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Engine basics => Engine set up tips => Topic started by: Leester on November 08, 2006, 10:09:46 AM
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Does anyone have experience with the phenolic engine pads ? Are they just as good as the aluminium ? They are thinner and less motor mount has to be trimmed away. And I would say lighter in weight. Any comments ?
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Does anyone have experience with the phenolic engine pads ? Are they just as good as the aluminium ? They are thinner and less motor mount has to be trimmed away. And I would say lighter in weight. Any comments ?
There is really no reason to trim any motor mount away when you are using pads. Just set your mounts to a height that includes the thickness of the pads when you install them.
If this is a retrofit, phenolic comes in just about any thickness you want. I would think you would still want at least 3/32" (for a smaller engine) if not a full 1/8" to help spread the clamping force out along the motor mount. Remember that you want the pad to extend a good 3/8" (or more) in front and behind the mounting lugs or you are not achieving anything that the wood could not have done by itself.
If you use at least 1/8" pads, you can thread them and mount your motor directly to the pad. Makes changing the motor a lot easier.
Kim
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Kim: The fusalage formers are cut for the motor mounts to set in so the adjust the motor mounts up or down would require either trimming the mounts or the formers. To use engine pads without changing the highth of the engine would require trimming the mounts. The phenolic pads I have are 1/16th and would extend beyond the engine mounting holes front and back they are 2 1/2" long.
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I've been using phenolic square "C" shaped pads from Tom Morris on profile airplanes. I've been gluing them down to the ply. All engines are running well and predictable so far. At least as far as profiles go. Effective. But they're only one part of a rigid system that includes: motor mounts back to the leading edge of the wing, 1/8" five ply doublers, solid epoxy gluing to wing. Don't see how one part of the system can be separated from another. Full fuse airplanes have a different system of design.
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Kim: The fuselage formers are cut for the motor mounts to set in so the adjust the motor mounts up or down would require either trimming the mounts or the formers. To use engine pads without changing the height of the engine would require trimming the mounts. The phenolic pads I have are 1/16th and would extend beyond the engine mounting holes front and back they are 2 1/2" long.
Since the model is not yet built, I would modify the formers. The 1/16" pads are not thick enough. The purpose of the pad is to spread out the clamping force from the engine lugs so that they do not dig in. I think you would be OK at 3/32" up to a .35 from there on up I would use 1/8". As to where the engine actually sits, the nose is usually carved from some number of blocks so that moving its center line should not pose a big deal. If you end up lowering the engine that is not such a big problem as you will in all likelihood have to raise the tank a bit anyway. This gives you some adjustablility. Don't raise the bridge, lower the water. If you do not want to try this then at least use the appropriate thickness of phenolic.
If you need further help just ask or PM me and I will make sure you get it done right.
Kim.
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I have done as Kim says since pads became availableback in.........................??????????????
I move the maple mounts up 1/8" inthe fuselage, or let the engine C/L move down 1/8th". Either way is not really noticable when the plane is finished in either flying or esthetics. Cutting an extra 1/8th" out of the former and filling in the bottom (or as I do just make another former or two as needed) is really easy.
Then again, I HAVE cut 1/8th" off the maple mounts leaving them 3/8ths"X3/8ths" where the pds go!!! <= #^ n~
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Leester,
I used to use 1/16th aluminum & stainless steel. Stainless was good but you need a cobalt bit drill.
I have since gone to 1/8th inch unidirectional carbon fiber. It's lighter and stiffer and easy to drill.
I do not cut away any engine bearer wood.
Ted H^^
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I have about 500 flights on a set of 1/8 inch phenolic pads in my SV25 Shrike. They still look brand new to me so I wouldn't hesitate to recommend them. I have another SV under construction and it will be using 3/32 pads.
Regards,
Monty
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Here's how I do my profiles:
I use a "C" composite plastic mount from Sig or similar. I made a template for my router to cut an inlay in the doublers. I set the router depth to equal the thickness of the profile pad - usually just cutting into the maple bearer. Using a bottoming bit it also insures both bearers are dead flat and level. Use enough epoxy just to seal off the mount to avoid fuel seepage. I also used a dab of JB Weld to fill in any gap between doubler and mount, sand, cover and paint.
The finished product is invisible and you won't crush any plywood or have a chuck of metal or phenolic rearing their ugly heads on your profile. Like, why do I need to offset my engine another 1/8" to the outside?
(http://home.comcast.net/~steve.scott8/images/pr2.jpg)
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Right on Steve, here's another