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Sep 02, 2021, 06:08 PM
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Hm! - I hit something, and it went logoff-no save???
Re: Red Dragonfly 03-09-21 (dd-mm-yy):
Looks like a brought one!

I used some Tamiya white with talc to cover up discoloration.
Another light sand, and I can decant some spray fixative varnish and paint it on for
a little gloss. - no spraying: it causes to much overspray.

I "popped" the rear torque tube-embedded in the foam, so I cut down to it and refixed it with CA.- the tail was a bit twisted.

It is taking a while to get the Radiomaster Tx sorted- I am going through the setup video.
Then I can bind the Rx, and test all the servos.
I will leave the prop nut loose.

I will fasten some things down with Velcro tape- not supplied.
The receiver and Esc could do with holding down.

The tail servo adjusters are those dodgy screw ones.

I have some medium threadlock here- I will put a blob on each.
-it will soak into the bore, and hold things a bit better.
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Sep 05, 2021, 05:20 AM
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Thread OP
Progress report on Red Dragonfly:

1) Cutaway added to clear propeller.
The new motor is a little further forward.

2) Wing servos replaced with sg90 ones I had on hand.
They were totally dead.- wiring seemed to be OK.
I didn't slop paint on them this time.

3) This receiver won't bind with the Radiomaster transmitter.
- I ordered some more compatible transmitters.
2x 6 channel,(DSM-compatible), and 1x s-bus only unit.- Walkera Devo- compatible

4) Fully assembled and bound with the FSM transmitter - some issues with servos.
I did have to run the throttle trim down a bit to get it to arm.

I have remounted all servos to be easily removed, and will swap them out for
RaceStar MG 90 units- I have quite a few on order.

5) I may add some rudder and elevator extensions later. The surfaces look quite narrow.
1/8" balsa will do.

6) I am checking the COG. it is right at 25% of the chord, so may be usable without a counterweight. Maybe a little up-trim??

It is supposed to be at 32% chord, but that is probably a little tail-heavy. Is that a thing?
- in that it will want to fly slightly nose-up.
You would think ground-retrimming the elevator slightly down would fix that.

7) I modified the tailwheel steer/rudder horn unit to improve pushrod run.
The pushrod was bending quite a bit. The pushrods are quite flexible.
The mod looks pretty solid.
<edit>
Did the rear surfaces extension. + 20mm (3.4") . Looks good.
This should help with COG counterbalance, too.

Full assembly and some photos later today.

We have to wait a few days to get down to level 2 covid shutdown , then I can go out and try it.
In the meantime, freshen up on the simulator!
Last edited by Owen_bern; Sep 05, 2021 at 05:48 PM.
Sep 05, 2021, 07:07 PM
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Thread OP
Red Dragonfly photos:

These show the alterations:
- new motor and propeller.
-new wing cutaway for propeller.
-increased dihedral.
-extensions to rear planes.
<edit>
Looking at prop and motor rotation,
launch roll will be to the left, viewed from the rear.
These things tend to swerve violently even when standard, so I will watch out for that.
The takeoff roll may need some aileron to the right.

This would make a good belly launcher on grass, but the tailwheel is difficult to extract.
That could use wire skids mounted on the wings, to stop a wing digging in.
The tall UC front legs aggravate swerve on takeoff.
I see on Xjet, that belly launchers fly pretty flat once they get off the ground.
Last edited by Owen_bern; Sep 05, 2021 at 07:41 PM.
Sep 20, 2021, 06:34 AM
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Thread OP
Lovely colour side view of a Mig 3.

That is one mean looking machine!
I don't think it was very popular with Russian pilots at the time, being difficult to fly.
The cockpit looks well back, like on the Corsair.
Maybe they jammed the fuel tank in there, too.
I will look for a cutaway drawing.
<edit>
No, that is the ammo for the top cannons.

The Russian fighters had some really heavy armament stuck on top of the fuselage

Maybe this is why the FW 109D cockpit is so far back, too.

<edit>
No it is a tank. -maybe glycol mix, though it is pretty big.
The tank behind the radiator looks like a fuel tank.
I shall looks for a readable version of the labelled cutaway.
Last edited by Owen_bern; Sep 20, 2021 at 04:42 PM.
Sep 25, 2021, 03:17 AM
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Thread OP
I got the small catapult glider out today, and gave it a go.

It is still quite unpredictable when launched, either banking sharply, or pitching up and spinning, even at quite high speeds.
Maybe the banking balances excessive up-elevator- it seems to be more stable in a steep bank.

I did manage to fly it onto the roof, breaking off the lower fin.
I moved over the road after re-gluing the fin, but it never flew that well again.

There was a fair breeze, and quite a bit of turbulence. - maybe 8-10 mph breeze?

The delta angle is not as sharp as the delta dart.

I have modified it yet again:

1) removal of the leading edge conical camber.
I think this is adding an upwards pitching effect?? - opposite to a straight wing.
I think it also cancels out the dihedral.

2) Add more dihedral-to reduce the tendency to drop into a banking turn.

I shall see if this is an improvement.

It seems to have the COG far enough forward, and plenty of rear fin area, and

a bottom fin to help balance up the finger grip and slingshot hook.
Sep 25, 2021, 01:01 PM
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Coupez's Avatar
Here's some hand launch gliders from an informal "meet" during my grad school days (1983).

The unpainted gliders were mine (tip: they're lighter that way).

Try building and trimming a couple that look like this. There's some art involved in adjusting them, especially so they do a climbing turn after launch and roll out into a stable glide.

Once you've gotten proficient with a conventional design, you'll have a better feel for how to deal with unconventional ones.
Sep 30, 2021, 12:48 AM
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Thread OP
Modified Layout of my catapult glider.
---------------------------------------------------------

I have changed it to a semi-canard layout, with a delta foreplane fixed at the main wing angle.
I am not confident that a full delta of these dimensions, and this weight, is actually
capable of stable flight.

This layout is extended from a previous experiment with mid-plane slots.
This lead to continual breakage at a butt joint.

I could either add an overlap splice, or remove this section.

The gap should also act like a notch, breaking up the scroll vortex.

I am refinishing the whole thing at the moment, and will report back on its flying behaviour.
a possible future mod could be an additional notch in the foreplane,

This depends whether the uncontrollable pitch-up continues.

This layout shouldn't pitch up and spin like it did.

This shows behaviour as if the COG is too far to the rear. which it doesn't seem to be.

The COG close to the leading edge of the rear plane shouldn't be too far back.
Possibly adding rear wingtip elevons would help.

Flow could be too disturbed in close to the tail, where the current elevons are located.

Partially experimental also is the semi-circular wingtips with a low aspect ratio.

There is likely to be some interesting leading edge effects.

The problem with having a foreplane in line and close to the main wing

is that the front lift vortex effect tends to reduce rear lift, and possibly add to pitch-up.

Addition of forward elevators with a slight upward deflection may be needed as well.
<edit>
Now that I have made a cut, why not go the whole way, and rearrange it properly?

1) Section the nose and move the cockpit forward.
2) Cut off the front planes and re-attach them up 1 inch.
3) Add a fake jet engine section, for looks, and a tail cone.
4) raise and reshape the rudder.
I will keep the parallel front and rear planes, and will add elevators later, if needed.
The outline of the front plane is problematic.

At higher angles of attack, it gives an out of-balance upward pitch shift.

If needed, I will reduce rake below 45 degrees and add crop tips.
Last edited by Owen_bern; Sep 30, 2021 at 03:34 AM.
Sep 30, 2021, 05:05 PM
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Thread OP
Re small slingshot glider:

This is looking good, and is practically unrecognisable.

It looks like a proper Canard jet plane.

I can see whey they were called Canards.
With a shoulder forewing, it looks a lot like a duck chick!

I am still going to rely on the rear elevons , for now, with parallel front and rear planes.

First undercoat in this version.

Now to level off the balsa "Fur" , and have another round of balsa filler.

COG seems a bit forward, at the trailing edge of the Canard.

I will try it, but it may need to go back a bit.

This is going to be pretty heavy, but I can launch fairly quickly with the slingshot.
Oct 03, 2021, 01:04 AM
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Thread OP
Latest version - Slingshot glider.

The vertical tail is way too small. I have increased it by 75%, but now it looks way to big!
I am now making more use of gloves, having had a case of methylated spirits poisoning,
absorbed through my palms!
Oct 03, 2021, 08:31 PM
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Thread OP
Notes on slingshot glider: 4-10-21
----------------------------------
-not really a mid-size monoplane?
micro-sized??
The gloves I have (latex) are no good for solvents, so I have ordered some thin nitrile ones.
The battery article says these are the right ones to use.
- they should arrive in a couple of days.

I gave the Tamiya light-cured filler a go, but it is a bit hard, and needs quite coarse
sanding - 80-100 grit.

I gave it a coat of the Valleja grey undercoat, and you can see where the bare balsa is.
Maybe I will spot-patch with balsa filler, sand the next day, and bind it in place with more undercoat.
At least I can sand most of it tonight with finer grades of sandpaper.
I will get sheets of 240 grit dry, plus wet and dry, and more 400 grit.
I need more 80 grit dry as well, to build up my stocks.
80 grit wet would be handy, to.

I have been binding loose bits of filler back with CA glue.

that Rubberised medium CA does a good job.
It doesn't bubble up when I use the accelerator, and is easier to sand.
the nozzle is a bit damaged on this 1 oz tube, so I ordered more.

I can keep using the tube I have for "blob" application.
It is good for stiffening up balsa- it sets slowly, and I can use rubber gloves to spread it,
then clean the gloves with acetone.

I don't think the acetone is as toxic as the meths, for skin application.
- you shouldn't drink it straight, though!

Regarding appropriate use for joints:

I can use it to join 1/8" balsa edge on, and it seems bend-resistant.
(Across the grain)

It probably works for thicker balsa, too.

It doesn't make bend-resistant joins in PP foam, but is OK to hold motor mounts
in place, and a few other jobs.- ply to foam, balsa to foam.

Apparently there is a special foam glue, but I haven't needed that yet.

The rub. CA didn't work holding a tail skid in place on the surface of the foam-
That peels a thin layer of foam off parallel to the glue.

Would this be a form of peel (lack of) resistance?

You get this with harder woods and CA as well.
Oct 04, 2021, 08:20 AM
Registered User
Coupez's Avatar
Do yourself (and the rest of us) a big favor.

Put the slingshot glider, and all of your finishing products (paint, primers, dope, etc.) in a room of the house where you don't go often. Lock them up. Give someone else the key. This will avoid the temptation of doing any further work with them for the time being.

Now, take your delta glider plan. Cut a wing, canard, and profile fuselage out of 1/8" balsa sheet. Cut a vertical tail out of 1/16" balsa sheet. Cut slots for the wing and canard out of the profile fuselage.

Now, go to work with your sanding block and shape the wing and canard into airfoils. Thin the back of the fuselage to reduce weight. You can use as fine sandpaper as you like to smooth the surfaces, but DO NOT USE any dope, sanding sealer, primer, or paint OF ANY KIND. DO NOT coat any surfaces with thick CA glue in order to "toughen" them. They don't need it and this adds weight.

Assemble the pieces using the ABSOLUTE MINIMUM amount of glue necessary.

You now have a LIGHTWEIGHT profile delta glider. You can use this to find the CG position and incidence angles needed for stable flight.

DO NOT launch it with a slingshot. Instead, find an area covered with something soft (a meadow with long grass is ideal), and give it a gentle toss. If you built free flight models as a kid the same trimming rules still apply.

Don't worry because it isn't "pretty" - it is a TOOL made to do a certain JOB. It's expendable. Fly it, break it, fix it (add no more weight than necessary).

ONLY when you have this model flying well should you return to the painted one. Then you can apply what you have learned.
Oct 04, 2021, 03:07 PM
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Thread OP
Quote:
Originally Posted by Coupez
Do yourself (and the rest of us) a big favor.

Put the slingshot glider, and all of your finishing products (paint, primers, dope, etc.) in a room of the house where you don't go often. Lock them up. Give someone else the key. This will avoid the temptation of doing any further work with them for the time being.

Now, take your delta glider plan. Cut a wing, canard, and profile fuselage out of 1/8" balsa sheet. Cut a vertical tail out of 1/16" balsa sheet. Cut slots for the wing and canard out of the profile fuselage.

Now, go to work with your sanding block and shape the wing and canard into airfoils. Thin the back of the fuselage to reduce weight. You can use as fine sandpaper as you like to smooth the surfaces, but DO NOT USE any dope, sanding sealer, primer, or paint OF ANY KIND. DO NOT coat any surfaces with thick CA glue in order to "toughen" them. They don't need it and this adds weight.

Assemble the pieces using the ABSOLUTE MINIMUM amount of glue necessary.

You now have a LIGHTWEIGHT profile delta glider. You can use this to find the CG position and incidence angles needed for stable flight.

DO NOT launch it with a slingshot. Instead, find an area covered with something soft (a meadow with long grass is ideal), and give it a gentle toss. If you built free flight models as a kid the same trimming rules still apply.

Don't worry because it isn't "pretty" - it is a TOOL made to do a certain JOB. It's expendable. Fly it, break it, fix it (add no more weight than necessary).

ONLY when you have this model flying well should you return to the painted one. Then you can apply what you have learned.
Unneccesary.

I am learning quite well with my Canard "missile", thank you.

It only has side area instability left, Pitch , roll, COG are taken care of.

It will be ready for another test flight very shortly.
Oct 04, 2021, 05:04 PM
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scirocco's Avatar
The best place by far for these monologues is your blog. A forum thread is for useful interaction with other users. That ended about 1000 posts ago.
Oct 04, 2021, 05:49 PM
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Thread OP
Quote:
Originally Posted by scirocco
The best place by far for these monologues is your blog. A forum thread is for useful interaction with other users. That ended about 1000 posts ago.
It is a mixture of build notes, design notes, and some questions.

Once I get more experienced at small builds and actual flying, I will start a blog.
can I have a blog with multiple threads?

It is nice to have a thread for every build, design, or sub-topic.
it does make it hard to find out where my last reply ended up, though.
- there are now 5 mig-related threads, I think.
1) Physics,
2) VTOL
3) batteries and plugs,
4) Large EDF.
5) Scratchbuilt - not used for MIG??
Monoplanes is also in Scratchbuilt.- it is currently used for the slingshot plane only.
All other monoplane, single prop projects are on hold, or shelved.
I will check.
Should I close some of these?

Physics of nozzle-type chambered vectored thrust is not popular.

If I cannot get a good diffuser system in the space, I may look at getting a 3D printer again, for centrifugal compressors.

Possibly egg-crate diffuser inserts will work??
Last edited by Owen_bern; Oct 04, 2021 at 05:56 PM.
Oct 04, 2021, 07:22 PM
Registered User
Coupez's Avatar
Quote:
Originally Posted by Owen_bern
Once I get more experienced at small builds and actual flying, I will start a blog.
You can start your blog at any time.

Look on the "MyRCGroups" taskbar where it says, "Welcome, Owen_bern".

Click on your username. That will open a dialog box - on the third line is "My Blog".

Click on "My Blog", and a box titled "Welcome to your blog!" will open. Read the information carefully. Note that YOU control your blog, and can keep out comments that you don't find useful.

Then click on "Make a New Blog Entry" and away you go.

Using your blog, you can put all of your information in one place, rather than scattered among different threads.

Those interested can still find your projects, and you can add a post to each thread directing people to your blog for further updates.


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