Liquid Foam?

[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.

 

[r1dermon]

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]

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]

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]

Then you've had better luck than most

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

 

[powderburner]

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]

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]

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

 

[BlueNinja]

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]

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.

 

[Stymye]

the "great stuff "is not very heat friendly,

the 2 part foam (such as pml's) is made by NHP, the same people who make hobby epoxy's... most of the offerings you may find on rocketry websites are typically the NHP stuff,, with a different name on the bottles.

https://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXBH62&P=FR

 

[powderburner]

Originally posted by stymye
the "great stuff "is not very heat friendly

Can you elaborate?

 

[DumasBro2]

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]

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]

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.

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

Scott

 

[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.

 

[aksarben10]

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]

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

 

[Missileman]

What, no pictures? HMMM

 

[stealdesk]

Here are some pics I took tonight

 

[stealdesk]

Another of the fin fillets

 

[stealdesk]

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

 

[stealdesk]

and another of the business end

 

[stealdesk]

HHHMMMMM?? no comments, I figured there would be a few

 

[Mister Rogers]

Originally posted by stealdesk
HHHMMMMM?? no comments, I figured there would be a few

Okay fine..........it is BEE-U-TEE-FULLLLL!! Very impressive.

 

[Karl]

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

 

[xenon]

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]

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]

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]

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