removing my bilge keels for improved windward performance

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reliclax
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Joined: Mon November 15th, 2010, 6:21 pm

removing my bilge keels for improved windward performance

Postby reliclax » Mon November 15th, 2010, 6:26 pm

I have a 26 foot eventide and wanted to ask advice on whether i can remove the two bilge plates and just keep my centre ballast keel of about 600 lbs. Are the bilge plates any use other than for standing upright. Or are they part of the yachts ballast. Many thanks

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Kevan
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Joined: Sat June 26th, 2010, 9:10 am

Re: removing my bilge keels for improved windward performance

Postby Kevan » Tue November 16th, 2010, 6:23 am

I am certain you will have considerable feedback from the Eventide owners but I have just about finished analysing a Riptide for stability etc. and can confirm that the extra mass makes quite a difference to the stability numbers. Mind you the http://www.sailingusa.com formulae aren’t fussy about the depth of the ballast so take it with a grain of salt – they may assume that all ballast is at the bottom of the keel. On the Riptide the Angle of Vanishing Stability (AVS) score without the bilge plates is about 134 degrees and with the extra 300kg ballast it is just over 141 degrees.

I note on the Eventide the bilge keels appear disproportionally smaller than on the Riptide, and the change in mass may not have a similar effect.

I also note that the keel ballast mass on the Eventide dwgs is 1020lb not 600lb as per your post – something I missed?

I haven’t sailed with/without plates so can’t answer from experience, but why should removing the plates increase windward performance. I would have thought at heel the leeward plate would help dig in – just my thoughts mind you. Granted there would be a decrease in wetted area.

I have also read on the internet of a Golden Hind(?) owner who did remove them for an ocean crossing but the rolling was more of a negative than any slight increase in performance.

Good luck and let us know how it turns out! Kevan

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Fiddler's Green
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Re: removing my bilge keels for improved windward performance

Postby Fiddler's Green » Wed December 8th, 2010, 11:46 am

Remove bilge keels? Not a good idea unless you drop the main keel and increase the ballast weight and depth to match the fin keel version. CD of drawings that includes all of this available to enrolled members for cost. £5.00 UK, £6.50 over seas inc P&P.

The design weight of the keel on a 24 is 1020lb now and deeper by 2 or 3 inches than the early versions.

Bilge keels, if just 2" shallower than the main keel will work well when sailing to windward, as the lee keel will be almost vertical and if fitted correctly will have a slight toe in, thus pointing the boat up wind.

Having said that Eventides are not the best to windward in the original design, with 560lb keel or 780lb keel. The later boats built with deeper main keels and more ballast will give most modern twin keel boats a run for their money to windward. Off the wind you should leave them in your wake!

OK having the extra surface area of bilge keels slows you down slight ly, maybe 1/8th of a knot at full speed, I can live with that. The advantages of the bilge keels are many.

Apart from easy beaching for a scrub off or just to get to the beach for the kids, I am recovering my Eventide onto her trailer this week, a doddle. I sail in shallow waters with impunity, if i ground, I put the kettle on! None of this 45 degree stuff for me.

Long distance cruising sorts reckon the bilge plates damp rolling, they could do but as I have never sailed an Eventide without them I cannot tell.

My Eventide 26 has a ballast keel of 15" depth at the deepest part of the hull, (shallowest part of the keel) as opposed to 9" of earlier versions. My total ballast is 2240lb or 1 ton.

OK she is stretched to 27'3" in the building, but on the drawings now we recommend min of 2,000lb as opposed to the 1660lb shown on the 1973 drawings.

I have written a lot on keels and weatherhelm, you can find it on the 'Owners Tips' page.

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

GHM
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Joined: Thu March 10th, 2011, 9:36 pm

Re: removing my bilge keels for improved windward performanc

Postby GHM » Thu March 10th, 2011, 10:03 pm

I've met several owners who were enthustiastic about removing the bilge keels, especially a couple of Americans (?). Having built 6 GH31s and a GH26 I've occasionally been asked for my opinion re the "improvement" in the performance of the GH31. I have always pointed out that the keels weigh 330kg and asked if they would be happy that the boat performed "better" if they just threw away 1/3 ton of ballast? The usual response is silence and a rather worried look.
In a rather more analytical sense, I did a lot of rework on both the 31 and 26 to get them through the RCD (Recreational Craft Directive). I can confirm that the very significant decrease in stability which results from leaving them off excludes the 31 from Cat A (Ocean) and the 26 from Cat B (offshore) stability ratings. It's really a question of deciding where your priorities lie I guess.
Mark.

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Fiddler's Green
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Re: removing my bilge keels for improved windward performanc

Postby Fiddler's Green » Fri March 11th, 2011, 11:35 am

Brilliant response Mark, that is just what this site is about!

I would never agree to remove mine, and I have often connsidered adding a little weight to the bottom of them, rather than, as it is, screwed down lead ingots on the inside of the boat as trimming ballast... but have never quite got round to it. the bilge keels work well for me!

Regards,
John
Proud owner and builder of 'Fiddler's Green'

helenrose
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Joined: Tue October 31st, 2006, 2:25 pm
Location: uk

Re: removing my bilge keels for improved windward performanc

Postby helenrose » Sun March 13th, 2011, 7:04 pm

I would like to agree with John about adding ballast to the bottom edge of the bilge plates, in my case it was in the form of 80x12mm lengths of flat steel welded on.
They added a fair bit of low down weight and as a result my E24 used to suprise quite a few newer boats with her turn of speed.

I miss that old boat.

Wooden Boat Fittings
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Joined: Tue February 12th, 2013, 11:26 pm
Location: Canberra

Re: removing my bilge keels for improved windward performanc

Postby Wooden Boat Fittings » Wed May 15th, 2013, 3:22 pm

... and along the same lines, Sanderling (YM 3-Tonner) had both bilge keels and internal trimming ballast of about 1/4 ton (in the form of sash weights under the bottom-boards), and I wouldn't have done without either.

Mike


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