Sailing With A Fixed Prop

[GILow]

Originally Posted by Dockhead

You guys won't believe what the problem was.

Loose shaft anode apparently caused enough vibration to destroy the cutless bearing.

Glad to hear it was something simple (and not too pricey.)

Can't quite imagine how the shaft anode could come loose and cause that problem, but don't need to understand it because I don't have one.

[Pete7]

That's a bit of luck, best buy a Euro Lottery ticket this weekend then

[Dockhead]

Originally Posted by GILow

Glad to hear it was something simple (and not too pricey.)

Can't quite imagine how the shaft anode could come loose and cause that problem, but don't need to understand it because I don't have one.

Well if a couple grand is "not too pricey", then I guess I'm lucky


Well, of course, I AM lucky, very much so.


I couldn't imagine that either, but my crew guessed it, and was right.

[Dockhead]

Originally Posted by Pete7

That's a bit of luck, best buy a Euro Lottery ticket this weekend then

Yep! . . .

[GILow]

Originally Posted by Dockhead

Well if a couple grand is "not too pricey", then I guess I'm lucky

Compared to the $tories I hear every day I go down to the marina... yeah, I'd say very luck indeed.

Have a great trip.

[a64pilot]

Originally Posted by Dockhead

You guys won't believe what the problem was.

Loose shaft anode apparently caused enough vibration to destroy the cutless bearing.

There was still a bit of rubber left and the shaft was fine. Nothing wrong with the prop.

Motoring now smooth as butter.

Bank account lighter by nearly two euro boat bucks, but it could have been far worse.

Nice boatyard in Kalmar, by the way. Called Kalmar Marina, run by a guy named Jürgen. Very helpful pleasant and skillful people.

Curious, how bad was the vibration inside of the boat?
How long did it take to chew up the Cutlass?

[Dockhead]

Originally Posted by a64pilot

Curious, how bad was the vibration inside of the boat?
How long did it take to chew up the Cutlass?

Well, it was pretty bad. Obvious something was going wrong, but not so bad that we couldn't continue the journey.


We had a more or less dead calm for two days -- unusual and good weather for 57n - 60N around the equinox, otherwise against the prevailing wind here. So we motored a lot.

[Stu Jackson]

Great news, Dockhead. Cost a lot but a LOT LESS than the worst case... Safe journey back.

[Dockhead]

Originally Posted by Stu Jackson

Great news, Dockhead. Cost a lot but a LOT LESS than the worst case... Safe journey back.

Thanks!

[SailRedemption]

Originally Posted by malbert73

Yes the factor that is in play here is prop tip speed. So diameter is limited by clearance most often and also by tip speed. So with clearance and a deeper reduction gear you can translate pitch into diameter which is better for slow speed, non planing performance. Like a sailboat.

That's exactly it. We spin our prop at 1000rpm at full 2700 RPM. We are below I think the 1200rpm that Dashew? recommends for tip speed on displacement sailboats/boats.

[a64pilot]

Tip speed is of course a function of prop diameter and RPM, for example the little airplane we made at work had a 106” prop and turned it at 2200 RPM, which gave it a tip speed for just over .90 Mach which made it quite loud, and was a little faster than it should have been for max performance.

So in other words a small prop at 2000 RPM may have a lower tip speed than a larger prop at 1500 RPM.

[model 10]

[QUOTE=a64pilot;2988716]Tip speed is of course a function of prop diameter and RPM, for example the little airplane we made at work had a 106” prop and turned it at 2200 RPM, which gave it a tip speed for just over .90 Mach which made it quite loud, and was a little faster than it should have been for max performance.


I sold my Cessna 185 to pay for our boat. It had a seaplane prop that I turned it up to the limit of 50 rpm over redline, pretty amazing noise.

[a64pilot]

Funny I sold my M6-235 Maule to pay for our boat.
I turned it 100 over redline, but that was, only 2500 RPM and was quiet.
Only thing louder that an IO-550 with a seaplane prop is maybe a T6 Texan at TO RPM.

C-185 was too rich for my blood.
Always wanted a Helio Courier, had friends that flew them in Vietnam.

[model 10]

[QUOTE=a64pilot;
C-185 was too rich for my blood.


It was an investment to pay for a boat someday. I could never afford to fly one. I'm a 105 hp guy now.
Boats and planes, great way to spend money.

[a64pilot]

I kept the C-140
So I guess I’m an 85 HP man. It’s actually pickled in long term storage.