Keel band for boat.

[lexi]

Although my mild steel Keel bands on the bottom of boats last about 9 yrs, (fresh water)I am putting a stainless one on this boat.
I reckoned 304 to be good enough as 316 was shocking price. Flat bar is 6m x 25mm x 6mm.

First: There is a gentle bend of 90 deg at the transom keel. I have heated SS and bent before, however this metal will be in fresh water. Will the heat reduce my stainless properties much? The bend will have to be formed first as fixings are delicate ( no 12 316 screw into a layed up glass keel)

Second: Can the steel be improved rust wise by sanding the mill scale off and then polishing? Is this worthwhile.

 

[fizzy]

Have you thought of aluminium? Also there are companies doing self adhesive rubber ones now. Dont know how good they are though.
Depends on what the hull is made of.

 

[lexi]

I did think of Aluminium........the stainless one is paid and ordered. It is the grounding when going ashore that takes the rust off and with it goes a thickness. Then new rust forms as boat is moored. Freshwater has acids and growth. Even galvanised chain gets rusty in the fresh.

I doubt a stick on one would do. The boat is just over 18 feet with GRP hull and keel.

 

[hotrodder]

http://www.bssa.org.uk/topics.php?article=2 heat tint and corrosion resistance of stainless steels

 

[Paul G]

25 x 6mm ? Surely you would bend that cold ?

I assume it's bent flat, but even on edge it's nothing that a hammer wouldn't shift.


Paul G

p.s.
Picked up a bargain the other day.
A 2lb hammer for £1.50

 

[balmerchris]

As Paul g says, no heat needed for that size. Get the hammer swinging!

 

[cumbriasteve]

I used to fit keelbands on a regular basis and aluminium was always the choice due to cost and it's long lasting life even in our marine environment, we did however do a few stainless ones, mostly 3mm thick and they were easy enough to shape cold.

The 6mm will be a bit more of a challenge but manageable, I would make a former out of some think ply or similar and gently tap away with a hammer into the former, usually the former was made smaller than the actual keel/transom curve to allow for the spring in the stainless.

 

[lexi]

I would make a former out of some think ply

This was the plan as I have 18mm birch ply. I probably wont bother polishing it? If mild steel lasts 8yrs even 308 with the mill scale on will last double that?

 

[cumbriasteve]

Can't see any point in polishing it apart from visual appearance for any that shows above the water line.

We launch and recover onto a concrete slipway, often sliding the boat off onto the ground while we put the trailer away and get sorted by which time the tide has come in a bit to push off and when there is a rough cross sea we recover and drag up a shingle beach.

One of the boats, an Orkney Longliner has had the aluminium keel bands on for about 20 years and still not worn down to the heads of the countersunk screws, would estimate another 5+ years life left in it at least, there is only one boat still here with the stainless band on (also about 20 years old) and although scratched to hell there is no damage or visible wear at all, can't see us ever replacing that.

Your 6mm band should easily be a lifetime fix unless you are like those crazy Aussies who come it at 60knots and ride a mile up the beach to the nearest pub.

 

[lexi]

Thanks Steve. I am careful with the boats. The band will polish when beaching on sand I suppose so the mill scale will come off. No issue with the look of stainless as never seen.
Once the band is a nice fit I put it on with thin a bed of Sikaflex, then the screws. I have received a 4m and 2m length. I have 316 rods so will weld it together nicely and dress it.

 

[AndyStobbs]

Try to get your welded joint on a straight run of the band. Sorry if thats teaching granny to suck eggs.