Hunter 30 needs help

[Dalliance]

Re: 'Ideal' fix for H30 compression structure--?

I think you are on to a good solution in a case where the whole steel structure has corroded to a point where it's structural integrity is in question. It would be a major project, but it sounds feasible. The hardest part would be access, but in such a case, it could save an otherwise good boat from the scrap heap.

In cases like mine and Chokrisandy, nothing so drastic seems warranted at this point. Far from it. The most vulnerable part of the structure is the little 7 or 8" high post which sits down in the bilge sump and corrodes under the fiberglass that was wrapped up around it. If only that post is deteriorated to a point where it is questionable, it can be relatively easily cut out and replaced with a new stainless steel post to maintain a design that, aside from the corrosion issue, has been otherwise trouble free for 30 years. Or, the post could be replaced with a variation of the bilge bulkhead you describe underneath, and possibly straddling, the horizontal portion of the steel structure under the sole.

I say this with more confidence than I had a few weeks ago because I recently discovered something about the '82 H30 that I did not know before. We pulled out and glassed in the overboard pump out through-hull yesterday. No need for it in Lake Michigan. It's located under the lav sink about 5" forward of the steel structure where the steel tube is glassed to the hull and at least 30" to port of the centerline of the boat. The fiberglass there measured a full 1" thick! If, conservatively, 1/4" of that is accounted for by the glass that wraps up and over the steel tube structure, that is still a 3/4" thick hull in this area. From previous projects BTW, I know the hull is at least 3/8" thick about 3 feet forward at the head intake through-hull and 1/4" thick up at the toe rail.

I don't know if this is typical of all the Cherubini designed Hunters, but this strikes me as one solid boat. It may have a quirky, non-traditional rig structure, but I know what I have to keep an eye on, and I have complete confidence in the boat.

 

[chokrisandy]

Hello Dalliance
I have been sailing every weekend and i noticed that there is accumulation of corroded debris that fell from the vertical 8 in beam and it is getting thinner. The visible part of the horizontal beam have some corrosion . I am thinking to cut the vertical beam and install a new stainless steal, my concern is how you weld that to a corroded horizontsl beam, and it suppose not to be welded that how you secure it such that it wont move knowing that the compression post is off centre. A sketch is helpful if you can post it , also there was a discussion about using the rail and U-bolts instead but until now there was no clear confirmation from Cherbuni if that is feasable. I really like my boat and i dont want to loose it . Also did any owner of hunter 30 change the horizontal beam , there must be a procedure for that , with a little cut perhaps we can extract the corroded one and switch to stainless steal, the ideal is if Mr Cherbuini will post a sketch with mesurment so we can fabricate one . Thank you for your help and time

 

[Dalliance]

Chokrisandy

Before I cleaned up and painted the vertical post in my boat, it also had a lot of rusted debris falling off in big flakes. It looked way worse than it actually was because steel expands exponentially when it corrodes. You've also had a few people look at in person, tap it with hammers, and tell you it's fine, yet you are still worried by it. I heard similar assurances yet I was really worried about mine too until I literally dug into it and convinced myself it was OK.

So, use a Dremel tool to remove the fiberglass that covers the bottom end of the post and its base plate. Then wire brush it clean and see what's left. If you are satisfied that it is still solid, paint it (The POR-15 that Tomgrigsby recommended may be better than the Rustoleum that I used.) and go sailing. You know what you have to keep an eye on.

If you find the post really looks like it could fail, then I think the plan that I described earlier in this thread for replacement is a good solution. Sorry, I don't have a sketch to share and if I did, it's possible that the dimensions could be different from your boat anyway. The base plate under the post was off center to clear two keel bolts and it's possible that condition is not the same on every boat. You just need to replicate the post and base plate that you have, but shorten the post enough to add a good sized top plate for the horizontal member to bear on. You do not need to weld the new stainless steel post to the steel horizontal member and you should not do that with dissimilar metals anyway. My plan called for thickened epoxy under the base plate and 3M 5200 between the top plate and the horizontal beam.

Mr.C seems to be on to another solution with a more traditional glassed in stringer which I think could be adapted as a replacement for the post without replacing the whole, admittedly non-tradtional, steel structure that exists in these boats. He may or may not agree. Given the thickness of the fiberglass hull in this area, I'm sure it would also be a good solution.

I would not get into replacing that entire steel structure unless it is absolutely the last resort and from the photos you shared, I do not believe that is the case here. You do need to stop the corrosion though, so wire brush every bit of exposed steel you can reach and get it painted so that you don't get into that situation.

 

[DianaOfBurlington]

Dalliance, you make a good point-- one could merely add in a stringer or bulkhead under the mast, even in a proximate area, as close as possible to the metal structure without removing it. This, if done well, would serve to strengthen the whole boat (remember this is right at the forward edge of the keel too) and would not necessitate a removal of the rig in the process.

 

[vrm071]

John,
I have a 76 H30 and one thing I don't understand about the importance of the mast compression post being tied to the bulkheads is, how do keel stepped mast systems work?

 

[DianaOfBurlington]

VRM--

I don't understand about the importance of the mast compression post being tied to the bulkheads is, how do keel stepped mast systems work?

The quick smart-alec answer to this is that they don't.

First things first-- the keel is held in tensile under the boat (it wants to fall off via gravity). This is why I always insist that it be bedded in 5200-- because 5200 has exceptional tensile strength. No other cost-effective compounds come close. The PO on my boat reset Diana's in 'caulk', which is meant for compression (between wooden planks swelling together); and it leaked while still in the Travelift slings. I reset in in 5200 and then the yard moved the boat before I had torqued down all the locknuts... and the keel stayed on the boat by the 5200 alone. This is what it is meant to do.

The mast, on the other hand, is in compression. All of the rigging's work is pulling the mast DOWN. Think of the mast as the arrow and the boat and shrouds as the bow and strings. When you step the mast on the keel, the 'arrow' is pushing down at the keel, contributing to the forces trying to make the keel fall off the boat. The skin of 'glass under the mast step and above the keel must be very carefully made, knitted to the whole hull structure, with the layup extending well up the hull, maybe halfway to the shroud attachment points or (as in the case of our C44s) much further. This is far in addition to the usual stiffening of the hull in this, just about the widest part of the boat (and thus most susceptible to being distorted).

This is the only way a 'keel-stepped' mast in a stressed-skin boat like our fiberglass ones can possibly work. When you hear someone say he has a 'keel-stepped' mast, this is really what he means (perhaps without knowing it). You would never want to just stand the mast step itself on the skin above the keel, like where the keel bolts go through, without adding major additional layup. Of course the keel bolts' area is reinforced in much the same way; but given fin-keeled boats I wouldn't want to combine loads in such a small point without knowing for sure that the layup is adequate for both of them.

It is very common for some boats to have a sole-stepped mast, where the mast-step structure is on the cabin sole, which in turn is reinforced with beams (hopefully of fiberglass or epoxy-reinforced wood) transmitting these loads to the skin of the boat. This is the case in my boat, which relies on the compression post being securely fastened to the main bulkhead which in turn is 'glassed to the hull all along its perimeter. The bulkhead is essentially taking the load and transmitting it to the skin of the boat; the 'compression post' is really acting only as a knee to stiffen the deck, under the mast step, and to keep the plywood bulkhead from flexing out of line (vis., if the plywood bowed it would fail).

In my opinion the cheapest and easiest way to construct a budget-minded production boat is to have a full-width plywood bulkhead. The mast step should be directly above this, mounted on a solid-core section of deck, and a stout stiffening post should be fastened, with many small fasteners, along the bulkhead's full height, down to the fattest crossmember of the cabin sole, which in turn is 'glassed to the inside of the hull. The bulkhead should fill the whole space of the interior of the boat, from deck to bilge, with adequate limber-holes for water drainage and doors and openings with only rounded corners (like doors in a submarine, whose bulkheads are also in compression); and it should be robustly 'glassed to the hull. (I specified this in 1977 when drawing the interior plan for C44 no.7, now called White Hawk, which sort of set the parameters for limiting 'custom' interiors from then on).

The upper-shroud chainplates can be fastened to this bulkhead as well, but only through mounting holes reinforced with G-10 bushings epoxied in place (or a whole plate of G-10 set into a closely-fitted hole in the plywood). Given an aluminum toerail I'd use that for u-bolts instead and spare the plywood the risk of rot from water intrusion.

I strongly disagree with the metal structure transmitting the compression-post load to the bottom of the hull, atop the keel bolts, as people's pictures have shown. If this truly was Hunter's idea, it's unforgivable. As I said before the crossmember on which this post stands should be 'glassed into the hull-- and NO metal of any kind should be relied-upon if installed in the bilge, ever.