411 still the prop question shaft metric or imperial hello, i'm looking here in that nice forum for some helpfull answers.
i still have to decide, what prop an shaft i take.
i want to fill out a data sheed for calculating the proper prop size. there is the question about the theroretical hull speed.
does somebody knows this, doesent found information about this question.
another question: i have to change the shaft too.
what is the best, here in germany every thing is metric (ordering).
on my swan there is a imperial shaft.
i thoutght about to change in metric, 40mm shaft, pss dripless
and 3 blade fixed 19" 15 RH for my yanmar 4JH5 with 54 HP. Gear ratio is 2.61 in forward.
so i have only to change the rubber bearing.
is that a good idea?
for me looks easyer to get the metric parts, even if it the boat in the carribean.
Dear Goosiboy
Hull speed is related to waterline length, and roughly the same as top speed under power, about 7.4 knots.
If you change to a metric shaft you need a rubber bearing with the inside diameter metric, but the outside diameter 2 inch, and the length 6 inch, as it needs to fit the shaft strut.
The propeller pitch you mention is too light for the engine. It would be advisable to go to 21" diameter, this gives 15% added thrust, but also added resistance under sail.
I can give you the proper pitch for 21" diameter provided you choose a folding propeller :-)
Kind regards
Lars
is 21" for the propeller not to big?
i measured under water from middle of shaft to hull about 30 cm.
was also thinking about the dragging of the prop.
want to go for a fixed one. the engine might be overpowered, but i think already much better than the original constellation.
i`m right?
here i found a nice 411 for sale. look at the cockpit, they made a second entrance ;-)
one day my boat should look like this one with a new wooden deck.
but, step by step.
may be i can have a look at that boat, i need some measurements for the solarpanel holder.
Dear Stefan
The original propeller was a 2-bladed folding with 21" diameter. A folding prop has the blades further aft on the hub, and this gives more clearance against the hull.
2 blades are more efficient than 3 at cruising speeds.
The recommendation is that the propeller should match the engine power. I do not understand your remark about overpowering.
Kind regards
Lars
Dear Stefan
Pls read the post about propellers recommended earlier, you will see that a good folding propeller may be better than a fixed one, and my suggestion is to consider this.
Many propeller manufacturers will calculate the required dimensions for you.
Kind regards
Lars
Stefan, when you change the cutlass bearing make sure it is a phenolic cutlass bearing as the P bracket is S/S and use Duplex Stainless for the shaft. Distance of prop from P bracket should be no more than the diameter of the shaft.
Feathering blades are in my view much better than fixed, less drag.
hello lars and john,
thanks for your reply.
yes i would like to have a featuring prop, but i have many jobs on my boat to do.
so my budged is a little bit limited.
i was looking for used props, but there was no one in my dimensions.
may be somebody in this forum has one used for me for sale.
good hint with the rubber bearing and also the distance.
makes sense to be very close, so it doesent get easy out of balance.
thats what i understod.
Stefan, from experience of owning and restoring 4 yachts. Don't compromise on propellers. Match to engine, you have a great sailing yacht, why slow her down with sub optimal prop. Once fitted you will not change the prop for years. When trying to get home under engine in bad weather you need a good engine matched with the best prop. My knackered old Perkins 4108 with the wrong prop fitted was a disaster when I need power.
Hello and big thanks to all to help me, to make my decision.
I´ve been yesterday on a flee market for boats near hamburg.
i found a verry good used propeller with nearly that size i need.
20" and 13 pitch for 60,- euro.
amazing or?
my propeller builder was calculating a 50cm with 15 pitch.
the clearence between the hull should be ok.
he can change the pitch of the prop i bought.
i will start with that propeller.
of course, it will give me not the whole sailing speed, but i have some more budged for the rest of the boat ;-)
later i can change to a folding one.
the shaft i will take in imperial and 1:10 konus.
i need some more informations about measurements, but i will open a new thread.
Stefan
Thank you for the photo.
This is not the original propeller position, it is too far aft from the rubber bearing, as pointed out by John.
The fouling on the propeller blades and other areas causes a serious reduction of performance.
Kind regards
Lars
Hello, today i`ve been by the prop builder.
he said: verry good condition and he will change the pitch to 15
they do also the rest, shaft and coupling, nuts and zink.
so i´m looking forward to come back to grenada to install the arangement.
here some pics, and it can be more stuff growing under water that will reduce speed.
i the night it sounds like popcorn.
that´s another job when my boat is out of water.
Question: does somebody know the diameter of the Stern Tube Diameter, i need a new PSS Shaft Seal.
I hope, that i´m not boring this forum with all my questions.
