Mast step rebuild corrosion insulation

[DougM]

I am looking for a material for insulating the base of the mast from the mast step. The step is stainless steel, stepped on the keel. I will have to cut about 3/8" off the foot of the mast to eliminate most of the corrosion.

I have read some similar posts but I have not got the answers I want yet.

The mast step is the male type with 4 ears that extend into the mast. There was a large weep hole but being in the bilge moisture must still be a problem.

I cut about 1/2 " off the mast 10 years ago when rerigging for the same reason. I just added 1/2" ss plate under the step to take up the space.

This time I would like to do a better job that I hope will get rid of 90% of the corrosion. I want to us a plastic material to both build up the step and insulate it.

I want to fit it on top of the SS mast step and make cutouts for the vertical ears to fit through. I could also use an aluminum plate, but then I have to insulate that from the SS mast step too.

To choose the material I want to know the approximate load on the base of the mast.

The boat is a Seguin 44 with 10mm head and backstage, fore and aft lowers 5/16 and 1/2" shrouds at the deck that divide into D2 and V2D3 at the lower spreaders.

My guesstimate for the working load is 18000 pounds. Does this sound reasonable?

With a mast section of 0.185" the area of the mast is 4.6 sq in. Guessing about 80% of the mast in contact with the step gives about 4000 psi at the base of the mast.

OK ?

The next step is the material. I want something fairly easy to work and available at a reasonable price. Maybe a scrap of white Corian which should support 16000 psi. And is stable in the wet environment.

Any comments or suggestions ?

Thanks
Doug M

[Brion Toss]

Hi,
And first, the calculations would require more time than I can spend here, but G10 is going to be good for the job. But if I understand your plan, you would be shortening the effective length of the step's ears. Seems like a bad idea, as lateral loads would then be much more concentrated. I think I'd be inclined instead to smear everything with Tef-Gel or Eck, and just put the G-10 under the current step.
Fair leads,
Brion Toss