We are in the process of renovating Twister Fretta and wish to fit a 13 x 9 feathering prop. Have read Steve Taylor's excellent article but am reluctant to reduce the prop shaft and outer bearing as described, nor to cut into the rudder. Does anyone know of a 13 x 9 RH feathered prop that will fit without the engineering work detailed by Steve? Any advice would be more than welcome.
kind regards
Nigel
One thing I considered (but didn't implement, because I decided against a feathering prop) is using a high tech material to replace the cutless bearing. The material I looked at is called Vesconite, and it is surprisingly affordable if ordered direct from the manufacturers in South Africa, same order of magnitude as a standard cutless bearing, but you do have to add machining costs. The use of Vesconite allows you to reduce the length of the aft stern tube bearing substantially (by 50% or more) without compromising performance, thus freeing up maybe 2" of space in the fore and aft dimension. Had I done this, I would have been able to fit a 14" or possibly even a 15" diameter Featherstream without having to enlarge the aperture (which on Offcutt is already quite large).
That said, if you look at a number of out of the water Twisters, you will find many that have standard rubber cutless bearings that are considerably shorter than the recommended four times shaft diameter, eg 4" for a 1" shaft, and these installations appear to perform perfectly well.
It is also worth noting that the relatively large aperture meant that I could get the current 3 blade fixed prop off (I used a home made prop puller, two steel plates with three studs with nuts for a three blade prop) and so remove and replace both the shaft and cutless bearing (both of which needed doing anyway) without having to take the rudder off. Taking the rudder off isn't that difficult (unless you have loose nuts on the middle strap bearing...in which case your day will suddenly get to be a whole lot more interesting - solution is to use full length studding, which removes the need for internal nuts), but if you don't need to do it, it is one less thing to do.
Finally, shortening a prop shaft (assuming it is serviceable and doesn't need replacement) once it is out of the boat is a five minute job with a hacksaw and file to tidy up the cut end.
85
12
1 Guest(s)