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Old Nov 13, 2010, 01:18 AM
Yes, "that" Karl...
karl k's Avatar
Canada, BC, Burnaby
Joined Mar 2007
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Zenith STOL CH 750

Has anyone done a foam version of this plane?

http://www.zenithair.com/stolch750/

Ugly as sin, but I love bush planes.

I haven't scratch built before, but I can't see the fuse being too hard to build.
The wings should be able to be hot wire cut easily enough.
I think that hot wire cutting the leading edge slats shouldn't be too difficult.

Because of the incredibly light wing loading of this plane, I was thinking that a 1/3 scale model could safely be 17 lbs without sacrificing performance. (17oz/sq. ft) That puts it at 119" ws. 52.5" per wing panel.
The only thing that worries me about this size is the fuse length. At 87", transport and storage may be an issue. Has anyone had luck making the fuse into 2 pieces so the tail can be attached at the field?

I have the power system to run it.

The plan so far is to use mostly standard building materials from Home Depot to build the plane. Possibly a 1x3 for the spar with a solid foam wing. The wings would be attached just like the full size, using no sort of wing tube, but rather a simple attachment. I was thinking door hinges.
The fuse would be built out of pink foam (1/2" or 3/4") with bulkheads for strength.

Ideally, I would build in a large bomb bay for dropping various payloads.

Just blue skying the idea right now.
Any suggestions?
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Old Nov 13, 2010, 01:20 AM
Yes, "that" Karl...
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Canada, BC, Burnaby
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Forgot to post the 3-view:



And a finished 1:1



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Old Nov 13, 2010, 01:23 AM
Yes, "that" Karl...
karl k's Avatar
Canada, BC, Burnaby
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Herein lies the true beauty of this plane:

Short take-off and slow landing in the STOL CH 750 light sport utility plane (1 min 2 sec)
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Old Nov 13, 2010, 10:54 AM
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I think it's a gorgeous plane, I sometimes have a hard time separating beauty and functionality though. I've been trying to talk my brother in law into building one in his newly bought house. I knew it could take off really quickly, but I didn't know it was THAT quick.

I've built a few planes with two piece fuses, although they weren't designed to come apart.
I think maybe 6 foot long spars(carbon fiber would be best but I'm pretty sure bamboo would work too if it's thick enough) spread around the fuse(one on the bottom, two on each side, one on the top) running lengthwise in a plastic sleeve(a straw maybe) and using neodymium magnets to keep sections together.
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Old Nov 13, 2010, 01:24 PM
can't dance..so let's fly.
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da zenith of indecision..
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I like it..someone has to model this plane.!
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Old Nov 13, 2010, 01:41 PM
Yes, "that" Karl...
karl k's Avatar
Canada, BC, Burnaby
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That's what I was thinking.

Could people with experience building larger foamies chime in to help with ideas for construction?

I may actually power this plane with a *gasp* converted string trimmer engine. If it proves too much of a pain to fuel proof the foam, I may just stick with 2kw or so of electrons to run it.

I've got some dubro 6" air filled bush wheels sitting around ready for the main gear. I'll grab another one for the nose gear an be ready for tough field landings.

Note: This plane uses flaperons as the control surface for the wing is actually separate from the wing. Because of the length of the control surface, would it be advisable to run 2 servos on each flaperon to avoid too much twisting of the surface?
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Old Nov 13, 2010, 04:38 PM
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Dayton Intl, Ohio, United States
Joined Jan 2000
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We have a full scale locally that drops in at our rc field occasionally. We have a 900 ft runway and even loaded with a passenger I've never seen him use more than a third of our runway. I particularly like that the stab is flat on top and airfoiled on the bottom. An rc version would be awesome.

Azarr
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Old Nov 13, 2010, 04:46 PM
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FWIW, I worked at Zenair for a while, and did a little bit of work on the original 701 prototype . So I never thought it was ugly.
It has also been widely copied, perhaps more than just about any other plane.

http://www.zenithair.com/stolch701/7-photo-copies.html

Zenair actually has info on their web site to help modelers out, including drawings you can download

http://www.zenithair.com/stolch701/7-rc-model.html

Pat MacKenzie
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Old Nov 13, 2010, 06:02 PM
Yes, "that" Karl...
karl k's Avatar
Canada, BC, Burnaby
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Quote:
Originally Posted by pmackenzie View Post
FWIW, I worked at Zenair for a while, and did a little bit of work on the original 701 prototype . So I never thought it was ugly.
It has also been widely copied, perhaps more than just about any other plane.

http://www.zenithair.com/stolch701/7-photo-copies.html

Zenair actually has info on their web site to help modelers out, including drawings you can download

http://www.zenithair.com/stolch701/7-rc-model.html

Pat MacKenzie
Since you worked there, maybe you could answer a question I have about the controls.

It is mentioned that the plane uses flaperons. Is the full length of the control surface always moved as one? From the drawings it looks like the flaperons are in 2 pieces for each wing. That is why I'm wondering this.

Concerning the wing:
The airfoil is listed as a NACA 650-18 mod (before cutting the slot for the slat)

This leads me to believe that I could cut that airfoil for the wing, then hotwire away the leading edge slat. Then hotwire the slot portion away, then use small portions of the slot material as brackets to glue the leading edge slat back into place. Does this method sound reasonable?
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Old Nov 13, 2010, 06:15 PM
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On the 701 the flaperons were full span and move together
The look like they are in two parts because the outboard half is at a lower angle then the inboard to reduce the chance of outboard stalling.
They are joined by small plates that sets the relative angle.


Pat MacKenzie
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Old Nov 13, 2010, 07:20 PM
Yes, "that" Karl...
karl k's Avatar
Canada, BC, Burnaby
Joined Mar 2007
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Quote:
Originally Posted by pmackenzie View Post
On the 701 the flaperons were full span and move together
The look like they are in two parts because the outboard half is at a lower angle then the inboard to reduce the chance of outboard stalling.
They are joined by small plates that sets the relative angle.


Pat MacKenzie
Were the flaperons any different on the CH 750?

I can't believe my luck having you help out with these little details!
Usually, I'd imagine it's an exercise in watching video and looking at photos to figure out some of these points.

Thanks for everything so far and I hope you don't mind answering some more questions as I get them.
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Old Nov 13, 2010, 07:28 PM
I don't want to "Switch Now"
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750 is past my time there, but I doubt they would have changed that.
If you watch the video at 7 seconds in you can see the curved slot in the fuse where the flap connects to the controls. Looks exactly the same on the 701.
Most of the changes on the 750 versus the 701 seem to be minor tweaks, not a redesign of Chris Heintz's original concepts.

Pat MacKenzie
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Old Nov 14, 2010, 01:16 PM
Fremont, CA
United States, CA, Fremont
Joined Jan 2009
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Here's a clip of a model taking off from a car top
http://www.youtube.com/user/argyrisb.../0/No4dtuPjZwE
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Old Nov 14, 2010, 01:33 PM
CNC Cutter
birdofplay's Avatar
United States, IN, Indianapolis
Joined Dec 2005
8,674 Posts
I have always kinda wanted to do this plane.
I've seen them at Oskosh.

A N D I've always seemed to MISS the start of some really neat projects in this forum.

SO OK Is anyone Doing this design in CAD yet ?

It looks fairly simple to do.

If no body is working on it already I'll give it a go.

Do we want to use a built up Wing ( could be foam ribs and covering )
Something with a fairly thick low speed High Lift foil.
That way we'd get all the STOL that this bird has to offer !

And What size ?
Since it's going to be a SLOW flyer with terrific STOL it can be a lot larger than
typical fast park foamys.

36", 48", 60"

Model preference : 701 801 750

Or are they all close enough for foamy modelers to not really care ?

When we are done I can cut them on my CNC
or just share the plans her for you to build on your own.

Let me know - I can get started in a flash !
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Old Nov 14, 2010, 02:21 PM
Yes, "that" Karl...
karl k's Avatar
Canada, BC, Burnaby
Joined Mar 2007
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I'm looking at doing a 1:3 scale CH 750
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