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Liquid Foam?

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stealdesk

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I am building a PML Black Brant VB 38mm
I want to fill the fin can with foam , What is the best to use for this? I will be using this for my L1 cert. later on but for now will be flying on G motors. I want to be able to get the foam localy like a hardware store or as such.
 

r1dermon

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i had this stuff called tuff stuff i think. medium expansion. dont apply too much if you get this stuff though, it'll expand with force and could crack through your fin can, if its not like...CF or something.
 

rstaff3

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The 2-part liquid is much better than the spray cans you get at hardware stores. The latter requires moisture to cure and is unpredicable. I don't know of any hardware stores that carry 2-part foam, but a boating supply place probably will. I bought mine from Giant Leap online. I think PML also sells some. Finally, a local hobby shop here carries some, so you might check them also.

PS Yes, be careful with the expansion. It's best to have a way for it to get out while it cures. Then trim it off, add the final centering ring, etc.
 

GL-P

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I have used Great Stuff Low Expansion foam for my foam jobs. Yes it's only 1-part but it seems to be quite predictable.
 

rstaff3

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Then you've had better luck than most :)

But then I use the canned stuff most of the time. :eek: I still recommend the 2-part to others when they ask.
 

powderburner

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The two-part foam may indeed be a better product, but I have used the 'great stuff' foam-in-a-hdwre-store-can lots of times and it has always worked great for me.
This issue has been hashed and re-hashed several times already. You could probably dig up some more background info by doing a search on the old TRF threads.
One more option to point out: gorilla glue will foam up to something like 4 or 5 times original volume when mixed with water, sticks to everything, and cures hard.
 

BlueNinja

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I've heard the canned stuff can expand after it is "cured" when exposed to heat, eg a hot day the rocket sitting on the pad or from the heat of a motor. I use the PML stuff.
 

stealdesk

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Can some of you give a product name please that would aid in making my mind up
Thanks
 

BlueNinja

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Public Missiles 2 part expanding fom, found on their adhesives page. $15 for a set, but it lasts awhile due to its HUGE expansion rate.
 

rocketsonly

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Originally posted by stealdesk
I am building a PML Black Brant VB 38mm
I want to fill the fin can with foam , What is the best to use for this? I will be using this for my L1 cert. later on but for now will be flying on G motors. I want to be able to get the foam localy like a hardware store or as such.
I think the stuff is also referred to as "A B foam". As in you need to mix part A with part B so that it'll turn into foam. Try Home Depot or Lowes.
 

DumasBro2

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Why even use foam? Epoxy would do just fine. If you ever have to replace a fin it will make it a PITA. That said, www.mrfiberglass.com also sells the 2 part foam is several weights.

steve
 

BlueNinja

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I just remembered the US Composites foam, I think the 2lb density stuff is the same as PML/NHP foam, but it is like 2 quarts for the same price.


Rocketsonly, I haven't seen the 2 part stuff anywhere other than the internet and Giant Leap at a launch. How much is it at Rocket Depot?
 

aksarben10

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Use the two part foam not the foam in a can. There are several reasons that the canned stuff does not work. It needs air to cure and can expand for a long long time.

The two part stuff was developed and or used mostly by the Marine (boats) industry. It is a two-part liquid, expanding into rigid urethane foam and it comes in three densities, 2lb, 4lb and 8lb. The heavier the foam the harder and denser and stronger it is, I use the 4 lb foam alot. It locks in fins without internal epoxy needed.

US Composites is a very good brand. You can also get it from places like Giant Leap and PML. I do not know what brand these are but most likely they are the US Composite foam re-branded.

Try this link for info on the differences in the densities.

http://www.shopmaninc.com/foam.html

Scott
 

Missileman

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Again the question, why use foam at all?
I only use foam under 2 conditions.
If I plan on flying rockets to extreme limits (Endeavour under full J redline)
or if construction leaves no feasable way to get a good epoxy fillet. (aft fins in boattail on a Velociraptor)
Keep in mind the foam will add aft weight.
 

aksarben10

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Originally posted by missileman
Again the question, why use foam at all?
I only use foam under 2 conditions.
If I plan on flying rockets to extreme limits (Endeavour under full J redline)
or if construction leaves no feasable way to get a good epoxy fillet. (aft fins in boattail on a Velociraptor)
Keep in mind the foam will add aft weight.
Well you named a few reasons right there.

It makes for very solid fin cans and can add to the structural strenght of other models.

I just depends, use it where it makes sense and don't where it does'nt, its just another tool.

Scott
 

stealdesk

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Its done now thanks for all the input. I found a hobby shop hehe that had the NHP foam and it worked great. Now I am just waiting for my rms cases to get here to make a retainer for it.
Thanks again
 

stealdesk

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Here are some pics of it all done ready to fly but got rained out for Windom.
 

Karl

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Sweet! The fin fillets look awesome! It looks somewhat like my level 1 project :D Karl
 

xenon

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Looks very cool!

Please be sure that if there isn't a thrust ring on the adaptor to put one on the end of the motor with quarter in masking tape wrapped around the end of the motor
 

stealdesk

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Yes there is an engine block installed for a G80 and its deep enough for a 29/40-120 rms case, that I am still waiting on.
 

xenon

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Okay, good, it looked like a PML adaptor, and I knew those didn't have thrust rings, but if you put one in, that works too
 

aksarben10

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I like to motor retention, very nicely done. I use a lot of coat hangers for mine and while functional they are not as pretty.

Scott
 
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