Zenith STOL CH 750 - Page 5 - RC Groups
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Nov 21, 2010, 10:37 PM
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biznak's Avatar
thats pretty impressive!! the foam definately adds some strength
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Nov 22, 2010, 12:23 AM
Retired CAD guy
birdofplay's Avatar
The older , no longer available, RCFoam product was ~ 1/8 thick but the density
of 6mm Depron. It did have a Skin side that was fairly tough too.

Oh well depron won out - but I still have a little left and like it.

Tonight I decided that the wing TE needed some stiffening
so I added a strip of 1/32 ply on the bottom.

I believe it will come in handy when mounting the flying Flaperons.

I also did the Main LG tonight.
Just some bent wire a quick wire wrap and some solder.

Tomorrow I have to cut into the bottom of the cowl to make that access hatch.
Plus I have to add some beef to the Firewall and do the motor mount.
not to mention the Nose Gear.

I may still put the Flaperon servos in the Fuse.
I rethought it and N O electronics in the wings sounded good to me.

Nov 22, 2010, 02:39 PM
Retired CAD guy
birdofplay's Avatar
I partially covered the final bottom sheeting before gluing in place.
After glue application the sheeting was placed and the edges Ironed down on the bottom and TE.

I should have done the ply strips before any sheeting and
glued up the sheeting to size before starting.

20/20 hide site !

Working on Nose gear and Motor mounting today !

EDIT l8r: added pix of Wing tip work.

I simply set my 6" belt sander to 60 deg and sanded off the tips
until I got to the highest point on the top edge.

Perfect Horners !

I will most likely add a thing sheet of something to cover over the
dual colors and slight gaps.

I replace the tips on my PA-28-180, back when I owned it.
The Piper Lipstick Look went away,
And it reduced the Stall by a coupla MPH.

T's all for now
Last edited by birdofplay; Nov 22, 2010 at 03:22 PM.
Nov 22, 2010, 04:18 PM
Yes, "that" Karl...
karl k's Avatar
Excellent work!

I won't be able to start on mine for a bit as I have some other obligations that need to be taken care of.

Enjoying seeing how yours comes together, though.
Nov 22, 2010, 11:07 PM
Registered User
biznak's Avatar
are you doing internal wing bell cranks or external bell cranks then to keep the servos out of the wing?
Nov 23, 2010, 12:07 AM
Retired CAD guy
birdofplay's Avatar
I believe that the full sized version merely connects the ENDS of the flaperons
to whatever moves them in the Fuse.
There is some discussion about how to align and cut the ARC slot in the side of the fuse
to connect the flaperons.
You can just barely make out the slot between the 2nd and third windows on the Yellow bird
in 1st page of these posts.

So I was thinking that a similar idea might work just a well on this one.

I plan to use hard balsa for the flaperons.
Even so I kinda expect a bit of warp in use.
then again this is one slow flying STOL plane with light aero loads.

The full sized also split the flaperons and moved the outer parts to a lower AoA
to help prevent tip stalls.

I might do that also.

This PM I pulled out a motor, ESC and RX from another summer casualty.

I also have the Slat mountings glued to the wing. see pix.

Whether they work on not will only be told during flight !

And as you can see in the second pic ,
Grizzly came thru with the Gorilla glue.

Whereas, HK only Just got my pkg out of country , sigh ...
Last edited by birdofplay; Nov 23, 2010 at 12:13 AM.
Nov 23, 2010, 06:18 PM
Retired CAD guy
birdofplay's Avatar
Before the weekend / Holiday becomes a Non building weekend,
I thought I'd post some more progress.

Motor mount and Nose gear block in place.

Not shown but I have the Slats started but not completed.

The wheels are old crap that will be replaced with new hopefully lighter stuff.

The only parts not on the scale are the Struts and control linkages.
I even tossed in a 2200ma 3s1p for good measure.

That danged LG and motor + mount really tipped the scales.

Whatchagonnado ?
Nov 23, 2010, 10:40 PM
Registered User
biznak's Avatar
wow it got heavy fast!!
did you include some servos in that??
Nov 24, 2010, 12:50 AM
Retired CAD guy
birdofplay's Avatar
Oh yes !

I tossed in everything except the To Be Built Flaperons and their pivots
and the struts.
RX, Servos, ESC, Lipo the LG and wheels and the tail parts were Pined on.

I may replace the fairly heavy Nose gear with something home made.

My GP Cherokee flies well if not Fast at 5.5-6 lbs and it's 60" too.

3+ lbs lighter should still make for some serious STOL performance.

I also note that the Nose seems a bit too large proportionally.

I was looking at the Zenair site and noted that most models seem to
taper more to the nose than the drawing depict, IMHO.

Not sure what to do about it at this point in my build.

With all the "models" on the Zenair site there are NO PLANS that I could find.

I suppose some day a Cowl mold could be crafted and some pieces pulled
out of plastic. ( vac formed )

but thats for later too.

Happy Holiday weekend.
Nov 24, 2010, 05:38 PM
Retired CAD guy
birdofplay's Avatar
AS things turned out I had some time to day to work on the wings.

The Slats are now all but done.

What a HOOT these things are.

Kinda of a pain to build and NOT you usual built up wings.

And they look kinda ugly - sorry , but they just do:-(

I used 1mm depron to make them to their shape.
Using lots of "dent" scoring every 1/4" on the back sides and
then gently bending the sheets one score at a time.
Then I got the idea to tape one edge to an aluminum pipe and
While wrapped partly around it I used a JUDICIOUS amount of Heat Gun
to "set" the curves before gluing them on.
I used lots of blue tape to hold things in place while the glue set up.
Eventually I will cover over the ends of the Slats but I had to take pix of the
structure as it is right now for the build records here in rcg.
Wheew !

They are going to be delicate. but the weight is seriously saved
using the 1mm sheeting method.

See the pix.
BTW that pix with the Wings On is just a dress rehearsal and NOT the real dihedral.

If they work as advertised this should be a real STOL Floater !

This is gonna be fun to fly !


In other news, I found a CH701 or more in FMS simulator.
It flys Lousy in the sim as provided ! :-(
So, I have taken the opportunity to modify the .par file to
"adjust" the characteristics and make it more realistic in the FMS Sim.
The "pardes" program was used for the adjustment.
It's getting better with fiddling :-)
Last edited by birdofplay; Nov 24, 2010 at 05:43 PM.
Nov 25, 2010, 12:27 AM
Registered User
biznak's Avatar
wow that looks huge!!
though the rudder looks tiny!!

could be the small prop too though
Nov 25, 2010, 10:22 AM
Retired CAD guy
birdofplay's Avatar
Agreed ! on all counts.

Note that the wings are NOT at their intended dihedral.

In spite of the full sized pdf that depicts the slats and their stand off distance
that I used for reference, MY Slats appear way too large or too far stood off ! :-(

That said, I believe that it should fly well with these "enhancements".
Fatter should work well at lower speeds.

All the movies I've seen show a narrowing Cowl but the 750 3-view show a fairly
squarish non tapering Fat Cowl.

I'm going to have to go look at things again.
Artistic Drawings are almost always misleading, I have found.
Never square, never symmetrical, never exact. too much artistic license for my tastes.

The Rudder Does LOOK Tiny.
But Look at https://www.rcgroups.com/forums/show...82&postcount=2

I'm going to go to the full size dimension and see how they scale to 60 " size.

I will say that the FMS sim has paltry rudder action.
I went in and edited it to some serious rudder control.
Usually in FMS I have never been able to get planes to act "Scale"

I now have the FMS CH701 acting much better, for my tastes anyway.

Finally, the only progress since the last post is that I've covered over the
Wing tips and Slat ends with some 1mm sheet.

Happy Thanksgiving
Nov 25, 2010, 06:39 PM
Live to fly... Fly to live
mudman1959's Avatar
Cool Model! I helped a friend wire up a real one of these and it flies great! Hope your model flies the same... Mudman1959
Nov 25, 2010, 09:10 PM
Yes, "that" Karl...
karl k's Avatar
Originally Posted by birdofplay
The Rudder Does LOOK Tiny.
But Look at https://www.rcgroups.com/forums/show...82&postcount=2
Did you build your rudder as all flying, or conventional?

Zenith used the all flying rudder to maximize control at low speeds
Nov 28, 2010, 03:17 PM
Retired CAD guy
birdofplay's Avatar
All flying rudder yup yup yup

That HK order is Still not in country ! ?
They sent it by Swiss Air and it took forever to get out of China then it went to
Singapore then to Zurich ! Cheeeez it's been since Nov 17 !!!
Slow Boat across the pond would have been faster !

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