Mugi with 3 or 4 mm coroplast?

[jimw1956]

I am planning to build a mugi design wing with coroplast. I really don't want to have to order the 2mm stuff if I can help it. I can get 3 or 4 mm locally. My question is with a speed 400 would the added weight make it unflyable, or just a lot tamer than the lighter wing would be? What if I reduced the size by 25 - 30% to drop the weight some, or maybe used foam for some of the reinforcement peices to lower weight? This would be my first delta and I really don't care if it is not a complete speed demon as long as it flies well.

[fdix]

I never built a Mugi, but several Pibros. The idea is basically the same, the Pibros is made of 3mm depron though. It's very pleasant to fly with a speed 400 up front and 3s kokam 1500 (yeah they are very old ).

I guess that 3mm coroplast would be okay too, or why not try depron?

Here are some pics

[falingtrea]

These people carry 2mm Coroplast in many colors and are pretty reasonable. They will even cut before shipping.

https://www.harborsales.net/

[Up&Away]

You could go with the 2mm coroplast, but put either a carbon rod, or a hardwood wingspar the entire width on the CG location.
I am planning a 120cm Mugi myself with 3mm coroplast, but for slopesoaring only. I will include a wingspar, even without motor.

[dimadee]

I have built a number of Mugi's. The first was 3mm and it was good, but the 2mm ones were awesome!

I used a QRP 6V reverse timed speed 400, a GWS 5 x 4.3 prop and a 2200 mAh 3S LiPo pack. The 2mm Mugi was a blast to fly - very aerobatic and really fast! I ran the motors in backwards in a glass of water, and every week or 2 I would put a drop of synthetic oil on the front and back bush (this definitely makes a difference)!

One of the best bang for buck planes on the planet!! Get some 2mm if you can.

[srdougm]

Would you please explain the glass of water break in technique? First time I have heard of it.

[dimadee]

Sure thing!

First thing you need is a glass of water! Solder a couple of wires onto the motor and connect them to the battery so that it rotates in the opposite direction to what it will when installed in your plane. You use a single 1.5V battery (AA or anything else you have - I use a charged NiMH).

Submerge the rotating motor into the glass of water. I normally bend the wires so that they hook over the rim of the glass and hold the motor off of the bottom. I let it run for 10 to 15 minutes. You will see that the water becomes grey - this is carbon from the brushes as they bed in.

After 10 - 15 mins, remove the motor from the glass and disconnect it from the battery. Blow the water out of the motor (by mouth or compressed air) and then spray some WD-40 or CRC in the motor to ensure all of the water is displaced.

Wipe the motor down and it is ready to install!

[redgiki]

Originally Posted by dimadee

...connect them to the battery so that it rotates in the opposite direction to what it will when installed in your plane.

I agree with the advice except for this part. What his procedure would do is set the brushes so that they have the most contact area in the opposite direction from the way you are using them.

You want to break-in in exactly the SAME direction the motor will be used in your plane. You can break-in both directions, of course, but that does reduce your surface area somewhat. If you break-in in the opposite direction, you're left with a motor that runs about as if it hadn't been broken-in in the first place.

[Up&Away]

Something like this:

[dimadee]

Originally Posted by redgiki

I agree with the advice except for this part. What his procedure would do is set the brushes so that they have the most contact area in the opposite direction from the way you are using them.

You want to break-in in exactly the SAME direction the motor will be used in your plane. You can break-in both directions, of course, but that does reduce your surface area somewhat. If you break-in in the opposite direction, you're left with a motor that runs about as if it hadn't been broken-in in the first place.

Thanks for your comments redgiki. I did not come up with this process myself, but rather researched the web and took the most common elements, including the reverse rotation for running in.

I am definitely not an expert, so you may be right.

I do think it a little extreme to suggest that running a motor in in reverse would make it perform as if it was not run in at all!

[kushal_22]

I would suggest if you are going wit 3mm to get a Inexpensive BL motor there are Many out there right now Warp4 HET Himax Mega E-Flight Just to name a few. Try Something like a Mega 4 turn or HET 4 turn that would push your Mugi around at a great Pace. I Myself made one and am using a Mega 3 turn. But like i said a 4 turn with a 6x4 prop and a 3S Lipo pack would make this thing Haul.

Regards
Mal

[xray328]

Any of you cats have the plans to make one of these outta 2mm?

[falingtrea]

I believe the standard Mugi plans on the Mugi website is using 2mm coroplast.

http://www.mugi.co.uk/evo_intro.php

[hauts]

I still haven't been able to get a Mugi to fly.

I used 2mm, 330 grams / square meter coroplast like they recommed on the website, and built it light.

First tried with a speed400 and 8x1000 nimh as suggested, no success. On the best tries, when I threw the plane hard, into a lot of wind, it would float around a bit with nose up and then stall and fall after 50-100 meters or at least when I tried to turn even slightly.

Then I tried a bp2410-12 brushless with 3s 2000 lipo, which are much lighter weight and have way more thrust. The plane would almost stay in the air but not really fly, it was still only floating kinda like a pizzabox flyer but faster.

I believe I exhausted the possible COG's and thrust angle / elevon reflex / control throw settings and all I have is a bunch of broken props and a bit crumbled Mugi that still hasn't flown anything like the ones in the videos. In the end I cut off way more coroplast from the middle of trailing edge to get the motor more forward, but that didn't help either.

Just doesn't pick up speed, seems to fly only on the motor thrust like there's no lift from the wing at all.

I'd really like a usable Mugi, as it'd be the perfect portable plane and also it seems spectacularly fast. Anyone have similar experiences, any idea why mine perform so poorly?

[Up&Away]

What props are you using, and (I know this sounds silly, but like many before me, I've done it wrong once or twice) are the props mounted correctly for pusher config?

[hauts]

Yes I mount them the right way

And I've used and destroyed many props, at least these:

4.75 x 4.75 with speed 400
7x4 with speed 400
7x6 with brushless
11x7 cut down to about 7x7 with brusless

There is a lot of static thrust, and I've flown heavier planes with the same motors / props.

The brushless motor is 1530 rpm/v and doesn't easily get hot with these props and 3s lipo. The speed 400 got hot, way too easily, with a 7x4 and 8 cell nimh, but still gives good thrust for a larger wing plane (dAzi).

Any suggestions for better power system? Should I have more rpm / pitch?

I do have a much bigger motor and some thick coroplast to make a 250% or slightly larger Mugi, but I'm afraid it'd be waste of time. Maybe if I find some depron or similar foam, I'll try with the current power system again.

[dimadee]

I have built a number of Mugi's with excellent success, so I am a bit puzzled.

The only thing I can think of is that the prop is spinning the right way, but is mounted backwards. I have seen this twice (it is easy to do) where other flyers were flying planes that seemed to have very poor performance, and when we looked, the leading edge (front facing) was actually the sharp, trailing edge of the prop. Although it was making reasonable thrust in our hands, it was not enough to fly the plane positively as it created lots of drag and turbulence when flying.

The last Mugi I made had a 6v speed 400 with a 3S lipo pack and a GWS 5x4.3 prop. These props are fantastic with a speed 400 as they make a good balance of power and thrust without drawing too much current, and they are nice and quiet. This last Mugi was my favourite, and flew really fast! I flew it 2 to 3 times a week in my lunchbreak for 9 months.
You can see a picture of it in the gallery on my website for anyone who is interested.

I'm sorry I can't think of any other reason why your Mugi is not right.

[hauts]

All my functional planes at the moment are pushers and I can assure you, the props have been correctly.

Now that I ventured to the Mugi site... the videos and pics just make me want to try it. Again!

I think I must rebuild it once more and try again. This time even lighter. At least it's cheap and quick.

[falingtrea]

This may sound silly,:o but are your folds on the inside or outside of the Mugi? I would think exposed flutes, especially on the leading edge, would cause loss of performance.

[hauts]

Folded as per the instructions, there's no exposed flutes (except on couple of spots that have hit the ground too hard too many times)

Will fold another one and try again, anyway the current one is so mutilated and crumbled it's time to put it in trash.

[dimadee]

Before you put it in the trash, are you able to post some pictures of it please?

A picture is worth a thousand words!

[hauts]

Huh!

Yesterday evening, during three beers, I cut, bent and glued together a new Mugi. I'm getting quick at that.. this is only the third Mugi I made.

I made the airfoil much slimmer than before, just to see if that's a problem, and:

I put in micro servos instead of standard. I only recently bought some micros and had them sitting around, and hadn't really realised how much weight that would save.

This is my first non-rtf plane where I put micro servos, and I'd never taken out the ones that are in my Beginair. Weighing the servos and then the planes in my hands I realized there's tens of grams difference. That would of course get much worse with the brushed motor and heavy nimh battery that I was mostly using before.

This morning, on only the third throw I got the plane in trim and it flew just good. FAST. And very easily controllable when I got the throws right (needed surprisingly wide throws).

Adrenalinny little plane, I circled the field a few times and did some very fast rolls, scary sounding low passes and some pretty unstraight loops - the elevator response probably isn't totally symmetrical, but it was a maiden flight anyway. Landings easy and floaty, I got the plane to literally land at my feet.

I suppose the standard servos + the space they needed (thick airfoil) might have been the cause for the previous Mugis being such unflyables.

So ... I can't complain. Except about my own ignorance. The new one with 9gram servos, thin music wire pushrods with z-bends, and all gear in except battery, feels about the same weight as the old one with old Hitec servos and Sullivan snakes + clevises. The only "problem" was I had to put the lipo way more forward to balance the plane - also stupidity at play here, because I put the servos more backward than necessary.

Another minor difference is that the previous one had elevons being of the same piece of coroplast as the main wing, with coroplast slot hinges, so the elevons were level with the underside of TE. I remember seeing pictures of others doing that and thought that doesn't matter.

Now I used tape hinges and made the topside level. But still I can't know if that can affect it so much.

I used the same BP brushless with cut down 11x7 -> 7x7, and 2000 3s1p lipo as before. Almost level thrust angle, very very little reflex on elevons. It just speeded up and climbed in a steep angle when I gave it some throttle and very gentle up elevon.

Now I believe this would also fly with a speed 400 or 380 easily, but the insane speed it has now is addictive... It wants more power, not less! And probably a carbon spar.

I wonder how much more I'd need to get the unlimited vertical. Now the best it does is climb a few - ten meters up straight. Maybe 4s lipo would help.

Dimadee, I'll try to post pics of both tonight. The old one, though, is stripped of parts except for the big servos. Maybe I won't trash it after all, but just fix some damage, replace the servos and rods and otherwise make it more like this one.

Still the most fantastic thing is that I can carry this plane strapped onto my backpack. Until today, my fastest and best flying plane had a 1.6 meter span... no carrying that around on a bike, and not nice carrying it on public transport.

[hauts]

Hehe. WOT, a couple of fast circles around the field, then a slight misjudgement. I've saved the plane many times from a similar situation but no luck this time.

First time I really destroyed a motor. Shouldn't have soldered it directly onto the esc wires... now it needs to be rewound. The bearing in the motormount end was already destroyed anyway, still the plane flew very well and fast until the last stupid dive.

Other than motor and prop, the horrible crash did quite little damage, one control horn broke off and the antenna wire came off the rx. All will be fixed tonite. The coroplast returned to its normal shape in a couple of minutes all by itself.

The lipo didn't swell or smell so it'll get more punishment tomorrow morning. It still has most of the charge left.

Some of the nose crushedness came from trying night flying a couple days ago. Not easy, leds or not... I hit a lamp post and then a tree, not to mention the ground.

Luckily these ebay bl's are cheaper than speed400's at my local hobby store - brand new replacement arrived from HK just yesterday. Just in time!


Other than flying this brushless speed monster, I put a 380 motor in another Mugi. Hey, it flies too! Much slower and more relaxed flying though.

edit:attachments

[hauts]

And yes, the picture of the failed Mugi beside the one that worked... now I rebuilt the old one partially and put in 9 gram servos and a 380, and it flies.

It's not clear from the pic but it's a lot fatter than the new one. As far as I can tell the size difference of the fins is not important and servo placement is totally noncritical, but stay away from big servos.

edit, blahhh

[flybilly]

Originally Posted by dimadee

I have built a number of Mugi's. The first was 3mm and it was good, but the 2mm ones were awesome!

I used a QRP 6V reverse timed speed 400, a GWS 5 x 4.3 prop and a 2200 mAh 3S LiPo pack. The 2mm Mugi was a blast to fly - very aerobatic and really fast! I ran the motors in backwards in a glass of water, and every week or 2 I would put a drop of synthetic oil on the front and back bush (this definitely makes a difference)!

One of the best bang for buck planes on the planet!! Get some 2mm if you can.

I'm new to e-flight, and like all that I read on the mugi. However, being uneducated on 'e-motors', sizing ect. I am curious on the reason to go with a reverse vs. normal motor (I'm looking at Air Craft's GRP hyper 400). a LHS guy, who's border line arrogant, says use a normal motor with a pusher prop.. vs a reverse motor.. whats the difference?? in configuration?? Thats for any suggestions
My goal is to get this 2mm coroplast mugi up and dancing... and have some power to climb and do mild aerobatics.
Any threads?, suggestions??.. Thanks in advance to all contributors!!