|
|
Post by Dave.K on Jun 27, 2011 19:46:54 GMT 12
Hi, Mainly for Bruce, we have an Avid wing with a leaking fuel tank, on opening it up we found it to be covered with Stits Polyfibre. Can we put a patch on with ceconite or does it have to be done with stits. It is on the bottom of the wing the repair has to be done.Any info apprciated.
|
|
|
|
Post by DragonflyDH90 on Jun 27, 2011 20:40:15 GMT 12
You'll be fine with Ceconite, interestingly enough most of the poly fabrics are woven in the same factory on the same looms.
Just try to avoid mixing the paint systems.
|
|
|
|
Post by yak2 on Jun 27, 2011 21:09:17 GMT 12
My understanding is that both Poly-fiber fabric and Ceconite are similar Dacron polyester style products. The problem arises when mixing finishes. You need to determine what was originally used on your aircraft eg. Poly-fiber, Randolph etc. , and stick with that system. Never mix systems is a rule of thumb. There is good information on the various manufacturers sites. And note:This is my opinion only. I am a homebuilder, not an aircraft engineer.
|
|
|
|
Post by Bruce on Jun 27, 2011 21:18:47 GMT 12
Yeah for non - certificated aircraft you'll be fine - as Ryan says the fabric is the same stuff anyway - Polyester Dacron. There is a little difference in the filler / glue / paint systems and this is where care needs to be taken. When you glue the patch on, take the coatings off the glue area right back to bare fabric (Acetone should clean it up nicely) and make sure you glue fabric to fabric with decent overlap (2" minimum) for bigger areas, make sure you come back to a rib or other structure. With the glue fabric to fabric, you wont have compatibility issues. shrink it off and then use whatever system you have- just dont mix and match. Mask off the existing coatings as Polyfibre is an Acrylic based Lacquer which isnt compatible with Butyrate dopes often used with Ceconite. How the top coat blends in will depend on what the colour coat used is - Polyfibre have two options, a single pot Acrylic, which has a satin finish and comes off with Acetone, or a flexible two pot system which has to be peeled off. The former is really easy to blend repair patches into. the 2 pot stuff is quite hard to finish nicely - it will take a bit of sanding, and you may have to repaint an entire rib bay to hide the joins. send me a PM if you have any problems.
|
|
|
|
Post by Dave.K on Jun 27, 2011 21:20:16 GMT 12
Thanks guys, sometimes homebuilders are more up with the play than engineers. Will get the owner to contact the builder for finishing info, it doesn't smell like dope.
|
|
|
|
Post by slackie on Jun 28, 2011 13:19:30 GMT 12
Just a hint though... steer as clear as you can from Randolf products... they were great once, but have fallen well below the mark now... and customer service is atrocious!
|
|
|
|
Post by DragonflyDH90 on Jun 28, 2011 22:04:24 GMT 12
Agree with that for sure Slackie....100%, and the customer service is a bit lacking from some of the other manufacturers as well. Weird considering the current financial climate, you would think they would be helpful to the N'th degree to get and keep the business.
|
|
|
|
Post by Dave.K on Jul 5, 2011 20:14:33 GMT 12
If we can't get Randolf products, what do you fellows suggest, can we buy some off Colin at Mandeville Ryan as we only need enough to put a large patch on so don't want to buy it by the gallon.Acetone disolves the paint so it is easy to clean up.
Have got the tank reglassed, just need to pressure test it, the Avid manual says to 2 psi.
|
|
|
|
Post by DragonflyDH90 on Jul 5, 2011 21:26:12 GMT 12
1.5-2PSI will be fine for the tank test, you can use soapy water and check for bubbles or fit a small balloon to a vent and pressurise over night and see if its flat in the morning (doesnt have to be much pressure for this test.
What colour are you after Dave, we dont have alot of stuff in stock and only buy in what we intend to use and we dont tend to have any polyurethanes at all (other than what I have on my Pitts). Is it poly or is it dope, shiny or dull finish?? Is it definately Randolf (Randothane).
Randolf dope should be OK, the polyurethane has a few adhesions problems which Slackie knows about.
Have a chat with a couple of the paint companies and see how you would go with mixing and matching systems, I know it isnt recommended but if done carefully it may work out OK. By that I mean minimal colour overlap, testing on an old piece of fabric or an inconspicuous area.
Truthfully the paints are much of a muchness with regard to chemicals composition and the thinners are generally the same.
Try the local Superflite distributors, you will likley find they have the colour you want instock and potentially it will be available in a 1 pint tin, they may even have a small leftover bit to get the job done.
My 2 cents and its worth exactly what you paid for it.
|
|
|
|
Post by lumpy on Jul 6, 2011 7:56:50 GMT 12
1.5-2PSI will be fine for the tank test, you can use soapy water and check for bubbles or fit a small balloon to a vent and pressurise over night and see if its flat in the morning (doesnt have to be much pressure for this test. Or you could hook a small diameter clear plastic hose ( maybe 8- 10mm ) up to a breather and suspend it 2-3 meters up in the air , then fill the whole lot with water so that the water level is near the top of the hose . The height of water will privide the pressure you need , and any change in water level over a day or two will show any leaks . Ive seen this used very sucesfully on boat fuel tanks . |
|
|
|
Post by Bruce on Jul 6, 2011 12:53:51 GMT 12
generally not good practice to put water into aircraft fuel tanks - even for testing. you cant always be sure you've got it all out again.....
|
|
|
|
Post by lumpy on Jul 6, 2011 17:32:27 GMT 12
generally not good practice to put water into aircraft fuel tanks - even for testing. you cant always be sure you've got it all out again..... Yes , of course - for some reason I was picturing a tank that would be removed for repair ( and therefor pretty easy to dry out ) , but I guess thats not the case . |
|
|
|
Post by eieio on Jul 6, 2011 18:53:08 GMT 12
It is a petrol tank, perhaps it should be tested with petrol, history will be littered with subsitution not representing the true use of items.
|
|
|
|
Post by Dave.K on Jul 6, 2011 20:40:52 GMT 12
Thanks Ryan, have been ringing around some locals who have built aircraft and have located some dope hopefully, will find out at the weekend, unfortunatley these things take time when work gets in the way of plane stuff.Re the colour it is white, trying to find out which shade,and it has had touch ups with what looks like house paint. Aircraft is FYI, a speedwing aerobat that was with Mercury bay Aero club for a while, some of you chaps might know it.
|
|
