How do I work out.....

[BarryH]

.....what length oars do I need. I've got a little Bonwitco dinghy that I use for pottering on the river now and then. The oars, that are probably older than me, came to the end of their life a few years ago.
Stupidly the wife chucked the old ones down at the loacl tip a year or so ago. Asking around I've had conflicting views as to the length of oars that I need. Is there a formula or rule of thumb for working out the length of oar for a given beam?

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[rich]

as long as possible, yet still fit inside boat. (side by side)

<hr width=100% size=1>rich ) <A target="_blank" HREF=http://www.jersey-harbours.com>http://www.jersey-harbours.com</A><P ID="edit"><FONT SIZE=-1>Edited by rich on 08/10/2003 21:07 (server time).</FONT></P>

 

[powerskipper]

to reach the water!!!!

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[BarryH]

hmm, thats what I thought. But the boat is 12 feet long. So roughly 11 foot oars. The problem starts cos the fulcrum is to close to the effort. That makes rowing damn tiring. There must be a formula for working out the correct length.

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[Dave1258]

Fit a small outboard, end of problem /forums/images/icons/laugh.gif

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[BarryH]

Hmm, fair enough Dave, I'll sling the 20 horse Mariner sitting on the stern off and fit a smaller one. Still doesn't sort the problem of the oars though does it!

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[rich]

i will go and have alook at my whit. i think it 10 or 11ft,

<hr width=100% size=1>rich ) <A target="_blank" HREF=http://www.jersey-harbours.com>http://www.jersey-harbours.com</A>

 

[jfm]

about 6 or 7 foot oars for a 12 foot dinghy. The fulcrum needs to be about 40% along the length from the handle end

 

[BarryH]

Aha, now we're getting somewhere. So with the beam of the little Bonwitco being somewhere near four feet, working on the 40% rule, 7 feet would be somewhere near the mark. Cheers

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[jfm]

I'm not following your maths. I meant the fulcrum should be 40% from the handles, and thus 60% from the blade. So if dinghy is 4 foot beam, then you want 2 foot of oar inside the boat. Hence 3 foot of oar outside boat. 5 foot overall. That sounds a bit short, try 6 foot.

The 40% isn't written down afaik. I just measured a few sets I have in the garage and they were all 35-40%

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[rich]

a lot depends on how strong you are,

<hr width=100% size=1>rich ) <A target="_blank" HREF=http://www.jersey-harbours.com>http://www.jersey-harbours.com</A>

 

[Col]

Depends on what speed you want to achieve.
Short ones will get you out of the hole quickly with no top end, so ideal for water skier.
Long ones will give you more top end for a more comfortable cruising speed.

Hope this helps.

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[whisper]

Suggest you contact www.willsmarine.co.uk or 01548 852424. Ask for Martin Wills - his Dad is "Mr Bonwitco" - so he has been involved with With dinghies for most of his life. He should be able to tell you the answer if you give him the model no.

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[BarryH]

Ah well did try ringing them but couldn't get a word in edgeways! This dinghy is an early With 300. Its older than me and I'm nearly 40. Its been in the family for as long as I can remember Why they called it "300" is beyond me 'cos it 12 feet long. They still make a version of it called the 375. Same hull moulding but different interior moulding.
Anyhow, ordered the oars now and JFM was the closest with his answer. The oars that I've been told to order are 2.10 mtrs, or 7 feet as near as damn it.

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