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#1
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Teflon gap seal tape...
I need to replace the flap/aileron gap seal tape on our LAK-17A. The
control surfaces are bottom hinged, and the gap was factory sealed on the bottom with what is apparently ordinary polyethylene tape. The tape cracks over the hinges, which I would have to patch periodically, plus it shrinks over time, limiting control movement and increasing stick forces. It seems like Teflon tape is the way to go. I poked around and found multiple online sources of 1" x 18 yard Teflon PFTE tape with high temperature silicone adhesive on one side, available in thicknesses from ..0035" (~$25/roll) to .0115" (~$75/roll). There are less readily available variations with acrylic adhesive, along with "High Density" PFTE (100% stretch instead of 300%). Does anyone have any idea what thickness and type of tape would be best for my needs? Thanks, Marc |
#2
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Look for teflon tape on this page
http://www.streifly.de/Price1-00.htm If you ask they will do you a complete kit, I'm on my third kit and haven't been disappointed yet, third glider in 4 years, LS7 Cirrus and Ventus cT |
#3
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Not sure that tape is the way to go, Mark. I have found that properly
installed Mylas is all that is necessary. Proof--------when the seals on my Nimbus 3 needed replacing, I eliminated the internal seals and also got rid of that ridiculous lower mylar that went inside the gap, never did understand the reasoning there. Replaced it with Mylar on top and bottom, nothing else. She climbed and cruised right with another Nimbus 3 with factory seals. Another data point..............The ASW-20 had a terrible reputation for dropping a wing and entering a spin, when they first came out.................then the spin problem seemed to go away, why? Most 20's today have Mylar, top & bottom. Was the external tape triggering separation at low speed? Something to think about, JJ |
#4
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I agree with J.J.
Make sure the edge of the tape wipes and makes contact at the bottom of the aileron when deflected. Install samples at discrete points to find out if you have the correct radius and position for the Mylar. Bottom hinged flap/aileron Mylar seal require a slightly different approach versus the top. Regards Udo "Marc Ramsey" wrote in message m... I need to replace the flap/aileron gap seal tape on our LAK-17A. The control surfaces are bottom hinged, and the gap was factory sealed on the bottom with what is apparently ordinary polyethylene tape. The tape cracks over the hinges, which I would have to patch periodically, plus it shrinks over time, limiting control movement and increasing stick forces. It seems like Teflon tape is the way to go. I poked around and found multiple online sources of 1" x 18 yard Teflon PFTE tape with high temperature silicone adhesive on one side, available in thicknesses from .0035" (~$25/roll) to .0115" (~$75/roll). There are less readily available variations with acrylic adhesive, along with "High Density" PFTE (100% stretch instead of 300%). Does anyone have any idea what thickness and type of tape would be best for my needs? Thanks, Marc |
#5
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#6
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Mark,
We installed mylar seals on the bottom just behind the tubulator tape. We installed the 1 1/4" wide teflon tape attaching 1/4 " to the wing just behind the 1/2" wide adhesive for the mylar seals. The thickness of the adhesive and the teflon is the same about .007". With the flaps pushed up to simulate max refax ( the flap and airelon will go up farther), You can mark the flaps and airleron only with the aircraft assemble and refaxed with full airleron stick deflection. With the wing turned upside down and the flap and airleron set to the previously marked position you can then apply the teflon tape. The teflon tape is not easy to apply and get the edge straight. I suggest you practice on some scrap pieces before yo attempt to apply the 25' of continuous application you will need. If someone in your club has previous expertise you may want to ask for help.Wings and Wheels sells the tape which is lite brown in color and costs about $50. The last tibbit of info is that getting the teflon down flat and without airbubbles will offer you an additional challenge. If you are an absolute perfectionist, you may want to investigate professional installation. It will be difficult to do without flaw. Good Luck, Bob Fidler "Marc Ramsey" wrote in message m... I need to replace the flap/aileron gap seal tape on our LAK-17A. The control surfaces are bottom hinged, and the gap was factory sealed on the bottom with what is apparently ordinary polyethylene tape. The tape cracks over the hinges, which I would have to patch periodically, plus it shrinks over time, limiting control movement and increasing stick forces. It seems like Teflon tape is the way to go. I poked around and found multiple online sources of 1" x 18 yard Teflon PFTE tape with high temperature silicone adhesive on one side, available in thicknesses from .0035" (~$25/roll) to .0115" (~$75/roll). There are less readily available variations with acrylic adhesive, along with "High Density" PFTE (100% stretch instead of 300%). Does anyone have any idea what thickness and type of tape would be best for my needs? Thanks, Marc |
#8
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the Mylar would seem to me to be every bit as likely to trip the airflow as the Teflon tape. Second, the point behind external tape (or internal seals) is to prevent airflow through the gap. Are properly fitted Mylar seals actually going to prevent this flow? Would it make sense to use Teflon tape to seal the gap, then put Mylar over the tape? Thanks, Marc I have seen it done this way (mylar & tape) Just have come to the conclusion it isn't necessary. I fit foam rubber in the flap well to seal any cross-flow at each end of flap and aileron, then the mylar comes over this area and prevents any air from entering. I believe the big bug-aboo with tape only is the leading edge starts to come loose and this = some real drag on that wing. JJ |
#9
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Udo Rumpf wrote:
The edge of the Mylar tape .010" plus the edge tape .002" it should not effect turbulent flow. A gap, covered by a sealing tape could. The Mylar seal if it wipes it will seal. If you were to have difficulties with this a separate seal would be the way to go, as long as it does not interfere with The Mylar. Sometimes if the hinge is to close to the bottom surface it would be difficult to get a wiping action through all the motion of the flap and aileron. I hope I understood your question. Yes, it does answer my question. I suspect the best solution is that used by Bob Fidler on his LAK, use Teflon tape to act as both a flow seal and a wiping surface, then put a Mylar seal over it. Thanks to all, Marc |
#10
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If I recall correctly, Dick Johnson tested Sam Fly's Ventus 2 with oil flow
and found that the mylar alone did not prevent cross flow from bottom to top. He removed the ailerons and installed S-seals and stopped the flow. As I further vaguely recall, this did only a little for the performance! There was considerable data scatter. Does anyone know of any hard data that shows, one way or the other, if the mylars are effective? Hartley Falbaum ASW27B "KF" USA wrote in message oups.com... the Mylar would seem to me to be every bit as likely to trip the airflow as the Teflon tape. Second, the point behind external tape (or internal seals) is to prevent airflow through the gap. Are properly fitted Mylar seals actually going to prevent this flow? Would it make sense to use Teflon tape to seal the gap, then put Mylar over the tape? Thanks, Marc I have seen it done this way (mylar & tape) Just have come to the conclusion it isn't necessary. I fit foam rubber in the flap well to seal any cross-flow at each end of flap and aileron, then the mylar comes over this area and prevents any air from entering. I believe the big bug-aboo with tape only is the leading edge starts to come loose and this = some real drag on that wing. JJ |
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