Stainless steel lift keel and aluminium case

Hi ya all,

Question for the metal heads............

I am restoring a 20 year old double diagonal moulded ply 24' sailboat designed by Alan Warwick of NZ. This one is lying in Australia at Lake Macquarie, and I'm based in Sydney.

While the boat is in need of some gentle TLC which am quite happy to provide, it is in pretty good condition. Most of the stuff I can handle and I also have the help of a shipwright for all the tricky bits, however I have a couple of issues with the keel for which any info would be much appreciated.

The boat has a stainless steel lift keel encased in fibreglass. The whole lot slides into an aluminium case and the two metals are only a few milimetres apart under the waterline. Now when I tell people this they jump and and down and say that these two metals are non compatible and the aluminium will be eaten away in months. The thing is, the set up was put in some 10 years ago, and while the aluminium shows some corrosion under the waterline, it really isnt that bad.

The boat is now on hardstand and i have pulled everything out for the refit. Because the edges of the aluminium case have become very uneven due to the corrosion and some water was starting to weep through the hull and case join I was thinking of replacing it by a stainless steel case. I am yet to get quotes, and am on a somewhat tight budget.

Questions

- Should I make every attempt to have a stainless steel case built, or is it acceptable to repair the aluminium case given its past resistance to corrosion ?

- If I keep the aluminium case what are the ways i can isolate it from the stainless steel to avoid future corrosion ?

- last question and quie different ; according to the shipwright the keel has a poor profile, and I would gain by improving it. The keel is basically a straight blade with a lead bulb on the bottom. I've heared of NACA profiles, but I really don't know where to start my research, and any info needs to be accessible for an amateur like me. Thus far what i have found is way above my head. Apparently there is a formula available too for this sort of thing. Can anyone point me in the right direction ?

If need be I can post photos too.

Cheers all and any advice is much appreciated.

 

Hello Boony, and welcome,
I am certainly no pro in any of these regards,
but am interested in a few of the things you are inquiring about.

Having just today finally put my boat (30 ft ply Van De Stadt Seahorse) back in the water (unfinished), giving up its hard stand of nearly two months (with the scorching yard fees) I wish you the best of luck with yours.
"Gentle TLC?" thats what I thought... You better knock on wood- lucky thing your a wooden boat owner...
Tight budget? Sorry, I don't mean to laugh, but, budget???
I don't mean to be cynical, I love my boat, but I have finally got used to the fact that she is one who sets the buget, not me...
(p.s. guys who have followed, I promise I will post some pictures and details soon- sooo busssy)


For the curious, and the pro's, photos of your keel and the casing would definately be good (might as well put one in of your boat too). As well as dimensions wheights etc.
How thick is the aluminium?
How difficult would it be to remove?
How is it attatched to your hull?
Does the wheight of the keel rely on it, or is it simply a guide?
Do you know who modified it ten years ago, who put it in, and if they actually knew what they were doing? (the stainless aluminium combo makes this seem doubtfull)
What was the original keel as per design?
How does it sail? and what was the reason for this modification?
Hopefully you have or could find out this sort of info from the previous owner.

Now I don't have any answers for you,
you obviously have a lot of different options available to you.
Depending on the dimensions and shape, it really may not be that hard to make a stainless case yourself. Basically four sheets of metal, and four welds.
Depending on the situation it may be just as hard or easier to do this than to make or repair the aluminium. At least you can weld the stainless yourself.
Check your local metal salvagers and recyclers for the appropriate stainless, 316 or better I assume. If you don't want to weld yourself, then still to save money you could at least measure and cut it all out, tack it together and then hand it over to a pro to weld, and then even clean it all up and polish yourself. This would save you heaps of money.

Then again, now that you have it all out, and have the opportunity, you may want to put in a whole new keel.
Lifting, fixed? I don't know-
This would of course depend on what sort of sailing you want to do in it. Where and in what conditions.

Best of luck..
Especially with that budget.
Hans.

 

At lake you have fresh water?
I think thats much better than salt water

Maybe just a lot of glass and epoxy will be enough?
That would be the easiest way.

The picture shows a keel box for an alu kell with 100kg bulb.
The keel profiles was used as a male mold for the glass box.

 

Hi Raggi
Thanks but this is a saltwater lake.

Hi Hans
Thanks for this reply too. i will be putting some pics up when I have a bit more time, and will post more info about the keel. Should be this weekend.

 

Tnread continues at this link

http://boatdesign.net/forums/showthread.php?t=12013

Scud or Warwick 24 - Wooden..............................

Thanks all