is it possible to reduce draft? cut off keel?

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mattnj

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does anyone know if it is possible to reduce a keel an a yacht?
We have a 2.05m keel and were discussing over the weekend if it was possible to have it reduced, maybe a bit cut off and a bulb or wing type arrangement added to keep the weight/ballast the same? 1.75m would be much more agreeable...
Just a crazy idea after some wine, is it possible....
 
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I read an article in a magazine about just such a project. The keel was reduced by about 1/2m, if I remember correctly, and a bulb was added. I remember that the keel was eventually cut off using a chain saw!
I believe the owner consulted the boat's designer before asking the yard to do the job.
 
Many designs like my Bav 37 were/are availabe with two drafts. In many the difference is not much such as 1.8/2.1. On mine the difference is more 1.35/1.85 (although I think from my measurements it is nearer 1.4). The stability curve is said to be the same as the keel is longer and has a large, shaped bulb at the bottom. The loss is primarily in windward ability, but difficult to tell without making direct comparisons. The hull design is not known for its excellence in this anyway. Our choice was dictated by our plans to go through the French canals where anything above 1.8 is generally a no-no.

Other designs use different rigs with different keels, or different designs of keel such as a Scheel or wing keel in shallower draft versions. Therefore when buying, one may have a choice, but often, unless draft is critical, other factors may be more important. Not woth trying to modify an existing boat - except perhaps deepening a keel by fitting a spacer.

Better to change boats if you don't like what you have!
 
was just curios really to see if it is ever done....only a bit of lead/glass after all....
i love the idea of chainsawing off the bottom of my keel :-)
 
1' or better 18" does actually make quite a bit of difference when looking at natural sandbars or even boat yard cills ... Having gone from the 1.8m down to a 1.4m it opens up many more possibilities in our local sailing area - such as Newtown, Poole & even up Beaulieu river ...
 
mattnj said:
does anyone know if it is possible to reduce a keel an a yacht?
We have a 2.05m keel and were discussing over the weekend if it was possible to have it reduced, maybe a bit cut off and a bulb or wing type arrangement added to keep the weight/ballast the same? 1.75m would be much more agreeable...
Just a crazy idea after some wine, is it possible....
Click to expand...


possible is definitely possible

back in IOR times, we saw off a bottom slice of the keel, replacing with some lead ballast inside the bilge, then eventually added a wooden profile to bring back the keel to its original draught

senseless isnt'it, what rating rules may force you to do :laugh:


there is a yard that offers sort of ready made solutions in terms of bulbs to replace a part of the fin, I'll dig into the favourites to find it but IIRC it was in the US
 
also, I for one would be a buyer of an easy practical system where you have the capability to increase draught by say half a meter when you plan to sail to windward, for example by adding a neutral buoyancy prothesis to the keel,

then easily take it off while coastal sailing

:smile:
 
is it possible to reduce draft? cut off keel? Reply to Thread

I've been looking at doing this for a while. I'm after a GK which are available in Deep fin & shoal draft, the latter being pretty impossible to find.

These guys do it and have good information on their site: http://www.marskeel.com/

You cut off the bottom & add about 20% extra weight to the lead bulb bolted onto the keel. You can use a chainsaw, but ONLY if you have a lead keel.

Simon
 
mattnj said:
does anyone know if it is possible to reduce a keel an a yacht?
We have a 2.05m keel and were discussing over the weekend if it was possible to have it reduced, maybe a bit cut off and a bulb or wing type arrangement added to keep the weight/ballast the same? 1.75m would be much more agreeable...
Just a crazy idea after some wine, is it possible....
Click to expand...

I'm sure it is possible but despite all my best efforts in unintended keel bashing , rock hopping and drying out on all kinds of rough surfaces, our keel refuses to co-operate and refuses to shed any weight. Where am I going wrong??:)
 
mattnj said:
does anyone know if it is possible to reduce a keel an a yacht?
We have a 2.05m keel and were discussing over the weekend if it was possible to have it reduced, maybe a bit cut off and a bulb or wing type arrangement added to keep the weight/ballast the same? 1.75m would be much more agreeable...
Just a crazy idea after some wine, is it possible....
Click to expand...

.
Anything is possible, after all any sailing boat is no more than a collection of compromises.

To get this compromise right you will have to add more weight to the keel than you have now so may need more calculations to get this final draft right.

You also need to establish what material your existing keel is made of and what if any ballast is used and how it's contained.

No fun cutting into the keel and a tonne of lead shot dropping onto the ground.

Lead torpedoes are mostly through bolted to the existing keel, then fared with Micro Balloons.

This has been done many times on any number of designs, however you should discuss this with the original designer or builders before proceeding and get their response in writing to keep your insurance people happy.

Hope this helps.

.
 
Matt - the following is mildly interesting though not sure it's directly relevant to what you want to do but....
I recall a boatyard on The Broads (Whelptons?) converting a couple of S&S 34s by reducing draught.....and LOA(!)....and sail area(!) (reducing mast height/boom length - called Tempest and Typhoon?) Some 'Broads sailor may be able to add/correct details. Similarly, I witnessed a yacht at what was Martham Ferry Boatyard (White Lady?) having 6 inches or so sawn off the fin keel - IIRC this was done with a large hacksaw, by hand, cutting through the lead. For 'Broads hire use I guess these measures could be justified if knowingly undertaken.
 
I would be very cautious about trying to cut off the bottom of a keel without at least talking to the designer (as others have said), or a keelboat naval architect. If its cast iron, it will be a devil to cut (tourch?) and attaching a lead bulb would not be that easy. Cast is not easy to drill or cut without the right kit.

Also, unless you reduce the rig, you would need to add more weight than you removed (assuming your boat was well designed in the first place) which would affect displacement. Not one to just play with unless you get some expert advice.
 
It would be cheaper & easier to change your boat. A chainsaw will not touch a cast keel, but an angle grinder will - in due course!



Attaching lead bulb to iron keel? Seemples; Two large bolts with penny washers or steel bar recessed into the base of the bulb & screwwed into threaded holes in base of keel.
 
Shortening your keel

Well I am all in favour of experimentation. Certainly a shorter keel will make shallow sailing a lot easier. Around here it is common to jump in the water and put your shoulder against the hull to push it off a sand bank. hence the draft is very critical. However even a 1.75 metre keel would be too deep draft (over 2 metres) A draft of less than about 1.6 is neede for this approach to running aground.
You suggest your keel is just fibreglass and lead. In that case yes you can cut it with a chain saw. You should weight the removed portion to determine what change to ballast you have made. You will need then to fibreglass over the bottom of the keel. The shape of the bottom of the keel I think is important. A flat bottom is good for standing the boat on the keel on the hard but a rounded bottom both in shape front to back and sideways will make for better windward performance.

Regarding attachment of a bulb or wings. This is doable. I actually fitted an additional shoe to the bottom of my fibreglass keel. A vertically lifting keel I was able to lift the whole thing out and stand upside down for work. I made a fibreglass mold of the bottom of the keel. Removed it and mounted it in my case about 1 inch above the existing keel tip. I filled the gap with molten lead. I screwed some self tapper screws into the keel tip to aid attachment. The f/g mold melted and smoked but I had a lovely lead shoe on the keel tip which i then covered with fibreglass. it has remained for about 15 years now. I d0o appreciate the additional 15kg righting ability.

In your case you could use large coach bolts to attach a lead bulb or wings or I think I would advocate shoes of lead on each side of the bottom of the keel.
Certainly you will lose windward performance but that may not be a concern to you.

A friend had a Thompson 9.7 m boat a real racer. It had a keel which could be lifted by crane up through the removed cabin top section. It was a really deep draft but it could be operated with the keel raised by about .7metre or lifted right up for trailing. all just different thoughts... good luck olewill
 
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