What type of foam board works with Poly?

[Mark42]

I just mixed up some polyester resin and tested it on the rigid pink foam insulation board available at the home centers. It melted it. Just poured a spot the size of a half dollar and before it set, it was bubbling as it slowly melted into the foam.

Also tried some on a piece of old foam cooler (compressed balls style) and it melted it too. Same with a foam disposable dinner plates. In fact, every piece of foam I could find in my house melts when in contact with polyester resin.

So, what type of foam board do I have to ask for at the supply house to get something that will not melt? What do they make surf boards out of?

Grrrrr.. This is frustrating.

 

[Mark42]

Re: What type of foam board works with Poly?

Dummy me. I just did a search on "surfboard blanks" and found that the surfboard foam used with polyester resin is polyurathane foam.

Now to call the supply house to see what dimensions it comes in to start making the hard top for my Bayliner.

 

[drewpster]

Re: What type of foam board works with Poly?

Mark, did a google search using the term 'marine foam'. Here is a supplier.

http://www.mertons.com/Floatation/scored_foam.html

http://www.fiberglasswarehouse.com/core_foam.asp

You may also want to research 'vacuum bagging techniques'. It is a process for laminating foam cores using fiberglass. It involves covering the wet glass part in plastic wrap basically and using a vacuumed pump to vacuum the resin and fiberglass to the part. The part comes out super and with complete lamination. It would be simple to do on a flat panel.

 

[KnottyBuoyz]

Re: What type of foam board works with Poly?

Most foams used in marine cores are as you mentioned polyurathane foams or SAN foams. Name brands that come to mind are Core-cell, Kledgecell, Divinycell. Most are engineered to use epoxy based resins as opposed to Poly or vinylester resins. You'd have to check with the mfgr. Although you're likely to pass a 3" gall stone when you see the price of the stuff.

There are also honeycomb materials that are suitable for marine use but they require different working methods to finish the edges and splice the panels together. The pink & blue insulation boards from Lowe's etc. are styrofoam and any resin containing "esters" will eat it up. Here's what a test of styrofoam (blue stuff from Lowe's) looks like when infused with epoxy resin.

You'll notice that the laminate failed. The epoxy bonded to the styrofoam but the foam itself failed. Foams engineered for structural purposes are not that weak.

Hope that helps.

Rick

 

[drewpster]

Re: What type of foam board works with Poly?

Here is a link to a good article on bagging. I would like to try it myself. The was a guy recently that posting a bagging project in the forums. He used a plywood base with a tire stem through it. He placed the part on top and used plastic poly sheet (in a roll at home center) to cover the part taped to the board. He used a vacuum pump to draw through the tire stem. Cool setup and looked simple once he got it together. The advantage is the ability to laminate multiple layers all at one time. No waiting for cure, then sanding, putting on another layer, blah , blah. Just suck it flat and wait for cure. You can also do both sides of a part at one time! Sounds cool to me.

http://www.fibreglast.com/contentpages-Vacuum%20Bagging%20Equipment%20and%20Techniques%20for%20Room-Temp%20Applications-230.html

 

[KnottyBuoyz]

Re: What type of foam board works with Poly?

You may also want to research 'vacuum bagging techniques'. It is a process for laminating foam cores using fiberglass. It involves covering the wet glass part in plastic wrap basically and using a vacuumed pump to vacuum the resin and fiberglass to the part. The part comes out super and with complete lamination. It would be simple to do on a flat panel.

Yup vacuum bagging & vacuum assisted resin transfer molding are hobbies of mine. We're building a sufficient knowledge base to allow us to build our own boat using those methods. Here's what a small part looks like laid up ready to infuse.

And here's what the finished part looks like.

This was just one half of a sump hole cover. Sorry not very sexy but it was part of the learning process. Vacuum bagging and infusion aren't that easy to achieve good results without a lot of practice. I know I've got plenty of "epoxy art" items kicking around the shop! With practice though they can produce superior laminated parts.

 

[drewpster]

Re: What type of foam board works with Poly?

I saw some suppliers listing balsa core sheets that were very reseonably priced. Would that work?

 

[drewpster]

Re: What type of foam board works with Poly?

Is infusion and bagging the same thing? I though infusion is where resin is drawn on to the part. Different from regular bagging, yes?

 

[KnottyBuoyz]

Re: What type of foam board works with Poly?

I saw some suppliers listing balsa core sheets that were very reseonably priced. Would that work?

Balsa is quite common as core in boats. It again requires special handling to ensure a thorough infused part whether with vacuum bag, hand lay up or infusion.

The core material doesn't actually add much strength to the panel. What happens is the core holds two layers of a reinforcing fabric apart. That's where the term "sandwich panel" contstruction comes from. Think of a cross section of the panel as an I-beam. We all know how strong they are. Well the core is the web of the I-beam and all it really does is hold the two tops of the I's apart. When stressed one will be in tension and one in compression. It's the opposition to these two forces that gives the "laminated panel" it's incredible strength many more times that of the original components.

http://www.compositesworld.com/ct/issues/2003/October/238

 

[KnottyBuoyz]

Re: What type of foam board works with Poly?

Is infusion and bagging the same thing? I though infusion is where resin is drawn on to the part. Different from regular bagging, yes?

Yes two different methods.

In vacuum bagging the part is laid up then saturated with resin. A peel ply (porous) layer is put on top then a layer of breather material is laid on top of that. The entire layup is then enclosed in a vacuum bag and the air is vacuumed off. The vacuum bag is essentially a vacuum press. When it is compressed the excess resin passes through the peel ply and is absorbed into the breather material. The part is left in compression until the resin hardens.

With infusion the part is laid up almost identically w/o the breather. A resin inlet tube is inserted into one end of the vacuum bag and the vacuum outlet is at the other end. You can see that in the picture I posted. Once you have the bag under full vacuum you open the resin inlet and the resin will flow through the layup towards the vacuum outlet (hopefully) this is where the experience comes into play. You have to be able to predict how the resin will move through the layup. There are other materials used, flow media, to help that process along.

Here you can see a flat panel being infused. The resin inlet is on the right. The resin moves along the part towards the vacuum outlet on the far left off of the pic. The part is left under vacuum (which is the hardest part of the whole process) until cured.

This site gives a much better explanation of the benefits of both systems.

http://www.fram.nl/workshop/controlled_vacuum_infusion/cvi.htm

You can see video's and simulations of the infusion process on the hulls of a foam core trimaran. It's quite informative.

 

[Mark42]

Re: What type of foam board works with Poly?

Thanks for posting all that info. I have been browsing those retailers and the price of foam is outrageous! I think the 1/2" balsa would work fine. I can glue strips along edges where it needs to be 1" thick. The price is much less than the foam, and being a part that will (hopefully) never be below the water, being balsa (in case of a break and water absorption) is not a problem.

Another aspect of using balsa over foam is that balsa works great with polyester and vinylester resins, and that means lower cost resins, and lower cost finishes like gel coat. If I went with those foams, epoxy is prefered and that means higher costs and fewer choices for finishing products.

I think I will pass on trying the vacuum bagging. It would take me longer to learn the technique than to just use traditional layup methods.

BTW, Do you think that two layers of glass, inside and out, would make the 1/2" balsa (with 1" perimeters) strong and rigid enough? Or plan on 3 to 4 layers?

 

[KnottyBuoyz]

Re: What type of foam board works with Poly?

Thanks for posting all that info. I have been browsing those retailers and the price of foam is outrageous! I think the 1/2" balsa would work fine. I can glue strips along edges where it needs to be 1" thick. The price is much less than the foam, and being a part that will (hopefully) never be below the water, being balsa (in case of a break and water absorption) is not a problem.

Another aspect of using balsa over foam is that balsa works great with polyester and vinylester resins, and that means lower cost resins, and lower cost finishes like gel coat. If I went with those foams, epoxy is prefered and that means higher costs and fewer choices for finishing products.

I think I will pass on trying the vacuum bagging. It would take me longer to learn the technique than to just use traditional layup methods.

BTW, Do you think that two layers of glass, inside and out, would make the 1/2" balsa (with 1" perimeters) strong and rigid enough? Or plan on 3 to 4 layers?

Hey Mark

If you use balsa make sure you seal all the exposed edges etc. If you have to drill into it to attach something, over drill, fill the hole with thickened resin, let it set, then redrill. This will keep water out.

Yes vacuum bagging and infusion take time (and money) to learn but can result in a far superior product. For a one-off hard top it's not worth it.

What kind of glass? Biaxial fabrics are far stronger. One layer of 1208 or 1708 biaxial fabric will be stronger than 3 or 4 layers of a lighter woven fabric. If you're not going to dance on your hard top you can cut back on the glass/resin and make it lighter but just as strong. The downside to the biaxial fabrics is you'll have some fairing to do to get an acceptible finish.

Have you considered 1/4" marine ply? Not much of a weight penalty over balsa especially if you use biaxial fabrics.

Gelcoat isn't really a paint. You'll have a tough learning curve to get an acceptible finish trying to use it as such. Look for a good quality Polyurathane paint such as Interlux Bright Side (or similar). Roll & tip method produces a good extremely durable finish. There are others though.

 

[redfury]

Re: What type of foam board works with Poly?

So, what is closed cell poured foam then ( I haven't tried googling )...

I was thinking I could pour 12lb foam into the open stringers I have now and then glass over what I have existing....my concern being that the foam is there to provide the shape I want ( and something that won't leave any hard spots in the bottom of the hull ), not necessarily the strength I need as the fiberglass would be the strength of the stringers....

 

[KnottyBuoyz]

Re: What type of foam board works with Poly?

The poured two part foams are for flotation. They won't give you anything for structural support.

For a structural repair to stringers or a transom check this out...

http://www.seawolfindustries.com/seacast.html

 

[redfury]

Re: What type of foam board works with Poly?

Seacast is already in the books for the transom, but I just can't justify the cost for my stringers, besides the fact that I want to keep my weight down.

If the pourable foam ( closed cell ) will bond to the old fiberglass, and not melt when I get resin on it when laying up over the old stringers, then I'll be happy with that.

Besides, there is pourable foam that is hard enough that you will be pressed to put a fingernail print into if you want something super rigid/dense.

 

[Mark42]

Re: What type of foam board works with Poly?

....Have you considered 1/4" marine ply? Not much of a weight penalty over balsa especially if you use biaxial fabrics.

Yes, that was my original plan. Use 1/4" luan with ripped 1x1 fir for parimeter then cover with 2 layers of glass. Then I got worried about the weight, and started looking into foam.

I think I may be over-engineering this . A large percentage of the surface will be lexan or plexy windows. So there is not much frame and solid surface. It may be easier, quicker and cheaper to go back to 1/4" ply.

Next is a corrugated cardboard mock up. Then I'll know just how much wood will be needed. I took measurements today. The length of the side is 62" long and 27" high. Probably 2/3 of that window.

I'll see after the cardboard mock up is done.

 

[kalla man]

Re: What type of foam board works with Poly?

Mark , check my link below and look at my live well construction pics. Its called "R-MAX" I got from homedepot. Like 7$ for a drywall sized piece. the board had foil on both sides, in order remove the foil in one clean pull i used the heat gun on the low setting and warmed the foil up as I was pulling it off. (could prolly use a hair dryer). it worked VERY well with polly resin and mat/cloth and bonded extremely well. good insulator too!!

 

[drewpster]

Re: What type of foam board works with Poly?

kalla man may be on to something here. I did a little research and found out that R-Max is made of polyisocyanurate foam. This foam is mentioned in an article I found about foam cores used in the marine industry. I have not read the complete article yet. I did see where polyisocyanurate foam is mentioned along with polyurethane foam in board form. This could turn out to be a good source for some inexpensive core material in light marine construction projects. The links to the sites I found are below. Chime in kalla man,

http://www.boatdesign.net/articles/foam-core-properties/index.htm

http://www.rmaxinc.com/Sheathing%20Products.htm

 

[i386]

Re: What type of foam board works with Poly?

Mark , check my link below and look at my live well construction pics. Its called "R-MAX" I got from homedepot. Like 7$ for a drywall sized piece. the board had foil on both sides, in order remove the foil in one clean pull i used the heat gun on the low setting and warmed the foil up as I was pulling it off. (could prolly use a hair dryer). it worked VERY well with polly resin and mat/cloth and bonded extremely well. good insulator too!!

Cool! I will have to remember that if I decide to get creative with my project boat.

 

[Mark42]

Re: What type of foam board works with Poly?

Ohhh! Out standing information! I'm going to stop at the Depot and check this stuff out on my way home.

The one artical said this stuff was "friable" (deteriorates with time), but it didn't say what the time line was. I'll assume because it is a home building product, it should last the life of a typical home. (probably a poor assumption on my part- hee hee).

Thanks for the follow up!