Mast base flange. How to fit deck curvature?

[gears]

How about G 10?

[Chotu]

Originally Posted by gears

How about G 10?

Needlessly made of epoxy when Extren is available

[toda]

A piece of waxed paper on the deck, a big squirt of 5200, another layer of waxed paper, set the base flange in place and smush it down until the center if it is firmly on the crown of the deck. Walk away. Leave it for a couple of days... When the 5200 is cured it will be a firm perfectly formed interface between mast flange and deck. Peal off the waxed paper. Assuming the mast flange is going to be fastened to the deck, bed the 5200 interface in sikaflex or some other removable bedding compound. Cured 5200 is very firm in compression loads. Cheap, not particularly toxic, and easy. If you want the mast flange "permanently" mounted, skip the waxed paper. You'll always be able to get the mast flange off with heating, but you'll have to grind the 5200 off the deck.

[OneBoatman]

Deck stepped mast base plates are typically fabricatting from 300 series stainless steel, the non magnetic type of stainless grades suggested 304L
316, 316L. L grades have lower carbon content tolerate welding better such that they retain corrossion resistance better after welding without requiring annealing. Purchase it at 3/16" thickness, specify your order as half hard so that you will be able bend up tabs on the sides where you want to drill 3/4" holes in order to fasten turning blocks. For deck mounts usually the base plate must have an interupted centered, raised structure which fits inside or sometimes outside the mast to keep it from moving. If inside it is not seen once the mast is stepped but is such that halyards and electric cables serving instruments and lighting can pass. The flat portion surrounding the mast must extend approx. 1 1/2" aft and about 1" on the sides before the tab bends so external blocks won't lay against the mast itself. Bend tabs to about 4o degrees off of vertical. Lay a template the same dimensions flat on the deck to determine how much you have to add to the base perimeter to compensate for the deck curvature and weld extra material to the base so she is properly supported drill and bed it with 5200. Of course you need a compression post for a deck stepped masts.

[rslifkin]

Originally Posted by Chotu

OK. There are definitely a lot of votes recently for a thickened resin.

i’ll look into it. But it will be polyester or vinylester. And I still will have to wear a full face respirator. Because I have been having problems with those as well.

The other option is to use the extren sheet material that I have been using here and there to avoid a lot of chemicals. It’s extremely expensive, but, much cheaper than health problems. Similar to starboard actually. So I will look at starboard as well. It might be cheaper.

I think this last page really has some workable ideas. Thanks for the input.

It mostly comes down to whether it proves more practical to get the shape perfect by making something in place for a perfect fit vs shaping material to fit. Either method can work if done well.

[Chotu]

Well, the plastic panel prices are certifiably insane currently. Thousands of dollars for these things. So, I’ll be dumping resin in there. I’m just going to dump it in a liquid state with some glass fibers mixed in with a dam around it. So it levels itself.

I’ll just wear a full face respirator for it so I don’t get any exposure and use polyester. Has a really good compressive strength that way.

[Don C L]

I have seen the the local WestMarine sells cut pieces of Starboard, you don't have to buy a whole sheet. Also, you might check with local yard or riggers, sometimes they have left over pieces too. That's how I got my piece.

[Chotu]

Originally Posted by Don C L

I have seen the the local WestMarine sells cut pieces of Starboard, you don't have to buy a whole sheet. Also, you might check with local yard or riggers, sometimes they have left over pieces too. That's how I got my piece.

I did see that, but as it turns out, starboard isn’t as up to the task as you’d think. It’s not great in compression.

[gregjm]

I would use mold release and create a pattern from mat and resin on the deck. Make sure to mark on the pattern (which you will pull off) the margins where you want the heel plate to land. Take it to a CNC machine shop and they will use the pattern to program the deflection and cnc it out of aluminum plate. You can then weld/secure the mast shoe to the plate.

[Chotu]

Originally Posted by gregjm

I would use mold release and create a pattern from mat and resin on the deck. Make sure to mark on the pattern (which you will pull off) the margins where you want the heel plate to land. Take it to a CNC machine shop and they will use the pattern to program the deflection and cnc it out of aluminum plate. You can then weld/secure the mast shoe to the plate.

If I am going to use resin and fiberglass, why would I remove that and then make it out of metal? That I don’t understand.

Why wouldn’t I just leave it there and use that as the adapter plate?

[OneBoatman]

You may be over thinking things a bit. Fabricating a mast saddle that is curved to the contour of the deck and flat on top is certainly an option but that isn't the way its normally done. So is the underside of deck also curved? Do you plan to use curved bolts. Strange that the builder seems to forgot that the boat was going to put a mast somewhere. So much easier to have made the deck flat for the mast to rest on a standard flat mast base. Make a dam all around using Mylar tape and clay. Wear a respirator and pour a pad of epoxy thickened with glass and microballons in the relatively small area required.

[Chotu]

Originally Posted by OneBoatman

You may be over thinking things a bit. Fabricating a mast saddle that is curved to the contour of the deck and flat on top is certainly an option but that isn't the way its normally done. So is the underside of deck also curved? Do you plan to use curved bolts. Strange that the builder seems to forgot that the boat was going to put a mast somewhere. So much easier to have made the deck flat for the mast to rest on a standard flat mast base. Make a dam all around using Mylar tape and clay. Wear a respirator and pour a pad of epoxy thickened with glass and microballons in the relatively small area required.

Yes. This is what I’m going to do. Not going to use epoxy however. I’m going to use a different resin. A respirator isn’t nearly enough to protect me from Epoxy. Not even close.