Carbon/aluminimum sandwich

Latest from the experimental workshop.

A core pf the type of aluminium gauze that generally comes in motor car body repair kits with a single layer of 16 g/m2 carbon tissue + epoxide either side somes out at a finished weight of 100g/m2. This is proabably epoxide rich.

A panel 7 cm x 8 cm cannot be visibly deflected by hand.

Could probably be used with advantage for building hard-chine hulls (curvature in one plane is easy) and is a cinch for mechanically loaded flat components - decks (or parts thereof), transoms with transom hung rudder, servo-trays. Could also be good as a basis for fins.


Ok going Hi-Tech, although maybe not really necessary for a footy, but is this little bit too much perhaps?


Why is going Hi tech on a Footy build different to say a M class?

That is actually being unfair to the high-tech. For once the materials were genuinely from the box under the bench - the carbon tissue left over from laminating a hull and the aluminium gauuze came with a packet of body filler used to re-fair the plug after a disastrous experiment!. It is genuine ‘box-a-bits’ stuff in the spirit of many Footy builders except that the box of bits has 21st century materials in it.


Good question.
My response: I don’t think there s a fundamental difference between going Hi-Tech in a Footy and, say, a M class. The real question is: “is it worth?” Personally I don’t think so. You can build a mold for an autoclaved vacuum molded CF footy hull, but would you save enough weight compared to the same fiberglass, or balsa hull, to make it worth? Or does a footy need all the structural strength and stiffness of a “A core pf the type of aluminium gauze that generally comes in motor car body repair kits with a single layer of 16 g/m2 carbon tissue + epoxide either side somes out at a finished weight of 100g/m2. This is proabably epoxide rich. A panel 7 cm x 8 cm cannot be visibly deflected by hand.” even for a keel that has to hold a 200gr?, I can understand it if you are like Bill and like to take on solings and other heavier boats, in that case you will need a bullet proof hull, but otherwise probably an overkill (Btw how do you, and can you shape the aluminum gauze/CF to a foil section?). I can see the need of weight reduction and the need of an exceptionally stiff keel in a M boat, but I really don’t see the same advantages in a footy, not because the footy is less technological than a M but because the size makes the weight gain or stiffness gain really negligible, my hollow balsa/epoxy shaped keel with a 250gr bulb has probably less lateral deflection than a Skalpel keel with bulb.
Personally I would invest more Hi-Tech(nology) into the development of more efficient foils (keel, rudder and sails) and hulls designs than the use of exotic materials.
You want to have a “21st century material” boat no problem, but is it going to make a difference, especially if you have a 20th century boat?


Hi, Gio. I suspect that my views differ from those of Brett, who is vastly more experienced than I am in the ways of Footies. For what they are worth.

I do not believe that a Footy can ever be anything but a leadmine. Leasdmines need ballast to work. If we say that a typical Footy has a 200 g bulb, saving a total of 20 g (not that hard) means an increase of 10% in the weight of the ballast for the same displacement. Viewed very, very simplistically this can be taken as a 10% increase in power/weight ratio - which has to be worth having.


That’s the point, do you need CF to save 20 gr on the hull?


I don’t know whether it’s the best way, but it is a way. If I had the development resourcs of Airbus, I could probably tell you: as it is I am making guesses.


By saving weight in the hull, are you suggesting that would also allow you to reduce weight in the keel bulb?

I don’t see it as increasing the ‘weight’ of the ballast, because the keel bulb is mainly a way to right the boat due to the heeling forces of the sails. So saving weight in the hull decreases the displacement, but you still need that righting force.

No - I think the right answer is to put the weight saved in the bulb to increase stability and hence sail-carrying power. The sensible alternative is to maintain the same sail carrying power by increasing bulb weight but reducing draft, thereby reducing the fore-and-aft polar moment of inertia (i.e, reduce the tendency to hobby-horse)


An interesting debate, for which we don’t yet have an answer.

I personally don’t believe that a lighter boat is necessarily a better or faster boat. I do believe, though, that weight in the bulb is always preferable to weight in the hull.

Tomo, a hull is designed to sit on its waterline at a given displacement (weight.) If you lighten the hull AND the bulb, the boat will sit higher on the water than intended. This might improve acceleration, but probably not overall performance. If, though, you lighten the hull and add that weight to the bulb, the hull still sits correctly, but you’ve increased its righting moment. That means you can carry more sail into a heavier breeze.

That’s the theory, so let’s encourage Angus to be innovative. He’s using materials that are reasonably available, and regular tools and techniques, so if he discovers something worthwhile, we should all be able to use it if we choose.

Of course, as Gio asks, “is it worth it?” How much difference will a couple ounces really make? We’ll never know unless Angus continues his experiments…so GO ANGUS!

Bill H

Thank you Bill. My sentiments exactly.

And (probably mis-) quoting my great hero Olin J. Stephens, ‘Its the seconds that add up’.


Bill, and Angus, despite what may have been perceived; I too have to agree with you on this one.


I agree with your hero, Angus…seconds count. But to play devil’s advocate, that’s why I think I’ll go to the pond and practice sailing my Footys while you spend the time in the shop trying to make yours lighter!

But keep up your research…I’m really interested.

Bill H

I think that however any of you construct your boats will add to the overall experience level in the class. In truth no one really knows what is the best tack to take because we have no real benchmarks, so we are all guessing at this point.
My particular point of view is that the class is too limited in beam, and that the 12 inch overall length should be the only measured dimension. That is the derivation of the class name. But the beam is currently limited by a box (not currently part of the class name) until I can convince enough of you out there that the box is too restrictive and a bad idea.
My fear is that we will soon determine the prototypical hull shape for these boats, under these rules, and someone with the knowledge and infrastructure will produce a boat that the homebuilder will not be able to compete with. Then this exciting repartee and building frenzy will be supplanted by manufacturers and semiprofessional sailors dominating the scene (vis-a-vie IOM and M Class).
I also believe that before we get too head up about saving an ounce or two with hi-tech construction materials and methods, or how that potential saving should be distributed we should be revising the rules regarding the r/c power source. If we encourage hi-tech building then shouldn’t we endorse the same approach to the r/c? I discussed this on a different thread but I think that the rule should limit voltage rather than specify cell type. This would not only save unnecessary weight and improve righting moment for boats built for racing but it would open up new avenues for experimentation that could only benefit the class, and would not bar anyone from using AA cells if it were more convenient for them.

I agree with some of your statements, but not all. I know that you have your reasons why you don’t like the box restrictions, tho, it seems to me that we would get some really odd shaped boats if we did not have it. Not sure why you consider that the box rule will cause the pros to go crazy. If they want to, it will happen whether the box is there or not.

In spirit I agree with you Neil, but I am unconvinced that any opening up of the electrics is ever going to make the Footy anything but a leadmine - a slightly more frisky leadmine perhaps, buty still a leadmine.

I am also dead certain that the ideal shape for a Footy, whether measured in a box or not, is very odd indeed - simply because they are so small. The cardinal sin in yacht design is use of the elastic tape-measure - and a Footy is about half the size of anything that has ever been raced seriously before. That is a pretty powerful piece of elastic.

My current efforts fill me with terror - they just look wrong, and maybe they are. However, all the design reasoning stands up when I go through it with other people. We shall see - but I am pretty sure that the boat will be described by most people as a ‘freak’.

Furthermore, it is highly unlikely that I will be the person who hits the magic formula - if only because I am 54 on Sunday and the fires of imagination and lateral thought are burning down. We need some bright kids in here who will show us silly old buffers how it should be done.

Incidentally, don’t be too hard on the professionals: in full-size boats - and probably even more so in models - a high propertion of the greats were essentially amateurs who became professionals because they succeeded - Stephens, Clark, Illingworth, Carter, Farr, Peterson, Holland …

Well these boats are displacement hulls, there is no getting around that. And perhaps these boats appear to be “freaks” to some and toys to most others. But what this grand discussion is about is brainstorming how to best make a foot long sailboat perform. And to Bob, yes without the box we might end up with some “odd shaped boats”, but more than likely really fast odd shaped boats. Unfortunately, with the rules narrowly defined as they are (pun intended) so early on in the development of the class we won’t know if a broad boat might be the most efficient Footy hull type. What can be gleaned from all these posts is that the Footy as it is today has a very limited wind range in which it performs well.
That perception has been related to me by other sailors from other classes as a reason for dismissing the Footy as a serious sailboat. As an example of my train of thought my Bantam design (7-5/8ths inch deck beam) can carry a 20" rig in 12 mph winds, and has posted a respectable internet course time in choppy conditions.
But I have digressed from the point I was trying to make. Back to the lead-mines - you need only to surf the web among the robotics sites or the r/c flyers to get an idea of of the technologies that will be trickling down to model yachting in the not too distant future. Our boats are small and don’t require robust equipment to handle the loads so it is logical that the Footy lead model yachting in this direction. So, while these boats will always be displacement craft, cutting the r/c and battery weight (weight that we carry in the hull not in the bulb) in half or better is the area where most of the performance gains in sail carrying ability will be realized. That is assuming the beam restrictions aren’t rescinded in the future.

Just a curious question — “Why must they be lead mines?”

Not that there is anything wrong with that. :smiley: Could they be “Lead Assisted” perhaps?

Sorry Dick - that is the ultimate in US marketing spiel!!!