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Engine mount ? Hardwood

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Engine mount ? Hardwood

Post  oldguy on Thu Jan 11, 2018 5:21 pm

I'm going to be scratch building my first S1 R/M. I have a piece of 1/4" red oak. This should work for making my mounts out of for the S1, right?
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Re: Engine mount ? Hardwood

Post  Jason_WI on Thu Jan 11, 2018 5:55 pm

Oak likes to split along the grain. I would use birch, beech, or maple. Something closed grain. Spruce would work too in a pinch.
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Re: Engine mount ? Hardwood

Post  Ken Cook on Thu Jan 11, 2018 6:42 pm

The Sterling S-1 A  ( Sheeted leading edge ) used poplar for the mounts. Engine mounts should be 3/8"x 1/2" for a .35 size engine.  The box didn't lie, it said hardwood mounts. Poplar is a hardwood due to it's species but the wood itself is far from being hard enough to use for it's designated purpose. A&J Free Flight kitted The YAK and F-51 Mustang in the 80's  based exactly on the Sterling Kits using the Sterling's instruction sheets. They used red oak for engine mounts. While it wouldn't be my choice if I was building one today, I wouldn't hesitate to use it. I've had my A&J planes flying since 1987 and they're still flying today.  Just let me mention though that a Sterling nose is very poorly designed. The engine bearers are 2" long and  only encapsulated between the 2 doublers which prevents the doublers from being squeezed together but doesn't do much for stiffening the nose from vibrations. Running the engine bearers back into the fuse offers a much stronger front end. The doublers on a stock Ring only extend to the back of the leading edge. Very very poor which sets up a stress riser allowing the  nose to break off directly in front of the wing. Reduce the stock 1/8" doublers to 3/32" 5 ply not 3 ply birch and extend the doublers to the high point of the wing and you won't regret it.
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Re: Engine mount ? Hardwood

Post  roddie on Thu Jan 11, 2018 7:09 pm

I would personally use maple Jim... and 1/4" is NOT thick enough.

My S1 fuse is 1/2" balsa. If I were to re-make beams/bearers for it.. I would cut them to a 1/2" x 3/8" dimension. The 3/8" dimension is what would be drilled-through for the machine-screws to mount the engine. Note Ken Cook's advice on the "length" of the beams..

Actually... you might want to go with 1/2" x 1/2" if you opt for installing threaded-inserts.

In any case; the plywood nose-doublers are used to cap-off the beams. Note Ken Cook's advice on the grade of plywood.. and extending them back further than noted on the plan.

See if you can find an old maple bureau that's being thrown out. Seriously.. one solid-maple drawer-panel would have enough square-inches of stock to make beams for dozens of models. Ripping strips on a table-saw is not difficult.
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Re: Engine mount ? Hardwood

Post  oldguy on Thu Jan 11, 2018 7:46 pm

Ken, Robbie.
 I meant to say I would double the 1/4" redwood.  And looking at the plans I see what you are talking about, running the engine bearers and doublers back further over the wing. I will take your advice on that, and use the thinner 3/32 doublers. And Yes the fuse is 1/2".
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Re: Engine mount ? Hardwood

Post  pkrankow on Thu Jan 11, 2018 8:12 pm

Hard maple, not any of the soft maple varieties. Order through Brodak, or find a plank, old chair, locker room bench and go to town with a table saw.

Yes i said chair, maple kitchen and dining sets are almost exclusively hard maple and a broken chair has a lifetime of wood in it.

Since this is a contest plane that may not fly much oak might be fine. White oak would be better.

Phil
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Re: Engine mount ? Hardwood

Post  oldguy on Sat Jan 13, 2018 4:01 pm

Well I went ahead and ordered up some maple 1/2 x 1/2 from Brodak.  I will be mounting a McCoy .35 on the nose of this R/M. I'm also debating with myself, whether to order a set of ribs or make myself. I have always made them myself but nut for a .35 size plane.
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Re: Engine mount ? Hardwood

Post  pkrankow on Sat Jan 13, 2018 8:20 pm

Bigger ribs are easier than small ones. Dont sweat it.
Phil
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Re: Engine mount ? Hardwood

Post  oldguy on Sat Jan 13, 2018 9:19 pm

pkrankow wrote:Bigger ribs are easier than small ones.  Dont sweat it.
Phil

Hey thanks for that.
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Re: Engine mount ? Hardwood

Post  RknRusty on Sat Jan 13, 2018 10:48 pm

I'm glad you went ahead and got the Maple.
You know oak has tiny xylem tubes through its length. Pick up an oak dowel and suck or blow into the end grain. It will pass air like a soda straw. I expect that betrays some undesireable weakness.
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Re: Engine mount ? Hardwood

Post  Jason_WI on Sat Jan 13, 2018 10:51 pm

RknRusty wrote:I'm glad you went ahead and got the Maple.
You know oak has tiny xylem tubes through its length. Pick up an oak dowel and suck or blow into the end grain. It will pass air like a soda straw. I expect that betrays some undesireable weakness.
Rusty

Only red oak does that. They make whiskey barrels out of white oak. White oak has tyloses which seals the ends of the pores. red oak does not.
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Re: Engine mount ? Hardwood

Post  Ken Cook on Sun Jan 14, 2018 10:45 am

I can tell you from experience, red oak works just fine . It wouldn't be my first choice but it does the job. I've used it on several combat foamies and have stuffed them into the ground without failure. In addition, it's far stronger than the rice wood used in the ARF models that use larger engines than the Ringmaster. Your only trying to keep the doublers from squeezing. The nose of a Ringmaster in it's entirety is far weaker than the wood bearers themselves. In other words, the nose is going to break at the wing's leading edge before the mounts can be broken.
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Re: Engine mount ? Hardwood

Post  Cribbs74 on Mon Jan 15, 2018 1:04 am

Hickory is the hardest wood we have in the US as far as I know. I have a bunch of it at my disposal. Luckily hard rock Maple is stockpiled at my home.
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Re: Engine mount ? Hardwood

Post  Jason_WI on Mon Jan 15, 2018 1:39 am

Cribbs74 wrote:Hickory is the hardest wood we have in the US as far as I know. I have a bunch of it at my disposal. Luckily hard rock Maple is stockpiled at my home.

Hickory is pretty hard stuff and available most anywhere. We have trees that grow around here called ironwood. Some kind of hornbeam. We use it for wood bearings. I cut some on my bandmill into boards to be used in the bottom of an auger bunk feeder that the auger rides on. It threw sparks off my saw blade when cutting it. It wears better than uhmw plastic.
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engine mounts

Post  Eddy on Wed Jun 27, 2018 11:20 am

I know there might be laughs over this, but I have since the 70's, used new popsicle sticks for beam engine mounts. They are made from White Popular, I epoxy between the layers and clamp together. For the .35 size engine, I use six sticks which will give a 1/2 inch width for the mount. For a .15 engine, I will use five sticks, it will give a 3/8 mount. And for 1/2 A, only 3 sticks are needed for a 1/4 mount. In years past when I flew some combat, a scratch built from plans, I still used this method for engine mounts. Simple and easy, an in all honesty no problems at all. If you have a Hobby Lobby near, a box of 1,000 popsicle sticks goes for under $5.00.
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Re: Engine mount ? Hardwood

Post  GallopingGhostler on Wed Jun 27, 2018 12:58 pm

Eddy wrote:I know there might be laughs over this, but I have since the 70's, used new popsicle sticks for beam engine mounts. They are made from White Popular, I epoxy between the layers and clamp together. For the .35 size engine, I use six sticks which will give a 1/2 inch width for the mount.

Eddy, I'd say instead perhaps you had the last laugh. Basically you were making plywood. Even though the grain was going more or less in the same direction, the Epoxy was imparting strength to the layers, and also strengthening the wood by soaking into the pores.

Plus, you've given me thoughts on how I can manufacture engine mount beams and other aircraft uses. One of the oldest hobby shops in Amarillo Texas closed a couple years ago. Another in Lubbock did too. All that's left is the one hobby store in Amarillo that sells mostly R/C car fuel and related, not much aircraft stuff.
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Re: Engine mount ? Hardwood

Post  oldguy on Wed Jun 27, 2018 1:06 pm

Eddy wrote:I know there might be laughs over this, but I have since the 70's, used new popsicle sticks for beam engine mounts. They are made from White Popular, I epoxy between the layers and clamp together. For the .35 size engine, I use six sticks which will give a 1/2 inch width for the mount. For a .15 engine, I will use five sticks, it will give a 3/8 mount. And for 1/2 A, only 3 sticks are needed for a 1/4 mount. In years past when I flew some combat, a scratch built from plans, I still used this method for engine mounts. Simple and easy, an in all honesty no problems at all. If you have a Hobby Lobby near, a box of 1,000 popsicle sticks goes for under $5.00.


Hey Eddie, no laughs from me as a guy who just mostly scratch builds and fly's for fun i'm always looking for ways to do things out of the norm.I'm going to try your idea on my next build what ever that turns out to be.
Thanks eddie
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