Water Based Polyurethane Varnish and 10-15% Nitro Fuel

[David Davis]

I am finishing off a DB Sport & Scale Auster. I haven't yet decided which motor to fit but a Thunder Tiger 91 FS is certainly in the running. I usually run this engine, and all of my Japanese four-strokes, on fuel containing 10% nitro and I have been given a gallon of 15% nitro. The model is covered in white Solartex which is fuel-proof but which soon starts to look scruffy unless it's coated with something.

 

I was thinking of using a water based polyurethane floor varnish brushed on over the Solartex but I would like to know whether this type of varnish will withstand fuels containing this much nitro.

 

[Ron Gray]

Simple answer, no, Clearcoat or a 2 pack will give the best protection.

[Jon H]

I have also come to the conclusion that you need a 2 part paint to resist glow fuel. Nothing else seems to work at all. 

[Paul De Tourtoulon]

2 hours ago, David Davis said:

water based polyurethane floor varnish

As said, no or even ordinary polyurethane varnish won't work, it must be a two pack.

[gillyg1]

Automotive 2x pack as previously mentioned, or " Delux materials" Aerokote, which is a 2 part mix, dries to a gloss finish, for which you can buy a matt additive to dull it down..👍

[Engine Doctor]

If you get a 2K aerosol made up ask them to add a little plasticiser . Its excellent at keeping 2K flexible over covering or anything bendy or flexible .

 

PS use in open space and wear some breathing protection . Of course if you can find some Clearcoat its a simple application and probably the best fuel single pack proofer ever made . I believe Solarfilm still have stock but wont supply the trade or post ? Its collect only from Lancashire .

Edited January 26 by Engine Doctor

[PeterF]

I believed the hype on Poly-C from RC World stating that it was fuel proof, I used it on a plane and ended up with a sticky mess.

[Engine Doctor]

Poly C was an overrated product . I covered the tail surfaces on  large model using glass matt and Poly C  only to find it could just be peeled away from the balsa . Absolute rubbish and good job I found out before covering the rest of the model with it . Removed sanded down and re-covered with glass and epoxy ... proper Job .

[Glenn Philbrick]

I've covered a couple of models with poly c and glass cloth and never had any delamination issues, I applied a sealing coat of poly c before covering maybe this helped. The water based varnish will only offer limited fuel proofing if left for at least a couple of weeks to harden. Aero cote or two pack aerosol is the best solution. The two pack aerosol can be had in different sheens from full gloss to flat matt.

[i12fly]

My tests a few years back showed Ronseal water based polyurethane was quickly attacked by neat 10% nitro fuel, but the high VOC solvent based was ok when neat 10% nitro fuel was left on for half an hour. The only 'problem' now is that after about 5 years the whole plane has turned a slightly brown colour....  🙄

[Jon H]

As i have posted before i am testing some 2k clear intended for use on custom painted motorbikes. Its half the price of the modelling equivalent and my test model is looking good a year into the test, which is much better than the guild fuel proofer originally used as this lasted about a week before giving up the ghost. 

[Alan Hilton]

Poly c is water based polyurethane floor varnish, so its not fuel proof .I second Jon  2 pack is the way to go but use a chemical proof face mask .These are usually available from auto paint suppliers . 

[Jon H]

7 hours ago, Alan Hilton said:

2 pack is the way to go but use a chemical proof face mask

 

Yes absolutely. Adequate safety precautions must be taken as its deadly stuff