TheFoxes

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I'm trying to reduce the nose weight on an 50cc Edge with a G-62 up front. Right now I'm using a greatly reduced piece of 3/4" plywoood and a stack of three steel fender washers per bolt to get the 7/8" spacing I need. What can I use to make lightweight stand-offs that will not press into the firewall, and will seat nice and flat on the back of the engine?

Thanks!

Forrest

KenLambert

My Feedback: (107)

aluminum standoffs don't weigh much and with the large flats on the end will not crush the firewall unless you realy overtighten the bolts

Big_Bird

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I used a 1" red oak dowel to make standoffs for my ZDZ80RV. The dowel is available at Lowes or Home Depot. It's light weight, strong, readily available and best of all, cheap.

altavillan

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Do what BB does but sand the dowels flat to evanly contact the engine after they are positioned and CA'd to the fire wall. Ca'ing them to the firewall will help to keep the firewall from crushing. Get or make some aluminum washers (1" hole saw) that covers the end of the dowel. Then sell the 62 and buy a light engine.

BillS

Big Bird’s approach works well. As you can see they were very strong. The engine jumped out in the air.

Bill

Big_Bird

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Bill, sorry to see the crash but it looks like the standoffs were the strongest part of the plane.

altavillan

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Looks like a succesful test of how much nose weight is needed to succesfully destroy an airplane.

Tired Old Man

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You can go for the flash and style, be lazy, like to spend money, and buy aluminum standoffs that usually require that you add washers or spacers to get the length correct, or, you can make them out of wood, be just as light or lighter, reduce vibration levels, have the exact and correct length every time, and be cost free. Hardwoods and drilling straight holes are the only requirements.

72

BB- Do the bolts go all the way through he dowels or are there bolts from both ends into the dowel?

Big_Bird

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The 10x32 socket head cap screw goes through the dowel and into a T nut located behind the firewall. If you have trouble finding a long enough cap screw you can probably find it here.

http://www.microfasteners.com/

BillS

Don’t laugh I didn’t build the airplane. The construction was better than my building skills but I did mount the engine and equipment.

Postmortem revealed the firewall had been out sometime in the past. In addition a slightly out of balance prop had been run for 5 to 10 flights (by me unfortunately). Best guess is that the out of balance prop destroyed the firewall epoxy joints, which may not have been the best to start with.

After the 6 pound engine parted company with the airframe flight control was still available. At 6 pounds out of balance I was unable to deliberately put the airplane into the ground in a safe location and it floated merrily along its way over a neighbor’s house and cars and finally landed in his front yard. An embarrassing event, which could have been very expensive.

Bill

72

BB- Thanks for the quick reply. Getting the long socket heads is what I was worried about. Another Q? Alloy or stainless?

TheFoxes

My Feedback: (2)

So, hardwood seems priced right, after doing some online shopping and comparing. I only need 3/4" of wood plus a 1/8" aluminum washer. So, any reason I can't use a 1" holesaw on an oak board? Or use plywood for that matter?

Even just switching to aluminum washers will save a couple of ounces I suppose.


By the way "altavillian", the G-62 is the lightest, most reliable engine I've ever run - for free.

ff

Big_Bird

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I usually use the black alloy but stainless is OK also.

Big_Bird

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The reason that I used a redwood dowel is because it has very little crush in an end grain application. Use whatever you like. Just remember to recheck the screws for tightness after you have run the engine. I always put blue Loctite on the screw threads.

Rcpilot

My Feedback: (78)

I've used a 3/4" and a 1" hole saw to drill out aircraft ply donuts. The hole saw just happens to have a 1/4" pilot bit.

I'll stack up 3 layers of 1/4" ply and drill through them before emptying the hole saw out of the collected donuts. Then drill another stack. Continue until you have enough 1/4" donuts to stack up. Sand smooth and knock the burrs off.

I epoxy them together with a slow setting glue. Run a nylon 1/4--20 bolt covered in wax paper through the middle for alignment and clamp it overnight. Wipe off excess epoxy while it's still soft.

The longest standoffs I ever made like this were 1". I'm not sure if they would still work as well if you went up to say, 1.5" or 2".

altavillan

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FF; hard to beat free. I recomend dowels over plywood or cutting circles out of hard wood. Hardwood dowels are usualy made from maple. Becase it's the hardest wood. They will not compress enough to notice. Especially on the ends. You will see how hard they are when you start to sand them flat. Put a pencil mark on the ends and it takes 10 minutes to get it off. Blind nuts come in different lengths through the threaded area. Get the longest you can. Do not locktite the bolts into the blind nut. Just check them and re-tighten them after the first 4 then 6 then 12 etc. flights. Most of the loosening you will have will be the blind nut stretching and seating in the firewall.

altavillan

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Bill; Good job of flying dude, Rule #1 fly the plane away from people to crash. Yea I saw the wing was hardly hurt. again good job.

altavillan

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Read your post wrong ; you said you were "not" able to fly it. Well at least you tried.

TheFoxes

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I like to jam a Nylock nut behind the blind nut. Easy to tighten up without having to re-apply locktite, and it "firms up" the back of the blind nut. Maple it is! Thanks!

ff

altavillan

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Super; I was going to say put a lock nut there if you want to be more secure. The blind nut will spin before letting go of the bolt if you locktight them.