bobrev06x

i really need to coat my firewalls with something and was wondering what everyone was doing to theirs. i know thinned out epoxy works well but seems like alot of work. plus i'm not sure about the procedure for this method. anyone else wondering this same thing ? ( input welcomed ) RCKEN....nice models in your profile. check out my profile "THANKS ALL!"




"I need more flying...i need more flying...i need more flying"..gimme gimme gimme

RCKen

My Feedback: (9)

bobrev06x,
Using epoxy to fireproof your firewall is really a pretty easy procedure. First of all, try to avoid using alcohol to thin the epoxy if you can. The reason for this is because alcohol actually changes the chemical composition of the epoxy and can weaken it. And if you get to much alcohol in the epoxy it will never harden properly, but instead it will stay a soft gooey mess. Instead use heat to thin your epoxy. You're going to need 30 minute epoxy (use 30 minute because 5 minute epoxy will not give you enough working time to complete the fuelproofing), a covering heat gun, and epoxy brushes (these are disposable brushes designed for one use only. They are also called acid brushes). Mix up your epoxy using a 50-50 mix of resin and hardener. Then take the epoxy brush and use it to put a "blob" of epoxy on the area you are working on, now use the heat gun to heat up the epoxy. As it heats you will notice it thinning out and start to run, at this point use the epoxy brush to spread it out over the wood. Keep this up until you have your entire firewall/cowl walls coated. You will also want to fuelproof the inside of the fuselage where the fuel tank is mounted (if you can get to it) so that a fuel leak won't soak into the balsa.

One of the greatest advantage of using heat is that when you heat the epoxy it allows it to soak into the wood better than without heat, and this protects the wood better.

Hope this helps

Ken

bobrev06x

thats a huge help...thanks ken. i've got three to do so i'd better get started...haha. trouble is, they're all built. guess i should've done this first.....duh! anywho.....chow all....."lets fly!"

bkdavy

My Feedback: (1)

While the heating method works for easily accessible areas, there may be cases where you can't adequately access the area. In those cases, I like to use acetone as a thinner. Mix it about 50/50 with the 30 minute epoxy. The acetone quickly evaporates as the epoxy spreads out, so you don't get the softening you do with alcohol. You get a very nice, fuelproof finish. Its perfect for pouring into those hard to reach spots. Turn the fuselage as necessary to get it to flow into all the spots. For spreading, I wear a latex glove and just use my finger. Dispose of the glove when you're done, since the acetone will weaken the rubber anyway.

Now there are those that will be concerned with the acetone fumes. I typically only use about a tablespoon or less of acetone to completely fuelproof a fire wall, then maybe another tablespoon or so to fuelproof the tank area. My wife and daughters use more when they do their nails. I wear a respirator, and open the windows, and within a few minutes, all the acetone is gone.

Heat gun or acetone, your choice. Just explaining the option.

Brad

bobrev06x

thanks brad.....options are a good thing. "I WANT SPRING!"

CGRetired

My Feedback: (1)

I have some fiberglass resin, two part epoxy stuff, sets up hard in a few hours, but is thin and easy to work with and coats everything I want coated with a small acid brush.

I do it the night before, let it set overnight, and it's ready for me to start assembly the next day.

I also use it to seal where the ends of the covering may meet the wood, like on the wing saddle, or along the cheeks of the engine compartment with those that have such a thing, or where the covering meets the firewall under the cowl, anywhere that covering meets wood. I just brush a little over the junction and let it set overnight and it provides a nice, sealed, and fuel proof covering not only in the engine compartment but everywhere else.

DS

Dr1Driver

Both the methods listed work well. So does soaking the whole thing with thin CA. Unless your engine really coats the compartment with fuel and oil, it will last the life of the plane.

Dr.1

bobrev06x

well, it's like i've been told i have to do something to the firewall because it will get soaked and weakened over time. so, what are we talking for time here anyway......5 years???....8 years???.....holy crap. i cant keep a plane for very long, i get bored with it and end up selling it or something. not only that, how much strength does the firewall really lose to this fuel soaking . and fuel soaking itself is another thing. granted, fuel does get on the firewall a bit but, if fuel is going on the model like that, wouldnt it be a good idea to direct it away with tubes and such if it's coming from the exhaust? my models stay pretty darn clean...and i know it depends on the model and all...i use pitts mufflers and they really direct the exhaust away from everything. i dont know...i'm still going to do it because i've been hearing about it quite a bit now.....might as well go along. nice. thanks for all the input. so many little things can go wrong with these planes during a flight.....i guess you really have to be on top of it. let's be safe! "PRE-FLIGHT!" check it over good thanks again ......

CGRetired

My Feedback: (1)

Fuel proofing is sort of basic. It's been done for years and really does protect the wood. One oil soaking is just about not removable. Once that oil starts to soak into bare wood, well, that's it. And, it does get heavy, and very quickly. You would be surprized at how fast it accumulates. It takes one evenng and an overnight set and it's done, and well worth it. Oil can and will seep through junctions such as where the muffler mates up with the engine, or if a rear plate bolt comes slightly loose, it will seep out of there, or if the fuel supply tubing develops even a slight leak, that fuel will get all over the place in the firewall and make a real mess.

I forgot to do it on one of my planes, the wood is a mess with oil soaked in. Once it starts to soak in, you can't coat it, the epoxy won't soak in and setup right.

Your choice.

DS.

horace315

My Feedback: (15)

i use clear dope to fuel proof firewall/ tank compartment and the areas where air can get into the radio compartment.epoxy has an advantage of adding strength but, does add some weight,depending on the model i normally use dope and havent had a problem with fuel soaking into the wood.

bobrev06x

thanks guys and i'll be getting started right away. so, someone said if this does take place and the firewall gets oil soaked, there's no way to dry it for the treatment to work? makes sense to me......does anyone know of a way to even partially dry these things out? maybe once they're wet like that, they're damaged? or unusable? maybe even dangerous? oh man....i'd hate to see a motor come flying off the model while in flight. anyone ever hear of that happening? anyway guys, thanks again and happy flying.

bkdavy

My Feedback: (1)

K2R spot remover (if you can find it) does a good job of removing the oil from the wood. Put it on, let it dry, brush it off, repeat a couple times.

Others say corn starch will also draw out the oil from soaked wood. Again, takes time and effort.

Brad

RCKen

My Feedback: (9)

K2R is the best product I have found to remove fuel from balsa wood. If you can't find the K2R then use kitty litter. you'll have to leave the affected area in the kitty litter for several days, and rotate the litter every few hours (6-8 hours), but it will get most of it out.

If you have a firewall soaked with oil or fuel don't try to remove it, it's a waste of time because the firewall strength will have been compromised. Instead you'll want to cut and install a new firewall. Most balsa can be left in place on the plane after removed the soaked up fuel.

Ken

Montague

Also, fuel soaking can cause glue joints that were quite solid to come apart. I have seen more than one plane have the firewall just come off, and in all cases there was quite a bit of fuel soaking around the glue joint.

RCKen

My Feedback: (9)

Thanks for mentioning that, because I had forgotten to say it. But this is very true. I had this happen on an Ultra Sport 60 I had. Had a fuel tank leak that soaked the F2 former (the one that the front of the wing mounts into). I used K2R to get the fuel out, but didn't do anything to reinforce the joints of the former. While doing an outside loop the former pulled loose. The fuselage turned into a really nice lawn dart and proceeded to start it's journey to RC plane nirvana. The wing very gently fluttered to the ground and landing in the top of a scrub tree, didn't even put a hole in the monokote when it landed!! [>:]. Oh well, lesson learned. The best way to avoid this is to seal your wood so that it can't get soaked.

Hope this helps

Ken

MinnFlyer

My Feedback: (4)

Just to go against the grain I'd just like to say that I still use the "Epoxy thinned with alcohol" method for several reasons:

It works great

It's easy to do

No nasty fumes

And it only takes a few drops of alcohol to thin out the epoxy. If you use so much that it effects the epoxy, well, you're using too much!

Also, even if there IS any loss of the epoxy's integrity, so what? You're using it for fuel-proofing, not structural strength!

I've been doing it that way for years and I see no reason to change.

Charlie P.

I use the thinned epoxy, too. I've handled a lot of epoxy with boatbuilding and repair over the years and I am comfortable with it. I get West System in quart cans so it is also readily available. I actually cut it about 30% with solvent alcohol AFTER letting it set a few minutes (it has to cross-link with the hardener) and it goes on very thin and dries well.

I have heard of some using floor finish polyurethane but I have not tried this.

Montague

For small bits or easy to work on flat firewalls, I often just use regular old 20min epoxy. I smear it on with a broken propeller, and then wipe off with a shop towl. Sure, it's slightly more weight than necessary, but it does penetrate in to the wood well enough and it's fast and easy to do. And on most planes we're talking about a an itty bitty faction of an ouce, not enough to notice.

Chocks_Away

As an alternative to epoxy as a fuel proofer, certain types of paint are also fuel proof, but I'm not certain of all the types.

One that I am certain of though is what I use on my planes.

I work in the Automotive trade as a vehicle paint sprayer, and get hold of the clear laquer thats used on cars, to use to fuel proof my planes.

It is a (2 pack) clear laquer, that is mixed with hardener, much like epoxy resin is mixed with hardener, and when set, forms a fuel proof layer to the areas you need it.

You can brush it on, or spray it, but beware that you need proper air fed breathing equipment if spraying it, as the airborne spray vapour is Toxic.

It is ok however to use with a brush without danger.

A little goes a long way, and once mixed, will take overnight to set at room temperature, unless heat, or an accelerator is used to speed it up.

Probably an advantage over epoxy, is that, as it is very thin, even a couple of coats of it is very likely to add less weight than epoxy will.

bobrev06x

i like the kitty litter trick too, it sounds like a good idea and huh..guess what???....we have a cat right here! haha so i'm going to get some and load this beast up and see what happens. i'll let you know.

ChuckW

I use a 20 minute epoxy from the LHS that is labeled "finish cure". It is thin and brushable once it's mixed. The working time is just long enough to coat most firewalls. It also works well on fiberglass tape.

da Rock

It says on the can that Acetone is made to thin epoxy. I can buy Acetone about as cheap as lacquer thinner or Denatured Alcohol.

Denatured Alcohol is also an ok thinner for epoxy, but why bother. I got the can of Acetone. And the Acetone is great for wiping CA spills off Ultracote. That can of Acetone is about the best dollar or two I ever spent on that kind of stuff.

Just avoid drugstore alcohol. A major component is water and that screws the epoxy's strengthing effect.

You might also buy a bag of acid brushes. They're very cheap. They're the ones with the handles that're made of "tin" wrapped into a tube and then pinched down on the bristles. Work great for getting behind bulkheads. Just bend the handle into a half circle. Throw 'em away when you're done.

K2r works great.

bobrev06x

"I think i'm gonna have fun being addicted to thuis stuff!"[8D]

Kaos Rulz

ROGER THAT!
It's a great hobby with so many options on most everything involving the buying, building, flying and lieing.

Jarrah

Hey guys i was just wondering, i recently purchased a funtanax50 and have had my saito 82 on it running it in, well in that time the firewall has soaked up some oil/fuel ect, is it too late to fuelproof it using the expoy heat gun method? its only got minor oil not totally soaked or anythign

cheers.