Are Cats Made from Duflex Panel Kits Strong ?

[mikereed100]

Originally Posted by smj

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.

Much of my boat is made from Nidacore and the PO in his wisdom neglected to exclude the core from under the thru-hulls, then bedded them with silicone.
There was some water entry of course, and when I repaired the areas there was a foul smell as the water drained, but this was caused by dead marine organisms, not by rotten Nidacore. Beiland has it right. Polypropylene may break down under abuse, but it does not rot.

Mike

[smj]

Originally Posted by mikereed100

Much of my boat is made from Nidacore and the PO in his wisdom neglected to exclude the core from under the thru-hulls, then bedded them with silicone.
There was some water entry of course, and when I repaired the areas there was a foul smell as the water drained, but this was caused by dead marine organisms, not by rotten Nidacore. Beiland has it right. Polypropylene may break down under abuse, but it does not rot.

Mike

The problem on the boat I was talking about had the bad core under a thru hull above the waterline. It was turned to mush by fresh water. This was a mid 90's boat so maybe Nida Core has changed since then.

[beiland]

Unlike nonwoven polyester geotextiles, polypropylene does not absorb water nor does the presence of water have any effect whatsoever on tensile strength or other mechanical properties.

Since polypropylene does not support, attract or deteriorate from fungal growths, Propex Geotex nonwoven geotextiles are rot and mildew resistant.

When properly stabilized and buried, nonwoven polypropylene geotextiles have been expected to last for up to 200 years.

...more here...Engineering Bulletin
http://www.geotextile.com/downloads/...ypropylene.pdf

[beiland]

Interesting comparision table:

End Grain Balsa Wood used for lightweight structural bonded panels. Comparison Table

[mikereed100]

Originally Posted by smj

The problem on the boat I was talking about had the bad core under a thru hull above the waterline. It was turned to mush by fresh water. This was a mid 90's boat so maybe Nida Core has changed since then.

That's a puzzler. I wonder if they might not have used one of the old paper core honeycombs?

Mike

[smj]

Originally Posted by mikereed100

That's a puzzler. I wonder if they might not have used one of the old paper core honeycombs?

Mike

That's possible. I wonder if the original Nida Core was a paper core honeycomb. I'm pretty sure it wasn't intended to be used as coring for a hull when it first came out.

[colemj]

Originally Posted by smj

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.

Yes, Manta switched to Corecell at some point in production because of the better strength properties. All of the boats built with Nida Core used polypropylene core and not paper.

I only mentioned the lower sheer strength of Nida Core, and nothing about rotting.

Mark

[cat man do]

Originally Posted by colemj

I only mentioned the lower sheer strength of Nida Core

It makes you wonder
There is a 40ft schionning powercat that I know of that used it throughout inc hulls
And there are these using a "same same but different" version
http://www.polycore.com.au/News--and--Events.php

[colemj]

While polypropylene honeycomb core has lower shear strength than balsa or structural foam, it is perfectly suitable for boat building. Catana used it extensively during the period of the 401, 431 and 471 - their best built boats. It was used on Endeavour and Manta, and many monohulls - and probably many boats I don't know about. Shear is not an issue for almost all parts of a boat, and where it is, the structure can be reinforced to accommodate it or a different core used.

Mark

[beiland]

Originally Posted by cat man do

It makes you wonder
There is a 40ft schionning powercat that I know of that used it throughout inc hulls
And there are these using a "same same but different" version
http://www.polycore.com.au/News--and--Events.php

Do you know specifically of that power cat by Schionning design that utilized this 'polycore material"?

I have a gentleman who has expressed the desire to possible utilize NidaCore in the place of Duflex for a Schionning's design. But the response from Schionning would seem as to not recognize this material as a viable substitute to be used for his designs??

The second vessel you posted there became known to me only recently when a gentleman asked on one of the forums if I was aware of this aft-masted vessel. I said no and posted it in my discussions of same.
Lyra's Rig

[beiland]

Now that I look at that first image (powercat), I believe it may be a Tenannt design rather than Schionning one ??

[barnakiel]

Originally Posted by colemj

While polypropylene honeycomb core has lower shear strength than balsa or structural foam, it is perfectly suitable for boat building.(...)

What about the resin/core bond when using polypropylene? I glued woods and I also glued (attempted) polypropylene sheets with resin. The polypro bonds failed every time.

So, my issue is, how good is the bond between the polypro core and the resins used to form the sandwich?

b.

[colemj]

The core material has a fabric scrim thermo-bonded to the polypropylene honeycomb that the resin bonds the first layer of glass to.

Mark

[beiland]

Originally Posted by barnakiel

What about the resin/core bond when using polypropylene? I glued woods and I also glued (attempted) polypropylene sheets with resin. The polypro bonds failed every time.

So, my issue is, how good is the bond between the polypro core and the resins used to form the sandwich?

b.

That single factor was always a reservation I had with that product. But note that they thermo fuse a polyester scrim onto the core so that you are now bonding your skins to that polyester sub-skin.

And thus far I have not found a lot of negative problems with bonding to that scrim if done properly. That is one of the reasons I bought up this Nidacore subject again...to have a fresh look at this material that I had ignored with initial prejudice for years.

[44'cruisingcat]

Originally Posted by colemj

Shear is not an issue for almost all parts of a boat, and where it is, the structure can be reinforced to accommodate it or a different core used.

Mark

Sheer and compression strength are very inportant in the core. The core's job is to keep the laminates apart, and in position relative to each other. A core which is weak in either compression or sheer will result in a less stiff panel, all other factors being equal.

I've met "Lyra"'s designer/builder, and he has mentioned the lack of sheer strength in his cores. (He makes a brief mention of it in his article too.)