Ed Wolfe, 3/24/2008
We have a Perkins 4-108 and the prop rotates under sail. Are the alternatives to a prop lock or folding prop?
Art Fowler, 3/25/08
In addition to the folding props (eg. Martec) there is the "feathering" Max-Prop. I have the 13" 3 blade Max-Prop on my boat with the Perkins 4-108/ Borg Warner "Velvet Drive" transmission. My prop rotated continuously prior to installing the "Max" and it drove me crazy, although it was acknowledged to do no harm. Interestingly, not only did the rotation stop with the Max-Prop, but it also ran smoother than my old fixed 3 blade prop.
There is a technique for getting the Max to feather because of the free wheeling properties of the transmission. You simply shut the engine down with the transmission in the forward position with at least 2 to 3 knots of boat speed. The sudden reversal of torque force, though very brief (only momentary), supplies enough negative torque to get the prop to feather. That (might we call it "the feathering force") is only available at that moment due to the "dreaded" free wheeling properties of the transmission.
I surmise, after all this, that you are really looking for a simpler, more straight forward, and yes, much more cost effective alternative, however. I'm just not sure, outside of the brake, if there is really any other way to stop that rotation without getting some kind of forces acting on that shaft/prop combination. I looked at all the alternatives, myself, and ended up with the Max-Prop, which has worked flawlessly and effectively (once I learned the feathering technique, something the distributor, PYI, needs to make more readily available).
Hal Newell, 3/25/08
Hi Mr. Fowler,
Per your recent post about the Max Prop: I just wanted to qualify that your Perkins 4-108 with the Borg Warner Velvet Drive was the same set up as in my 1977 3I6. Does your tranny have a 1 to 1 ratio?
All the prop guys we checked with said that these specialized props wouldn't work with the 1:1 tranny (said that we'd have to go to a 2:1).
Just curious what you have / experience has been?
3I6 Mariah (in refit)
Art Fowler, 3/25/08
I believe that the ratio IS 1 to 1 on my engine/transmission combination. My engine handbook is on my boat at this time so I can't check that, but I've sent this to Rick Van Mell, who will know the answer.
I CAN tell you this, that is the set up I have, and it sounds like yours is the same, works very well with that Max-Prop. I have the blade angle set at 14 degrees, and with the 13 inch diameter propeller, that equates to a six inch pitch. (13 x 6)
Rick Van Mell confirms that Vanishing Animal also has a Parkins 4-107 with a Velvet Drive it 1:1 transmission and has used both fixed 2 and 3 blade and 2 blade folding Martec props. The fixed 3 blade prop spins when under sail. Turning the engine off with the transmission in forward tends to keep the prop from spinning until boat spead gets over about 4 knots. In days past when long distance racing (with a folding prop), we tied a piece of marlin from the shaft coupling to the frame of the transmission to keep the shaft from turning when we ran the engine for an hour in neutral twice a day to charge batteries. At the end of the race we'd just start the engine and put it in gear which would break the marlin line. At the starting line before the start of the race we would be sure the shaft was turned so the 2 bladed ver vertical and would fold without one hanging down. For a major race, we'd have a crew go over the side and put a rubberband around it!
I gues you could try to tie a piece of marlin around the shafe of a fixed 2 or 3 blade prop to keep it from spinning while pleasure sailing too. I think that would increase the total drag, but if the noise bothers you more than losing a little speed, it's worthha try, though a bit of a pian to rig up each time you go out. (That's what they make shaft brakes for.)
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