To balsa core or not to balsa core?

[BigCat]

"An epoxy, rather than a polyester or vinylester, hull is technically more moisture resistant when correctly applied." Nope, all the cool kids are using vinylester these days. It's used as a water barrier layer by a lot of manufacturers who use poly for the layup. Vinylester is just as strong and elastic as epoxy--as I demonstrated once I finally got Gideon to post the properties of the epoxy used on African Cats. It is about 80% as impervious to water as epoxy, and costs about 1/2 as much--and is easy to make fire resistant, and is much less toxic to the workers. You won't worry about water penetration of your boat if it burns to the waterline!

[44'cruisingcat]

Originally Posted by BigCat

I finished out a boat with a balsa deck, and over 30 years and 50,000 NM later, it's in great shape-so mileage may vary.

Please read the whole post. The boat I referred to is in great shape. It's simply that where they had stepped the mast on a 16mm balsa cored deck with 800gsm laminates - contrary to the plans - that part - and only that part - needed repairing.

[Weyalan]

I have done a lot of sea-miles on a balsa cored 40 footer that was built & launched in 1981. It is still stiff and in very good shape.

[BigCat]

[quote=44'cruisingcat;150561]Please read the whole post.

[DGK]

Originally Posted by Robertcateran

Not cheaper than polyprop honeycomb, the stiffness and the quality if done well, especially the factory made panels, and is pretty fire resistant. Then again stiffness is not all, as this can bring about failure of the inner skin in the case of collision. Polyprop honeycomb is stiff enough to do the job if designed properly and is more forgiving of bonding problems, water intrusion, and collision. Sheer stiffness is not the same as sheer deformation to failure. If the later is compared, the honeycomb comes out well
Robert

Robert, I have worked exstensively with Poly propolyne and have tested the 4 major suppliers. The French and US type is good but exspensive and we have had some small problems with scrim variations, the Chinese produced Hexacor far exceeds what they advertise, their film adhesion is greater than the US and French and can be used in vacuum panels without resin intrusion into the cells, but is very hard to vacuum infuse as the holed cells take up to much resin. From the other chinese producer we have had delamination due to poor film adhesion, and that is unacceptable. Twelve months ago when we completed, evaluation of Poly Propolyne it could not be used for survey vessels in Australia in class one areas , and cannot be used in Europe in class one areas, as it was not approved. It is approved for class 2 areas and is very good in laminated bulk heads and furniture ect. I do not believe this has changed. Hence End grained Balsa is our prefered building material. for class 1 Areas.

[Robertcateran]

Originally Posted by DGK

Robert, I have worked exstensively with Poly propolyne and have tested the 4 major suppliers. The French and US type is good but exspensive and we have had some small problems with scrim variations, the Chinese produced Hexacor far exceeds what they advertise, their film adhesion is greater than the US and French and can be used in vacuum panels without resin intrusion into the cells, but is very hard to vacuum infuse as the holed cells take up to much resin. From the other chinese producer we have had delamination due to poor film adhesion, and that is unacceptable. Twelve months ago when we completed, evaluation of Poly Propolyne it could not be used for survey vessels in Australia in class one areas , and cannot be used in Europe in class one areas, as it was not approved. It is approved for class 2 areas and is very good in laminated bulk heads and furniture ect. I do not believe this has changed. Hence End grained Balsa is our prefered building material. for class 1 Areas.

I hear that polycore is getting approval for survey in Australia. They also do a factory heat pressed epoxy and glass sandwich. Pacific multi hulls are making their kits out of it. I was considering prepregging and then vacuuming full length sheets. I don't have to get a really low resin to glass ratio in the prepeg as the scrim needs some of the resin. This avoids the extra weight from the holes being filled up with double sided infusion. I have also seen some vacuum infusion done using bird mesh between the table and the peel ply to good effect, though it leaves an interesting pattern, I was also looking at infusing over a holey table. For the amount of sheets I need, the prepreg seems to be the least work
Robert

[DGK]

Originally Posted by Robertcateran

I hear that polycore is getting approval for survey in Australia. They also do a factory heat pressed epoxy and glass sandwich. Pacific multi hulls are making their kits out of it. I was considering prepregging and then vacuuming full length sheets. I don't have to get a really low resin to glass ratio in the prepeg as the scrim needs some of the resin. This avoids the extra weight from the holes being filled up with double sided infusion. I have also seen some vacuum infusion done using bird mesh between the table and the peel ply to good effect, though it leaves an interesting pattern, I was also looking at infusing over a holey table. For the amount of sheets I need, the prepreg seems to be the least work
Robert

Robert, Polycor is doing some great work in poly propolyne field, and yes I have seen the laminates they produce, they use Hexacore PP so they are getting the best for the customer, the highest grade of PP available as far as I am concerned, the survey issue I cannot comment on, other than it is nght mare to get through Australian marine authorities, the easiest way is from one of the societies such as DNV, Loyds ect. Up untill 14 months ago no one could prove a shear strength of over .79 (.8 is foam) for PP, but Hexacor I believe has done this, Wether or not they are seeking DNV I am unaware. Marine is only a small part of Hexacor's area.
Reference the bird mesh, yeah it works, so does 60% shade cloth, but again not for production. Ensure that the pp you are using is for vacuum, there are disfferent films avaialable., I hope this helps
Cheers

[Robertcateran]

Originally Posted by DGK

Robert, Polycor is doing some great work in poly propolyne field, and yes I have seen the laminates they produce, they use Hexacore PP so they are getting the best for the customer, the highest grade of PP available as far as I am concerned, the survey issue I cannot comment on, other than it is nght mare to get through Australian marine authorities, the easiest way is from one of the societies such as DNV, Loyds ect. Up untill 14 months ago no one could prove a shear strength of over .79 (.8 is foam) for PP, but Hexacor I believe has done this, Wether or not they are seeking DNV I am unaware. Marine is only a small part of Hexacor's area.
Reference the bird mesh, yeah it works, so does 60% shade cloth, but again not for production. Ensure that the pp you are using is for vacuum, there are disfferent films avaialable., I hope this helps
Cheers

Thanks for the input. I have had a good look at the products, and the quality of the film. I imagine I need to go to the highest grade film. It is only a couple of dollars a meter more. I was concerned about the quantity of resin taken up by the scrim and joins under infusion, which is why I was looking at bagging after laying down prepreg. If the price on the made up panels aren't too much I will probably go that way for most of it, but was wanting to do one side at a time for the bits I want curves in. I am not sure about the layup either, as having a one off system means that you can align some uni in the right place to help transfer loads round hatches, etc and thus be more weight efficient with the glass. The sheer strength for survey seems to be based to some extent on stiffness rather than ultimate strength to rupture. It seems plenty stiff enough for the job from what I have seen. Robert

[DeepFrz]

Is this a thread hi-jack?

[Thenaz007]

"It (Vinylester) is 80% as moisture resistant as Epoxy" Thanks for backing me up Big Cat.

[44'cruisingcat]

Originally Posted by Thenaz007

"It (Vinylester) is 80% as moisture resistant as Epoxy" Thanks for backing me up Big Cat.

Yes, 80% isn't as good as 100% you would think. Still, if you're trying to do something on the cheap, near enough might have to be good enough I guess.

[ssullivan]

Originally Posted by DeepFrz

Is this a thread hi-jack?

Everybody put your hand where I can see them!!!

he he...

[BigCat]

Originally Posted by Thenaz007

"It (Vinylester) is 80% as moisture resistant as Epoxy" Thanks for backing me up Big Cat.

I don't know if you are following it, but we are having a major discussion about vinylester at http://www.cruisersforum.com/forums/...tml#post150920

--My hands? You mean both at the very same time? How about one at a time? Work with me on this, I'm willing to meet you half way--

[jzk]

Ok, so I am looking at these Gulfstar 60s from 1982. They all have Balsa cores and I am told are all dry.

Sully did your Gulfstar have Balsa core in the hull? If so, is that the trouble that you are talking about?

[ssullivan]

Originally Posted by jzk

Ok, so I am looking at these Gulfstar 60s from 1982. They all have Balsa cores and I am told are all dry.

Sully did your Gulfstar have Balsa core in the hull? If so, is that the trouble that you are talking about?

Yes, the Gulfstar did have the balsa core, but I didn't have any trouble with it on my boat. I saw some other boat in dry storage having its decks ripped apart (Skil Saw process I described earlier). It was in indoor dry storage for the fix all summer and the guys working in the yard just shook their heads in disbelief. It was a new-ish boat, something expensive. I can't remember the make. It doesn't matter, really. The manufacturer didn't do the deck hardware correctly and the core was soaked.

They had to cut it apart, dry it out and re-build the decks. Ouch. Soooooo expensive, it even had the yard worker shaking their heads.

But, if you can DIY, that saves some $$ for sure.

The boat I saw will never look the same again, since the joinery inside made it impossible to do the cuts inside the boat. They had to take a Skil Saw to the outside on deck. Not a repair I'd want to have to do.

The trouble I ran into, personally was on cats from the 90's that were in my price range. Many (most?) of the ones I looked at were delaminated in some way or another, and I passed on them. It frightens me to think that a boat that is only 10-12 yrs old can fall apart like that. Imagine paying top dollar as the first owner... wow.

Thank god there are rich guys out there buying the boats new... ha ha I'd be in the poor house if my boat fell apart like that.

So that's all I was saying. I'm kind of pro-solid glass these days, but do not wish to debate it. It's a choice like mono or multi. To each their own on that. These are just my personal experiences.