Fiberglass Insulation

[AK Mauler]

Just finished my annual. I found some corrosion on the belly stringer. The fibergalss insulation was saturated in a few spots and created some corrosion. I sure am glad my mechanic pulled out the insulation and had a look. A few more years it ccould have been a lot worse. This stuff does not drain or dry out. We decided to completely eliminate the fibergalss in the belly. I found some FAA approved black closed cell foam rubber stuff that is supposed to have superior noise supression qualities. I glued it to the bottom of the floor boards to keep the belly open to allow better air circulation and not trap any moisture. The back section where there is no insulation was completely clean and no hint of corrosion anywhere. I am wondering if all the fiberglass insulation in the wing roots helps much. I put it back in for now, but if it is wet next annual it will be coming out. Has anyone else had similar experience with the fiberglass? I sanded out the corrosion areas with emery cloth, cleaned it up real good and coated it with 2-part epoxy primer. The only other discovery was another crack on the exhaust, which is a recurring theme with the Maule. One of the stub stacks was cracked nearly 270 degrees, I had FA Dodge weld it up, but I will bet I will be looking at it again next year. I really wish Maule would STC the PA-18 180 HP super cub exhaust from Leading Edge. I am sure it would work with some minor tweaks.

[a64pilot]

Well, if anyone should STC an exhaust for a Maule, it should be the exhaust manufacturer, not the airplane manufacturer.
I have a tendancy to agree with you on the insulation, but I hadn't thought about putting it on the back of the floorboards.

[210TC]

Good idea on the replacement of the glass in the floor.
On the wing root I use three strips of duck tape. One on the airframe 30%, one on the wing also 30% (all length ways). The final strip ties the two together. No moisture or air gets inside.
I fly at high altitudes and did this to keep a little warmer.
At annual I remove the tape and clean the old tape residue off with some berrymans sprayed on a rag.
Your exhaust may be cracking from vibration at the end of the exhaust.
I have suffered this same type of crack (not on a Maule). I was told too tie the two tips together (exhaust outlets) with what looked like a very stiff battery ground strap. It was weaved with no insulation and it cured the problem.
Consider installing a brace with about a 2 inch gap to install the flexible cable.
I was told the brace needed to be flexable yet absorbe some of the shock instead of the flange at the engine. Food for thought

[TomD]

The fiberglass insulation is a bleeping sponge!

When I was at Moultrie several years back ( BD was still in his rocking chair) there was a new M7 on the production line destined for a float operator in the Caribbean who had given explicit instructions to leave all the fluffy stuff out since her last Maule had MAJOR corrosion problems due to the moisture the fiberglass held next to the structure.

I pulled mine out early on after I bought my M5 but the damage to the wood stringers and some of the tubes was already done.

I have replaced it with something non-permeable but I am liking the bottom of the floorboard idea.

TD

[AK Mauler]

Thanks for the validations on the fiberglass removal. I wish I knew what the product code was for the black foam I found is. All I know is it is FAA approved and manufactured by 3M. I have some left over, so I might try and fit some pieces for the wing roots. On the exhaust issue, the crack may have been from setting up the U-bolt too tight the previous year and getting some vibration concentrated back at the stub stack. Now there is enough play to where the vibration should not be an issue. Not sure if that makes any sense, but if the exhaust is completely rigid, the vibration will concentrate near the anchor (the engine) and eventually fatigue. Hard to say exactly what happened. Now that I think about it it would be nice to have taken some pictures to post! Oh well, there is bound to be something next year. The Leading Edge company will be in Anchorage for the May aviation show and I will see if they have any intentions of making their product available for the 0-360 Maules. Any interest out there?

[belandd]

Yeah, I found the same thing in mine. Corrosion from the fiberglas insulation. You can switch to encapsulated fiberglass if you want but I think the stick on sound deadening foam is a good idea.

FA Dodge, good man. I have had him do some work for me and have bought some of his Cessna mods.

good flying

[Ian]

Hi

I had similar issue- I removed old cleaned up tubing where necessary and coated with POR rust preventative, which seems very good. I then repaired stringers where necessary and put back new fiberglass insualtion. I also sealed fairings with good quality ducttape and attaache thin rubber seal to fairings as well. I also use Bruces custom covers over entire fuselage. The plane is dry now. Another item some folks are doing and I may follow suit is to put one of those marine heaters in plane - they do not get too hot are UL tested and help to keep miosture at bay.

[a64pilot]

The link that Jeremy had for seat cushion foam also sells a self adhesive FAA approved foam sound insulation, I think. I know they have a good price for seat foam.