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Expandable Urethane Foam

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skip_dye

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Do the various 2-part expandable urethane foams (not the stuff in a spray can, but the stuff that is mixed together, i.e. Giant Leap's Mega Foam) on the market physically bond to the airframe, fins, etc.? Or do they just fill up the empty space inside an airframe to prevent compression/bending of internal components?

Thanks,

Alan
 
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billspad

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Do the various 2-part expandable urethane foams on the market physically bond to the airframe, fins, etc.? Or do they just fill up the empty space inside an airframe to prevent compression/bending of internal components?

Thanks,

Alan
The ones I'm familiar with bond extremely well to most anything including skin and clothes.
 
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Micromeister

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What Bill said LOL!!!
I did not realize that once you start using an aerosol can of expanding from the nozzle does not shut off until the can is empty.
Luckly I was in the kitchen when I started filling a BT-80 nosecone but still managed to coat a lot of stuff between the kitchen, back porch and back yard with foam.... What a mess LOL!!!!
The better 2/3rds and I spent much of the rest of the afternoon and evening cleaning yucky brown foam from all kinds of stuff.
 

rcktman

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I just use regular polyurethane glue mixed with a tiny drop of water. I have used it on airframes up to 3 inches in diameter.
 

quickburst

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Do the various 2-part expandable urethane foams (not the stuff in a spray can, but the stuff that is mixed together, i.e. Giant Leap's Mega Foam) on the market physically bond to the airframe, fins, etc.? Or do they just fill up the empty space inside an airframe to prevent compression/bending of internal components?

Thanks,

Alan
Like Bill says, yup it sticks to everything and it's really hard to get it off.
 

Viperfixr

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I've tried the cheaper of the two Giant Leap foam offerings, and it worked fine. The shelf life wasn't as long as I expected, and I ended up throwing half of it away.

I then tried the PML "adjustable" foam. I've got to say I like it a lot better. The shelf life issues don't seem to be nearly as much of a problem, and the adjustable property is a great option, high density/low volume or vice versa and anywhere in between.

Either one sticks to anything--for good. It adds very little weight, and makes fin cans very solid. If nothing else, it's easy to do and gives my overbuilding tendancies a productive outlet!
 

nburns

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I have the PML foam and am very happy with it. I bought it about 2 years ago and just used it again last week and it worked great.

Nate
 

jj94

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I got some of ProLine's expanding foam (from Wildman) and I love it. It expands a bit slower but then I think of that as a convenient characteristic, you have more time to work with it. Once it's dry, it's very sturdy and hard.
 

ben_ullman

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my dad bought 2 5 gallon buckets of the US composite stuff and filled his 10" Nike Smoke nosecone. It works great.

Ben
 

ClusterNut

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I am planning to use foam to fill a nose cone in order to secure ballast. I am looking at the PML expandable foam mentioned above. I also noticed this product: Pourable Flotation and Insulation Foam, Closed Cell Rigid Foam by AeroMarine Products. It is used for boating I presume. Anyone have any knowledge of it?
 

Derek

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I used the pml stuff for the first time this weekend. that stuff sticks to everything!

make sure you wear gloves!
 

ClusterNut

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I had heard that. This other stuff is supposed to be just as messy. I am considering some alternatives as well.
 

SAC of MMMSClub

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I am planning to use foam to fill a nose cone in order to secure ballast. I am looking at the PML expandable foam mentioned above. I also noticed this product: Pourable Flotation and Insulation Foam, Closed Cell Rigid Foam by AeroMarine Products. It is used for boating I presume. Anyone have any knowledge of it?
I use some A+B foam from a Hardware store that is more about boat and glass stuff than anything else, and it works very well slow expansion and sticks to everything.

It was so no name brand it did not even have directions, just an A and a B on the cans. You should be able to add a drop of water or two to any A+B foam.

I have placed BBs in nose cone injected Part A and then Part B and rattle it around and soon the reaction starts. I found that oral syringes work good for getting A+B in the hole in the NC.
 

SAC of MMMSClub

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Do the various 2-part expandable urethane foams (not the stuff in a spray can, but the stuff that is mixed together, i.e. Giant Leap's Mega Foam) on the market physically bond to the airframe, fins, etc.? Or do they just fill up the empty space inside an airframe to prevent compression/bending of internal components?

Thanks,

Alan
Assumedly you have fin tabs and TTW fins in this scenario? I drill lightning holes in the fin tabs and internal centering rings to allow the foam to pass through and encapsulate the parts more.
 

ClusterNut

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I have placed BBs in nose cone injected Part A and then Part B and rattle it around and soon the reaction starts. I found that oral syringes work good for getting A+B in the hole in the NC.
How did you compute the amount needed to fill the NC? Or did you go a bit low and then top it off after? I am wondering if I can get away with a BB/epoxy mix, followed by stuffing with a light weight packing material after it sets and then sealing with epoxy. :confused:
 

SAC of MMMSClub

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How did you compute the amount needed to fill the NC? Or did you go a bit low and then top it off after? I am wondering if I can get away with a BB/epoxy mix, followed by stuffing with a light weight packing material after it sets and then sealing with epoxy. :confused:
I have filled several nose cones and found ten cc of A and ten cc of B filled a BT-70 nose cone from apogee. It just started to come out hole then stopped.
 

tonka

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It was so no name brand it did not even have directions, just an A and a B on the cans. You should be able to add a drop of water or two to any A+B foam.
What does adding a drop or 2 of water to the mix do? I know with the single component foams it will aid in curing, but what does it do to an A+B mix?
 
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tonka

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Assumedly you have fin tabs and TTW fins in this scenario? I drill lightning holes in the fin tabs and internal centering rings to allow the foam to pass through and encapsulate the parts more.
I've quit foaming the fin cans, it added weight at the wrong end of the rocket and while the fin can felt stronger most of mine broke just as easily as those that weren't foamed. Other reinforcement methods seemed to make them much stronger without as much of a the weight penalty, and Rocketry Materials testing seemed to bear that out as well.
 

AZ_Ron

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I've used 2-part foam in my fin cans since the late 90's. I'm a 100% believer in it. The proof in the pudding for me was a new 4"/54mm rocket I built.
Built it with Phelxible Phenolic tubing from Red Arrow Hobbies and 1/8" G10 fins. Flew it on a baby 'L' motor I'd made, had an early deployment, which unfortunately zippered
the booster all the way to the top CR. I had NO fillets of any kind on this rocket. I'd tacked the fins in with some 15 minute epoxy, then 2-part foamed
from the top CR to the bottom of the booster. Well, I knew the airframe was a loss, but I wanted my G10 fins so I could build another booster.
I swear to all of you, this is the truth... It took me about 45 minutes to get the 3 fins out. I was beating on the airframe with a hammer at one point, just
trying to break the bond. Once I finally got the fins out, I sanded the foam off (Very easy), stuck them in a new booster and off I went.
I've flown 4" rockets through Mach more than one with no fillets, just foamed boosters. I DO rough up the hell out of the G10 where it is inside the
airframe so there's good bite for the foam. Work great when I use ply for fins as well. I try not to go through Mach with ply fins. :)

R
 

CarVac

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What does adding a drop or 2 of water to the mix do? I know with the single component foams it will aid in curing, but what does it do to an A+B mix?
I've never tried it with any random foam, nor have I used the foam in question, but PML's foam expands more and turns out less dense when you add a few drops of water to a particular one of the parts (I don't know which) before mixing.
 

Derek

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I don't think it really matters when you put the drops of water in, but it is easiest to add them after a before you mix b in. this way you are not wasting valuable seconds futzing with adding water drops.
 

BEAR

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I do not know if this will really add anything, but possibly laughter. I have put too much expanding foam into empennages on some RC planes. I poured too much in and it expanded 25 times or more and blew it apart. Then I had the building pleasure to do it over. Gee what fun. It will really warp wings too. I do love the stuff, but it takes some practice. I have also used Great Stuff in the aerosol cans. I think it works well, and the stuff I bought at Wal-Mart or Home Depot has a valve on top so that you start and stop the flow at will.

When I ran the shipping/receiving department for the helicopter shop, we would ship out things that needed to be packed really well and had to avoid damage at all costs. So I would buy the A and B components in 55 gallon drums. (Thought here, if you watch closely, you can find these expanding foam set-ups used and at deep discounts. Maybe a club might want to go in and buy one it if there is a need for such a massive amount) One of the side effects of mixing this foam is heat generation. So much heat that it will burn your skin. When it starts smoking and burning your skin, you flinch. When you flinch, you move off your target. When you move off your target you leave a trail of super hot, super sticky adhesive sticking to everything. Sticking to things that you would have never thought of, like, concrete floors, foam rubber floor mats, chairs, stools, desks, chain link fence, steel columns, steel beams, rolls of paper, fork trucks, computer monitors, key boards, mouses, 1000' rolls of plastic tubing, melting though it and destroying great amounts .What an incredible mess that does not clean up easily. WOW. WHAT A MESS. Super cool stuff. Takes great preparation. We used a 2 mil Mylar like plastic film that came in 2 and 3 foot wide rolls. You use this to wrap the inside a of your shipping box/crate/container, protecting the inside of your carton so that you can get your product out easier; and to wrap the component that you are shipping like a main rotor head or blades or gyros, etc., making sure there are absolutely no cavities that this stuff can force it's way into, and then spray in your foam. After some serious expansion, some serious shaking and bouncing around, some smoke, and a source of heat on a cold day, you have packaging with foam inserts that will not allow any movement. Tremendous product. You do have to do a bit of forward thinking on how you do this, because if you do it wrong, you will have to cut your shipment out of it's container which is not always easy. I found the safest method was to package my contents in plastic, seal it so that nothing can get through this barrier, then put my mylar film around this before I put in the foam. If it leaks through your barriers, you've got some serious issues.

I hope this has entertained you. I know the entertainment for you was not as much as I had in the first hand experience. LOL (Lot's of Luck, beside the Laugh Out Loud or any of the other variations.
 

AZ_Ron

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One of my best friends related one of his early experiences with 2-part foam to me a long while back...
He was building a 5.5" Phoenix, Dinner was just about ready, so he mixed up a large batch, poured it in, and went
inside for dinner. When he came back out to the garage, he phoenix was nowhere to be seen... just a big, huge
blob of crap sitting where he left the Phoenix. He'd used so much, that as it boiled up and expanded, the
top stuff started to cure and harden while the stuff in the middle was still expanding. Blew out the side of the rocket,
and just expanded all over it like the Blob... ;) Learning from his lesson, I've never had that happen to myself.
I thought I'd share it so hopefully anyone reading this will avoid the same fate.

R
 

BEAR

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I believe that if you are doing a large pour, it needs to done in stages, like pouring concrete. It is done in steps. Therefore, you pour a small batch and let it expand and set, then pour another layer and repeat the process until you have the area filled that is to be filled. If you pour all at once and one layer expands and sets in a void that is still being filled, you will at the least have an air pressure issue at work, and the worst case will be the foam itself building up the pressure and blowing your rocket to pieces. Foam under pressure becomes extremely rigid. I once built some cabinets for a lady who lived in Houston. We have big cockroaches down there that can crawl into the smallest of places. Thes cabinets were going to be lag bolted to the wall to keep them from moving. To keep the space between the wall and the back of the cabinets from being a hiding place for the roaches, I was going to place a 4' X 8' by 1/2" thick piece of foam rubber in the space and using the lag bolts, put the foam under compression so it would fill all the voids. I used 1/2" by 4" long lag bolts and used my 1/2" drive ratchet on them and broke every bolt. I ended up securing the cabinets without the foam and it worked fine for the anchoring, but I could not do it using the foam rubber; it offered too much resistance. Expanding polyurethane foam or any other will do the same thing. I learned a lot on that project.
 

Boosterdude

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I was wondering how you guys are putting the foam in a fin can. Do you install the rear ring with a hole that you use to pour it in so expands up to the ring? Or do you use another method?
 

Derek

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I was wondering how you guys are putting the foam in a fin can. Do you install the rear ring with a hole that you use to pour it in so expands up to the ring? Or do you use another method?
I didn't install the rear ring. I left it out and injected the foam with a syringe. you need to tape up the mmt and anything else you don't want foam in or on. afterwards, cut off the excess foam and fit the rear centering ring if you choose. I didn't but I did fill the gap with some epoxy just to pretty it up a bit.
 

AZ_Ron

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I do it very similarly to Derek... I'll epoxy the MMT in with just the forward CR epoxied to the MMT... The rear CR is just sitting in place to center the
assembly while the epoxy cures on the top CR. Then pop the rear CR back out, tape off the MMT opening, and either inject or pour the foam.
If there isn't 1/2" area between the MMT and inside of the airframe to fill with foam, I probably wouldn't bother. It's best when there's some
mass to it. I did it once on a Vulcanite (54mm airframe/38mm MMT) very small gap, very small fin surface area inside airframe.
Didn't hurt, but I'm not sure how much it helped. 4" Airframe/54mm MMT's, this technique really shines!

Once the foam is cured, say (15-30 minutes tops), I use a razor saw, or just a hack saw blade, to cut the foam off level with the aft end of the rocket
(It will expand up and outside of the airframe) then using a sanding drum on my dremel, I'll 'route' the foam out of the aft end down to the very bottom
end of the fins. Pour in a bit of epoxy, and then permanently install the aft CR.

I have built a few rocket before that I never installed the aft CR in. It isn't needed, unless you use it for mounting your motor retention hardware. The heat from
the motor will singe the foam a little bit, but there's no detriment to it. Also like Derek did, you can just pour in a thin layer of epoxy to just cover the foam.

R
 
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