Poll, Best Core material

[wogi]

Let me start by saying that I know there have been many posts, options, beliefs, BS and wives tails threads on this issue.
I would like to put it out there to you glass masters who have the experience with all the new products, using new and old technology.
The question to all y'all is a simple one. What readly available core material would you use if you were going to use epoxy resin on a 50 year old polyester fiberglass hull?
Please let's not make this a resin debate, that factor is set and will not change.
What I do want this tread to be is a discussion on what you feel to be the best core material to use in this situation, while considering the following
1) Cost
2) Availability
3) Strength
4) Weight, lighter being sought after
5) Bond
6) Ez of use
The lay up I am leaning towards is 1708 Core than 1708
But I'm very open to suggestions on this, and would like to hear from the glass masters on suggestions on the lay up schedule.
Thank all of you for reading and any and all input on this thread. And have a blessed day

[rjdubiel]

Epoxy, 1708 / 1808, core of your choice (or what you can get). I would also say I did my vking in epoxy, if I ever do another I will try vinyl ester and still use balsa and plywood. .

[XstreamVking]

Divinnycell for hull and deck, and a penske type core board for transom (25 # density). And (12# density) floor, stringers. . All 1708 glass. Used all this stuff in mine about 10 yrs ago. Still good as new. If I did it again, I would use the same materials.

[LakeFever]

I went back/forth around the bend and then a couple laps mulling this decision as well. Nothing i found, nor anyone i spoke with could argue two really substantial advantages for balsa and that is 1. Strength 2. Lightest weight. The only downside being balsa is subject to decay over time because its moisture absorption characteristics. The way balsa was explained to me is small tubes standing on end like straws. Very strong under compression. Where foam core is basically bubbles of air trapped in foam in a random pattern offering no compression strength to speak of which is why it is substantially less stout than balsa for core use.


Then i got hold of some old school reputable glass guys who warned me of two potential issues with foam core. 1. It doesnt bond nearly as well as balsa 2. so you better know what your doing with it and they suggested vacuum bagging was ideal for foam core. I was a total newb and concerned about bond so that scared me a bit and vacuum bagging seemed too far a reach for a first timer especially considering my hull needed a lot of repair first.


In the end i chose balsa for those reasons. I have read about flex being important and advocates for foam core for this reason but every time i saw a resto that went over the top with increased stiffness and a focus on strength with extra stringers and more core etc the owners raved positively about the results and the hulls handling.


So thats what i found and my choice boiled down to a simple choice. Did i want maximum strength? Or maximum water resistance? Thats really the choice between balsa and foam as i see it.




Epoxy resin and balsa has another concern you need to plan for and thats blush. If your hand laying you might want to use peel ply so you dont have to wash off the blush. Water and balsa definitely not ideal. i would probably lean to foam with epoxy because of this. Epoxy is great for vacuum bagging because you can set a much longer cure time and really could get crafty with your layup too.


That said vinylester is essentially a hybrid epoxy and for hand layups makes the most sense to use imo. It also has the best secondary bonding window by far! 12 days for the good stuff no sanding or grinding nec just keep laying. Its also 100% waterproof like epoxy and has more elasticity yet crazy bond strength. Anyways its what i chose in the end. Cant go wrong with epoxy though imo. For a rebuild im confused why anyone uses polyester.


My one build wonder 2 cents.

[XstreamVking]

Nothing wrong with wood. It's really good at sound and vibration deadening, where foam is not. Kept dry wood will last forever. And epoxy loves wood.

[transomstand]

The best core material is the one installed with the best workmanship...period.

[wicheckmate]

1. Epoxy
2. Transom "Coosa"
3. Core divynacell .. depending on where your using, core or stringers or bulkheads 3lb - 7lb
4. 1700 Not 1708 if working with epoxy.. no need for the matt. this also depends on where in the layup you are putting this and what you are using it for.

[wogi]

The best core material is the one installed with the best workmanship...period.

ya that goes without saying, I'm no newbee to the joys of the itchy scratchy game of fixing hydro -stream rotten cores this will be my sixth. All the boat l have done in the past, my first was 24 years ago have been over powered and have had no issues, my last was 12 years ago. I'm in contact with all my old projects and keep up with how they have held up. With this said, I guess I started this thread to see what if anything is new out there and users input on said products like the honey comb plastics the "Green board" and the nomax coding material that is now on the market.
I do thank all y'all for your input, building a drag boat and want to learn the latest and greatest in strong light coring. Thanks again

L

[skialot2]

Replace whatever core material is there with the same material. No need to reinvent the wheel. It lasted fifty years. The manufacturers construction is usually pretty shoddy with exposed wood all over the place. Seal any wood structure up tight from moisture and it will last forever.

[OnPad]

Not the expert your looking for! But I built snowboards a couple years out my shop and rebuilt my ltv. The boards I built out of wood, epoxy, triaxial glass and some other stuff that's irrelevant. In my opinion foam cored boards were light, but not stout enough to hold up. Lots of delams , blown edges, and hard to get stiff enough. The weight difference between the fancy lightweight material and wood isn't going to be that much in a boat that size. Doubt I used 50lbs total in my boat. What does the high doller stuff weigh 25lbs? The glass and resin is what adds weight.
I've also heard you don't use regular mat with epoxy.

Just my uneducated, off base opinion.

[rjdubiel]

no CMS only with fiberglass unless it is stitched for epoxy. The binder does not break down with the epoxy. Now 1708 or 1808 has no binder and the 8oz of CMS is stitched to the 17/18oz biaxial cloth. With epoxy you really do not need any CMS at all technically. But you must have CMS in-between layers of cloth when using poly resin.

[Mark Poole ModVP]

I get a chuckle out of the flats boat builders that use the hi tech carbon, kevlar, rigid foam core construction. You need stealth for inshore fishing and that type of hull is noisy!

When you get to about 60 years old you become aware that anything that you build that is built 'decent' is going to outlive you anyway!

[Mark Poole ModVP]

Can't think of the name but there was an offshore boat builder that said they used plywood as a core. I have heard of using voidless (marine) plywood to core a bottom by literally cutting the plywood into 2" or 3" squares and bedding it into 1.5 oz. mat. Seems that would be very heavy for a large monohull.