Expanding Foam (split from Launch Pad topic)

[Warren B. MusselmanModerator]

If you’re going to do the syringe thing, don’t draw it back into the syringe, get the syringe all set, remove the plunger and then fill the barrel directly, reinsert the plunger and go. You really don’t have the time to do it by drawing up into the syringe. Pour and plunge immediately.

Warren

[denverdoc]

Warren,
Makes sense tho I was taught never to do so for other reasons. We actually got it to work pretty well as w/o the fill tube, you can draw thru it up pretty quickly–at least in a 60cc with the nozzle nipped. Took some trial and adventure, amazing stuff.

PS off topic but I recently tried the Devcon 60 sec epoxy today for tacking on fins. When used with one of the 2 mixing chamber needle nose extensions supplied, worked fabulously. A big honking fin was tacked in place w/in 90 seconds. I know CA can be used for this but I don’t like mixing adhesives for some likely irrastional reason. Not as good when merging puddles. the othe rproduct (man I love/hate McGuckens–always buy more than intended) is an epoxy putty sandable w/in 20 minutes. Worked well.
John S

[Robby]

I’m looking for the right expanding foam application for my “Estes size” rocket project that has some 1/4″ gaps. -Any suggestions?

-Robby

[Warren B. MusselmanModerator]

A 1/4″ gap would be something I would try to resolve with epoxy or sandable filler. Foam would be great in between the airframe and the motor mount tube as a filler. If you have a visible gap in the airframe, the foam will expand out of it after pushing it out of shape. If you have a big gap along a fin root, use PC7 Epoxy or one of the other thick paste epoxies first to close the gap before putting in foam to fill the fin can.

Warren

PS: I may have totally mis-visualized what you’re talking about here, so if I have, just ignore me – won’t be the first time I’ve said something without knowing exactly what I’m talking about.

[Robby]

Warren,

Having never used expanding foam before, I imagined that maybe there was a brand out there that would be useful as lightweight filler for small rocket projects. Maybe it is not lightweight at all, I don’t know. I realize that most “high power flyers” use this application in between the body tube and motor mount.

I’m thinking of using the foam in a gap 3″ long with a girth of 16mm that is inside the forward end and hard to reach. I would say It’s inside the nose cone, but it is unique and not a typical nose cone. The foams’ purpose is to not let the gasses go in the 2 gaps and cause unneeded stress in the form of pressure. I would like that pressure to flow uninterrupted out of the cockpit releasing the window. I figure if it’s hard to reach use foam, but using sandable filler looks like a good option. What’s the weight difference compared to foam?

-Robby

[Warren B. MusselmanModerator]

Sandable filler is probably 5 to 8 times the density of foam… I’m speaking of the Elmer’s or other sandable wood filler. I’m really having a hard time visualizing what the application is. You can send me a Rocksim file at wbmussel@indra.com or post a picture in here if you’re savvy enough with forums and how that works.

Warren

[slipstick]

What is the density of the foam, or through your before and after measurements, how much weight did it add tothe rocket?

[Warren B. MusselmanModerator]

hard to predict and depends on the foam, how carefully mixed, how much space to expand. Weigh the liquid before you mix it, mix and pour. You can figure the density by figuring the total weight divided by the volume.

Warren

[Doug GerrardParticipant]

What is the density of the foam

Expanding foam usually comes in 2 lbs/cubic ft to 16 lbs/cubic ft depending on what you buy.

Doug

[Bruce R. Schaefer]

Well, I had always used a little bit of the GLR expanding Mega-Foam at a time, but not today… was doing two things at once… looked up from working on my av-bay only to see foam foaming out of my nose cone… the panic hits, and a realization that I never read what counteracts it in the instructions and probably never will. Paper towels and rubbing alcohol and a putty knife are grabbed while cursing under my breath… first clean it off the deck and a quick rationalization that I’d have to paint it this spring anyway… hands full of foam into the trashcan on the porch… on and on it goes… getting it up and off everything as best I can, realizing that I haven’t grown up at all from the time I tried to clean my messes before my parents got home, now it’s before my wife gets home… more cursing and cleaning up… I’ll never do things like this too quickly again, yeah right… I cleaned it up as best I could and set it in the garage. Tomorrow I will praise whoever invented sandpaper… what a mess!

[Author]

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