David and I have had a nice talk about his new Razor3, and he graciously gave me permission to share it. I thought you might find it interesting:
From the UK, I just thought you might be interested to know I built a Razor 3 to your design off the Footy website. It has gone very well so far. I won the Bournville Open, winning 12 races out of 16, and the Mid-Thames Open winning 8 races out of 12 and beating two of the latest Stollery ICE designs.
I am using a modified McCormack rig with spars made of 4mm Carbon fibre tube for greater stiffness than the wire rigs. I made up a rig to the “Intermediate” dimensions shown on your plan and that is my largest rig. I also have three smaller rigs, down to one with a 305mm height as in the original Footy rules.
I think you may have generally lighter winds than we have in the UK. At the Mid-Thames event it was quite windy and I went down to the smallest rig and the boat was still diving in the gusts.
I find the boat generally very well balanced and easy to control, much better than the three previous Footys I have designed or made. I think diving and losing control is the main problem but all classes do it if the wind is strong enough.
I’m very pleased to hear that you like the boat.
In Razor3, I gave up trying to prevent diving, as I think it’s impossible to do so. Instead, I tried to make a boat that handled all points of sail well, including submarining
Some of my earlier boats broached as they came back up from a dive, causing loss of control and momentum. With Razor3, I find I can sail a pretty straight course under water, and keep it pretty straight when it comes out of the dive…so there’s never really a loss of control.
Congrats on your wins…especially against ICE!! Roger sent me some pics of the plug he was making, but I haven’t see one completed yet.
The rig you use as the large one is my middle of 5…I have two larger (one huge for very light air) and 2 smaller…the smallest being 305mm to the original rule. The two times I raced in the UK, though, my middle rig was the largest I had the chance to use. In the USA, I’ve used them all.
Would you mind if I post your note on the RCSailing forum? I think it might start some interesting conversation.
Feel free to post it anywhere at your discretion
One or two extra details you might find interesting. The lead ballast I cast came out almost exactly to the weight you specified. We don’t seem to have fishing weights of the right size or weight over here so I used a body of revolution shape for a nominal 50% laminar flow, making a balsa pattern, a mould and a lead casting.
The hull was made from 2mm balsa and the fin and rudder built up from sheets of 1/64 marine ply glued together, intended to be a NACA 63A008 section. The whole boat as sailed came out to 400 gm, about 50 gm less than the design weight. This was probably because I used very light 8gm model aircraft servos, a 6gm 2.4GHz receiver and a 400mAHr battery weighing 32gm. These servos have enough power to pull the sail in and the battery lasts16 races without changing!
I put in a much bigger access hole in the deck than you had, for those vital bits of boat surgery that I always seem to need after costruction.
It does indeed tend to submarine in a fairly straight line and does not broach much. I think it would go faster with a round bilge hull instead of the hard chine so I am designing an equivalent curved hull. Or do you have one already?
Thanks for putting the design on the website. There was a lot of interest on it from people who could not catch me!
Thanks for the additional info, David…sounds like you did an outstanding job.
I’ve designed the occasional round hull, but decided some years back to champion what I call “kitchen-table boats” to prove that simple, cheap, easy-to-build boats can win races. That decision has brought me a lot of satisfaction when I get nice letters from people who have built my designs…like you