Help with Hull and Unusual Blistering - a slug!

[kbdozz]

Hi all.
An unusual situation.
Looking at a vessel to purchase that is actually the SLUG of the mold from which THE REST OF THE MODEL FLEET was created (that is, it's the ORIGINAL sculpted hull form the designeer used to create the series of yachts).
The issue is that the hull (of this slug), to be made true and flat, needed to be filled (with 'putty/bog) as all slugs are to provide the perfect surface for the next hull to be created from the mold.
So, whilst totally seaworthy and very strong, the hull forms quite large 'warts' (as blisters would suggest too small an descriptive) because the putty reacts with seawater and expands.
The result, more regular maintenance when stripping back the bottom to prepare for undercoats and antifoul.
Also, as I understand it, the slug is incapable of holding a gelcoat - because of the putty situation.
So, my questions:
- has anyone ever heard of this problem?
- if so, is there a solution to thwart this in the future?
- if no simple (or not?) remedy, is anyone familiar with the process to keep the maintenance schedule as minimal as possible?
Thanks for any input/feedback/advice.
Cheers

[psk125]

We have a friend with an aluminum hull that has similar problems. Filler gets saturated and develops "issues" with separating from the hull in chunks, or bubbles forming under antifouling. Changing the filler composition might improve the situation; ymmv.

[Bowdrie]

This was "old school", but a couple of "plugs", (one of which I was offered,) were built using a form of "strip planking", then glassed over and faired.
Is what you're inquiring about a solid glass plug, or of another technique?

[nuku34]

Run, don't walk away, from this deal. I assume the allure is its cheap... ya gets what ya pay for...

[Chotu]

The only way to fix this would be to get rid of all of the filler and take it back down to the hull. Then you could run an epoxy filler over it and fair it.


The amount of labor involved in faring a boat is incredible. Trust me.

So, this is probably not a good thing to buy unless it’s free.

[Benz]

You'll spend a lot of time re-sanding it smooth, but you could do it once, then coat it with epoxy so that water didn't access the putty and make it swell, and hope for the best.
Sounds like tons of work no matter what.

[Jim Cate]

I would be more concerned that the structure of the plug is not the same as that of a useful hull. The stresses imposed in an actively sailing hull are certainly different than those in making molds from the shape, and I'd be surprised if the engineers would spend the extra money to make it seaworthy.

The above is but an opinion, and not based on experience.

Jim

[Chotu]

Originally Posted by Jim Cate

I would be more concerned that the structure of the plug is not the same as that of a useful hull. The stresses imposed in an actively sailing hull are certainly different than those in making molds from the shape, and I'd be surprised if the engineers would spend the extra money to make it seaworthy.

The above is but an opinion, and not based on experience.

Jim

My concern also, even though I didn’t put it in my post.

A plug isn’t usually made with the same laminate schedule as a hull. Unless it was really just hull #1 and they used hull #1 as a plug later to make a mold.

Lots to watch out for here.

[Bowdrie]

Hulls generally do not make very good plugs, mostly because empty fiberglass hulls are really flexible and easily distorted.
When I was in the "scene", so to speak, the standard procedure was to use "hollow and round" sticker-run mahogany to strip-plank a hull over the molds.
This planking was the same thickness as it would have been had the designer drawn the plans for a wooden boat, this ensured stability and more importantly possessed a degree of rigidity that fiberglass cannot match.
After fairing, the plug was glassed and then final fairing and gel coating was done.
Then comes an amazing amount of waxing and polishing.
At that point it was ready to have a mold "popped" off of it, the mold had to be extensively reinforced by exterior framing in order to hold a shape that would retain the designer's lines.
A well-done plug is certainly capable of serving as a hull to build a boat from.
In essence it becomes a strip-planked, or cold molded hull that has been glassed.

[Dougtiff]

Reminds me of back in the 80'S when i lived in Singapore a Hershoff design [Tioga] sailed in, beautiful boat, built in New Zealand, i thought She was fiberglass, during a tour the owner said She was Ferro cement, couldn't believe it, a year later [the cruising community arrived each year] another Tioga arrived, during a conversation i mentioned "O'Kerry" from the year before, they knew the boat, as the ferro boat served as a plug to build the glassboat.



,

[Fore and Aft]

Kbdozz there's really no solution to your problem. My various experience of making plugs is anything goes when it comes to filler. There's a myriad of pin holes or slight imperfections that have to filled when getting a plug smooth. We used automotive filler mainly which is no good below the waterline, but sets quick. Once I remember we used spray putty on the whole plug. Normally a plug gets binned once a molds been taken so I wonder what filler was used on your boat?
Cheers

[kbdozz]

Originally Posted by Bowdrie

This was "old school", but a couple of "plugs", (one of which I was offered,) were built using a form of "strip planking", then glassed over and faired.
Is what you're inquiring about a solid glass plug, or of another technique?

Solid f'glass....

[kbdozz]

Originally Posted by nuku34

Run, don't walk away, from this deal. I assume the allure is its cheap... ya gets what ya pay for...

hahahah Yeah every fiber in my body is telling me that BUT...it's an Alberg 34....kind of my dream boat.

[kbdozz]

Originally Posted by Jim Cate

I would be more concerned that the structure of the plug is not the same as that of a useful hull. The stresses imposed in an actively sailing hull are certainly different than those in making molds from the shape, and I'd be surprised if the engineers would spend the extra money to make it seaworthy.

The above is but an opinion, and not based on experience.

Jim

This too was one of my immediate thoughts - but the vessel has been (allegedly) sailed for over 20 years by the present owner AND has done a circum' as well as lots of ocean trips into south pacific.....
And the fact it's an alberg kind of reassures me - but only slightly
A quandary to be sure, to be sure...
;-)

[kbdozz]

Originally Posted by Fore and Aft

Kbdozz there's really no solution to your problem. My various experience of making plugs is anything goes when it comes to filler. There's a myriad of pin holes or slight imperfections that have to filled when getting a plug smooth. We used automotive filler mainly which is no good below the waterline, but sets quick. Once I remember we used spray putty on the whole plug. Normally a plug gets binned once a molds been taken so I wonder what filler was used on your boat?
Cheers

I have had a brief phone conversation with the guy and he did mention various methods over the years that he has tried to reduce/eliminate the work-load on stripping back and preparing for bottom paints, but the only thing I remember is 'epoxy' so I have said to him I am going to email a list of questions and get some hard answers....
Many thanks!