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Thread: Thinking of removing the bilge keels this winter

  1. #1
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    Default Thinking of removing the bilge keels this winter

    I've thought about this for 25 years now and am deciding to remove the bilge keels. Removal is simple, plugging the bolts is a decision for a permanent solution or for refitting a year later!

    The history is Tiller Girl was built in 1963. A single design by the builder to satisfy the owner who wanted her like to look like above the waterline to be similar to a Laurent Giles 'Virtue' but shallow draught for the Thames Estuary and to dry out between tides off Thorpe Bay/Southend, on the south-east coast of England. To achieve safe drying out she has a long central keel with a straight bottomed iron ballast keel which will support her substantially. Her ballast keel is 18" wide! So she will balance dried out!

    Originally she had timber bilge keels but at some time they were removed. You can see in the image that the original bilge keels were over 6 feet long and I believe they were removed because the drag was significantly hindering her sailing qualities:

    [URL=http://s217.photobucket.com/user/rgaspar_album/media/Launching2011001.jpg.html]

    In 1985 she certainly was not 'wearing' bilge keels but the then owner added steel bilge keels as you now see her. The same owner also moved the mast forward about a foot and added ballast inside (a surveyor had thought she was a little 'light'!). The mast was moved because the owner complained of excessive weather helm. Whether the bilge keels were added to assist reduction of the weather helm or whether fitting the bilge keels had added weather helm I cannot say. All I can say is that on purchasing her in 1991, I removed a lot of internal ballast weight because it was poorly fitted (intending for trial and error to put it back better fitted if necessary). I then took her sailing and weather helm was perfect. No ballast was replaced.

    In 1995 I replaced the engine which halved the weight previously installed. Her trim was improved and her weather helm is delightful. Sufficient for safety, spot on for prolonged helming.

    So the issue: On the wind she will create two bow waves, one for the bow, a second for the windward bilge keel. There is no shape of the bilge keel and the steel plates are ugly montrosities in need of fairing. On the wind in a seaway, the windward bilge keel traps air and water and compresses the mixture as the waves past by. Whoompt is the sound and the vibration of the bilge keel can be felt. Not much but after 25 years it is easy to recognise. Also in those 25 years I have had to sister frames immediately after the position of the bilge keels. Do I get resistance from leeway? I don't know. She is never going to be close winded but she has as much keel, if not more than an Essex smack. So I doubt leeway will increase. But am I right?

    I can add some fitted ballast internally to replace the loss of weight from the bilge keels. I don't think the different weight distribution will make any change?

    [URL=http://s217.photobucket.com/user/rgaspar_album/media/IMG_0023.jpg.html]

    Note this image (sorry the end of season state!) but this shows clearer how long originally her timber bilge keels were.

    [URL=http://s217.photobucket.com/user/rgaspar_album/media/123-2315_IMG.jpg.html]

    Note the vulnerability of her splaying. Note how fair the hull will look with the bilge keels removed - and removing the batten showing the evidence of the 1980s. Oh incidentally, Tiller Girl were built by Seacraft of Leigh-on-Sea close by Southend who used to build Bawleys. Bawleys were sailing fishing vessels for trawling cockles and the transom and shape of Tiller Girl has obvious family similarities. The owner of Seacraft was the designer.

    So, intending to remove the bilge keels, am I:

    a. Very silly?
    b. Very sensible?
    c. Very curious that probably might be a good idea or might not?

  2. #2
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    Default Re: Thinking of removing the bilge keels this winter

    Interesting. One can see that this application of twins has two problems: the boat's heel being enough to cavitate the weather keel; and the wave making shape no doubt causing interferance.

    So sure, I'd be tempted to try getting them off and see how she sails. Worst case, make leeboards.

    Pretty boat.

    Keep us informed.

    G'luck.

  3. #3
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    Default Re: Thinking of removing the bilge keels this winter

    Pretty boat, you'll definitely reduce wetted surface and therefore improve light air performance. I imagine you'd lose some windward ability, but I'm only guessing, further postulation says that maybe what she loses in pointing will be gained in performance.

    Further concerns: She may roll more. If you do run aground she will no longer sit upright, but will be easier to rock her off if she's lightly aground.

  4. #4
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    Default Re: Thinking of removing the bilge keels this winter

    LastBoat also has a very wide lead shoe and I'd expect her to stand up on flat ground with no cross wind and no seriously out of balance loading. In other words, I'll give her legs, as LFH designed for the Golden Ball prototype in "The Compleate Cruiser" and as I used with my Alden 43 Goblin. And I have less far to fall if she rolls over. I recommend something similar for this boat.

    G'luck

  5. #5
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    Default Re: Thinking of removing the bilge keels this winter

    Well, Roger...
    Mark me as "option" c... and I have not an intelligent clue as to what would happen if you remove those keels!
    But I have to say, your post is quite intriguing and presented well. Noting that no-one has yet asked for more information, pictures or clarifications.
    There are some Naval architects/designers here that I hope will add their opinions.
    I'll be interested and following along. Cheers.

  6. #6
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    Default Re: Thinking of removing the bilge keels this winter

    Thank you all. I guess I would like to avoid lee boards but the rest I am up for the experiment. The quick option is to drop the keels - 10 nuts a side I think and then something to bolt up in place leaving the bolts in place until I have experimented - but the ugliness of the temporary arrangment! The issue of legs is a mystery. I have replaced a few years ago the starboard beam shelf; it had no facility for a leg. Port side there is a hole through the beam shelf but not the plank! Waht does that mean. A hole through the beam shelf must mean a leg but no one replaed the beam shelf starboard side before me (history is that the teak laid deck 1" over 1/4" ply in 1964 was fastened with steel screws - plain steel!. You can hear the builder telling the owner 'it will outlive you'. But 40 years later some steel screws had given way particularly starboard side and the caulking would not last a season. A substnatial part of teh starboad beam shelf had to be replaced. I had to left the teak and I replaced a substantial sapele ply deck instead - lovely and rigid).

    A naval architect /designer would be very interested + plus interested forumites

  7. #7
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    Default Re: Thinking of removing the bilge keels this winter

    I don't see much to be lost by removing the keels, sailing a season, and replacing them if you find it was a backward step. Just store the keels somewhere safe! My boat has twin keels but no central external keel, so such an experiment for me would be a much, much, bigger undertaking. I hope you come back and post results.

  8. #8
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    Default Re: Thinking of removing the bilge keels this winter

    They look like an after-thought, added purely to not go over when dried out. It depends on your MO (how often you dry out, if you can add legs etc) but I'd remove them in a shot. You have plenty of long keel to sail adequately to wind.

    +1 to post results.

  9. #9
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    Default Re: Thinking of removing the bilge keels this winter

    I'd say it depends entirely on whether your mooring / berth dries out or not. If it's mud or dries they could be well worth it , but if not, no.
    '' You ain't gonna learn what you don't want to know. ''
    Grateful Dead

  10. #10
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    Default Re: Thinking of removing the bilge keels this winter

    I have no issue with the notion of removing the bilge keels for a season as a trial. I am less sanguine than the group about how little she'll miss them. I expect you'll want to put bilge keels back on. Or... if you find the increase speed from the experiment (which could be anywhere from substantial to slight) is important to you... and you really are allergic to leeboards (many people are)... maybe add a fixed keel or a centerboard.

    But if/when you do add the bilge keels back on - do not put those crude slabs back. Instead - form some naca shapes... or semi-naca shapes. Any nod in that direction will yield noticeable results, methinks. I would be inclined to make a wooden staved blank - with some lighter, rot-resistant species for center staves. You likely know better than I what's available to you. And some rot-resistant denser species (Ipe? Merbau?) for the forward strake (to take an impact) and the aft strake (where it skinnies down to a bit of fragility). Shape, attach, fair the seam, then fiberglass and paint.

    I'd also be inclined to add a strip of polyester or kevlar or carbon fiber up the nose of the leading strake, as any of them are stronger in compression (the force imparted to that area from an impact) than fiberglass cloth. FG is fine for the rest, as it is strong in tension.
    David G
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    http://www.harborwoodworking.com/boat.html

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  11. #11
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    Default Re: Thinking of removing the bilge keels this winter

    Grateful for all the comments.

    My mooring does not dry; back in 1964 she would have done so. In the 25 years of ownership I have wintered in a mud berth for 3 out of 4 years to retain her mositure and the 4th year I have been lifted (this winter will be lifted as I am due an insurance survey [after 19 years]). The mud berth is lovely and soft and will retain her upright without the bilge keels. Indeed I have been conscious of the pressure on her bilge keels between them and the centre keel. 8.5 tons of weight compresses the mud and in occasional years when the mud has grown a little (annually it ebbs and flows a little) it has worried me. When I have used the mud berth years I have fitted out on an adjacent old 'hard' where she mainly stood upright but occasionally leaned on a bilge keel (quite safely). My growing years and a failing knee means that I need to find an alternative fitting out location so absence of the bilge keels will not matter.

    I guess I am not really allergic to lee boards - after all I am surrounded by Thames Barges - but I haven't thought through the complications. I have had an interest in a centreboard (our previous 25ft clinker yacht was a centreboader) and I think a solution could be very elegant. It would be interesting though to cut a slot in the iron ballast keel and alteration of the timber floors. I am hoping removal of the BKs would not cause excessive leeway. Perhaps as a preparation for the experiement I should start to measure the current extent of the leeway. Since I have a facility already to collect NMEA data (I conduct amateur surveys - see www.crossingthethamesestuary.com) it might be interesting to log Speed over the Ground/Course over the Ground/Heading/Wind Direction/Wind Speed data etc in the river negating any cross tide - umm a bit of interesting thinking.

    Replacing the bilge keels after the experiment? Yes but as suggested 'some shape'. Absolutely. Local timber easy availability would be Oak, Iroko or Teak (the latter very expensive, indeed the Chinese market 2 years ago drove down the availability of Iroko and the cost up). Other timber could be investigated. I am ignorant about shape so that would necessary research. (Bizarrely I wonder if the original 1964 Iroko bilge keels are still available. By a remarkable coincidence, the day after I bought TG in January 1991 she had been brought by road from the South-West England to the South-East. I was standing on the deck and a man walked past and revealed that in 1988 he had fitted the steel bilge keels, then in Sotuh Wales, and other things and he now had the Iroko bilge keels in his workshop. This spring while fitting out, the same man walked past and started talking - but I didn't ask if he still had them! I digress).

    Helpful thanks re the bilge keel thoughts from everyone.

  12. #12
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    Default Re: Thinking of removing the bilge keels this winter

    You can't cut a slot in that keel. If you must have a centerboard, make it off-center the board comes out hard alongside the keel.

    You'll need to do massive modifications. The bed log on the off-side (the keelson handles the other side) needs to be strong enough that (along with the change floors, frame hood ends and trunk itself) you'll not make the bottom weak.

    The water won't mind

  13. #13
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    Default Re: Thinking of removing the bilge keels this winter

    If you have a good mud berth i would not hesitate to take them off. Even if you had a drying mooring, i would remove them, but maybe just have a 4in hardwood stub fitted where the original bolts are, just to keep her bilge off the ground. I had a MG Bawley that could take the ground on her side, though it was not comfortable to be aboard at that angle, it was ok for a drying mooring. I would be surprised if those flat plates do anything for your windward ability, i also owned an MG Waterwitch that has a very similar under water profile as Tiller girl, never a good performer upwind, lots of leeway when pinched to much, but good for roll stability and drying out upright, but a bugger to get off if run aground hard unless you can back off the way you went on. Pros and cons. If you do not dry out much, and are going to make legs anyway, it could be a good performance enhancer!

  14. #14
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    Default Re: Thinking of removing the bilge keels this winter

    A lot of boats that have a long shoal keel and centerboard find that they can go faster to weather if they raise the board as they gain speed. The whole hull acts as it's own foil and gains more from that alone than the surface resistance of the board.

    Here is the big caveat: She might not tack, or tack easily, without the plates. And she'll wallow sideways going slow and hard on the wind so you'll absolutely need to start the sheets and over-tack to a reach and then trim and bear up with speed. Assuming she tacks without the plates, keep her a nudge off the wind - like five points rather than four (about 56 degrees rather than the sloop nominal of 45) - with easy sheets and she'll do nicely.

    If she needs more lateral to tack, it's really time to talk to a creative NA willing to play. I think you might to best modeling on a Sheel sort of cupping to the keel. Winglets would be my second choice.

    Either a sheel or winglets won't have the strength to hold the boat up even if they have the spread for stability. If you let her down on flat mud or sand with no side loading she might sit upright on her own bottom but I'd not trust that in all conditions. If you don't want to sleep on the slope, make legs.

  15. #15
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    Default Re: Thinking of removing the bilge keels this winter

    So ready to start!

    Lifted for winter on Friday, bottom cleaned and ready.

    =http://s217.photobucket.com/user/rgaspar_album/media/P1060054.jpg.html

    This season the water was remarkably clear this year and I hung over the side while we were on the wind. I could see the windward bilge keel clearly. First, it quite frequently formed a small vortex between the front flange and the plate of the bilge keel. The vortex would start as a small circle and then grow as a cylindrical vortex the full lenth of the keel. Once complete, the vortex would collapse and then at the right wave moment it would start again. Quite pretty really! Then much less frequently a much larger vortex started vertically on the leading edge. The vortex was much larger, as much as 9 inches or a little more in diameter - and would collapse the moment of the wave motion eased.

    So thats drag I guess? Got to be, as Ian and others have discussed. TG must not be pinched; chums with inexperience frequently pinch too far and the life goes out of her. She was never designed as a close winded yacht; she has always been for comfort I'm sure. The original owner want to keep her on a drying mooring and she was made to take the sand/mud area and so the central keel was deliberately broad.

    Ian,the point about tacking is very important. Grateful for the comment. The owner in 1985 didn't have the bilge keels fitted then and he fiddled moving the mast forward. It was said that was because of the weather helm (!) but was it because she was sticking in stays? The mast is still in that one foot or so forward. Unfortuantely I cannot contact the then owner.

    I have a surveyor on Tuesday for the insurance condition report and I will pick his brains as well. I am also seeing the sailmaker on Wednesday as well.

    Decision, decisions.....

  16. #16
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    Default Re: Thinking of removing the bilge keels this winter

    ^ Vortices can also mean lift, your problem is you can't tell whether the vortice is lifting to windward or leeward.

    The single bolt hole in one beam shelf tells a history, as you said one beam shelf is repaired, but it also suggests that the corresponding plank on both sides was replaced.
    It really is quite difficult to build an ugly wooden boat.

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  17. #17
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    Default Re: Thinking of removing the bilge keels this winter

    Just occurred to me, as she originally had bilge keels, keep the steel. Drill holes so that you can screw wood to the steel. Then galvanise them. Then if Tiller Girl indicates that she needs them, clad the wood with wood screwed on and set in epoxy, and shape it to create a foil section.
    It really is quite difficult to build an ugly wooden boat.

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  18. #18
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    Default Re: Thinking of removing the bilge keels this winter

    Umm, yes a very good idea on creating a foil section. Gosh, yes. I will keep the steels aside. Certainly they need some maintenance attention this winter anyway.

    The single hole (port side) is a conumdrum. Having repaired the beam shelf starboard side I did not detect any sign of earlier repair. I admit though a hole through the beam shelf is logic for legs. I have one image prior to 1985, not the clearest but I can't see any signs of a hole on the planking for legs. Mind you the hole is a little surprising aft and could just be under the fender!

    [URL=http://s217.photobucket.com/user/rgaspar_album/media/Original%20design.jpg.html]

    Note the mast a foot approx aft then, dog house was removed in the 80's (not necessary for headroom). Where the wooden bilge keels were fastened they were either longer or further forward. I'll check again but I think it is clearly evidence of being the full lenght to match the 'runner' still currently running ahead of the steel keels. Wouldn't those lines look better with the runner removed as well?

  19. #19
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    Default Re: Thinking of removing the bilge keels this winter

    Quote Originally Posted by tillergirl View Post
    Wouldn't those lines look better with the runner removed as well?
    Yes, of course, grind the cut end fair before sending to the galvo vat.
    It really is quite difficult to build an ugly wooden boat.

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  20. #20
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    Default Re: Thinking of removing the bilge keels this winter

    Responses from those present:

    The surveyor - get rid of those bilge keels
    The sailmaker - get rid of those bilge keels
    Professional builder - get rid of those bilge keels.

    So.... they are coming off. Information as it comes.

    General view was taht the removal of the bilge keels would improve the tacking performance.

  21. #21
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    Default Re: Thinking of removing the bilge keels this winter

    Next issue - is it significant to lose the weight of the steel plate bilge keels. I have estimated the weight of both bilge keels combined as 368lbs. I weigh 214lb (tonight). Doesn't feel significant. 100 litres of diesel weighs 187 lbs for example. The cost of lead in the UK at first look is around 400 plus cost of casting.

    I am kind of feeling adding some internal ballast using lead to replace the steel bilge keels is logical but not critical. Ironically when I replaced the engine in 1995 there was an apparent significant reduction; the balance was much nicer and she sailed well.

    Adding internal ballast is possible midships (ie in position where the bilge keels current are in position - in terms of fore and aft of course).

    Any comment chaps please?

  22. #22
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    Default Re: Thinking of removing the bilge keels this winter

    Any scrap iron ballast from the wrecks in the saltings? Pig iron or old rails?
    It really is quite difficult to build an ugly wooden boat.

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  23. #23
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    Default Re: Thinking of removing the bilge keels this winter

    Almost certainly... but all very difficult to recover in the v. muddy saltings I have a worn out knee! Having done some weight/volume maths, I suspect lead is going to be the best/only option to fit: TG has shallow bilges. Common opinion here seems to be to try first and add ballast if thought necessary. Last time the crane weighed TG she was about 7.5 tons (the 'Long Ton' or the UK ton @2240 lbs - we would never have a round figure). That is a displacement of approx 16800lbs so the bilge keels contribute only 2.2% of that. The central ballast keel was said to be is estimated at 2 tons, so arguably 4848 lbs is a total of ballast weigh of which 7.5% is down to the bilge keels. Umm. Not sure what that means ... or indeed anything.

    I have sought a quote from a commercial casting company to see how bad it is.

  24. #24
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    Default Re: Thinking of removing the bilge keels this winter

    As she was designed originally with timber bilge keels, they wouldn't have contributed to the ballast – so the original design must have considered just the ballast keel and any internal ballast.

    A traditional ballast ratio for a sailboat of this type would be between 35% and 45% (so the weight of the ballast would be 35% to 45% of the total weight of the boat, including the ballast). If TG weighs 16800 lbs and you have now removed (or are removing) the bilge keels she should weigh 16432 lbs.

    More than likely, the crane weight is greater than the designer figured for the purposes of a ballast calculation because of personal gear and so on – and because designers often err on the optimistic side when doing a weight estimate. So, say the design weight estimate was 15000 lbs – then commonly the ballast weight would be between 35% and 45% of that – 5250 lbs to 6750 lbs. At an estimated 2 tons (4480 lbs), the ballast keel seems a bit light – but if it is in reality, say 2 tons (5600 lbs), it would be well within the normal range.

    Personally I would (a) remove the bilge keels as she will almost certainly perform better without them, and (b) wait and see how she is without them in terms of stability; if she seems a bit tender, then add some internal ballast – lead gives you the best weight for volume – usually you can get standard 25kg pigs and they are not too difficult to fit in, which will be cheaper than having special shaped pigs cast.

    She is a very good looking boat!

    Cheers -- George
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  25. #25
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    Default Re: Thinking of removing the bilge keels this winter

    George - thanks for adding. I had not factored in the timber BKs issue. The ballast keel was estimated by the surveyor in 1985. I am going to get the tape measure this morning (this autumn morning has started more like a spring morning) and see if I can estimate myslef. Given the size of the keel it might have been underestimated.

    Absolutely right about the added weight point. Some internal ballast had been added in 1988 - I redistributed it in 1991 and fastened it (!) and trial seemed fine. I shall be happy to try and test. I have sent a quote for three even sized ingots matching the BK weight just to get a ball park cost. Oh, one other thing on weight. When I re-engined in 1995 I reckon I saved close to half of the engine/gearbox/clutch/reduction(!) weight. The trim was obviously better.

    I think I shall start discussions with the yard this morning.......

    Ah, found the comment in the 1988 survey: "The vessel does appear to be light and in the writer's opinion she should be ballasted down particularly in the forward area". There is some lead under the fore cabin, presumably added immediately then as there is acknowledgement manuscript mark added. Lead fastened by me I add!
    Last edited by tillergirl; 10-31-2016 at 03:39 AM.

  26. #26
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    Default Re: Thinking of removing the bilge keels this winter

    I have owned 2 twin keel sailboats.
    A Kingfisher 20 and my current Alacrity 19.
    I like the twin keels because they
    1. give the boat very good directional stability without requiring a full long keel
    2. keeps the keels shallow so the boat can launch from a trailer easier.

    Your sailboat
    1. Has a full main keel for directional stability.
    2. does not launch from a trailer.

    So I see no problem with you removing the 2 extra keels.

  27. #27
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    Default Re: Thinking of removing the bilge keels this winter

    I wonder why they were added? There is no reason to do so unless drying out and since you have an 18 inch wide shoe then if you did intend to dry out then a couple of legs would do the same thing. Sailing, they add nothing but drag, and from the sounds of it a lot of local and unnecessary stress. I would remove them, plug the holes and consign them to history. Trim the boat with lead ballast if necessary.
    whatever rocks your boat

  28. #28
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    Default Re: Thinking of removing the bilge keels this winter

    It is likely the original "timber" bilge keels added displacement, not ballast.

  29. #29
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    Default Re: Thinking of removing the bilge keels this winter

    Thanks for the comments.

    The commissioning owner lived in Thorpe Bay, Essex, perhaps was a member of the Thorpe Bay Yacht Club. The builder and designer lived and built her in Leigh-on-Sea down the road. The neighbourhood - Leigh-on-Sea, Southend-on-Sea and Thorpe Bay was one expanse of drying moorings: here is an image from the 3rd edition of the UK book 'East Coast Rivers - the 4th edition is out today.


    The commissioning owner wanted a yacht that looked like a 'Vertue' class but larger. A Vertue below the waterline would have been not the best to dry out; I would guess that legs would be prone to finding soft holes. The builder had built many Maurice Griffiths designs and so below the water line is very like an MG design. I would suggest that the long bilge keels (which were around 6' 6" long) would have been ideal with its very solid broad iron central keel.

    Tiller Girl was sold in the 1970's and went round to Merseyside near Liverpool. Perhaps the drag etc of the bilge keels were then removed. Certainly they were not there in 1985 when Tiller Girl moved to South Wales. The shipwright who did work in 1988 had the timber bilge keels in his shed in South Wales. The surveyor in 1988 - after the fitting of the steel bilge keels and the movement of the mast about 14" forward - made the comment about lightness - despite a rather heavy old fashioned diesel engine.

    I have just done some calculations on the weight of the ballast keel - an estimate of 4634 lbs which is 2 UK tons plus 150 lbs or so. Difficult to be precise because the keel is nicely shaped - albeit wide. Quote today in the UK for six lead ingots totalling 370lbs to replace the steel bilge keels is just under 400 inc of tax and delivery. Cost of replacing the 'runners' sandwiching the bilge keels on the planking is quoted at 101 plus tax.

    Decison is the bilge keels will be removed in the next month or so. Can't make up my mind yet whether to replace the weight immediately or see how she performs.

  30. #30
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    Mar 2013
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    South West UK
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    58

    Default Re: Thinking of removing the bilge keels this winter

    I think you hit the nail on the head when you said you would get data for heading, leeway and speed. I would data log first. Remove the keels, then repeat the process. I think you will find an increase in speed regardless. She looks quite shallow draft and ballast seems a little light for such a shallow draft. You also mention that lead was added forward so that should be taken into account for the ballast.
    I think you would regret adding a centreboard whether offset or not. Seems like minimal cost to add a bit of ballast and remove the keels.

  31. #31
    Join Date
    May 2013
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    West Mersea, England
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    110

    Default Re: Thinking of removing the bilge keels this winter

    Yes Bob. Agree. Unfortunately the data for heading, leeway etc was spectacularly useless! I am going to take them off, probably next week. We pulled a bolt today to measure for dowelling the bolt holes: bolt was like original but frankly the timber will be better off to see the stainless bolts. Clearly they don't like each other (the bilge keels are standard steel plate). Paint doesn't adhere in the way of the stainless bolts. The timber is still rock hard but the lack of paint and a little oxidation indicates they are not good partners. The nuts are surprsingly easy to undo. I wouldn't claim they were lose but they were hardly very tight!. Not leaking though.

    You might not know that the ballast keel is wide; 10.5" at the front, 12" mid and 8.5" aft. I judge it to be @ 2 tons (UK). Best to replace with some lead internally.

  32. #32
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    Jul 2011
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    Lindstrom, MN
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    1,657

    Default Re: Thinking of removing the bilge keels this winter

    If you plug the holes with galvanized carriage bolts, they can be removed easily to replace the bilge keels in the unlikely event that you change your mind. I would pot them in with wax or tar so they could be driven out if needed. The heads will not create significant drag.

    Scrap lead, 330 lb (150 kg) for 250.00 http://www.ebay.co.uk/sch/lynpar3/m....p2047675.l2562
    You may be able to shape it well enough without melting?
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  33. #33
    Join Date
    Oct 2001
    Location
    Flattop Islands
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    2,167

    Default Re: Thinking of removing the bilge keels this winter

    I would agree with taking them off. The boat will certainly be faster without them, measurable or not. Don't worry too much about the weight difference, two people sitting on the sole downstairs will be the same....ie, hardly noticeable. The thing the bilge keels do provide is roll damping, which can be a big issue with a high center of gravity (shallow draft) boat. The boat is inclined to want to roll farther than a deep draft model, and the keels damp that out quickly. So motion will change, if that's okay then all should be good.
    ___________________________________
    Tad
    cogge ketch Blackfish
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    http://www.tadroberts.ca
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  34. #34
    Join Date
    May 2013
    Location
    West Mersea, England
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    110

    Default Re: Thinking of removing the bilge keels this winter

    Sample bilge keel bolt (stud) pulled. Not very tight but not leaking. Condition - perfect. Bit of putty in the threads in way of the stringer.



    Interesting idea about the glav'ed bolts. But I have just bought the timber for the runner (which will be nicely fashioned)! You would have been right about the lack of drag. When I look on the inside of the bilge keels - OM they need fairing. The thought of the drag!

    The ballast issue. Umm yes. I am tending to replace it. It is certainly right that we are talking about one and a half adults which doesn't seem significant. But the height of gravity issue I think is important. When I bought TG the trim didn't look good (1991)! (It's the yacht behind with its genny in shreds)



    With the internal ballast redistributed (and fastened!!!!) and the lead under the cockpit removed I would suggest the trim was better (1992):



    Then I replaced the engine. The old engine was a BMC 1.5 diesel (marinised version of the London Black Taxi), with very heavy gearbox, a separate clutch assembly(!) and reduction box (heavy on is own). Replacement was a Volvo 2030 - nice smooth and not that heavy. I reckon at least a third of the weight of the engine was reduced. Might even have been halved. But the trim still look ok (1995) - I think). Sorry its a dark image:



    So? TG weighs about 7.5 tons (UK) on the crane with fuel, ex water. Ballast keel about 2 tons (UK). TG is substantially built - all planking 1" iroko, substantial scantlings etc. So the 'fabric' of the vessel is heavy and I can see the argument that the weight low is quite light (I have actually been reducing weight aloft recently because in 1991 I unnecessarily over spec'ed the running rigging). So I am tending towards replacing the weight of the bilge keel as low as possible internally. I have calculated the space available on top of the keelson exactly mid-way in way of the bilge keels. I accept the positive role of the bilge keel over roll (sic) is good but the reduction of drag is seen by me as happier . Time will tell. I suspect I shall be reporting in May, 2017!

  35. #35
    Join Date
    Nov 2004
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    Port Townsend WA
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    10,423

    Default Re: Thinking of removing the bilge keels this winter

    I find your in-depth experiment to be fascinating! It makes me think of sailing a model yacht with variations to appendages and rig. Very interesting indeed! Just looking at your sheer, mast height and placement makes me think that adding a mizzen and making her into a ketch might add to her sailing efficiency. In some respects I am reminded of my own H28. This clever Herreshoff design is one that is of shallow draft that depends on efficiency of hull form rather than depth of keel to realize hydrodynamic lift to weather. I find the mizzen is a great balancing sail that greatly adds to the speed of the boat on reaches and down wind.
    Jay

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