lemke]

A waste of time? Hard to answer, as there are some who swear BY the foil, while others swear AT it!

On my 1 Meter tri, I had a fixed foil (about 3 degrees negative) and found it did not cause stern to "squat" until the wind really picked up. In light to medium winds it "seemed" to work OK but hard to tell.

I have doubts about it, but I would probably scale down the size of the rig first. The Mini40 size boats are known to have a bit too much sail area for most wind conditions. If/when you get your plans you will see the designer suggest four rig sizes as I recall. For a new boat, new sailor - I would encourage you to consider starting with a full size mast, but maybe sail set 2 or 3.

If not too complicated, give an adjustable trim a try, but also remember - you aren't on board and can't tell what the boat is "going" to do - only see what it has already done - and maybe abit toolate. The foiler I mentioned earlier had adjustable front foils, but I can't recall if the back also was adjustable.

Here is a photo of angled foils that Alan Hayes of New Zealand used on his GHOST TRAIN. Also note use of some small bow planes to help keep bow up as well.

[Doug Lord]

Martyn,the kind off foil used on the ORMA 60's doesn't have an altitude control system because it is designed to only partially lift the ama when the main hullis flying. Crashes occur on the big boats when they go so fast that the foil lifts the ama clear of the water and now the foil becomes a surface piercing foil and because the lift is so close to the air/water interface it will very likely ventillate causing a catastrophic loss of lift and a probable crash. On models, for some reason, hydrofoils don't have a great tendency to ventllate so even in the above circumstance there would probably not be a crash for that reason.
Models, however, have far less relative pitch stability than do full size ORMA tris and part of the "partial lift system" is to use the ama to help control pitch. Only a couple of the ORMA 60's use rudder t-foils because pitch is managed thru the continued partial immersion of the ama. But on a model because of scale effect that won't work- and you'll need to augment pitch stability with a rudder t-foil. There are a couple of ways you can look at it that will capture the essence of the way te ORMA's work: 1) a model tri is VERY difficult to fly the main hull at a particular altitude; unless you have a very long rudder on the main hull the rudder foil is very likely to come out of the water. You could consider a single hydrofoil on the main daggerboard using a wand(altitude control) preset for the angle of heel you want . The foil will lift the main hull before the heeling moment does and then automatically change over to a negative lift to hold the boat down-all automatically.
But then you have to change out the main daggerboard and rudder in light air because of too much wetted surface. 2) An alternative would be to have small rudders with t- foils on each ama that would control the boat in pitch and only one set would be immersed at a time. Then in light air you could simply raise them vertically in a "cassete" trunk as you would the curved ama lifting boards. If you'd like to discuss this further feel free to e-mail me at :[e-mail] .