Replacing the mast base on my N-20. What's the preferred goop for installation? Regular old silicon? Silicon/poly? 4200? Looks like regular silicon was in there before (doesn't look like original install), just wondering whether to do more.

I used a silicon based caulk - It was nearly impossible to remove the original mast base because I believe it was installed with 5200...I thought I was going to destroy the mast. I finally got it though.

There's plenty of surface area for sealant...no need to go with anything extreme.

I'd do 4200, It's made to be removable and seems to hold up a little better than silicone. As long as it's sealed it probably doesn't matter, though.

You guys have captured my thoughts exactly - no tie breaker yet! Does anybody know just how "removable" 4200 is?

It looks like the mast base I removed was sealed in with regular silicon (and not particularly good stuff), but in cleaning things out, I found what looked to be remnants of something more like 4200 or 5200. That stuff didn't want to come out.

The shape of the mast base is such that it doesn't contact the mast all the way around except at the base flange. Does anybody make an effort to fill up the areas that don't contact the mast on the inside, or just do enough to seal it at the rivets and bottom?

I'd seal everything. If you go turtle you'll wish you had.
4200 is removable, I've used it plenty in the past. 5200 is a bear.Like I said before, your just sealing not bonding so either would probably be fine. I just feel better using an overpriced product that was made for that application, and it seems to hold up well. I rarely use silicone because it seems to peel off rather quickly.

No doubt on sealing everything - I'm with you on that. In fact the new style base has two holes in the bottom that seem to be for the Infusion internal diamond adjusters - those will need to be sealed as well.

It's just that the inside of the base has four contact areas with the mast interior. These are the point the rivets go in. In the front, and on the sides, the interior section of the base is flat. Filling all that area with goop would require a lot of goop and seems like it might be overkill (it would certainly make things hard to get apart). That having been said, I'm trying to find out if that's the practice. The piece I took out was not filled in completely in those areas, but again I don't it was the original (and maybe not correct) job.

Here's what I mean by the contact areas:

I would use epoxy stick to fill onthe holes.

Are you converting to the infusion style downhaul or cutting those ears off?

(work just cutoff our forum access through our firewalls - so my interaction will be throgh a phone and with typos !)

Sikaflex.

Converting to full infusion style. Drilled lots o' rivets out. Moving the rotation arm down, using the halyard sheave in the new mast base. Pulled the old halyard block and rotation blocks off the front beam. Have to mock things up to see where to reattach the cleats for the downhaul.

So, I went with Todd's advice - 4200. Hopefully I'll have moved to a new F-20 before I need to pull it apart! ;-) Sealed up the two bolt holes with silicon.

Maybe we can split one(F20)

That's a deal! We'll just have to work out whether you move north or I move south so we can sail the thing!