[Public-List] Public-List Digest, Vol 3998, Issue 4 Two blades prop

[Gordon Laco]

Many years ago in Touch Wood, my wooden Folkboat, we sailed across to Port Dalhousie and tied up at the sailing club there in the mouth of the old Welland Canal.  There was a considerable current which cause the knot meter to log ten miles during the night.   I tied the tiller over a few degrees so the boat was trying to pull away from the wall, in effect flying like a kite away from the stonework.  No fenders needed.


Gordon Laco
www.gordonlaco.com
426 Surprise



> On Apr 26, 2020, at 8:00 PM, Greg Aldworth via Public-List <public-list at lists.alberg30.org> wrote:
> 
> Our berth is in a river, with a lot of current especially during the spring freshet. Some shaft and prop combinations might spin in such a current when alongside. 
> Some ships/boats have shaft brakes to stop this from occurring to limit wear and tear on shafts, stern glands/stuffing boxes etc., not to mention the owner’s nerves listening to the damn shaft spinning when we are clearly alongside and not going anywhere soon.
> 
> Sent from Mail for Windows 10
> 
> From: Greg Hounsell via Public-List
> Sent: April 26, 2020 7:55 PM
> To: Alberg 30 Public List -- open to all
> Cc: Greg Hounsell
> Subject: Re: [Public-List] Public-List Digest, Vol 3998, Issue 4 Two blades prop
> 
> Oh.. silly me.. don't know why but I was assuming that you weren't under
> sail, just in neutral at the dock lol..
> 
> Greg
> #592
> 
> On Sun, Apr 26, 2020, 7:41 PM Greg Aldworth via Public-List <
> public-list at lists.alberg30.org> wrote:
> 
>> The prop will “windmill” with the engine in neutral. The vessel is moving
>> forward under sail and water is flowing past the prop. With the 3 bladed
>> prop, there will always be enough prop. surface area exposed to keep it
>> spinning. I think with a 2 bladed props, they tend to lose thrust when in
>> the shadow of the keel.
>> I have a larger motor vessel and if we shut down one engine, that prop
>> will windmill when we are underway.
>> Does this sound right Gord?
>> Greg
>> 
>> Sent from Mail for Windows 10
>> 
>> From: Greg Hounsell via Public-List
>> Sent: April 26, 2020 6:49 PM
>> To: Alberg 30 Public List -- open to all
>> Cc: Greg Hounsell
>> Subject: Re: [Public-List] Public-List Digest, Vol 3998, Issue 4 Two
>> blades prop
>> 
>> I don't understand how a prop would cause rotation when in neutral. Is
>> there a strong tide or current?
>> 
>> Greg
>> #592
>> 
>> On Sun, Apr 26, 2020, 6:06 PM Daniel Swords via Public-List <
>> public-list at lists.alberg30.org> wrote:
>> 
>>>    The PO of my boat had replaced the original two blade prop with a
>>> three blade prop, but fortunately had saved the original. I disliked the
>>> three blade so much that I paid to have the boat hauled just to replace
>> it
>>> with the original two blade.
>>> 
>>> 
>>> 
>>>    If left in neutral the three blade spun continuously and noisily and
>>> created enough turbulence to feel through the tiller. If left in gear
>>> (something Yanmar recommends against) the transmission would lock-up with
>>> even the slightest forward motion such that the safety interlock would
>>> prevent starting the engine.     As far as I can tell the two blade prop
>>> does not spin in neutral and typically parks vertically behind the keel.
>>> Also, I did not notice any significant advantages with the three blade
>> prop
>>> so I gave mine away and have never considered going back.     Currently
>>> sailing on Lake Pontchartrain, winds 15 gusting to 19 knots, double
>> reefed
>>> main and 110% jib. Daniel SwordsSolitude, Hull #525Mandeville, Louisiana
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