Massive hull blisters

[Jcorstorphine]

Watch the pressure

Nigel, that sounds like a great idea, but if there is water still in the keel, where will it be collected under vacuum!!
I have 2 vacuum compressors which I use for laminating timber together, I am having difficulty understanding where the water will be collected, and if there are various holes penetrating the hull, this may prevent the vacuum from sealing and extracting. I'll give it a try to satisfy my curiosity.

Cheers Stevie

I have used vacuum pumps for a great number of applictions on my boat but just watch the pressure which can be exerted by the atmosphere. If your pump gets down to a few mbar then in old money, the pressure will be a ton per square foot. May crush your keel if there are voids.

John.

 

[Swinranger]

Stevie,
if there is still a large quantity of water to remove, try a wet and dry vacuum cleaner first.
Once the area is dry enough, you can switch to the vacuum pump.
I imagine that the internal ballast will prevent your keel from collapsing, but leave a small vent hole at the top just in case!

 

[Raymie]

My old wooden Arden 4 (GUSTO) which I think was No 16 is still sailing up the West Coast by an guy who rescued it from a certain Youth Organisation who were leaving it to rot.

I think No 16 (Gusto) is the boat that is on the Arden brochure as i spoke with Geo Hulley and he said that the boat on the brochure was wooden although they were promoting the new fibreglass yachts.

R.

 

[alan006]

With the amount of liquid that has come out of the keel I would suggest a different approach. I would peel off the gelcoat on the keel, then pressure wash the grp with steam several times ( to flush out any unwanted chemicals) then leave to air dry. Once the moisture content is down ( use a meter) then apply about 7 coats of gelshell. Fair off, and use a primer then antifoul.
This sounds a lot of work but it is not too tricky. The gelshield goes on by roller and you have to follow the application times on the tin. It comes in 2 colours so you can see you get full coverage on each coat. It is a high build paint. When I did a Hardy it took a couple more coats as the gelcoat is fairly thick on them.
I hope this helps.

 

[Jcorstorphine]

Is the problem not deeper than just the gel coat

With the amount of liquid that has come out of the keel I would suggest a different approach. I would peel off the gelcoat on the keel, then pressure wash the grp with steam several times ( to flush out any unwanted chemicals) then leave to air dry. Once the moisture content is down ( use a meter) then apply about 7 coats of gelshell. Fair off, and use a primer then antifoul.
This sounds a lot of work but it is not too tricky. The gelshield goes on by roller and you have to follow the application times on the tin. It comes in 2 colours so you can see you get full coverage on each coat. It is a high build paint. When I did a Hardy it took a couple more coats as the gelcoat is fairly thick on them.
I hope this helps.

I think the OP has to look at the complete glass fibre matrix as it looked as if the blisters were not just from the surface but emanated from the inside of the keel. If as I suspect, he has ground away the blister, then the remaining thickness of laminate will be thin at the centre.

John

 

[oldsaltoz]

It wasn't cement that was used in the bedding of the lead on the Arden, it was believe it or not wet sand that was used at the time. I spoke with Mr Hulley about it and he assures me of this, Strange choice of material but remember fibreglass hulls were a relatively unknown quantity in the 1960s and in its infancy as Mr Hulley said. Obviously any leakage of the cabin sole, or more likely from the bilge, would penetrate in to the sand to maintain moisture and in turn penetrate the porous inner gelcoat over the years resulting in these blisters. I agree that this may be delamination of the hull due to the moisture within the keel but there is still some osmotic fluid present too. I wonder how many Arden's are suffering from this?

R Cracknell

If this is correct, the only way to stop the problem reoccurring would be to remove the contents of the keel, dry it and the keel structure out, then replace it with the original lead and a mix of resin, closed cell fillers and lead shot.

Then work on the keel housing from the outside, removing whole sections of the skin if necessary.

Good luck.

 

[Steviecracknell]

It's a good point you have made regarding the implosion of the keel, John. I vaccum bagged a Charles Ames style chair once, using a former, without the correct amount of internal braces, and the dam thing imploded, to my surprise, good learning curve though. I don't think I'll experience the same mishap this time, as there are plenty of air holes, combined with lead and sand internal structure, stabilising the keel.
Alan, the Arden is suffering from delamination between the fibreglass, originating from inside the keel, probably caused from the blasted wet sand that was used to bed in the lead ingots. I feel it's probably not necessary to strip the remaining gelcoat, at least not yet. I'll wait a few years and monitor the repair work beneath the water line, I'm not adversed to stripping her!! but not yet.
John, I was wondering, do you know if the first fibreglass Ardens were formed, using a mould taken from a plug of an older wooden, carvel hulled Arden. The reason for my curiosity, is the topsides above the water line show heavy rippling, reminiscent of a poorly faired boat plug!!

 

[Jcorstorphine]

Lots of answers

John, I was wondering, do you know if the first fibreglass Ardens were formed, using a mould taken from a plug of an older wooden, carvel hulled Arden. The reason for my curiosity, is the topsides above the water line show heavy rippling, reminiscent of a poorly faired boat plug!!

As far as I know, GUSTO was the last wooden Arden and was built down to a weight and a price for a guy who just wanted to race. My Arden had a 6 HP Briggs and Stratton air cooled engine with a centrifugal clutch so the boat was far lighter than one built with an MD1 clunker. However I do not know if Gusto was the plug for the GRP hulls but I do recall the hull was very fair and had no ripple being stripped planked.

Going back to the vacuum pumps and having been involved in vacuum engineering for most of my working life I can advise that if you wish to use a vacuum pump to remove water, then you will require to get below 15 mbar at which point water will boil. However it will also freeze due to the loss of heat caused by rapid evaporation from the surface so you need plenty of mass in the area to keep it warm.

Whilst on the subject of vacuum, I came up with the concept of the what is now called HOTVAC when osmosis started to rear its ugly head years ago but was too lazy to do anything about it. Oh well, just need to wait for the next flash of inspiration.

 

[alan006]

I think the OP has to look at the complete glass fibre matrix as it looked as if the blisters were not just from the surface but emanated from the inside of the keel. If as I suspect, he has ground away the blister, then the remaining thickness of laminate will be thin at the centre.

John

Yes, you are right John. There is more to this than I first saw. I still think it would be a good approach to peel the gelcoat and then hotwash to remove contamination. If you try to deal with the contamination on a blister by blister basis I think you will find it very difficult to clean and dry it properly before the surfaces are repaired.