I was working on the design for my take on ths CK trainer today (mor of soon), and I wanted to find if a cheapo winch would do the job, in order to keep costs down. My design will have a bulb weighing 0.9kg, on a strut 200mm long, max cant being 55 degrees. I found that I would have space for a 55mm lever inside the boat on the other end. I did the numer crunching (if anyone wants the proof ill post it) and the force needed at max cant (boat flat) worked out to be 2.7kg, and with the boat heeled to the point where the strut is parralle to the water it came out at 3.25kg.
So, to the kitchen (warmer than the garage!), clamp winch to bench and raid the cupboard for water bottles:
The bottles weigh 1.5kg each, and it lifted them with ease, it managed 3 slowly. I was using a 6v pack with about half charge. So, I thik it may just work, just got to adjust the travel now…
I ran the calculations, and I got the same numbers you did. You may want to add in a small fudge factor to account for things like hull slamming, and wind puffs.
Matt, your numbers are fine except for the strut length,I think.
With such a short canting keel on a 30" boat I’m afraid you won’t be able to carry enough sail area. Perhaps it may work ok with an ultralight dispacement boat but I would suggest you seriously consider a strut at the same ballast of at least 355mm even if that requires a different winch. If the winch can handle 7.2 volts you might consider a regulator and 7.2v batt…Just a suggestion-you might consider analyzing the Righting Moment , Sail Area and Heeling Moment of boats in that size range(if you haven’t already).
What is the winch model,voltage, weight , cost and rated torque?
Right been having a think about this…
It seems that most of the <font color=“red”>^ model</font id=“red”> ck boats built or in build are based on keeping the same ballast and adding to the sail area, So i think what Ill try is a seriously light displacement boat with equal or slightly less SA than other boats of the same size. I think I am going to take your advice Doug on increasing the strut length, but I’m going to use it to dump quite alot of ballast. These are tne numbers I’ve come up with:
Aprox displacement (most likely less): 1.1kg
Ballast: 0.52kg
Sail area:0.3m^2, 0.21m^2 small sail (+re-moveble mast section)
LWL .75m (30")
sa/dis=0.25
wll/dis=0.64
Its a ‘bit’ on the mental side, I’m pretty sure which sail will get the most use round here anyway, although im working on a de-power system…
Matthew, if you look closely at full size boats you’ll see that the opposite is more prevalent-- keep the sail area the same and reduce ballast. It was done that way on the Schock 40 and the new maxZ86’s. If you look at Grahams F100CBTF design compared to an IOM it has less displacement and more sail area; looking at a US One meter: more displacement and more sail area. In both cases the canting keel boat has two times or more righting moment than either fixed keel boat at a 20 degree angle of heel.
I’ve done part of the design work on my 30" CK prototype -it was particularly easy since the hull is based on a reduced 36" skinny hull. Tested a hull from the mold reduced to 30" and came up with: max displacement: 3.45lb.(1.56kg)-canoe body only; beam to length ratio at the wl=8/1(30"wl-.76m); fin-14-16" ; ballast:2lb.'s(.9kg) ; sail area 515 sq. in.(.33sq. m).
Mast length approx 43"(1.09 m); reefable; una rig. This means I can buid a molded 30" prototype along with the 24 almost immediately. Only one off work will be the fin, lateral resistance , rudder and maybe the mast step boom though the one for the microMOTH may work. The 30 will use a 280 Guyatt with special drum; the 24 a 3801. Both boats will be able to move the keel 55 degrees in one second and both are testing a simple canting keel trunk that may be used in the F100. The beauty of the system among other things is that it can allow the keel to
be easily removed; it can allow keel rake adjustment and it can be modified to allow fore and aft movement of the keel while still 100% watertite…I’m finishing up two spinnaker boats this week and will be full time on the two one off(?) prototypes and the F100CBTF tooling by the first of next week I hope.
UPDATE: the new canting keel installation system I’m testing also eliminates the charactristic “bump” on the bottom of most canting keel boats.
Doug Lord
–High Technology Sailing/Racing
Sorry Doug, got the idea in my head that most of the f100’s being built went for same displacement and more sa… but anyway, do my numbers sound ok, or is it going to be a bit too much on the tender side? I really dont want to have to use an expensive winch…
Matthew, if you don’t lengthen the fin you have 90% of the sail area of my boat and only 55% of the RM: if you could go to a 12" (300mm) fin you’d have 84% of the righting moment and 90% of the SA.
As it is I’d say the boat was too tender. In fact one kg of ballast on a 30" boat is pushing it for both of us but should work fine with a deep enough fin. Another advantage to the deep fin: improved handling deaddownwind where the canting keel makes no difference at all…
