Quick Question on Profile Landing Gear Attachment

I usually attach bent aluminum or CF landing gear to the sides of profile fuselages with two 4-40 screws passing through the fuselage at a maple beam or hard point added for the purpose. I have been spacing the two holes vertically about 7/8" apart and not really close to the bottom of the fuselage. My new fuselage has some space problems due to reduced height (just 3.0") and difficulty in getting tanks of my previous size with pickup tubes oriented right AND without globs of solder rattling around.

Before trying to re-plumb a really nice new tank though (and I'm pretty sure my inexperienced hands will not do that job well), I'm thinking of attaching the gear lower on the fuselage, below tank level. So I'm wondering how low and close together I can place these mounting holes vertically and not run into structural difficulties that will show up in my occasionally ugly landings in our wind.

Below is a drawing. The tank outline shown is for the old tank. The new one must be placed rearward. Since it is to be recessed, there will not be space for the gear attachment at tank level, unless I re-route the fuel pickup to the side. The total height of the fuselage is 3.0" The question really boils down to whether I can safely anchor landing gear on and below the bottom engine-mount beam in the area marked by "X X".. Thanks!

[photo not recovered: 32891.jpg]

SK

Attachment #1, (jpg file)

Serge,

I would glue a piece of motor mount where the lower hole will be. From the lower motor mount to the bottem of the fuse.

It will prevent any balsa crushing when you crank down on the gear bolts.

If the plane is not built, then adding a piece of motor mount stock probably would not hurt. If the plane is already built, then I would drill the hole larger and insert a brass tube epoxied in place to act as a spacer.

Thanks, guys. That's what I'd planned, regardless of where I placed them. It's time to attach the second (right-side) doubler. So, if you think it will be OK down there with the reinforcement, I'll probably do that, rather than attack the tank with unskilled intent.

Serge

Why not set the bolts in a horizontal configuration rather than vertical?

[photo not recovered: 32901.jpg]

Attachment #1, (jpg file)

Or use wire like a Twister?

I stole this idea from one of my flying buddies.
Works great.
Photo's not that great.


Paul Taylor

~I wish I knew everything you have forgotten about C/L.

Check out my Blog@
http://rootbeard.rcuniverse.com
A link to a slide show of a fun day: http://www.youtube.com/watch?v=V-_sR0ZydSQ

[photo not recovered: 32902.jpg]


[photo not recovered: 32903.jpg]


[photo not recovered: 32904.jpg]

Attachment #1, (jpg file)
Attachment #2, (jpg file)
Attachment #3, (jpg file)

The way it is shown, a hard landing is going to fold the gear back. I would reverse the gear.

Paul

Ray-

I think that on a heavier, say 36-oz, plane, there would be an awfully large leverage placed on such a small (vertically) plate area. That's one reason I was concerned about reducing my own vertical spacing near the bottom edge. I can see why your idea could work well on the smaller models though.

Thanks guys, for the comments and pictures!

SK

A hardwood block with inserts between the doublers about 2 inches long min. It also adds stiffness to the fuse at the leading edge of the wing.
Greg L. Bahrman

[photo not recovered: 32914.jpg]


[photo not recovered: 32915.jpg]

Attachment #1, (jpg file)
Attachment #2, (jpg file)

Very nice planes. So, these are bolted on from below?

SK

Serge,
On his new Ringmaster Gold kit, Pat Johnston shows a wire landing gear bolted completely to the bottom of the fuselage. He uses a stack of plywood pieces set into the bottom of the fuselage clamped between the plywood doublers. A short section of engine mount beam could be inset the same way to support an aluminum gear. Sorry, but my camera is on the fritz so no photos.
Steve

YES
Greg L. Bahrman

This setup works too, and is easy to maintain. The mount is a 1-2 in. piece of motor mount stock between the doublers. You can use one or two 6/32 sheet metal screws. The same method works fine with sheet aluminum gear. If you are worried about the block splitting(it takes an hellacious pancake landing to do it), put a couple of dowels through crosswise. Three strips of 1/8 ply, as mentioned above, would also be fine.

[photo not recovered: 32931.jpg]

Attachment #1, (jpg file)

>Ray-
>
>I think that on a heavier, say 36-oz, plane, there would be an
>awfully large leverage placed on such a small (vertically)
>plate area. That's one reason I was concerned about reducing
>my own vertical spacing near the bottom edge. I can see why
>your idea could work well on the smaller models though.
>
>Thanks guys, for the comments and pictures!
>
>SK

Yes, the plane in the picture is a (large) 1/2A--well, .061-powered. Even then, you're right, a really hard landing (up-right slap-in)might tear it out--but, as a certain one often says, "Build them to fly, not to crash." Best advice I ever took.

>If the plane is not built, then adding a piece of motor mount
>stock probably would not hurt. If the plane is already built,
>then I would drill the hole larger and insert a brass tube
>epoxied in place to act as a spacer.


One thing I learned a long time ago is that any type of high stress area like this it is best the bolts go through hardwood if you want the model to last a long time. That means maple, or birch or beech second.



JAK

Serge, here's a solution I used on the Twin Flight Streak


[photo not recovered: 32940.jpg]

Attachment #1, (jpg file)