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Aug 15, 2003, 05:38 PM
sloping addict
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3D elevator construction techniques


Hi all

I've already built a "3D" sloper 1.75m span, and used a hollow fuse built up from Depron foam glass fiber covered.

Used a carbon rod and a 90 angled thing to move the elevator, see attached phto.

Now I'm building another smaller 3D capable sloper, 1.30m, thicker wings, less draggy fuselage. I sanded a fuse from core-wings foam so this time it's not hollow. I'd like to set up a pulley type system for its precision but I lack ideas of how to do it w/o digging too much into this fuse. The tail boom is only about 2" high and finishes by the fixed part of the rudder. I can eventually fit a HS55 in the boom but the boom would crack someday...



Ideas/photos on how to implement the system are welcome... Mine include having servo head + rigid pushrod on one side of fuse, or pulleys with kevlar cabling running just flush from the fuse. But there must be better ideas !

Thanks
Proto
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Aug 15, 2003, 05:45 PM
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The previous plane with trial wings (from a HLG !! : flied well but I I had to be careful with the elevator there). Buit up new wings since using (plywood over foam, polyurethane glue, vacuum bagged, and this is still light @ 500g the finished pair)

Can't take photos of the new one just yet...
Aug 15, 2003, 05:52 PM
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McGrrr's Avatar
Quote:
Originally posted by Protocooler
Can't take photos of the new one just yet...
Why? Too hot outside?

I souldn't say anything, It is 99*F outside my office right now.
Aug 15, 2003, 05:57 PM
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No just that I don't have a digital camera just yet ... Ordered a Canon one month ago - long delay, they sell like pancakes - should get it August 22....
Aug 15, 2003, 07:10 PM
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davensocal's Avatar
Proto-
Could you do the pull-pull by mounting the elevator servo on it's side? Then use a large 2 arm servo horn on the servo side.

I think the hardest part is how to attch the other end to the pivot rod of the elevator..

Could you maybe use a very large four arm servo horn to attach to the elevator? Take off one arm, so now you have two arms, plus another arm at 90 degrees. Use the horn mounting hole as the pivot point, the upper and lower arms for chord attaching, and the 90 degree arm for elevator movement..

I will try and make a sketch, sorry my explanation is so bad..
Aug 15, 2003, 07:19 PM
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I think this would work..

You could have the chords running along one side of the fuse, just under the skin..

You could even have the second elevator arm on the outside of the fuse. It would look funny, but it would work good.

Probably would nee to test it to make sure you can get enough throw, and the chords don't get loose at one end of the travel..

The blue outline is a guess where the elevator would be.

I know there are some very large servo horns available as well..
Aug 16, 2003, 12:27 AM
Quote:
Originally posted by SD-Flyer
Why? Too hot outside?

I souldn't say anything, It is 99*F outside my office right now.
No you SOULDN'T say anything girlfriend



Johnny................
Aug 16, 2003, 04:28 PM
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Thanks Dave, I'd thought about this setup. Actually for big throws pulleys will be better, but the issue is more that I'd like to avoid 2 cables running on one side + servo head popping outside. Not neat, and grass etc will always get stuck in the wires...
I coud dig the wires slightly below the skin but I will glass the fuse, so it means a cover plate atop the wires before glassing. and at 10mm thich the end there's barely the room fr all that.

I think I'll use to small Kavan tubes, one running on top of fuse, one on bottom, dig those tubes and let them out in a cavity each side (one in rudder for elevator pulley, and one in the middle of the fuse right behind the wing were the sevo could be located sideways). Then I could run kevlar wire inside the two tubes and turn it around 2 pulleys. I would stuck one pulley onto servo arm, the other pully between 2 small plywood plates

Anyone having photos of existing "3D" control setups, or other ideas? Photos are definitely a source of inspiration.
Also, any good trick to build light pulleys (without a mill)? I can't find any pre-made plastic ones the good size..

Thanks
Proto
Aug 17, 2003, 12:52 AM
Super Member
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If you really get stuck, I do have a mill

Good Luck!
Aug 17, 2003, 01:47 AM
CaliforniaSailplanes.com
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I am somewhat confused.... how are you going to make a slope plane do true 3D? If you mean simple aerobatics, I understand.

It seems though, today when someone talks 3D they mean a plane that will hover vertically and torque roll.There is no prop or power to hang the plane in the air. No way to torque roll, and rudder does not seem to be a useful item for most aileron slopers.

And... elevator... you don't really need much.

I'm just trying to see what you are looking to accomplish.

Steve
Aug 17, 2003, 02:58 AM
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Steve, Ok I suppose such sailplanes are not very common. Actually the only commercial ones I know of are:
- Kulbutin 3D (doesn't fly too good, mine has shown better)
- JR MadFox 3D (never seen one but could be amazing)
- to a lesser extent: Voltij but needs a mod of the elevator

First, rudder is a must have to do a number of figures, or to do them clean. A cuban 8, for example, cannot be done flat & clean without rudder input in the middle. It's distorted with no rudder. Even basic thermalling is much better with rudder and little counter order of the ailerons...
And there's no way you can do knife edge with no rudder.


As to the things you can do with a sailplane (no motor) and high throw elevator + good dynamic conditions, this may cause some jaw dropping from spectators . here you are for secial manoeuvers:

- Harrier: full up elevator facing wind, plane will stop and slowly go down vertically, you can even land that way from 5 m height like a helicopter. It doens't stall (mine at least). The trick is different with a powered plane.
- Waterfall loop (tail over nose)
- Kulbuto plunge - go to safety height (> 70m ) then full down, full up and so on and the plane will "slowly" go down like a pendulum

- Parkinson loop (still trying to figure it out - should be like an octogon)


So no need for a motor to do crazy things ! Just need enough of thermals or dynamic to gain height + a well oriented wind (not that often though to get correct wind direction & force + no rain)
I'll try to shoot a small video when possible.

Picture of MadFox 3D:
Aug 17, 2003, 03:28 AM
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Kulbuto plunge:
Aug 17, 2003, 11:48 AM
CaliforniaSailplanes.com
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OK....I understand.... How about posting a video of your current plane or your new one so we can view the aerobatics?

Thanks for the reply.

Steve
Last edited by stegre; Aug 17, 2003 at 11:53 AM.
Aug 30, 2003, 03:20 PM
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Here is the fuse that I shaped onto which I want to put a +/-70 flipping elevator, and one of the wings. I had already two pairs of wings that size (one balsa covered, one fiber+balsa), so this justified creation of the new fuse. I am not too motivated to finish it - another plane to repair first (felt 100+ meters on big bare rocks after lossing its elevator in flight following a flutter !!)
Last edited by Protocooler; Aug 30, 2003 at 03:23 PM.
Aug 30, 2003, 03:23 PM
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The picture:


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