Polypropylene honeycomb panels for hull construction?

[brian eiland]

...more on my hoped for utilization of this plastic honecomb material....

This is the plastic honeycomb material I want to utilize to build the superstructure(s), ie ….cabin sides and roofs

Plascore PDF
www.plascore.com/pdf/PP_Honeycomb.pdf

I'd like to use a relatively thick section of PP honeycomb (1 to 2 inches) to get a relatively stiff panel, with a minimum of layup of fiberglass skins on both inner and outer surfaces. The skins of this sandwich structure can be varied in their layup depending upon the required strengths needed for roof panels, cabin-side panels, etc. I don't foresee a need for big shear resistance in these panels that will be basically glued together to form the big 'box' structure of the main cabin and pilot station. Here are two illustration of that basic 'box' structure with bold lines to emphasis the structure.

Note also there is additional support for this 'big box cabin' via the vertical support tubes / columns that are anchored in the steel gunnels / bulwarks and then reach up to support the outer edges of the cabin roof. With these columns and the stiff panel walls there should be no other requirements for any internal framing inside the cabin box. Possibly there will be some additional corner braces added to the inside and outside of the 'cabin box', and these may appear as finishing-trim pieces.

This entire cabin box structure can be quickly assembled from pre-cut honeycomb sandwich panels off over in a corner of the shop, right on the shop floor, then lifted onto the deck of the vessel and glued or mechanically attached down. Built of primarily hollow honeycomb panels, this superstructure should be pretty light-weight.

There is no electrical wiring nor plumbing contained in the walls of this cabin-box. These services are all provided for by way of the floor of the cabin,....underside of the deck.

And speaking of the deck, I would wish to construct the main deck of this same Plascore honeycomb sandwich material. It would have a slight crown shape across the vessel, and will have sufficient glass layup on either skin to support big loads. It would also be molded by resin-injection to insure an excellent resin glass ratio, and a very thorough bonding between the skins and the core, thus preventing any water migration along the bondline.

 

[brian eiland]

So here is Groper's initial reply to my postings...

Brian- I believe you asked me about polycore once before. I explained that a friend of mine is building a pacific 40 catamaran entirely from polycore near where I live. It's more time consuming and less friendly to work with compared to foam core. Any joins or edges need to be decored and back filled first before bringing the join together , gluing and glassing over so there is an extra step of decoring and back filling not the mention the extra resin to fill the core along the joined chine. If you don't do this there will be air bubbles all along the Chine when you tape over the Chine
. This was a cnc cut kit of prelaminated polycore panels, and be has been on it for 5 years full time - so it is still not a quick method to build IMHO.

The next issue my friend had was out gassing due to so much Trapped air in the polycore. He always had to wait till Temps were falling to get a good glassing job done or the dreaded air bubbles would arise.
Also- did you see the thread recently where a large cat in Thailand built from polycore was completely saturated with water in the core? They pulled it out and drilled holes in it and the water just kept coming - they posted videos and all on here. You'd have to search it out I can't remember the name of the thread.
So No- I wouldn't use it except for perhaps again- certain key areas in the interior such as small bulkheads with no cutouts etc made from pre-made panels to save cost. Perhaps the front 3 watertight bulkheads for example. Certainly nothing outside like a deck which is full of leak points from all the hardware mounted all over it...

And of course because it not infusion compatible, you can't use it to make large panels yourself via KSS....

 

[brian eiland]

another reply

The saturated hull is here;
http://www.boatdesign.net/forums/materials/repair-water-core-material-fibreglass-boat-56743.html

Here is some handy info on using polypore/nidacore;
http://boatcraft.com.au/informationpages/nidaplast_working.htm

 

[brian eiland]

Originally Posted by groper
Brian- I believe you asked me about polycore once before. I explained that a friend of mine is building a pacific 40 catamaran entirely from polycore near where I live.
Is that Pacific 40 the same cat design as the Solitary Island Catamaran?

Has he had that project under way for quite a while? I believe Solitary Island stopped building their kits a number of years ago due to financial difficulties of the boat market in general.


Originally Posted by groper View Post
It's more time consuming to and less friendly to work with compared to foam core. Any joins or edges need to be decored and back filled first before bringing the join together , gluing and glassing over so there is an extra step of decoring and back filling not the mention the extra resin to fill the core along the joined chine. If you don't do this there will be air bubbles all along the Chine.
That is if you have a hard chine in the hull design.

I believe Solitary Island had a solid glass 'shoe' below the waterline?


Originally Posted by groper View Post
The next issue my friend had was out gassing due to so much Trapped air in the polycore. He always had to wait till Temps were falling to get a good glassing job done or the dreaded air bubbles would arise.
That's interesting

Wouldn't out-gassing (of core materials), and trapped air be 2 different things.? There can always be 'trapped air' in any fiberglass layup procedure, regardless of core material?

I would be particularly concerned if it were the chemical make-up of the core that might be producing gassing after layup.

Originally Posted by groper View Post
So No- I wouldn't use it except for perhaps again- certain key areas in the interior such as small bulkheads with no cutouts etc made from pre-made panels to save cost. Perhaps the front 3 watertight bulkheads for example. Certainly nothing outside like a deck which is full of leak points from all the hardware mounted all over it..
Agreed, decks have many potential leak points, and regardless of what cores they are built of one has to take extra precautions at mounting deck hardware.

Balsa cores are off my list as there is just too many documented cases of water following the bond-lines and eventually rotten decks.

Lots of foam cores do not hold up well in the heat of sunlight, and tropic conditions.

I believe I had read in a number of cases that bond line failure of Nidacore type products did not occur if the job was done correct? And another thing that had impressed me about the Nidacore type product was its 'ductility'. This property helps the sandwich structure stay intact, and not delaminate so easily.


Originally Posted by groper View Post
And of course because it not infusion compatible, you can't use it to make large panels yourself via KSS....
I believe i also discovered there were some examples of utilizing these core materials in an infusion process? I just can't recall right now.

Thanks for bringing this to my attention. I will have to look back and re-evalute
Brian

 

[groper]

Brian - i also edited some of those previous postings to include more information. Please reread the following;

When i say "chines" i dont just mean underwater chines of a hull. I mean anywhere there is a change in plane between 2 panels. These exit everywhere - deck to cabin, hull to deck, chamfer panel to floor, a multitude of places throughout the interior and furniture, the list is endless... and everyone of those edges had to be decored and backfilled before glass taping around these edges or "chines" as i call them. If you dont you end up with 2 abutting polycore edges which you cannot remove all the air bubbles from when you attempt to glass around that edge. Think about it - often these edges dont fit perfectly, so the panels must be shaved back a bit to get a good fit before glassing together and even the simple process of sanding an edge flush is difficult with polycore as the plastic doesnt sand down easily. If you attempt to grind it - it melts etc. Then your left with this open cell edge which you need to round off so the glass will wrap as you cant glass wrap a sharp edge. But you cant round off open ended cells - you end up with a rough jagged edge which is full of open cells to wrap. So the process my friend used was to decore and back fill after he trimmed panels to fit - then round off the cured bog edge and glue/glass around it. With foam core panels none of these difficulties exist. You can trim it, cut it, rout it, sand it, plane it, grind it, and you can glass around them directly as the foam core itself can be neatly rounded off (usually with a router) and glassed over directly. Using routers was difficult with polycore as the router bits tend to rip out the plastic rather than cut it. Everything about the stuff is just difficult..

The major issue above all else tho, is its not compatible with KSS! You cant infuse PP core or the cells fill with resin. Flat table infusion allows a single worker to infuse a giant panel (upto 100kg of resin )with a perfect finished surface in a single day! I was having breakfast in the morning before starting with a bare table, then laying everything up and infusing my topsides panels before clamping off the lines and going to lunch! - You cant beat that in terms of man hours by any other method, period.

And yes - the solitary island (pacific 40) uses an infused hull 'shoe" with a foam core which is all below waterline as i doubt the designers felt polycore was suitable below waterline either - that and its not an efficient material to attempt to obtain that shape with in terms of time. They used double cut foam which conforms to the compound curved mold and infused it. So despite foam being more expensive - it allowed them to produce the part quickly and saved time = $$$.

You can (and people do) use polycore anywhere on boat. I wouldnt use it below waterline for fear of water migrating between cells in case of damage. The solitary island uses it everywhere else including decks. Every peice of hardware mounted to it must be carefully decored and backfilled so water never gets into it. Basically need to treat it the same as balsa. Except balsa is easier/quicker to work with...

 

[brian eiland]

Bondline(s)

...from another forum...

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?

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.

I was initially the same
The first breed that was around several years back had quite a furry (read thirsty) scrim on it plus the scrim to me seemed able to be peeled away easier (pre resin) than I would have liked.

Samples I have seen since seem to be considerably better and if I was needing more sheet material, I would be looking seriously at it for my own use on any flat panel area.

This bondline between the skins and the core is certainly an important one for any core/sandwich construction material, and these PP cores depend on a very viable thermo-fusing process. Two questions came to me recently,
1) that observation above about an early production PP core that might have had 'furry scrim' material applied
2) Chinese made stuff, (that I always question quality). That is one of the reasons I had asked about the builder of that cat in Thailand that was experiencing problems....where did their PP core come from?

One item in PP's favor is its ductile nature that would keep it from cracking along this bondline as do quite a number of rigid foams might do when slightly over stressed.

 

[groper]

If i had a bigger budget, or was a commercial catamaran builder - i would build a flat table or floor mold large enough to infuse the entire deck of the design i intended to build.

Then i could infuse, the entire deck in 1 shot. The entire bridgedeck floor in a second shot. And, ALL 4 topsides panels in a 3rd shot.

Each one of the above shot - could be setup and infused in no more than 2 days per shot by a single experienced worker. The deck would be complete with all high density inserts for cleats and hatches etc.

Its costly because you need alot of floor space and an overhead gantry to lift such big panels around the place... fine for commercial builders but a bit much for low budget home builders like me...

 

[groper]

i dont have any issue with the mechanical properties of PP core panels. They seem plenty tough and strong enough to me - and testament to this is many PP boats going strong provided they are built carefully. The issue is the man hours it takes to use PP core, it may be less expensive at the end of the day, in terms of time = money, to use a more expensive core like foam...

 

[brian eiland]

Pacific 40 vs Solitary island 40

Hi Groper, ...greatly appreciate you joining this subject thread.

I've attached two PDF's, one I had for Pacific 40, and one for the Solitary Island vessel. It appears that the Pacific 40 vessel preceded the Solitary Island attempt to build these kit boats.

And it appears as though the Solitary Island guys adopted a little bit more sophisticated method of joining the polycore panels together?

"the Pacific 40 kit Catamaran Reborn as the Solitary Island 12"

So your friends' boat might be one of those very early ones?

Here are some samples of random panels from the CNC routed kit. Note that there is a minimum of joining to do with all the nesting
done on large 5800mm x 2240mm panels. In fact there are no panel joins on any of the interior fit-out or cockpit kits and with only one or two joins on the larger parts such as the topsides and bulkheads. This could save you weeks of building time (not to mention fairing time) while the integrity of your boat is not compromised by hundreds of joins.

Polycore produce PP8PG panels with DNV approved epoxy fibreglass skins. http://polycorecomposites.com/Polycore-Preglassed-Panels.php

 

[groper]

Brian- please know that I have intimate, first hand knowledge about this stuff. I'm not an Internet armchair critic.

This kit boat from Mark Stephens is supplied with half boat length PP core panels in addition to the infused foam core shoes. The panels are made like so;
1. They use a wet out machine to wet out full width rolls of glass and lay it out on a flat table.
2. They layup the sanwich panels with PP core and between panels use a layer of plastic to separate each panel from the one below it in a stack.
3. Once multiple panels have been layered and stacked, the whole thing is vacuum bagged and left to cure.
4 . It takes 3-4 people working like crazy to get this done using a slow cure epoxy.
5. The surface on each panel is pretty good, but not good enough to paint directly, it requires a little filling of pinholes and feathering of glass overlaps etc which still means that every square cm of surface area still need to be sanded, faired, primed, and painted - a huge amount of work in itself.
6. The panels are cnc cut and packed into a container for shipping.

The boat is then built as per a Duflex build- the difference is you only have to join once along the length of the boat rather than every 4ftx8ft Duflex panel. However there is no z joint in the polycore panels so taping together leaves a raised bump to fair out.

All of the points I raised about rhe difficulty in working with PP sandwich panels are still valid. Where do you think I learned all about it? - it was through the building of this very kit which is happening 15mins from my house and have become good friends with the builder. Weve helped each other out on numberous occasions...
So far he has used an enormous amount of fairing compound and highbuild primer - over 500kg so far, and has employed 2 full time fairing/painting professionals for 6 months.

I will say tho however - the standard to which they are building this boat, is equal to or better than, a professional boat yard. When this boat gets its final coat of paint it will look absolutely mint. This is also in part why its taken 5 years full time...

 

[groper]

If you wish to read more about it i suggest you read his build blog here- https://diy-yachts.com/forum/viewtopic.php?f=23&t=1021

 

[brian eiland]

Hi Groper,
I've been away from the forums for awhile with some sort of flu, and not over it yet., so haven't done much follow-up on our subject. But I did just 'rediscover' this other subject thread that had lots of good material submitted by yourself.
http://www.boatdesign.net/forums/fiberglass-composite-boat-building/polycore-21319.html.
Your contributions are significant.

I'm going to look back thru both subject threads when I get to feeling better, and perhaps after my planned visit to Thailand for 2 months.

BTW, did you see this subject thread and the problem that power cat experienced in Thailand with core and water.
http://www.boatdesign.net/forums/materials/repair-water-core-material-fibreglass-boat-56743.html

I met with a boat builder there years ago, RB boats, on a couple of occasions, and saw where he was using a 'nidacore like' product in many of his constructions. I don't seem to recall any major problems he has had with the boats in regards to core problems?
I was trying to find out if that power cat with the water problems might have been built by him, but thus far have been unable to get the gentleman who posted that subject thread to respond any further??

 

[brian eiland]

If you wish to read more about it i suggest you read his build blog here- https://diy-yachts.com/forum/viewtopic.php?f=23&t=1021

Just peeked at that link, and it looks real interesting,....thanks

 

[groper]

The problem with this material is the ease of which you can work with it- or lack thereof. Like is said before, I don't have anything negative to say about its structural properties.

It's also not compatible with infusion, which is a huge loss in terms in terms of being able to efficiently layup the structure of a yacht. Infusion is being embraced by all leading manufacturers now , and I can tell you from personal experience that's it's a lot quicker in terms of man hours to use infusion processes. There's a reason so many boat builders have gone overseas and it's entirely driven by labour costs being such a high component of boat building.

Polycore is not conducive to efficient building hours. Yes it's cheaper to buy compared to foam, but it'll cost you more in labour...

 

[Sunsine]

PP Honeycomb Panels

Interested in the thread of honeycomb panels applicated in the ship building.
Recommend a qualified honeycomb supplier.

PP honeycomb: https://polyhoneycomb.com/honeycomb-panel-products/polypropylene-honeycomb-core