Sealing the firewall?

[RDavidson 183]

The directions for the Magnum say to use silicone to seal the firewall to the fiberglass...

What have you guys used?

[akflyer 1427]

I used foam door seal with the sticky back.  I insulated the cockpit side of the firewall so I had something for the foam to stick to.  I have seen guys seal it off with muffler wrap riveted to the steel firewall as well.

 

[dynomike 91]

mine has foam seal with silicone spread on to the three exposed sides of it .I did it that way on the doors also and it seemed to work well

[RDavidson 183]

Thanks guys!

Mike I just looked at your old posts to see your paint job...that is one of the best looking Avid paint jobs I've seen!

What paint did you use?

Is that Piper Cub Yellow?

I'm planning on using the Piper Cub yellow and black. That silver sure looks good too!

Any painting tips or lessons you want to pass on?

Thanks,

Ron

[RDavidson 183]

Which insulating material do you guys suggest for the cockpit side of the firewall?

Should I look into insulating the fiberglass engine cowls? My engine fills the cowls and I'm concerned about the heat causing the fiberglass to sag. Is this an issue?

[EDMO 1078]

I just read an article about lining cowls with metal to protect the fiberglas - Now got to find it and remember what it said - I think it was mostly in the exhaust area.

EdMo

[RDavidson 183]

It sounds like a good idea Ed, I just wondered if you did the entire cowl if you would actually be baking the engine like a aluminum foiled potato and make the engine temp go up!

Around the exhaust makes sense...

[akflyer 1427]

I dont see it as being a problem.  A lot of planes running big continentals have fiberglass cowls.  You should have plenty of air running through there to keep it cool.  On snowmachines we use foil tape on the plastic at strategic locations around the exhaust to keep it from melting the plastic. 

 

ChrisB has a magnum he puts some hours on.. did you have any issues with the fiberglass cowling warping due to heat?

 

[EDMO 1078]

Ron,

      The article I read was in the May 2014 Kitplanes mag.   I don't see where anyone writing the article is making any profit, so I guess it is just an opinion based on his years of experience.

      IMO, the most extreme heat the cowl should have would be after shutdown, when no air is blowing.  some folks have put an automatic door in the top of the cowl which is regulated by a VW thermobellows from the junkyard or dealer.  I don't know that it helps the exhaust areas much.

       To try to put it in a nutshell, I will condense what the article says:

Only the parts of the cowl subject to high heat need to be covered, especially those areas closer than 3/4 to 1 inch to exhausts, and definately any area closer than 1/2".

Level 1 - To seal the cowl from oil contamination, paint a coat of fuel-proof laminating epoxy on the inside, and paint with white or   silver paint.

Level 2 -  Seal with epoxy and apply self-adhesive foil from Spuce or Vans.

Level 3 -  Epoxy and 1/16" Fiberfax attached with Pliobond contact cement, and covered with foil about 2 inches wider.  

I added this:   Level 3.5 -  Fiberfax is also available 1/8" thick.

Level 4 -  Epoxy and Firewall 2000 - this is 1/4" of insulator sandwiched between stainless foil and aluminum foil.

Hope this helps or gives you an idea or two.

EDMO

Edited 10 May 2014 by Ed In Missouri

[RDavidson 183]

Perfect, thanks Ed!

[EDMO 1078]

Ron,

      I left out that the guy writing this was a retired aircraft exhaust manufacturer - He also said, "If you wrap the exhaust, You have doomed it to failure, and defeated its purpose as a heat sink."

EDMO

Edited 11 May 2014 by Ed In Missouri

[dynomike 91]

Ron ,

thanks ,I bought the plane from an aircraft painter with new wings so paid him to do the fuse to match .its federal yellow from stewerts systems.amazing paint but hard to work with .super shiny though

[wolves200 31]

I have a Rotax 532 inverted and on the pilot side (left side) the exhaust burn the surface of the cowling and heat inside of the cowling was intense, after an hour flight I couldn´t touch my cowling with bare hands, however somebody suggested to wrap the exhaust between the first elbow until the second down elbow before the big muffler. This solved 2 problems, one burning cowling, two engine performance; you could see in some of my pictures my side vents are large, well even those couldn´t keep temps down inside of the cowl. 

 

But then again it´s not a 4 stroke engine...

 

Regards

Dimi3

Edited 14 May 2014 by Wolverine

[High Country 69]

I have a Rotax 532 inverted and on the pilot side (left side) the exhaust burn the surface of the cowling and heat inside of the cockpit was intense, after an hour flight I couldn´t touch my cowling with bare hands, however somebody suggested to wrap the exhaust between the first elbow until the second down elbow before the big muffler. This solved 2 problems, one burning cowling, two engine performance; you could see in some of my pictures my side vents are large, well even those couldn´t keep temps down inside of the cowl. 

 

But then again it´s not a 4 stroke engine...

 

Regards

Dimi3

not to steal this thread but i'm in the process of mounting my inverted 532 on a C model. could you put up some FWF pics of your install, I'm still looking for ideas on how others have done it.

 

Thanks Robert

[RDavidson 183]

I always heard that wrapping the exhaust was a performance gain in HP and the only downsides were the extra weight and faster decay of the pipes due to the confined heat. Anybody know if that is true or false?

[wolves200 31]

quite the opposite, there is no decay on the pipes, I explain, and I heard this from a European car mechanic in comparison to American car, all metals contract in cold and expand in heat, meaning this temperature changes fatigue the metal and that´s why the exhaust pipes rust, because they get warm and cold rather quick, at least on cold weather countries, and much less in warm weather, I remember back in Venezuela 20 years ago, we didn´t have any problem with exhaust rusting as fast as they do here, VW top end models have their exhaust pipes wrapped and for that reason no need to change the exhaust pipes.

 

Wrapping the exhaust will prevent this RAPID expansion and contraction of the metal, especially for vehicles that are turned on and off very often, this apply to airplanes in some extend... Helicopters wrap their exhaust to prevent heat inside of the engine compartment. check Rotorway Exec or talon for example.

 

Regards

Dimi3

Edited 16 May 2014 by Wolverine

[wolves200 31]

This are some of the OLD installation photos I had on hand, the electrics were VERY wrong, and the radiator as well was very badly installed... instead of bolting the radiator on a frame to the engine, I decided it to let it "float" on a small compartment on the front of the cowl, works quite well, but in HOT summer is not that effective, I will go for a belly radiator; far easier.

 

I will post more pics later.

 

Regards

Dimi3

 

 

 

 

[RDavidson 183]

Great pics, and great looking plane! The cowling mods are impressive!

Thanks for the exhaust explanation, it makes sense...

I guess that is the problem with info on the internet...even idiots have a loud voice, so you never know what info you are getting. I had really looked into wraps for my other project and I was scarred away by a few internet people saying "you'll burn through your pipes!"

Now I know opposite! Thanks

[EDMO 1078]

Ron,

     I guess you can find differing opinions on about anything.   The quote I made about not wrapping exhausts came from a guy who built Aircraft Exhausts for about 30 years.   He said that you defeat the heat sink purpose by wrapping, and will burn out your exhaust valves quicker,  and that the excess heat in the upper exhausts will burn out the chrome in the pipes. 

Doubt if VW puts chrome or stainless in their pipes which are going to rust out anyway, and their exhaust manifolds are cast iron, unlike airplane engines which use stainless. 

He probably never made exhausts for 2-bangers.

EdMO

Edited 16 May 2014 by Ed In Missouri

[RDavidson 183]

Ed,

Good points...I didn't think about it burning out the valves too.

I tell you what, after seeing those pipes glow on a Dyno stand I don't know how the stainless doesn't just melt into a puddle! That is impressive!

This is one of those topics that gets a pretty even split on pros and cons.

One thought though, if Helos are doing it we shouldn't be afraid of it because those are the same certified engines used in certified GA aircraft...right? If it were really horrible for engine wear or exhaust it would definitely be proven and documented by now.

[EDMO 1078]

I thought all Helios were now turbine?  At least the last civilian one I had my hands on took a while to spool up, and so did the Hueys..

EDMO

Edited 17 May 2014 by Ed In Missouri

[wolves200 31]

Guys;

 

after talking to an Airforce Helicopter Mechanic, which is actually opening a airplane factory, he pointed me the following.

 

in regards to 4 strokes. (which is the reason why I said in my first post, "then again my engine is a 2 stroke...")

 

he wrapped the exhaust pipes of his Rotax 912 with the bandage and it worked fine, until they hit 50 hours, and notice cracks all over the Rotax exhaust pipes. Wrapping the pipes will get temperatures really high ALL THE TIME, different from racing cars and other vehicles, this engine operates in constant RPM. meaning there is not enough time to the metal to cool down and so it becomes red glowing. the original material cannot withstand the extreme heat.

 

his solution was, welding a metal plate onto the pipe with a gap of about 5mm letting the air flow through and preventing burn the cowling, much like a MC to prevent burning your leg,

 

however this does not solve high temps inside the engine compartment, so they changed the original pipes to STAINLESS STEEL pipes and open bigger vents under the cowling.

 

so at the end wrapping is not the answer either, i´ve been running my engine for 40+ after the wrap, and see no cracks, BUT THEN AGAIN is a 2 STOKE ENGINE!!!

 

Rotorway building manual clearly says, should be wrapped to lower the temp and painted with high temp paint to prevent any drop of oil becoming flame inside of the cowling.

 

I`m just sharing my experience here with you guys, if anyone has a better solution, by all means, share it with US, PLEASE...

 

so far, the wrap worked for me but I don´t want to burn my engine either!

 

Regards

Dimi3

 

[RDavidson 183]

Dimi3,

That does not only look functional, but it looks cool too!

What Helo are you building?

Thanks,

Ron