Oars - ideal proportions...

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Oars - ideal proportions...

Patrick Horton 3310
This post is a request for anyone going to the AGM on 10 April who might be able to bring along what they believe to be a good oar for a cruising dinghy.

I have bought some heavy 11ft oak oars which appear unfinished.  My plan is to shave them down to the right proportions for my Falmouth Bass Boat.  The attached photos show how the blades are very crude (or unfinished) but maybe this is how they were supposed to be - I was told they were lifeboat oars.  I know oak is heavy but I think I could take a great deal of wood out of the oars before they become too weak for my purposes.

I also hope to learn to scull and any advice on a transom rowlock and special features of a sculling oar would also be welcome.

Hours on the internet have failed to provide any useful oar dimensions and there don't appear to be any oar design books out there either.  I am confident with my woodworking abilities having recently produced a new main mast.  If anyone can offer advice or allow me to copy the dimensions of a good oar I would be extremely grateful.  Hence my request for an oar to inspect at the AGM.

Looking forward to the AGM.

Patrick
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Re: Oars - ideal proportions...

Tom A
Hello -
My first post here, but I may have a useful link for you :

http://www.shawandtenney.com/how-size-your-oars

This is from Shaw & Tenney, in Maine, US
It's really just a length formula, but there may be some other info (and certainly a lot of pictures) on their site.
I will say, I have a set of 10' spruce oars from them that I use in my 15' Mercury, and they are a WHOLE lot thinner at the blade tips than those oak ones - You should be able to take a lot off .

Good Luck,
Tom
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Re: Oars - ideal proportions...

Osbert Lancaster 2756
Administrator
In reply to this post by Patrick Horton 3310
Wow, they look like beasts.

Some advice from John Welsford here might be helpful:
http://www.duckworksmagazine.com/05/columns/welsford/5/free.htm
"Selkie", a Drake rowing boat by Clint Chase
"Scratch", a Walkabout dinghy by John Welsford
Mainly sailing and rowing on the Firth of Forth
forthsailoar.osbert.org
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Re: Oars - ideal proportions...

Patrick Horton 3310
Thank you Tom and Osbert.  

John Welsford in the Duckworks link looks looks like an amazing fund of knowledge.  I shall browse his archives for other stuff too.

Patrick
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Re: Oars - ideal proportions...

Roger Barnes 936
The oar length formula I include in my dinghy cruising book is from Collars the celebrated Oxford oar makers and can be found here: http://www.collars.co.uk/uk_galaxy/faqs/2/oars/answer/6/how_do_i_calculate_the_lenght_of_oar_i_need (as well as in my book, obviously).

From Roger Barnes by mobile

On 4 Apr 2016, at 23:57, Patrick Horton 3310 [via DCA Forum] <[hidden email]> wrote:

Thank you Tom and Osbert.  

John Welsford in the Duckworks link looks looks like an amazing fund of knowledge.  I shall browse his archives for other stuff too.

Patrick


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Re: Oars - ideal proportions...

Frank San Miguel 3252
In reply to this post by Tom A
Another source is B&B yacht design.  I made some 10', 3"' oars to their design and they turned out very well.  I've used them on the water quite a bit.

http://sail.fsanmiguel.com/2014/07/building-oars-and-oarlocks.html

Given the beam of my boat and the freeboard, I would have preferred 11' but I sized them to fit in the cockpit under the coaming.
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Re: Oars - ideal proportions...

Patrick Horton 3310
In reply to this post by Roger Barnes 936
Hi Roger.  I know my way round your book very well and most of my kit has been chosen on the advice in there - thank you sincerely for that.  Regarding oars, I chose the 11ft length of my pair based on your calculations.  It is the proportions such as blade thickness, shaft diameter and weight in relation to the weight of my boat which now illude me.  The oars I have could certainly do with loosing a few pounds and I am sure the blades should be shaved down.

Hence the request to see a good oar at close quarters.  If I could weigh one up in my hands I am sure I could recreate something similar.  There appear to be too many variables to expect to find a prescriptive plan anywhere for my requirements.
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Re: Oars - ideal proportions...

Patrick Horton 3310
In reply to this post by Frank San Miguel 3252
Hi Frank
Thanks for that.  There is an interesting comment at the bottom of the article about positioning the rowlock offcentre for sculling.  I think I might try that.
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Re: Oars - ideal proportions...

Frank San Miguel 3252
Yes - For years, Norm Wolfe has used nothing but a yuloh for auxiliary power.  I've seen his rig and it is very efficient.  The sculling motion of a yuloh requires that you keep it captive in the transom.  He has an ingenious quick release system for locking in the oarlock.

One downside is that his yuloh is very long.  I think it may break apart in two pieces but even so, it is very long.