Polypropylene honeycomb panels for hull construction?

[Tracy Huff]

What also impresses me is the large sheet sizes available by some suppliers (2.4wide x more than 9 metres long).

Could you please tell me who makes large sheets, Thank you!

 

[brian eiland]

I recently brought up this idea of utilizing polypropylene honeycomb core materials rather than foams over on another subject thread. This gentleman Groper had some interesting observations (mainly negative) about the use of the material that I thought should be given more considerations,...but I did not want to take that other subject thread off on a tangent. So I decided to look for another subject thread that might be acceptable for additional discussions on this matter.
Here it is.

Some good observations in these postings, particularly by Groper. Look at page 2.

Also on page 2 is my suggestion about the superstructure construction on the Pilgrim 40 trawler. (my memory bank is getting weaker at my age, so i have to remind myself of earlier postings)

 

[brian eiland]

http://www.trawlerforum.com/forums/s...8&postcount=85

This page opened correctly when I used Firefox browser, BUT did not so using Google chrome??

 

[brian eiland]

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

I could not find this PDF,...would someone know how??

Or just maybe I'm behind times, ....and info has been newly reorganized under the Plascore name??

 

[fallguy]

Post is over 7 years old.

 

[brian eiland]

Post is over 7 years old.

I think you are correct, ...I'm behind times.

I'm going to have to do a modern investigation of these PP honeycomb products,...perhaps starting with a site like this,..
Polypropylene Honeycomb - Plascore https://plascore.com/honeycomb-core/plastic/pp-polypropylene/

And I think I will start a new subject thread on it,.. as this one had 'hulls' included in the title. I am not addressing the use of this core material in the hulls,...but rather just the decks and superstructure(s)

 

[brian eiland]

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]

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...

 

[fallguy]

They erred.

When building pp core panels; the edges must be prepped. This means, for tabbing; you would first add a solid core laminate that was tapered, so for 6” tabbing; you would add 3.5” tapered foam core to the pp.

Then you laminate the panel. And then you can tab into the relieved core sections.

Not sure why you are quoting these, but the panel seller did no favors to the final builder. All so they could laminate a stack of flat panels in a single go.

 

[brian eiland]

I'm quoting these so as to make folks aware of the pitfalls with this PP core construction.

I was following the Nadacore developments at the time, but was always concerned with proper bonding to the PP core materials. I then learned of thermal bonding that was being utilized to add that 'skin material/polyester fabric' to the pp core that could then be used to bond fiberglass material to,...that eased my concerns about the Nidacore product,...BUT what I failed to appreciate was this edging problem that Groper points out. That's why I repeated his postings.

 

[brian eiland]

I was following the Nadacore developments at the time, but was always concerned with proper bonding to the PP core materials.

You might find quite a number of problems I was seeking out in those early days, ... if you utilize the 'search function' and type in "Nidacore problems"

 

[fallguy]

I used pp core on my cat build. It worked well for the bridgedeck construction; although there is some debate as to whether a double bottom was needed.

I also found it very thirsty. The problem is you must wetout the substrate first in order to get a good bond. And the veil/honeycomb layer will drink resins. Like, literally drink.

What I ended up doing was using a 3/8” paint roller and loading it and then running it as fast as possible across the pp veil layer. But I found my wetout rates for 1708 (I was aiming for some stiffness) to be about 120%. My bdeck was about 13x8.5 and double bottom, so I had 50 yards of 1708 or so. This means 50 • 2.2 • 25 oz or 172 pounds of glass and resin. I think, in the end, my cabin sole is likely to outlive me, but it is too heavy. 1” foam core panels with db1700 vac bagged would have been similar stiffness or more and the weight of resin and glass 50 • 1.6 • 17 or so or 85 pounds or basically half as much! And the resin delta is a large part of it…

And yes, I did edge prep. My pp was 1” and I purchase 1” aquacore and then cut out the pp minus about 1.25” and glued it all before glassing. I did so despite closing the edges because I wanted the bonding to be relatively easy as was 13’. The pp when cut requires buttering the edge with thickened resin. And that can also use a bit for any voids or ragged edges.

I have pictures, but not wanting to dig them up.

I made the edges 1.25” wide for my own sanity, iirc.

What I really liked is the bdeck was 102” wide and the panels came in at 120x60 which allowed me to hand lay it all.

But, would not do it same way if I could save 80-90 pounds….

The boat, if too light, does not cut the water as well, so perhaps it is fine, but this delta is perhaps part of the bow extension need. No all of it; the boat works much better with more forefoot.

 

[brian eiland]

The boat, if too light, does not cut the water as well, so perhaps it is fine, but this delta is perhaps part of the bow extension need. No all of it; the boat works much better with more forefoot.

Do you have some pictures and/or other info on that cat of yours?

I'd be interested particularly of any of your opinions about containing/reducing any of the wave slap that can occur under the bridge decks.

 

[Fellies]

Its the first product ive ever seen that you can roll up under your arm and carry it home.

 

[fallguy]

Do you have some pictures and/or other info on that cat of yours?

I'd be interested particularly of any of your opinions about containing/reducing any of the wave slap that can occur under the bridge decks.

Bdeck wave slap is simple to avoid.

Minimum clearance at 6% of beam midship and citing @Ad Hoc 10% at the bow.

There are some caveats.

If the “midship” clearance is further aft from the bow; this reduces it.

If you avoid massive sea states; there is less likelihood to encounter.

If you install a forward trampoline, a webbed one means the boat can tolerate a blast of water better.

On my boat, I also added two vee shapes. The bottom of the bdeck is a mild vee of about 4-5” per 4’3” each side. The front is also veed.

Prior to the bow extension design offered by @Ad Hoc, the boat was pitching and the bdeck slammed one time in a nasty heaving boat wake.

Since then, no sea state has resulted in slam/shudder. I call it slam/shudder because the entire boat is affected by it.

Now, to be clear, my boat was 8.5” negative trim prior to the extensions, so it was way down and hobby horsing a horror.

The bow extensions keep the front of the boat higher sooner, if you will. So, while the 5-6%/10% rule is good general guidance, a longer distance to midships also helps.

A naval architect like Ad Hoc may have this pinned down to a harder science using length to midship.

This picture is best at hand photo, can’t really see the vees well. She sits on a lift aft end in so I can get another pic if I take a boat out. Maybe another day another thread.