Polycore for flat sheet catamaran

[b_rodwell]

I would be interested in what the Oram builders (and others) think of polycore as an alternative to joining duflex panels.

Here is a site of a the result of such an approach:

http://www.polycore.com.au/News--and--Events.php

and here is a site describing how it was done:

http://buildacatamaran.com/lyra1.html

Let me know what you think.

Brian

[catsketcher]

This is a very personal observation.

I tried using it and wasn't very happy with the result. I wasn't able to do the same things I could do with foam. I am not sure how expensive it is but I would be very wary of using it on the basis of cost.

I didn't like the way it performed when I tried to dig core out and it seemed that the laminate was more flexible than foam. We had a supplier down here who would sell 10mm for about $100 a sheet. I could get foam for $150 so went this road.

cheers

Phil

[Triroo]

We are building a 38' river boat using Polycore with great success . Would certainly use it again. Northern NSW 02 66828557 give me a ring if you want to have a look. Paul

[rattus]

This is a quote from Derek Kelsall via Rob Denney on the Harryproa mailing list:

"This from Derek Kelsall
Two small samples were made. 2x460g
biax in one skin and one biax in the other, on honeycomb and on PVC
foam. Visibly, the laminates would pass any inspection. I held a hair
dryer to the honeycomb for half a minute and then held it under the cold
tap – the conditions on a deck, in a shower on a sunny day. 15% of the
cells had water in them.

end quote"

Ouch. 1% of the cells would be 100% too many.

Another concern would be regarding thermal insulation; the cells allow vigorous thermal transfer and thus would be far less effective than foam in keeping things cool in hot weather, and vice versa.

Mike

[brian eiland]

Originally Posted by rattus

This is a quote from Derek Kelsall via Rob Denney on the Harryproa mailing list:

"This from Derek Kelsall
Two small samples were made. 2x460g
biax in one skin and one biax in the other, on honeycomb and on PVC
foam. Visibly, the laminates would pass any inspection. I held a hair
dryer to the honeycomb for half a minute and then held it under the cold
tap – the conditions on a deck, in a shower on a sunny day. 15% of the
cells had water in them.

end quote"

Ouch. 1% of the cells would be 100% too many.

Another concern would be regarding thermal insulation; the cells allow vigorous thermal transfer and thus would be far less effective than foam in keeping things cool in hot weather, and vice versa.

Mike

I'd like to know more about this subject as well. I've written directly to Derek to ask about his alleged quote on this material.

If this is at all true, then these builders have something to worry about
http://www.australiancompositepanels...sland%2012.htm

...but I doubt they would have embarked on this ambitious project knowing that such a possible existed

[Alik]

We are widely using this type of material; major concern is shear strength is lower compared to foam of equivalent weight. Usually for boats below 10m in length shear strength of structure is satisfied for topsides, decks, cabins and bulkheads without any problems; for bigger boats one needs to reduce spacing between stiffeners to get structural compliance. I would not use this material on bottom of planing craft. Generally with this PP honeycomb material as core we use somewhat thicker FRP skins. The structure of equivalent strength win PP honeycombs is heavier compared to one with foam, but the cost is big advantage. It is also noted that normal compression strength and resistance to peel for PP honeycombs is higher.

To foresee this question, for small pleasure craft under RCD/ISO 'Small Craft' no certification of cores is required, and there are no minimal properties requirements for cores other than foam and balsa.

Besides some surveyors and 'industry experts' (most of those having no experience in design and operation of such craft) would tell horrible stories on this materials, we have monitored such structures on our boats after few years of use and no sign of delamination or buckling has been ever seen. As to water penetration, nothing excessive was observed and core is basically dry. I have few samples of such panels in my office some of them cut out of boats after years on water, and a lot of photos.

[upchurchmr]

Brian,

Sorry for the ignorance but what is a DUFLEX panel?

Is there something special used to bond the core to the skin? My understanding is that polypropelene is very difficult to bond to anything.

Marc

Originally Posted by b_rodwell

I would be interested in what the Oram builders (and others) think of polycore as an alternative to joining duflex panels.

Here is a site of a the result of such an approach:

http://www.polycore.com.au/News--and--Events.php

and here is a site describing how it was done:

http://buildacatamaran.com/lyra1.html

Let me know what you think.

Brian

[Corley]

duflex is a pre made composite sandwich panel with skins of varying weights laminated on both sides of a core which can be either balsa (more commonly used) or closed cell foam.

http://www.atlcomposites.com.au/atl_..._panels/duflex