Multihull Footy

Any progress on cat or tri Footy builds anyone? I saw some interest about the topic on another forum.

Just wondering.

I’m still slowly working on my carving in between builds.


Hi Nigel -

Length to beam ratios make multihulls a bit of a losing time and effort build.

The FOOTY box rule as established just doesn’t lend itself to modern high-speed multihull designs - cats or trimarans. One could make one that might resemble a catamaran of perhaps 1960’s vintage - but modern multihulls have very narrow beam hulls compared to their overall length, which eliminates ability to place electronics inside the hull. If you go with narrow hulls, then the electronics ride on top and between them - and hopefully they will provide the buoyancy to support radio gear, batteries and rig. To prevent capsize because overall beam is so severly limited, the rig/sail will be smaller - or else the builder will hang a keel and lead below :scared:, negating the “concept” of lead-free multihull sailing. :wink:

Of course nothing prevents building a fat or tubby set of hulls - they are just — well — esthetically unpleasing to my eye.

Keep in mind that the basic ratio of modern cats is a hull of 18 feet, an individual hull width of 2 feet and an overall beam of 11 feet. Include a mast of 30-31 feet, and you can scale down to 12 inches and see what is left.

Not the regular box rules for the new multi-class; but a new, cubed-box for the measurement box

like on another forum:

I suggest a part of the rules, that may develope for this class be:

-The boat must rest in it’s measurement box, like if it were floating in the
water (ie. on it’s waterline).

-Shearline at top of box when measurement is takng place.

-And pretty much anything goes from that. Cat, tri, proa, etc.

Even though a cube box might be too deep for the shallow foil appendages on a multi, the depth would allow for all sorts of experimenting.

Maybe hydroplaning foils if someone would like to try it.

Nigel -

here is a comparison of the points I was trying to explain. Using a standard 18 foot beach cat, without a lead keel, but using “human” movable ballast" suspended from a trap wire attached to the mast, the basic dimensions (roughly for this example) are:
Length = 18 feet
Overall beam = 11 feet
Hull width = 2 feet
Mast height = 30 feet

If you want to retain the overall length of a FOOTY class at 12 inches - here is what you would expect to see at that scale:
Length = 12 inches
Overall beam = 7-3/8 inches
Hull width = 1-3/8 inches
Mast height = 20 inches

and comparing to worldwide multihull standards of the recognized Mini40/Formula48 dimensions:
Length = 48 inches
Overall beam = 48 inches
Hull width = varies but 3-1/2 inches avg.
Mast height = 60 - 72 inches depending on sail plan

Thus - the fact you have selected the overall length to be a major limiting dimension, reasonable design parameters make a multhull of that length pretty limiting to also support the rig, electronics and battery and still have reserve buoyancy when sailing. That said - I suppose the visual senses of some aren’t compromised by two bathtub shaped hulls connected by a couple of carbon-fiber cross-tubes.

As they say, “whatever floats your boat.:slight_smile:

I always thought that a Footy cat or multihull would be so far ‘out of the box’ per se, that it would need a new or different rule(s) or amendments to the (Monohull) Footy CR. I once drew up a design that I thought would sail, and it had to go in the box on its side. (about 12" l.o.a. x 8" beam.)

It did require the use of small fins like electric powerboat cats use.

There was one design I saw that was ever attempted, and it did fit in the box, but I don’t know whtever became of it. Take a look. Maybe someone will own up to it?

I think I’d buy Nigel’s #3 hull if he ever did make a Footy cat. :wink:


Tomo -

forget for a moment ALL of the rules for the FOOTY class and look at two things - the overall length which IS it’s biggest limitation. At 12 inches long - any beam greater than 12 inches will inspire forward pitchpole instead of sideways tipping. Add lead to a single keel and hulls need to get wider and deeper to support added weight.

Narrow hulls which are easily driven through the water because of length to width ratios on a “normal” multihull are too small to house electronics. Thus they ride up on top and add to windage issues if sailing in windy conditions. Add a third hull (divide 12 inches by 3 ) and hull dimensions will be 4 inches maximum - so why build a multihull with hulls that wide?

One rudder or two, mast height, sail area, battery type, and all other FOOTY rules are all incidental to the main issue of hull design - that of width to length.

If you really “MUST”, maybe take a piece of foam, shape the hull into a large tunnel down the middle (like the old Hobie Cat 12) and have a solid deck. I “suppose” it would qualify as a multihull (in a sense) and might provide much needed space for electronics.

I know it needs a slight width adjustment but…

Coming along nicely.

I’ve been slowly carving away at a cross beam shape, in between builds now.

Just flash-cast one half of my sponson plug as well. What width beam you gonna try?

I’m gonna start with 9" (12"x9").


Footy Cat is at present 305 x 165 but i am going to try it as it is and then add adjustable spars so i can vary the width.
Footycat was originally planned for twin rudders however i am now working on a central spine to incorperate mast and a central keel.

I also planned on a swing rig with a direct drive from the servo - getting the increased movement from gearing the servo.

Batteries and reciever one side servos the other

mental model musings

Some other mental model musings for you to ponder on


Pardon :confused::confused:

Giving you the benefit of the doubt - has a lot of your diagram just not reproduced in the message ?



Note to self will have to draw it in pen next time


I see you have the same CAD package as I do - the early version with elastomeric “Delete” function


Note to self: stop drawing on toilet paper- use single sheets of A4 in stead. :devil3:


I would not be surprised of a successful multi Footy had a really Odd design to it, in stead of forcing te usual design to fit? Like maybe a bird flting backward (like a trifoiler)

Think this is wierd wait till you see the alternate rig for it.
i was thinking along the lines of an inverted kite

A bit of progress today.

Did a boyancy test on the sponson plug, and it displaced 150gm.
(X2) will give an all up of 300gm displacement. I figure my lajabless displaces 400gm (-200gm for the bulb), so I should have lots to play with, come rigging time.

I have the sponson flash-molds done, and one-half of the cross-beam flash-molds done. By tomorrow, the other half of the cross-beam flash should be done.

After they’re ready, I’ll cast some protos, cobble them together, and see what’s what.

And yes, pics will come in time.:slight_smile:

What about a dual-rig for a Footy cat?