Converting a bilge keeled Senior to centre-board

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Wagtail
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Joined: Tue September 8th, 2009, 8:13 pm

Converting a bilge keeled Senior to centre-board

Postby Wagtail » Sun December 27th, 2009, 8:36 pm

To; anyone out there with expertise or interest:
I have a Senior which in many ways is an excellent boat but I just can't get on with its windward performance. She makes too much leeway. I'd like to add a centre-plate but I want to keep those parts of the ballast keel which will not interfere with the slot. Does anyone have experience of doing this? I've heard the centre-board versions, as built to design, are very tender which would be one reason for holding on to the ballast keel. Any advice will be welcome.
Wagtail

Wagtail
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Joined: Tue September 8th, 2009, 8:13 pm

Re: Converting a bilge keeled Senior to centre-board

Postby Wagtail » Thu December 31st, 2009, 11:14 am

I'd like to recall the request for information about conversion to centre-board. A few moments' thought and a look at some pictures and the drawings show that what i suggested is not possible. An alternative seems to be to increase the depth of the bilge and ballast keels.
Wagtail

Athaena
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Joined: Wed July 22nd, 2009, 12:36 pm

Re: Converting a bilge keeled Senior to centre-board

Postby Athaena » Thu December 31st, 2009, 6:53 pm

Wagtail wrote:A few moments' thought and a look at some pictures and the drawings show that what i suggested is not possible.


I was going to reply that I thought it sounded like it might be quite some job, but I'm not familiar with the design or have the expertise and figured me saying "that sounds difficult" wasn't very helpful.

Replying now just so you know that while it's quiet in here, it's not a black hole! :mrgreen:

Chris

chris s
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Re: Converting a bilge keeled Senior to centre-board

Postby chris s » Fri January 1st, 2010, 10:55 am

When I built my GRP Senior I increased the draught by a foot and omitted the bilge keels, I also increased the ballast and hung it all off the bottom of the deeper keel, as you can imagine she now sails very well and will even head to windward in a force 6, albeit not very comfortably, she is also stable and has a very gentle motion when hove to under the same conditions,

There are only 2 drawbacks with this deeper keel, the first is that she now sits a foot higher on the trailer, so consequently need a foot more of water to launch, and secondly she dries out on the centre keel and the turn of the chine at a 45 degree angle, instead of upright on the 3 keels, but I feel that this is a small price to pay for the vastly increased sailing performance.

link to photos http://www.eventides.org.uk/senpic.htm Scroll down to Heretic

Wagtail
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Joined: Tue September 8th, 2009, 8:13 pm

Re: Converting a bilge keeled Senior to centre-board

Postby Wagtail » Fri January 1st, 2010, 1:50 pm

Thanks for that Chris. It looks like a good arrangement, though as you say you lose the advantage of sitting upright on the mud or sand. I have heard of another possibility which was Kenneth Gibbs' own idea which is to increase the depth of the bilge keels and the central keel by 6 inches. (The bilge keels were made from mild steel plate and attached with 4 inch flanges and hefty backing plates.) This was at the request of Martin lewis. I notice on the picture section of the website there is a boat called 'Compass Rose' which seems to have this arrangement with the difference that the central keel is taken right to the transom. That must make her directionally very stable but are there unseen costs (I mean to sailing performance) to this arrangement? Any suggestions welcome.

Richard 'Wagtail'

Wooden Boat Fittings

Re: Converting a bilge keeled Senior to centre-board

Postby Wooden Boat Fittings » Sun February 21st, 2010, 2:39 am

Richard, the YM 3-Tonner has a full-length central displacement keel, together with short bilge-keels. The keel itself carries external ballast and is unquestionably what drives her. (The bilge-keels are really there only to keep her upright on the mud.) So I wouldn't be concerned about Compass Rose's full-length keel affecting her performance.

Image

One possibility that may not have occurred to you is to follow Iain Oughtred's idea for his 'Eun Na Mara', and build two offset centreboards (bilge-boards, for want of a better word,) each one retracting into the front face of a cabin berth. This would avoid your having to tamper with any of the centreline construction at all.

Image

Whether you think the effort would be worth it or not is another thing of course.

Mike

chris s
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Location: Netherlands

Re: Converting a bilge keeled Senior to centre-board

Postby chris s » Sun February 21st, 2010, 6:49 am

The Winkle Brig also had a similar hinged twin drop keel arrangement, (I worked building them for a short while in the early 90s)

and to be honest is was far far better than even the bilge heel Senior at sailing sideways! :roll:

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Fiddler's Green
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Re: Converting a bilge keeled Senior to centre-board

Postby Fiddler's Green » Sat January 15th, 2011, 2:08 pm

There is always the Martin Lewis version....

He got Kenneth Gibbs to OK a deepened keel version. He dropped the ballast keel 6" and fitted steel bilge plates to match. the outcome was a Senior that sailed to windward, could beach on a foreshore and was easy to trail home. If you look at the Hints and tips page you will see Geoff's father did the same to Mikros with good results.

hope this helps
John
Proud owner and builder of 'Fiddler's Green'


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