Thread Tools
Jul 18, 2012, 09:40 PM
Registered User
Thread OP
Discussion

WBPU info


Hey guys,

I'm relatively new to the world of foamies and have some questions about WBPU(Water Based Polyurethane).

I understand people use it to make their foamies stronger but what sort of foam is it suitable to use on. Does it work on EPS, Depron and so on.

Also what is the deal with using matting with it. Is this similar to using fiberglass.

If there is any links to information about using it then that would be great because I did a search and couldn't really find what I was after.
Sign up now
to remove ads between posts
Jul 18, 2012, 10:12 PM
treefinder
springer's Avatar
It works on all the styrenic foams like fanfold, eps, depron, Dollar store foam, and MPF. You can just brush a couple coats directly on the foam to provide a stiffer, paintable and somewhat more damage resistant surface. (I use it when I want to paint a specific color, like OD for WWll planes). Or, if you are looking for water proofing, and more damage resistance, then use Fiberglas cloth (the light weight type), Polyester cloth (I think it's lining material, and there are at least two weights) or even paper. I found that coffee filters (the corrugated circular ones) make a very nice smooth, waterproof and dent resistant surface that is paintable with any kind of paints we might use. Once coated, I use Walmart rattle can spray paint. This treatment works well for water planes to waterproof the "hull". It's also a good base for the colored packing tape that's used for color. My OSS Seabee is done that way: wbpu and filters as a base and over coated with red packing tape.
Jul 18, 2012, 10:25 PM
Registered User
Thread OP
Hmmm sounds good.

Does it matter how thick or thing you apply it. Does it not eat the foam away.

Do you need to sand between coats to get a nice smooth finish.
Jul 18, 2012, 10:33 PM
Build straight - Fly twisty
Whiskers's Avatar
And it is a good glue. I discovered that fact when i found the lid of the can became so well glued on that I had to destroy the lid to remove it. Now my WBPU is in a glass jar with a piece of plastic under the screw-top lid.
Jul 18, 2012, 10:44 PM
Snipe the Skies!
snipeworm's Avatar
It is a water based product so there is no fear of melting the foam. It does offer rash resistance but finishing epoxy offers better rigidity. The epoxy is a little harder to work with but as stated earlier, applying light fiberglass or cloth ads a light of strength at low weight cost. I have used the wbpu to apply the cloth and it does offer more strength but doesn't cure as rigid as the epoxy, still a little bit flexible.
Jul 18, 2012, 10:52 PM
Registered User
Thread OP
I do like the sounds of this stuff then.

Whiskers. Being from Australia what brand of WBPU are you using.
Jul 19, 2012, 01:01 AM
Registered User
Another great way to reinforce any foam is to apply 5mm silk using WBPU.
The silk is fantastically strong and light and conforms very well to compound curves.
Just brush it onto the surface by applying WBPU through the silk and smooth it down with your hands. Plastic gloves are useful here.
I use really cheap EPS foam to scratch build and the silk gives a good finish.
Jul 19, 2012, 02:10 AM
Build straight - Fly twisty
Whiskers's Avatar
Quote:
Originally Posted by NOI53Y
I do like the sounds of this stuff then.

Whiskers. Being from Australia what brand of WBPU are you using.
Good question!
I bought it at Bunnings, but I forget the brand.
Like I said, the can glued its lid on so thoroughly that I destroyed the lid after a few brutal openings. So the WBPU went into a jar and the tin went into the bin.
Jul 19, 2012, 02:22 AM
Build straight - Fly twisty
Whiskers's Avatar
Quote:
Originally Posted by baz49exe
Another great way to reinforce any foam is to apply 5mm silk using WBPU.
The silk is fantastically strong and light and conforms very well to compound curves.
Just brush it onto the surface by applying WBPU through the silk and smooth it down with your hands. Plastic gloves are useful here.
I use really cheap EPS foam to scratch build and the silk gives a good finish.
Just a note here! That is not a great big slab of silk 5mm thick. No! It is very fine silk as seen in super light scarves.
Silk is measured in Mommes, and this is pasted from Wiki.

Mommes (mm) are units of weight traditionally used to measure the surface density of silk. It is akin to the use of thread count to measure the quality of cotton fabrics, but is calculated in a very different manner. Instead of counting threads, the weight in mommes is a number that equals the weight in pounds of a piece of silk if it were sized 45 inches by 100 yards. This is because the standard width of silk is 45 inches wide, though silk is regularly produced in 55-inch widths, and, uncommonly, in even larger widths.
Jul 19, 2012, 06:58 AM
Registered User
Thread OP
I'm glad you cleared that up Whiskers because that didn't make sense at first hahaha

I'd imagine silk would be a fair bit more expensive than if you were to use a fine weave fiberglass mat. Do you think that would be a fair assumption.
Jul 19, 2012, 09:33 AM
treefinder
springer's Avatar
One thing you need to consider is the plane type and intended use. If you're doing a slow trainer type that may be expected to be repaired frequently or wanting minimum all up weight then minimal treatment is best; perhaps just sharpie marker colors for orientation. If you are doing a scale plane with some detail, a waterplane or just want a sexy paint job, then the treatments noted are good to use.
Jul 19, 2012, 05:15 PM
Registered User
Thread OP
Hello Springer. Yes indeed, I'd only use this method on something of a reasonable size and yeah something I want a bit of detail on or a like you said a nice paint job.
Jul 19, 2012, 10:09 PM
Registered User
wizard of odd's Avatar
Hi

You can use Cabot's Carbothane from Bunnings- it's water based poly-urethane floor varnish. Otherwise use Deluxe Materials Eze-Kote, (as well as lightweight FG cloth), which is available from this http://www.christiantraders.com.au/c.../en-us/d1.html Australian vendor.
Jul 19, 2012, 10:46 PM
Build straight - Fly twisty
Whiskers's Avatar
I think it is the Cabot's product I have.
Jul 20, 2012, 10:02 PM
low tech high tech
vtdiy's Avatar
And, I never tire of pointing out, most people in the states on these forums mean acrylic varnish when they say WBPU, NOT water based polyurethane (as you Australians are using). Because they call Minwax Polycrylic "WBPU".

It isn't. Never was. never will be, polyurethane..

Somehow the "poly" in the trade name became more fashionable to say then the "crylic". The poly refers to "polymer" (an old name for acrylic paint) NOT polyurethane. Polyurethane and acrylics are very different finishes with very different properties.

If you are outside of the national selling range of "Minwax Polycrylic" and you want to try an equivalent, either go to an art store and purchase an acrylic varnish (used to protect acrylic paintings), or failing that, acrylic medium in the same store, or failing that too, go to a paint store and buy some deep tint base for exterior acrylic (called also "latex" in the U.S.) house paint.

The deep tint base is usually clear with no added white pigment. Well it looks milky until dry, like all acrylic mediums, then turns water clear. It is intended to be mixed with pigments (colors) to yield non-pastel shades. The other mixing bases (unlike "deep" base) all usually have more or less white pigment mixed in with them. They are for producing lighter shades.

True water based polyurethanes are dispersions in water, all are usually somewhat amber in hue by comparison with acrylic varnishes, and they will yellow more as they age.

Hope that helps clarify for those outside the US what people mean here by WBPU. They mean acrylics.

I'd love to see the term WBPU dropped, but people love acronyms.


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question Can I use a spray can enamel over WBPU? snipeworm Foamies (Scratchbuilt) 13 May 18, 2012 03:32 PM
Discussion finishing up edf foam - wbpu and fiberglass cloth le fou Foamy EDFs 2 Apr 23, 2012 01:09 PM
Question WBPU and Construction Paper snipeworm Foamies (Scratchbuilt) 4 Apr 19, 2012 10:13 PM
Rip Stop Nylon instead of fiberglass with WBPU GliderGuider Scale Kit/Scratch Built 2 Sep 15, 2002 10:11 PM
Question about glassing with WBPU... please help. NetForce2K Foamies (Kits) 3 Jul 25, 2002 10:20 AM