Hello Rick,
You say “keep full power to the Headsail” What rig has the boat got ??.
John.
I meant the jib. I want to be able to back off the main enough to stop the boat from rounding up while not easing off on the jib. Just experimenting a bit. The EC12 and the M12 that I sail are both very tender hulls and I’m hoping that if this works as I plan it will help.
Rick
Hello Rick,
If, the boat is rounding up into the wind, move the rig forward, that will fix it!.
John.
Hi Lester,
I appreciate very much your answer, but I’m afraid to have some applications problems since I 'm not familiar with Excell as many others readers.
What would be more practical, for the majority of modelers, without enegineer degree, is to find a link between this diagram providing the pressure on sails, based on Martin’s formula found on a book “Radio Control Model Yachts” of Trevor Reece, and re-adapted for the purpose of this discussion:
and the following Data base for servos in order to make the right choice without complicated calculations :
http://www.servodatabase.com/servos/all
The diagramme include most of the models sail surfaces, from MM, RG65, IOM, M, 10R, etc .
About M, I have a remark, since it is often considered the 800 sq inches of sail area from rules (0.5161m²) when the real surface is around 1100sq inches (0.71M²).
The point is that the wind pressure according to the Martin’s formula, is applied to an ortogonal sheet as when the boat is running before the wind. Practically, in my opinion, the boat speed should be also taken into account or deducted.
Differently, during close hauled run, the wind is not at 90° and therefore the pressure exercized on the sails should be, in my opinion again, adjusted with the angle .
For the servo selection (arm or drum) is therefore usefull to use the Running conditions or the Close Hauled with the angle and boat speed correction ?
Thanks
ClaudioD
The M/Soling comparison was just an example.
When I am trimming sails on a full size boat I always find it harder to bring in the sail at close hauled than on a run.
It would be nice if things were as simple as a straight Sail Area/Force ratio, but they are not. It provides a decent starting point though.
Well I have an IOM with 6000 sq cm (I believe) of area and an HS-815 arm winch with 25 kg.cm torque. It is all ball bearing and I would say it is adequate. Every once in a long while if I get hit with a big gust downwind I have trouble pulling the sails in. This works out to 240 sq cm per kg.cm (6000/25). If other people submit the same data we could probably come up with a reasonable figure. It’s going to be different for arm winches and drum winches because of the speed but it could get us in the ballpark.
Don
Just to let everyone know I ordered 2 Robotzone 800 series 3:1 ratio gearboxes. One for my EC12 and one for an as yet built 50 " planing hull from a Montreal builder.
Rick
Ricoh,
Another way to unload the main before the jib does is to move the main sail sheeting point forward. IOM’s and Marbleheads use this system.
IOM’s have the main sail sheeting post about 20 percent less than the head sail sheeting position.
I got my gearbox kits from servo city. These things are huge and WAY overbuilt. First thing I did was start lightening up the chassis with step drill bits on my drill press. Once I took out everything I could and got it all cleaned up I opened up the Hitec servo and followed the instructions. Clipped the wires to the servo potentiometer and put it back together. Installed it in the frame and soldered up the new connections as per instructions. Drilled out lightening holes in the big main gear and also in the swing arm. Connected it up to my DX6i and was very pleasantly surprised at the smoothness of operation and the speed it has. Very pleased with the quality and workmanship. mounted it in the EC12. Did not get a final weight all set up but it is a porker for sure but I am not worried about being able to pull in my sails now under any conditions.