Razor4 and Cobra5...developing the themes

I thought you might be interested in my latest developments with Razor and Cobra designs using foam panels.

I’ve decided to go to Orlando with a 300 gram boat this year. I had a chance to sail Razor4 a bit and was happy with its performance. I can never leave well enough alone, though…there’s always another idea to try. So I’m building Cobra5. The two boats are very similar, but Cobra5 has a finer bow, made by twisting the panels. I’m pleased with how well it went together. The only thing I’m not thrilled about is that C5 fits so tight in the box that I had to move the rudder forward to get enough throw…there’s always tradeoffs.

Hope I can try Cobra5 before March, but I think it LOOKS fast…which seems like a good reason to pick it!

The pics are jumbled together…can’t figure out how to sequence them, but the names tell you which boat it is when you highlight a pic.

Happy holidays to all…Bill



Is Razor 4 the same boat that you sailed in the Region 1 race in September? Or have you made significant changes?

Walt H.

Walt, that was Cobra4…my first foamie hull. That race was its first, and the rig was a bit too far forward. That prevented me from being able to point well enough to keep up with the leaders. After that race I put in another mast tube and improved her abilities. Razor4 was built since then, and Cobra5 is a sort of combination of developments from both.


Bil - there are three mast tubes in the hull - but only one thru deck. Does that mean you tested before applying the deck - or are there plug/patches to cover the unused tubes allowing them to be used if needed?


Hey Dick, there’s only one tube on Razor4…based on prior experience I was confident putting it in, and got lucky, too. Cobra5 has 3 tubes…for two reasons. First, the centers of flotation and gravity are a bit farther aft on this boat than my last few, so I’m less confident. Second, I have a new rig to test with a different center of effort that seems to indicate a more forward position than my other rigs. Hopefully, one of the three options will be good!


I use three tubes in all my boats, the versatility is worth the bit of extra weight.

Nice looking boats you’ve got there Bill. You should take them out to dinner though and buy them a hearty meal!

she’s a skinny little tramp…

OK guys…I can take the abuse…but I prefer to think of them as “lean and mean!”


Lean and mean, eh? And here I thought you were just running out of materials!

These difficult financial times require frugality :wink:

Very nice looking boats Bill, I do like the shapes you are achieving with the foam panels. Is this Depron sheet, and what thickness are you using?


Thanks, Graham…the foam is Gedlipac…very much like Depron. It’s 3mm thick. I discovered it through my other interest in R/C planes. It takes some getting used to, as the edges need to be more carefully beveled for good panel joints, and the glues are more difficult to use than what we are used to with wood. The payoff is in lighter weight, and perhaps in greater flexibility when bending the panels…something I’ve just begun to explore. I think it puts Moonshadow-like ballast ratios in the comfort zone of a competent kitchen-table modeler, but I have more to learn about the material and glues before I’ll be comfortable publishing a design for it.

Merry Xmas to all…Bill

I built two of Bill’s Cobra 4’s of 1mm Depron foam which sailed at a weight of 325g. The trouble was that I almost lost one of them when I unknowingly cracked a seam when changing batteries (the boat sailed across the pond with its deck under water and I was able to save the receiver, servos and rig). Since then I have built a Razor 3 and a modified Cobra 3 out of 2mm foam and like the feel of the hulls a lot better. The weight penalty is within the 5g accuracy of my scale so it seeme to be definitely worth it.

Well, non one has asked yet, so here it comes: Bill are you eventually going to post the updated plans, here or on the footy site, for both boats?

They both look very interesting and after sailing razor (1) for years, I’ve be looking for a narrower hull for my second footy.


I can highly recommend the Razor 3 from the “Plans” section. It is a narrow diagonal boat which I built out of 1/64 ply. I loaned mine to a friend and he beat me with it at the Region 1 Regionals this fall so it is plenty fast and is a well tested boat. I believe the “4” and “5” series are still experimental. I know my Razor 3 is as fast as / and maybe faster than my Cobra 4’s.


Scott is right, Gio…R4 and C5 are still experimental. C5 still hasn’t seen water bigger than my laundry room’s test tank!

I don’t publish plans for untested boats, because I want people to have the best chance of success with a design.

Razor3 is a more sophisticated, better handling, and faster boat than the original Razor. It’s proven capable in competition…and it’s easy to build!

I’m pretty sure you’ll like it, Gio.


Thank you for the reply Bill (and Scott). I understand, I was no trying to rush you or anything else, I was just wondering. I hope both design turn out to be fast boats too.
In any case I’m building a Razor3, unfortunately family, life and work are all conspiring against me lately … but I should have it done by the time the little water we have here will be liquid again.

Looks great Bill.

I’m now down to only a little lighter with Baker’s Dozen A. This transatlantic competition is good for the breed. We are now in the position that the major exponent of the Great American Muscle Footy is the (veryE nglish) Roger Stollery. I think that results are proving him wrong.


Well, Ladies and Gentlemen, I think it is high time that this conjecture on light boats being the cat’s meow be put to the blasted test. Will some competent sailor from the North take Angus’s Moonshadow, Baker’s Dozen A, Loaf on the Shelf, or what ever else is his current fave and take it into Roger’s backyard and get some head-to-head results to see who proves who wrong for real. 'Nuf said!