New to Folding Props

[Aja]

As part of the major upgrade over the winter, I fitted a new engine and went the whole hog and changed from fixed two-blader to a Gori two-blader.

Never having a folding prop before, can anyone tell me if it is normal to get a small thud when selecting forward?

I have reduced the tickover slightly and this has helped, but on talking to other owners with folding props the opinion is mixed. Some not getting any noise and some getting a thud.

What is the experience with other folder users?

Donald

 

[Twister_Ken]

Certainly we used to get thunks on the various race boats I sailed, if they had folders. Not a problem with feathering props though. Also, used to require a bit of welly to get folders to open when putting then into astern if the boat was moving forwards. Later models may have overcome this problem.

 

[TwinRudders]

Yes we get a thud with a Brunton Varifold. I don't like it. Always seems to be a longer delay before it opens when you really need it. And if you increase the revs the thud is harder - I've always thought it can't be very good for the drive shaft/gearbox?

 

[ChrisE]

Hmm, that's interesting because we don't get a thud with our Brunton. Is the varifold the same as an autoprop which is what we have?

 

[TwinRudders]

No I think they are different - but not sure in which way.

 

[claymore]

We used to get a clunk as the blades opened out. I found it quite reassuring really.
Are you finding any difference in performance when you engage reverse?
And the biggest question of all - have you found extra boatspeed with the folding prop and does now mean that you will be able to keep up with Claymore when the <span style="color:#666666"> Big Grey </span> is flown?

 

[Aja]

Claysie

You'll have to go some now. With the folding prop and and the new fully battened main the boat is truely transformed!

I may have to retire from this sailing lark. Sheena puts up quite a fight when its my shot of the helm! Blood may be spilt.

Donald

 

[claymore]

Stacpac?

 

[Aja]

In the Force 1 gale we had at the weekend the main was utterly controlable.

May have to think about these ropey bits to contain the main at some point.

Donald

 

[aluijten]

I've got the Gori two blader. The thud noise is quite normal. As the propeller starts spinning it meets the force of the water whilst the boat is still not moving. this makes the blades 'hit' the end of the movement angle with some speed/force. Haven't witnessed any problems with this though. As said by others, at least you know the prop is still opening and closing.

Don't worry about it, enjoy the extra speed when sailing /forums/images/graemlins/smile.gif

Arno

 

[claymore]

I find the stacpac is brilliant with the fully battened main - especially when there's just the two of us aboard.
You may as well - It'll only be another 4 - 500 squids

 

[Aja]

Turns both pockets inside out. Only fluff left........

Donald

 

[mobeydick]

Brunton Varifold (folder) and Autoprop (feathering) are very different.

I read somewhere that some folders invalidate Volvo and other saildrive engine makers warranty if not fitted with some 'thud minimisation' device (I am sure there is a technical term) such as plastic buffers; so they can create quite a shock

 

[kcrane]

We have Autoprop, and no thud, despite teenager working the throttles back and forward like a mad man.

 

[James_Calvert]

Listening for the thud is for me a vital confirmation that the prop has opened up to provide forward thrust. Early lesson for me: I was motoring astern and wanted to stop, engaged gearlever in forward and revved up...no thud, no forward thrust, ended up climbing over the stern to fend off.

Discovered that when the folding prop was new and still a little stiff to open, and engine out of gear but with some sternway, the prop was reluctant to open up when put into forward. The trick was to listen for the thud: if it didn't occur, to rev up gently in reverse (which did always open up the blades) and then immediately engage forward gear.

On the positive side of folding props, when motorsailing some years ago I had a midnight midchannel encounter with some flotsam which stalled the engine. On restarting the prop was clearly fouled - so reverted to sailing best course closehauled. At dawn I restarted the engine and found that the prop had managed to clear itself. A fixed, or feathering, prop would probably still have been hooked up to whatever rubbish I'd picked up.

 

[Aja]

Thanks to all who replied. This has convinced me that I dont have a problem.

Just that I fitted a new engine, stern gland and prop and was a bit jittery!

Donald