Campbell Sailor prop

[RAD]

I had my Campbell Sailor re pitched this season because I could not get the engine over 1500 rpm but it did make a great big difference in thrust and speed, now I can get the engine up to 2500 rpms but there is no difference in boat speed past 1800 rpm and over the weekend I was motoring right into the wind (20+)and chop and could not get past 3.5 knot and with a 4 cylinder engine and 30 hp pushing a 32 footer I think it should be better
The bottom and prop is clean with no growth on it (just launched In March and the water is still cold) so the only thought I had was maybe the prop shop took too much pitch out of it or my transmission clutches are slipping
I do have a Paragon tranny and there is adjustment for clutch and I would like to add that after removing the Campbell Sailor I put the 2 blade Michigan Sailor that came with the boat and also could not get past 3 knot pushing into wind and current last year.
Sooooo any thoughts and comments?

 

[Ross]

How much current?

 

[LloydB]

what is your max speed thru water

dead calm no current? BTW how do you measure it. In your stated situation were you sailing dead into the current,the wind & the waves? and what was the wave height? I don't know how to estimate your expected headway but I'm sure someone here can point us in a good general direction.

 

[Ross]

Re: what is your max speed thru water

I can go to the weather up to 2 knots of current at 4 knots with ten hp and a three blade prop. tell us more.

 

[RAD]

Wind was right on the nose 20+,white caps with about 2ft waves and I can only guess the current created by the direction of the wind.
I know only speed over ground from the GPS and that information was bouncing a different figure every second because of the inconsistency but never getting past 3.5 knots.
I had a friend with a Nauticat 32 with me and he knows my boat well and was suprised I was having so much trouble as he had to slow down for me to keep up with him.

 

[Don12364]

How confident are you in the accuracy of your boat speed measurement?
Logs are notoriously inaccurate unless recently calibrated and GPS is only any good when there is no current - even a wind driven current will throw your measurement out, particularly in a headwind.

 

[RAD]

Well having a friend nearby and going to the same anchoring place as me he verified my SOG, at first he thought I might be having engine trouble as I could not keep up with him and we travel a lot together and never have I had trouble keeping up.

 

[RAD]

Donalex

"GPS is only any good when there is no current - even a wind driven current will throw your measurement out, particularly in a headwind. "

This is an interesting thought, I don't have a speed log on board (had one but it never worked)so I understand about that being inaccurate
but because the gps was acting so erratic the SOG might have been more than recorded

 

[Ross]

Re: Donalex

Do some more research in calm water.

 

[RAD]

Ross,
my exact thoughts, great minds think alike and I'm a firm believer in the system of "Yak it up" with others before commencing with a project

 

[Ross]

Rad , the results that you are observing don't make sense. There must be an unidentified parameter that is being overlooked.

 

[RAD]

I'm going to do some more research with the boat in calm water, I did play with the throttle the day I was having trouble and it seems that @ 1800 rpm was the spot I would get max speed so in calm water I will watch and observe sog as I push the throttle past 1800 and also see what happens @ wot.
Historically I only use the motor for a short distance before putting up sail so I'm glad this situation has come up so early in the season

 

[Mike Holibar]

Rad, what is the rating of your engine? You say 30HP but it only develops that power at full rpm. Many modern diesels are max out at 3600 rpm. If this is the case with yours, have a look at the performance curves and you will see that at 2500 rpm it probably only develops something like 15hp. In your speed tests you manged a GPS SOG of 3.5 knots against and estimated current of 2 knots. That would make your speed through the water, which is the only speed that matters for this exercise, 5.5 knots, which is not too bad. When you do your calm water tests with the GPS do one run in one direction, take a reading, and then reverse course and take another reading. The average of these readings will be your speed through the water after the effect of current has been taken out. A boat the size of yours should have a hull speed of around 6 knots and a maximum around 6.5 to 7 knots. At full power WOT you should be reaching these speeds with the engine at maximum rated rpm, and no visible black smoke. If you can't get the speed or rpm and there is visible black smoke, you are still overpropped. Hope this helps,

 

[Ken13559]

I too use a Campbell Sailor prop and I find that if I polish the prop well it'll perform great. I can gain by as much as 250rpm.

 

[Steve Dion]

RAD: You may want to try your average speed over a marked distance. Get your average going one way and then reverse the direction.

Your linkage and throttle control research all make sense to check too. I would get someone down below to check these while underway.