Author Topic: Stability if no keel  (Read 3273 times)

nasvip

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Stability if no keel
« on: March 09 2019, 12:30 »
My original plan was to go from Mediterranean to Northern Europe through French canals, so I bought a Bavaria 46, 1997 - announced draft 1,65 m. After having the boat on the hard for the winter I got suspicious- and did a check - and found the draft to be 2,00 m.
So now I think about replacing the keel with a cheap temporary one giving draft 1,50 m, just for the trip on the canals and for protection of the rudder and keeping the manoeuvering properties. Off course the mast will also be dismounted, but such a keel, though, would only have a weight of 120 kg, so stability would suffer a lot.
I don’t have metacenter hight or other relevant specific data for doing an accurate stability calculation, but just from sketching I think stability would be ok for sailing without mast on canals. The boat has a beam of 4,45 m giving a good hull stability. If my estimated gravity center etc is not entirely wrong it would take a weight of 500 kg on the one side of the deck to give a list of 15 degrees which would be ok. But maybe it is constantly moving and not comfortable to stay in for longer period.
 Does anybody have experience with a project like this?

Yngmar

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Re: Stability if no keel
« Reply #1 on: March 09 2019, 14:53 »
Welcome to the forums! Unfortunately this sounds like a thoroughly terrible plan for many reasons.

On the upside, your Bavaria 46 with the 2m draft keel should have no problems coming down the long way via Biscay, and you get to enjoy Normandy, the Spanish Rias, Portugal and Gibraltar on the way to the Med. Can recommend this route, not least of all because you get to keep your keel, mast, insurance cover and the boat itself ;D
Sailing Songbird  ⛵️ Bavaria 40 Ocean (2001)

Symphony

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Re: Stability if no keel
« Reply #2 on: March 09 2019, 16:37 »
Agree with Yngmar. If you want to transit the canals buy a boat that is suitable. There are very few modern sailing boats above say 36' that are shallow enough to do it unless they have lifting keels. I used to own a Bav 37 with a 1.45m keel specifically because I wanted to do the canals. If your intention is to sail in N Europe, then ship the boat by road or sail it round the outside - a trip for which it is ideal.

Having said that, perhaps stability would not be a big issue with suitable ballast, but 120kgs sounds too little. Check the rudder draft as suspect it is also more than 1.8m which is the theoretical maximum draft in the deepest canals. You may well have to replace this as well to keep it under 1.6m which is the practical safe draft. 

IslandAlchemy

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Re: Stability if no keel
« Reply #3 on: March 09 2019, 18:44 »
To be honest, a 46 is a bit big to go through the canals anyway.  You'll struggle with the beam.

Bring it round the outside.  I'm sure there will be plenty of people on here that will be up for doing some legs with you.

Harry Brown

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Re: Stability if no keel
« Reply #4 on: March 09 2019, 21:13 »
Before you even think about anything else, the task of taking the Keel off is something that you really don't want to do unless there is a real good reason for doing so.
The keel is bonded to the hull with a two-part methacrylate adhesive (Plexus MA310) designed for permanent structural bonding. You literally have to cut it off the hull!

MarkTheBike

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Re: Stability if no keel
« Reply #5 on: March 12 2019, 13:58 »
Um, isn't it South to North, not North to South? That notwithstanding, it's an interesting idea but I agree with the others' view that taking the keel off a boat is a really bad idea unless it's absolutely necessary. And where would you get a 'temporary' keel that fits the holes?
ATB

Mark

nasvip

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Re: Stability if no keel
« Reply #6 on: March 12 2019, 14:22 »
Thanks for welcoming me - and thanks for the very relevant answers.
I agree with everyone recommending the western route - I’ve done it before - fine trip. I have some 7 grandchildren, though, and their parents like them to be in shallow and calm waters - so that was the general idea by sailing through canals.
The problems with beam maybe will be an issue - I thought that the locks were minimum 5 m wide - which of course also gives only 25 cm slack on each side. Hm...
The thing regarding the sealant between keel and hull sounds worse - Harry Brown - are you positive that also 1997 yachts have this hard adhesive?... that will make the project pretty tough and expensive.

Harry Brown

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Re: Stability if no keel
« Reply #7 on: March 12 2019, 22:02 »
- are you positive that also 1997 yachts have this hard adhesive?... that will make the project pretty tough and expensive.

I'm sorry, I do not know if Plexus is used on all Years of Yachts. Mine is a 2007 and is definitely used.
Be aware that it could be difficult to remove the keel which will stick to the hull, gelcoat and Laminate will be damaged during the removal process.

See attached procedure from Bavaria for Keel installation procedure.
If you look on page 10 it shows the washers and you can see the hard yellow substance (Plexus) around them. Have a look on your yacht and see if it's the same rock hard yellow stuff.
Also it states on page 10 that "After one hour drying time, using a torque wrench tighten lower nuts. The Bavaria Cruiser 56 uses 530 Nm, all other sailing yachts tighten to 363 Nm." As it states that all other sailing yachts use 363Nm, I assume that means all other sailing yachts use Plexus also?
You could also contact Bavaria to confirm.
Hope that helps.
 

Salty

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Re: Stability if no keel
« Reply #8 on: March 13 2019, 02:01 »
.
.
The keel is bonded to the hull with a two-part methacrylate adhesive (Plexus MA310) designed for permanent structural bonding. You literally have to cut it off the hull!

Those of you who read my posting about replacing the “Crazed Port Lights and Hatches” on my boat may remember that I had used a methacrylate adhesive. I had not used the MA310 that Harry refers to, but MA300 instead. In that posting I’d commented to the effect that the methacrylate seemed to be a pretty good glue, and here it is again. Clearly there is a different formulation in the MA310 to give it greater body, a different versatility, and a longer working time than the MA300 that I had used, but it was the same base adhesive.

nasvip

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Re: Stability if no keel
« Reply #9 on: May 05 2019, 19:24 »
Thank for helping on this topic - I think You're right about the glue - and it is too risky in regards to delamination etc - and probably pretty expensive - so it seams as if I should take the longer way around - or stay down south