|Jan 13, 2009, 11:27 PM|
FoMonie Motor Glider
My good buddy NoStep started a thread down in the Electric Scale forum some weeks past.
After developing Ply parts for his 1/3 scale project I decided to try my hand
at building Foam version - Hence the name FoMonie.
Fred and others have contributed lots of scale info in HIS thread.
Plans too in a different size, however.
My intent is to bring this scale powered glider to the Scratch Built Foamy Guys.
I've noticed quite a bit of interest in the few powered gliders that have
been introduced here in this forum.
Since Depron comes 1 Meter long I decided to make mine a 2 meter ship.
But then I thought, NO !
I have a Pile of FanFold and I wanted to use a Built Up wing so ...
I am going with about a 102" span using two 48" wings plus the fuse is about 6" wide. or about 38% of full sized.
"Moni" is 27.5' ws = 330"
1/3 scale = 110"
1/4 scale = 82.5
1/5 scale = 66"
1/6 scale = 55"
NoStep has plans already "at 1/3 Scale size" on the previously mentioned thread.
I've uploaded several pix to that thread of my current progress.
The thing that reminded me of this Homebuilt design from the past
was the recent news about a FULL SIZED homebuilt that was ELECTRIC POWERED.
here is inof about the Electric Full Sized AC
Here is info about the new IC powered motor glider.
Most of us decided that we didnt like the looks of the new wing tips.
I've done my designing in 3DCAD - Rhino specifically.
Then I cut all the parts on my CNC.
As I am building I'm making corrections to the plans so a PDF wont be ready for a bit.
So far , things like the inst panel weren't "just right" ,
and the Turtle deck was a smidge too small.
Later I may do the side by side seating fuse for the Xenos.
But I think the narrower fuse of the original Moni is more than sufficient
for anyones equipment , especially at this size.
Also those Wing tips on the Xenos look like they are Optional, at least from
some drawings that I've seen.
Finally, Horror of Horrors - I plan to use colored Packing tape for my "Finish" .
The Combat Flying Wing guys have been using it for years.
I've had good luck with the stuff on a Sloper that built.
And I just finished a Polaris and had even better luck with it on that project.
I also expect to get a lot of strength from the application of packing tape.
|Jan 14, 2009, 12:08 AM|
A few pix of wing progress.
I have discovered a very good use for OLD Nimh paks !
That is a 3 1/2 pound Bench vise sitting in the middle of one wing panel.
I'm thinking that after Packing tape covering there wont even be that much deflection.
For wing construction I have Cut the Fanfold leaving the Fold in place.
Marked ribs locations at every 2".
Marked where the lower spar goes and pin'd at either end a length of Kevlar thread.
Next a glue line and the 1/4" sq balsa spar.
Then glue on each of the 24 ribs, aligning them to ~ 1/4" from TE of lower foam.
Finally glue the top spar plus weights.
I used Elmers Ultimate, a urethane that does some foaming.
The TRICK is that the Front of each rib is NOT GLUED YET.
I'll do that when I glue down the TOP sheet half.
To do it all at once is nearly impossible ( for me anyway ) .
Plus I have to add the Wing plugin "stuff" before buttoning it up !
The Moni had Full Length Ailerons.
So I plan to use a balsa TE and a triangular balsa strip for the 'rons.
I'll trip the TE of the foam, glue on balsa, then hinge some TE stock to that
|Jan 14, 2009, 10:58 AM|
Before going to bed last evening I did a bit of wing building on the left wing.
I used some CF tubing left over from Kite Building.
Purchase at your local kite shop or try http://www.goodwindskites.com/index.shtml
I had some larger tubing for the PLUGIN section in the fuse as well.
Wing has .24" dia OD ( probably 6mm ) and the fuse will need a foot of 6mm ID.
Since the original Moni had sprung from new construction techniques I decided that
the foam version should attempt something new as well.
After gluing down the Ribs and bottom spar I located the CF tube between the spars.
Then I "Masking taped" between the ribs, on the back of the spars to close off
the thu holes. See pix.
Finally I squirted in Glue and let that set over night.
Pix show ...
the Tape behind the spars,
the Glue foamed up and set up the next AM
and final weighted down top panel glue down.
|Jan 14, 2009, 01:04 PM|
Regarding power setup.
I was 1st thinking of trying a SUMO 2814-08 motor
Thinking that I wanted to swing a bigger prop and could adjust the battery
to 2s1p instead of 3s1p if it was too much.
But now I've remembered thta I have a geared drive in my old Timer Dallair
which is about the same weight but built out of balsa and ply.
It has a Megadrive gearbox with a Hobby City 3900KV inrunner on it.
Formerly used in a Ducted fan F-15
The slower rpm, Higher pitch situation seems like a better choice.
|Jan 14, 2009, 04:54 PM|
Looks very intersting BOP,... I bet it would be a great camera platform. In my experience (albeit, limited) I have found that you don't need nearly as many ribs with a built-up FFF (or Depron, etc) wing as you do with a balsa plane for at least 3 reasons:
1. Aside from aesthetics, I think most built-up balsa wings have lots of ribs to maintain the airfoil shape... a long span of Monkote (for example) between balsa ribs means the covering between the ribs shrinks to a thinner wing profile... so you'd have varying degrees of lift and drag along the wing = turbulence and drag, and not very pretty.
2. Foam works in compression as well as tension to provide greater shear-strength between ribs. Monokote (for example) only provides tensile strength.
3. The very shape of curved foam is fairly strong on it's own. For the same reason that a tape-measure has a curved tape instead of flat, curved FFF provides its own support along the axis of the curve.
Generally speaking, I've found that rib-spacing roughly equivalent to the wing-chord is sufficient.
Just my 2 cents.
|Jan 14, 2009, 05:44 PM|
Thanx kram !
WarE : All good points !
yeah yeah yeah I know but what I didnt say here, but DID say in Freds thread
was that I got to arranging ribs for the CNC machine and just got INTO doing as
many as I could on a single sheet of Depron. Just seems more efficient ya know.
So since they dont weigh that much I decided to use as many as I could.
The UPSIDE IS - It oughta be UBER strong ! :-)
Got side tracked today with estimates for a NEW ROOF ! ! !
It's the NorthWest or is that Northwets :-))) suffice it to say,
We got a lot of rain here in the last month+ and , well ...
Some things became Self Evident :-(((
Cripes, we even made national news.
Bye Bye 20K ( that could have been A LOT OF FOAM )
|Jan 14, 2009, 06:48 PM|
So, I can't really tell from your previous photos because of all the glue, but I take it you are using a wood top and bottom spar and filling the gap with FFF? I wonder if there would be much benefit in adding a rear spar, to reduce flutter.
|Jan 14, 2009, 07:44 PM|
Remember, This is foaming glue.
Like Gorilla glue !
So with such an over ribbed wing and all the stiffness from the foam and two spars ,
exactly what flutter are you expecting towards the rear of the wing ?
B'sides ya get very far back on those ribs and they'd get Weak or difficult to cut out. or worse, two pieces.
I do plan to put a 3/8 balsa cap on the back of the ribs to make a solid Hinge point.
The aileron is going to be scale aka full length strip. Stiff as I can find.
I do not expect this bird to be anywhere near fast.
Just a "scale like" slow flying floater for calm times and early AM thermals.
|Jan 15, 2009, 02:03 AM|
Whatever ! or give full explanations, please :-)
One of us "isn't getting it", I guess, I dunno.
Tonight I managed to Hinge the Ruddervators , using Blenderm in "Z" fashion.
Plus I doubled the Fuse insides with a 2" wide piece of 1/4 balsa.
I want to do the Moni scale landing gear But at the same time I really like
the NEW Sonex style raked back dual wheel "look". I'm torn :-(
Regardless, the LG is going to need a well supported connection
and the wing mounting tubes will need it too.
So now comes the STUB Rudder at the rear most part of the Fuse.
To control it I need to run a rudder servo to it.
BUT, the rudder is also mixed in with the Elevator, hmmm ?
That means 3 pushrods going back because the stub rudder has to be
uncoupled from the Ruddervators.
Looking at the original Moni drawing I note a mechanical mixer was used.
Remembering an old Dubro mechanical mixer that mounted TO a servo output wheel
I decided to have a crack at designing my own version.
I liked the Ball End coupler usage and came up with this design.
It should be fairly easy to make from a piece of 1/4 thick plastic with only a drill press.
If the plastic is soft enough I might not even have to Tap the holes.
See pic and evaluate, please. Thanks
Here is the full sized pic of the GOAL
|Jan 15, 2009, 01:23 PM|
I'm starting ta feel like Rodney Dangerfield.
I weighed everything this AM just because I didn't feel like getting RIGHT to work.
The wings ~7 oz. each side
and the Fuse only 5 oz.
total 19 oz
So, just estimating and rambling on , I get ...
4 servos x 9g = 36 gm ( Ailerons 2 ea plus Elevator and rudder )
AR7000 Rx - 16 gm
40A ESC - 40 gm
Motor ~ - 125 gm
Bettery - 180 gm +-
totaling ! 14 oz for equipment
adding in the current weight I get 33 oz
It looks like 36 oz AUW is a realistic goal.
Making the wing loading 6.2 oz / sq ft
Unless we get crazy with Dummy pilots and stuff.
at 48 ox ( 3 lbs) that only 8.2 oz / sq ft
For motor sizing a glider can stand 100w / pound.
So anything around 250-300 watts ought to work.
|Jan 17, 2009, 12:54 AM|
OK here is a couple more pix of progress.
I have the TE blocks glued on and planed down and sanded.
Plus I made the ailerons from 1/4 balsa sheet stock cut to make the 8.25" cord
work out for the wings .
These were sanded from the sheets on a belt sander and sanded by hand for uniformity.
I HAD to go flying today as the NW had some unusually Good weather this week.
I managed a 1/2 hr with an EasyGlider plus two lipos of Polaris flights
and my F22 needed to be dusted off since last fall !
Oh, I also ordered some Ball link stuff from HC as well as a bunch of other stuff.
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