[alberg30] Cockpit drains and propellors

[Peter Amos]

George,Lee and Stephen.

George,yes,rigid tubes are not a good idea, the Pearson has in fact short connections of rubber hose at each end intended to  act as vibration compensators.I think the idea of drains low down in the cockpit stern bulkhead through to the transom to shift a lot of water quickly out of the cockpit is worth considering but needs to be thought through.
Lee, one of the things I did while Tait Tait was still in the water was to run a clear plastic hose from the cockpit through hull,via the port locker to the scupper drain. This gave me an accurate method of marking the locker bulkhead and the interior of the hull with the water level so I shall be able to see if the fall from the cockpit sole to an outlet above the waterline is enough for effective drainage.One of the objectives is to reduce the number of holes in the hull below water level. If the fall is not enough I shall go ahead and resite them anyway to get better access.Also the present relative positions of the drain and through hull make it difficult to fit hose between them without kinking and good quality hose being stiff exerts a permanent lateral pressure on both items.I'm using auto radiator hose now with a moulded bend in it( this is not a recommendation) which works for me but Tait Tait is out of the water for six months a year.When I shift the through hulls one of the factors that decide the new position will be a comfortable run for proper marine hose.
Stephen, thank you for the propellor information,I've learned something and I'm beginning to get an idea of  how to work out which propellor would give a good performance.My thinking goes like this: take an Alberg 30 known to have good performance under power like yours as a benchmark.The diameter and pitch of the propellor is known, also the shaft speed can be calculated from the engine speed and the transmission reduction. For illustration lets say that at 3000rpm your performance under power is 6knots.
Your reduction is 2.5: so shaft speed is 1200rpm.To get the same performance I need the same propellor as yours turning at the same shaft speed,so if my reduction is 2:1 I need 2400rpm.Other factors like weight differences ,relative cleanliness of hulls just mean that more(or less) engine power has to be applied to get the same rpm's. Why do I get the feeling this logic is too simple.
If anybody out there is really pleased with their performance under power I would like to know what engine speed gives them 6knots,their propellor diameter,pitch,number of blades,whether machine pitch or sail pitch and transmission reduction.To avoid clogging up the group with lots of e-mails I suggest this info is sent to me direct.

Peter Amos Tait Tait #478

p.a.amos at tesco.net.u.k
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