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Microballoons and other mysteries

Old 05-06-2008, 08:01 AM
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Bluebrew
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Default Microballoons and other mysteries

Howdy folks, I'm wondering if some could enlighten me to some of the secrets of building in wood. My questions are glue and filler specific. I'll start with microballoons.After hearing about this product for years, I finally found some on the shelf at the LHS. I found the mixing instuctions confusing(3/1 MB to epoxy, by weight or by volume?) so I mixed a small batch of epoxy and added MBs till it was like white peanut butter.Filled a joint with the mix and set aside. Came back later to find the balloons settled to the bottom of the joint with a thick layer of clear epoxy above. Obviously I mixed it too thin. Is there a rule of thumb to make a good batch?
My next question has to do with a substance I encountered while sanding a hull someone else had built. It was some kind of filler that was light brown in color and had a powdery texture. I could tell by the way it was applied that it was a rather soupy substance before it dried. What ever that stuff was it sanded very easily and left a beautiful suface. I'm quessing something like thinned wood glue and baby powder?
Finally while working on the same hull I noticed a glue that was a pale orange in color that was used in places i would expect to see epoxy. Is this that ambroid stuff I've heard of, but have never seen? Is it sold under a brand name?
Thanks for any replies and insites to these mysteries.
Old 05-06-2008, 12:39 PM
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Default RE: Microballoons and other mysteries

I've read another build thread/forum of wooden hulls using just regular lightweight wall spackle .Fills any open joints and inperfections.Sands to contour real good also,of course this is if your going to glass the hull then paint.Havent tried it yet but seems to make sense and was quite successful judging from the completed model[s].Same build thread was using TiteBond to do some of the gluing along with CA and epoxy.Just used what made sense and when and where it was needed.
Old 05-07-2008, 12:41 PM
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Default RE: Microballoons and other mysteries

Thanks Blkft1, that sounds like a good no muss no fuss solution.
Old 05-07-2008, 06:51 PM
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Default RE: Microballoons and other mysteries

Bluebrew, I have used microballoons for years in building both airplanes and boats and can honestly say that I have never encountered the micro balloons coming out of suspension in epoxy. I get my supply from West Systems and try to avoid the over priced hobby shop offerings. It's the same product. When mixing micro balloons and epoxy for filling gaps, dings and filleting I make the mix relatively stiff. As in meringue. The mixture should not flow when left to sit in the mixing cup. This makes an easily sandable filler when cured. It will feather well and still have a strong bond. I like to use a "looser" (almost runny) mix of micro balloons and epoxy or cabasil and epoxy to stiffen the epoxy when I bond a block onto sheet stock or install engine mount rails as in a hull, so I'm sure the epoxy doesn't leave gaps in the joint. As for the easily sandable powder stuff you encountered. It sound like plain old sheet rock spackling. The hobby products people give it a fancy name and dye it tan to match the wood but the same stuff is available at the big box stores in larger quantities for less money. I have used spackling for many years also but exclusively on balsa wood and certainly not on something that will see water. It's water based and will soften and wash out with water. If you do choose to use it on a boat, take Blkft1's advise and cover it with fiber glass cloth and epoxy.
As for "glue" you should use slow set epoxy exclusively. Any thing else is either not waterproof or not fuel proof. Slow set epoxy by it name cures slowly, giving it a chance to soak into the wood and give a strong bond.
You will likely get differing opinions on these subjects but I can say that after over 50 years in modeling these methods work for me. There is no magic and no short cuts. There is a hobby shop in Connecticut called Build Right Fly Right. How true and in goes for boats too.

Old 05-08-2008, 07:36 AM
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Default RE: Microballoons and other mysteries

Thanks for your time and tips John. Strange thing about the batch of balloons I mixed was that what remained in the mixing cup was fine! I popped it out and it was a pure white block that sanded well.
I quess every builder has their own secret filler formulas[8D]. The lightweight spackle is something I'll try, sounds perfect.
I use 30 min. epoxy mostly and don't intend to change that habit, but I'm still curious as to what "ambroid" is.
Old 05-08-2008, 10:22 AM
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Default RE: Microballoons and other mysteries

Ambroid has been around forever it seems......

Old 05-08-2008, 04:48 PM
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Default RE: Microballoons and other mysteries

Bluebrew, Ambroid is an air dry, possibly lacquer based glue that as Kmot said, has been around for years. And I do mean YEARS. I used to use it for model airplanes when I was a kid. Smells real good if you're into that sort of stuff. Most builders favored it over Testor Cement and some of the other "model airplane" glues. We have a much selection of adhesives today. Especially for the harder woods like the plywood and spruce we use in boats. Although Ambroid may still be in favor with the stick and tissue builders that are looking for strong joints and light weight. And of course the GOOD SMELL!!
Old 05-09-2008, 12:15 PM
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Default RE: Microballoons and other mysteries

Hmmm... I have never seen that stuff in any LHS I've been in, and these were R/C shops not toy stores.
Another question, what is the advantage to finishing epoxy over regular...thinner, more open time? If I heat regular epoxy to thin it, how much time does that get me? I assume you heat the bottles BEFORE mixing. At this point I have two layers of .75oz. glass on the hull. It's a riverboat that has the deck overhang the hull all the way around so I glued the deck down after glassing the hull. Now I want to glass it once more to seal the deck top and bottom. After sanding I guess it's time for the "showcoat". It's gone pretty well so far, but I'm worried about goofing it after all this work!
Old 05-09-2008, 01:18 PM
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Default RE: Microballoons and other mysteries

Here's some good advice on thinning epoxy [link=http://www.seqair.com/skunkworks/Glues/WestSystem/Thinning/Thinning.html]West Systems[/link]
The light tan you have found could also be fairing compound, on the [link=http://www.westsystem.com/]West[/link] site as 410 Microlight.
For heating I normally heat the wood a little with a heat gun (hairdryer ok), thins the epoxy and really allows the epoxy to penetrate the wood.
Old 05-09-2008, 06:16 PM
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Square Nozzle
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Default RE: Microballoons and other mysteries

Bluebrew, I don't use the heating method to thin epoxy. I use denatured alcohol to thin it. My choice only, because I think it keeps it's thinned properties longer. I think once the heated epoxy hits the cool surface it resorts back to it's original viscosity very quickly and you loose the penetrating capability. Again, this is me. I may be all wet because I've never treid the hot epoxy trick. Thinned with alcohol, it stays thin in the mixing cup till it's all used up and remains thin on the wood or glass surface only a few minutes. However M3bby's heat the surface has some merit in my eyes.
Old 05-09-2008, 10:50 PM
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west ozzy racer
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Default RE: Microballoons and other mysteries

hi there guys . i see your talking about micro balls /baloons.
well over her in the west oz i use to use micro balloons but dont bother enny more . the best thing to use is just plane old talc talcen powder .or other wise knowen as baby powder .
i find it works just as well and a lot cheeper . and it smeels great to just like a new born baby.
and arent all owe projets new borns.

my lattest is a 50 mono hull. and then to take a pug of it .and incress its size to 60 inch or more .well thats a nother story.

happy building r/c fans........ .
Old 05-10-2008, 10:53 AM
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Default RE: Microballoons and other mysteries

Thanks so much for the great tips guys! That idea about heating the work is very interesting. Thinning the epoxy with alcohol sounds like the most stable timewise. I haven't been to the West Systems site yet today(thanks for the link), but i have checked it out in the past and I beleive they were wary of thinning epoxy(generic) because it could(not would) cause an extremely long drying time. Think I'll test a batch first!
I really like the baby powder idea! When I bought the bottle of balloons it was in a ziplock baggie! got it home and read the bottles warnings[X(].Must be bad bad stuff! I was very careful while using it! How bad can baby powder be for you!?

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