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Old 02-05-2013, 16:30   #1
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Prop to hull clearnce

What should the correct prop tip to hull clearance be?

I am thinking of replacing my fixed 3 blade prop with a folding prop (probably a flex o fold) and want to make sure that among other considerations the clearance is correct.

My boat has a half skeg that has a rib that extends up the boat centreline past the shaft tube. ( see sketch)

Best regards

Patrick
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Old 02-05-2013, 16:33   #2
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What should the correct prop tip to hull clearance be?

I am thinking of replacing my fixed 3 blade prop with a folding prop (probably a flex o fold) and want to make sure that among other considerations the clearance is correct.

My boat has a half skeg that has a rib that extends up the boat centreline past the shaft tube. ( see sketch)

Best regards

Patrick
Oops here is the sketch....

Click image for larger version

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Old 02-05-2013, 16:57   #3
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Re: Prop to hull clearnce

They say around 10-15% of prop Dia. though you would think there would be a minimum clearance regardless of wheel size.
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Old 03-05-2013, 05:48   #4
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Re: Prop to hull clearnce

Clearance should be minimum of 15% of prop' diameter.

See ➥ Propeller Clearance Diagram - Cruisers & Sailing Photo Gallery
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Old 03-05-2013, 06:29   #5
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Re: Prop to hull clearnce

Quote:
Originally Posted by pgenovese View Post
Oops here is the sketch....

Attachment 60289
Considering your sketch, you can safely go with a 17 in. OD Prop, with the pitch determined by your engine power and transmission. Assuming you have sufficient space between the J-Strut and your rudder, a 3-blade Flex-O-Fold of 17 in. diameter would cost in the range of $2,160 USD (google CruisingSolutions) and would provide good power and a smooth running drive train.
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Old 06-05-2013, 00:42   #6
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Many thanks for the info.
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Old 07-05-2013, 01:29   #7
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Re: Prop to hull clearnce

I was always told a couple of inches so the prop doesn't thump to the hull
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Old 07-05-2013, 11:29   #8
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Re: Prop to hull clearnce

Mine's an inch and a half with a 16 incher and it thumps !
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Old 08-05-2013, 01:23   #9
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With a 16 inch i shouljd get about 2.5 in of clearance just a little bit more than 15% sounds about right.

Will the rib that morphs into the skeg have any significant effect ? The clearance i measured is to the highest point on the rib not the hull.

Regards

Patrick
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