Dope over foam (any and all types)

BillHones · Nov 05, 2009, 03:54 PM

hello! so i have a question. has anyone every tried to put either butyrate or nitrate dope over foam? any type of foam... i have an alula slope glider coming and im thinking of trying to cover it with jap tissue or silk span. im no chemist nor do i have any foam to play with... er test

slipstick · Nov 05, 2009, 07:40 PM

I've never yet seen any foam which is not instantly dissolved by dope (or at least its solvents). Of course some might exist that I just haven't met.

You could always try sticking the tissue on with WBPU (Water based polyurethane) instead of dope.

Steve

BMatthews · Nov 05, 2009, 08:51 PM

Bill, I'm thinking you posted this to the wrong forum?

BUt yeah, water based polyurethane for the win on this application.

I know there are some foams that are resistant to the solvents used in dopes but they can't be used for making airplanes.

John O'Sullivan · Nov 06, 2009, 06:42 AM

Could not resist this one. Just checked out two EPP planes with acetone and they did not react. If they can take acetone, dope should not be a problem.

EPP(expanded polypropylene) is that stiff rubbery stuff which makes durable planes. However Depron just goes to mush as does regular styrofoam (EPS).
Can't say for Multiplex Elapor foam but I suspect this won't take dope.

Just looking out at our first snowfall of the season - cars off the road everywhere.

John

BillHones · Nov 06, 2009, 12:40 PM

Quote:

Originally Posted by BMatthews

Bill, I'm thinking you posted this to the wrong forum?

i thought i may have, but i figured that the free flight guys may know a bit more about dope. i may put a link to this thread in the scratch built foam section.

there actually is a thread on here somewhere about glassing with silkspan using wbpu over foam. that would be fun but then i dont get to use my colored dope... i cold make a nice chalked (pastels) theme like easy built site talks about, it has its plus's and minus's. thanks for the info!

BMatthews · Nov 06, 2009, 01:34 PM

Once the foam is sealed behind the WBPU and tissue you may find that you can apply your color dope over the skin. But set up a little test panel. If the WBPU is affected by the dope thinner or is too pourous and allows the fumes to pass through to the foam things could get ugly in a hurry.

Making up quick and dirty test samples is a time honored way of trying out different paint and substrate combinations.

BillHones · Nov 11, 2009, 02:02 PM

seems like after thinking about all of the options, i may have come up with a solution. take a look here:

http://www.rcgroups.com/forums/showt...5#post13557175

thanks for the replies!

faif2d · Nov 17, 2009, 10:51 PM

Polyurethane foam can be doped. It is a brown color and is available in 2-3 lb/cuft weights. That is the good news the BAD news is you must not hot wire cut it EVER. It gives off phosgene gas (I have no idea how to spell it) that is one of the WW1 poison gases and it will damage your lungs / kill you. It does whittle and sand rather nicely. I have used it for wing tip blocks and it works quite well.

Nov 05, 2009, 03:54 PM	#1
BillHones Registered User Join Date: Oct 2009 Location: Sussex, NJ Posts: 32	Dope over foam (any and all types) hello! so i have a question. has anyone every tried to put either butyrate or nitrate dope over foam? any type of foam... i have an alula slope glider coming and im thinking of trying to cover it with jap tissue or silk span. im no chemist nor do i have any foam to play with... er test

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Nov 05, 2009, 07:40 PM	#2
slipstick Registered User Join Date: Nov 2003 Location: Staffs, UK Posts: 5,295	I've never yet seen any foam which is not instantly dissolved by dope (or at least its solvents). Of course some might exist that I just haven't met. You could always try sticking the tissue on with WBPU (Water based polyurethane) instead of dope. Steve

Nov 05, 2009, 08:51 PM	#3
BMatthews B for Bruce Join Date: Oct 2002 Location: Vancouver BC Canada Posts: 4,683	Bill, I'm thinking you posted this to the wrong forum? BUt yeah, water based polyurethane for the win on this application. I know there are some foams that are resistant to the solvents used in dopes but they can't be used for making airplanes.

Nov 06, 2009, 06:42 AM	#4
John O'Sullivan Registered User Join Date: Jan 2004 Location: Nova Scotia Canada Posts: 834	Could not resist this one. Just checked out two EPP planes with acetone and they did not react. If they can take acetone, dope should not be a problem. EPP(expanded polypropylene) is that stiff rubbery stuff which makes durable planes. However Depron just goes to mush as does regular styrofoam (EPS). Can't say for Multiplex Elapor foam but I suspect this won't take dope. Just looking out at our first snowfall of the season - cars off the road everywhere. John

Nov 06, 2009, 01:34 PM	#6
BMatthews B for Bruce Join Date: Oct 2002 Location: Vancouver BC Canada Posts: 4,683	Once the foam is sealed behind the WBPU and tissue you may find that you can apply your color dope over the skin. But set up a little test panel. If the WBPU is affected by the dope thinner or is too pourous and allows the fumes to pass through to the foam things could get ugly in a hurry. Making up quick and dirty test samples is a time honored way of trying out different paint and substrate combinations.

Nov 11, 2009, 02:02 PM	#7
BillHones Registered User Join Date: Oct 2009 Location: Sussex, NJ Posts: 32	seems like after thinking about all of the options, i may have come up with a solution. take a look here: http://www.rcgroups.com/forums/showt...5#post13557175 thanks for the replies!

Nov 17, 2009, 10:51 PM	#8
faif2d Registered User Join Date: Apr 2003 Location: Denton Tx Posts: 38	Polyurethane foam can be doped. It is a brown color and is available in 2-3 lb/cuft weights. That is the good news the BAD news is you must not hot wire cut it EVER. It gives off phosgene gas (I have no idea how to spell it) that is one of the WW1 poison gases and it will damage your lungs / kill you. It does whittle and sand rather nicely. I have used it for wing tip blocks and it works quite well.