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Old 13-07-2009, 17:05   #91
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Or not. In Duflex, the balsa is roughly 100mm squares, divided by solid epoxy glue lines. So it's quite likely the water and the damage would be confined to a small area.

With foam cored Duflex this would not be the case, so there is the possibility the water could spread further.
Exactly

I mentioned in another one of these various core bagging discussions the foam Crowther I saw that had a couple of hundred litres of water sucked out of the foam core before a step job/extension could be completed.

This was due to using contour foam (small squares with voids) where the resin had NOT filled the voids.

D
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Old 13-07-2009, 17:15   #92
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I think the posts on this topic relating to balsa cores are misleading.
As do I.

Any material can be made to look bad when a crap build and incorrect resin choice has taken place

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Interestingly, the damage to timber cores described above result from poorly installed deck and hull fittings. Using the correct installation techniques this type of damage should be eliminated. Another interesting point is the recommended method of installing hardware to a foam cored epoxy composite. That is, to cut out an oversize section of the foam and replace it with balsa, plywood or high density foam. High density foam may crush if bolts are over-tightened causing leaks and any type of timber is capable of rotting if not properly protected. So what you have is a timber core around the areas that cause most of the problems so why not have a timber core throughout and take advantage of its superior mechanical properties.
Sounds great to me.

Just make sure to use oversize holes filled with epoxy and re drilled where fittings go.

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Having built a foam cored boat I have to say the weight saving over timber is minimal given the additional laminate specified by the designer to support the foam core.
yep.
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Exotic fabrics, foam core and vacuum bagging is another story and should be used if weight saving is a priority.
I have only really seen foam Kevlar epoxy boats with a light external layer of glass for abrasion/protection come out in front of a well built light timber cored boat.

The difference in cost for the foam Kevlar epoxy build was considerable.



D
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Old 13-07-2009, 18:11   #93
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If water can eventually get through solid polyester GRP, it will cruise through balsa.
And foam.

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It is a very common problem in older boats even in just the deck core and it is very well documented.
And it is very well documented that these problems are almost universally due to owners or builders drilling holes in the decks without de-coring and sealing them properly.

And again, how many of these cases involve Duflex?
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Old 13-07-2009, 18:13   #94
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Exactly

I mentioned in another one of these various core bagging discussions the foam Crowther I saw that had a couple of hundred litres of water sucked out of the foam core before a step job/extension could be completed.

This was due to using contour foam (small squares with voids) where the resin had NOT filled the voids.

D
G'day Dave, haven't seen you here for a while. But then I haven't been around all that much either. How's the boat going? Getting close to splash day yet?
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Old 13-07-2009, 20:13   #95
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G'day Dave, haven't seen you here for a while. But then I haven't been around all that much either. How's the boat going? Getting close to splash day yet?
Is it getting closer, Yes, but not at the pace I am wanting, but forward is the direction.

Just got back from a couple of months OS, made a few purchases of boaty bits and checked out facilities and prices while there just to convince ourselves that we really want to go back in the boat and the answer is yes please, get me there now.

How about you?

D
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Old 14-07-2009, 01:20   #96
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And foam.



And it is very well documented that these problems are almost universally due to owners or builders drilling holes in the decks without de-coring and sealing them properly.

And again, how many of these cases involve Duflex?
Yes, I agree. Although at different rates, water will spread in both foam and balsa core, Duflex included.
If Duflex problems are not documented is only because 99% of boats out there don't use it. It is only used in custom boats which are a tiny percentage of the world wide production.
Overall it's a great product but it does have drawbacks like all cored composite.
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Old 14-07-2009, 15:46   #97
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Yes, I agree. Although at different rates, water will spread in both foam and balsa core, Duflex included.
If Duflex problems are not documented is only because 99% of boats out there don't use it. It is only used in custom boats which are a tiny percentage of the world wide production.
Overall it's a great product but it does have drawbacks like all cored composite.
So the ONLY possible reason is the lack of boats? . It couldn't possibly be the lack of problems? Given that there are now hundreds of Duflex boats....
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Old 14-07-2009, 15:47   #98
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How about you?

D
Not too far away now
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Old 14-07-2009, 16:42   #99
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So the ONLY possible reason is the lack of boats? . It couldn't possibly be the lack of problems? Given that there are now hundreds of Duflex boats....
I am sold on Duflex and I am going for it, I hope you are right and there are no problems. However, I keep on looking and feeling the samples I have and I find its strength to weight ratio amazing. The part that scares me is the .6mm glass fiber skin thickness and the ease with which your finger nails can crumble the core away.
It is definately a material for careful custom build and cautios use.
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Old 15-07-2009, 00:24   #100
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The part that scares me is the .6mm glass fiber skin thickness and the ease with which your finger nails can crumble the core away.
It is definately a material for careful custom build and cautios use.
Just like foam

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Old 17-07-2009, 09:59   #101
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There's a good article in the Oct/Nov issue of Proboat on what is purportedly the first balsa cored sailboat. Built of Contourkore in 1966. 43 years on and it's still racing competitively.

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Old 30-10-2011, 09:33   #102
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Nida-Core alternative?

Nida Core alternative

I was drawn to this forum discussion as I was doing some research on these Duflex and Durakore products from ATL. My memory of a product termed Durakore stretches back quite a number of years to a product by that same name that was marketed by a USA company that specialized in balsa core products....that company's name was Baltek if I recall properly.
http://www.amazon.com/Boatbuilding-Baltek-DuraKore-David-Brown/dp/007008212X




So over the years I've just assumed that all such products were all balsa related, but now I discover you might be referring to balsa or foam cores in products of the same name....somewhat confusing? I've seen so many different core products come and go that I've almost lost track....particularly with the numerous foam types.


Several honeycomb products have seen considerable use in boat building, the well known Nomex, and the lesser know Nida-Core. Then there are a number of honeycomb products from Plasticore, etc


Nida-core is unique in that it is a polypropylene material. Mostly we think of this plastic material as one which is difficult to glue together, and difficult to glue anything to it. Bonding on sandwich skins via their polyester or epoxy resins directly to polypropylene can prove fruitless. For the most part things need to be 'fused' together with heat. That's what Nida-core does. They thermo-fuse a non-woven polyester scrim material onto the edges of the honeycomb cells,...and they include a polypropylene barrier film to limit resin consumption by the hollow cells when skins are applied.


So it appears to me that it is this thermo-fused bond between the honeycomb structure and the polyester scrim that is the most important factor in making this particular cored construction one of the more viable ones out there. It will not rot like balsa. It will not sip any water thru the cell walls. If that thermo-fused bond with the scrim material is mostly all intact if should not allow water to migrate along the core cell structure. And it is relatively cheaper than many of the alternatives.


So what's not to like about this sandwich-core construction material...in comparision to those discussions above??
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Old 30-10-2011, 09:43   #103
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Re: Cats from Duflex Panel Kits - Strong?

Nidacore has much lower shear strength than balsa and foam. Our boat is made of Nidacore.

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Old 30-10-2011, 11:39   #104
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Re: Cats from Duflex Panel Kits - Strong?

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Nidacore has much lower shear strength than balsa and foam. Our boat is made of Nidacore.

Mark
Didn't Manta switch to Core Cell in their later boats. To say Nida Core doesn't rot is wrong. I've seen and smelled rotten Nida Core. Maybe they changed the materials to make Nida Core as this was a mid 90's Manta. I'm pretty sure Nida Core started of as a furniture core and boatbuilders started using it because of the low cost.
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Old 30-10-2011, 13:27   #105
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Re: Cats from Duflex Panel Kits - Strong ?

Seen one with serious issues. It was a boat built over there and sailed to EU. I think it was builder's fault, not designs nor designer's.

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