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Old Jan 08, 2013, 01:28 PM
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Originally Posted by Whiskey Whiskey View Post
I chose a 25C because theoretically it's supposed to work, and largely because it came out to $75 shipped from *bleep*. My power test showed the system pulling 101ish amps at WOT, which equates to 20C for a 5,000mAh battery.....
True at the beginning of the flight, they work. As you deplete the battery to say the last 1000mAh and 1x25C=25 deliverable amps. In fact you are undersupplying the motor demand after the first 1000mAh used from the battery (4x25C= 100amps). So from that 5000mAh battery, if you kept 20% left, that gives you 4000 usable mAh which after you've used the first 1000, its a slow decrease in performance from there.
And if you stay hard on it in the last few mAh of the flight, you can see that you are really pushing hard into the 20% reserve. This again depends more so on the lipos chemistry but they become less durable to this kind of above 3 minutes hard bursts that you may need for a go around and approach correction.

All brand or batches not being equal, that where the group is giving recommendations of approximates to both performance and life cycle.

The advantage is they are lighter. So depending on your flying mission, they can be useful.
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Old Jan 08, 2013, 01:39 PM
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Originally Posted by PeterVRC View Post
After a bit more investigation I opted for the 'scale' airbrake....
There was nothing of importance after the hatch, so that was a non-event to cut out. I used a printed out thin card template, made by that overlay of our model Su to drawings of the real one and cut/shaped to sit over the hatch outline for a reference.

My battery runs right at the rear of the tray area, so I have plenty of room for the hinge mechanism being further rearwards.
I have planned out all the parts and hinging system.... this will be ROCK solid!
Basically a plywood 'rail' is the basis of the whole assembly and strength, then the cut out foam outer just sits (glues) onto that. No stress/strength goes via foam. I have the same 'pivot arm extensions' they have to allow the airbrake to elevate above the fuselage when deployed, and it uses a 3mm pivot shaft across the ends of those which pivots off out-board 'bearing blocks' - and the pivot shaft has a control arm affixed mid way on that, so the drive system is powering the pivot rod, not an arm on the airbrake.

I made up half the parts, and should be able to get most of the rest done tomorrow night.

I just need to plan more on the 'under airbrake deck', because the negative part of my battery being more rearwards is that it comes very close to the inner top at the battery's highest point there, which is the point right at the rear end of the tray. This means that the inside 'deck' cannot be very thick at all - mainly there at least.
But I have a few ideas for that.

Servo... probably a 18g MG like on my elevators.

Oh... and I removed that 'fake' antenna stalk (hatch grip)... they don't even have one anywhere near as big as that anyway. I have an idea how to use the new 'much smaller' antenna stick I will put there to be used as a slide-catch release, and thus get rid of the magnet system. (or maybe keep it too - not totally sure yet).

I think I spent one hour deciding on where to have the airbrake!..... another hour pondering the 'scale' way and any problems it might cause - sussing out what things were exactly where and what interferences etc.... almost another hour deciding how to cut it (angles etc), and then to cut it all out and trim things up.... and another hour of planning structures and hinging etc, testing stuff.
I have to find, or get, a few bits for specific areas of it. I might have enough of the right things around here already anyway... hopefully.

I only took the first two pics after cutting and joining the airbrake "panel", can do others tomorrow.

...
Hey looking at the pics it appears you cut out the batt tray and re-in-forced with wood - was this to make larger? I need to do same since the 2 x 4s batts I bought are wider than specs from website (Also 46g heavier than stated WTH!?) Anyway will do the same today to widen the batt tray
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Old Jan 08, 2013, 01:44 PM
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Hey Pete, you can punch holes in the foam aft of the hatch to cool the ESC from the underside. Mid flight engage the brake every once in a while to add a blast of fresh cool air.
I guess no overlay though Hey its all good.
In fact the more I look back at ITTDs Al tubes, you could simply go with small robart peg hinges into CF tubes that extend into the brake with the hinge line placed forward of your cut to look like the scale lines of the 27m.
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Old Jan 08, 2013, 01:48 PM
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Originally Posted by IntheTubeDeep View Post
Hey looking at the pics it appears you cut out the batt tray and re-in-forced with wood - was this to make larger? I need to do same since the 2 x 4s batts I bought are wider than specs from website (Also 46g heavier than stated WTH!?) Anyway will do the same today to widen the batt tray
It was born of the earlier conversations about reinforcing the break points of the model. He didn't want to continue being a member of the broken nose club so he started his own broken wing club
Those wood panels he extended into the nose gear bay.

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Old Jan 08, 2013, 02:09 PM
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I hope I got the right battery for this jet. I bought 2-N4400.6S.65/24214 Turnigy nano-tech 4400mah 6S 65~130C Lipo Pack. They were just under $100.00 each so they are pricey. I figured the high C rating might come in handy.
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Old Jan 08, 2013, 02:15 PM
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Originally Posted by goldsworthy View Post
I hope I got the right battery for this jet. I bought 2-N4400.6S.65/24214 Turnigy nano-tech 4400mah 6S 65~130C Lipo Pack. They were just under $100.00 each so they are pricey. I figured the high C rating might come in handy.
More than fine but I found the same as CarreraGTSCS that the high C batteries seem more sensitive to storage.
If you get those on video I'll add it to the battery list archieve. We don't have a 4400 Nano, only the 4500 35C which I guess is an older version of the battery.
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Old Jan 08, 2013, 02:17 PM
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Originally Posted by Maxthrottle View Post
More than fine but I found the same as CarreraGTSCS that the high C batteries seem more sensitive to storage.
If you get those on video I'll add it to the battery list archieve. We don't have a 4400 Nano, only the 4500 35C which I guess is an older version of the battery.
I dont know where you are located?. I hope for a 3 minuite flight time per battery.
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Old Jan 08, 2013, 02:20 PM
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I dont know where you are located?. I hope for a 3 minuite flight time per battery.
3 hrs North East of you. When you reach Toronto, head North for an hour.

The way you can utilize a high C batt is high bursts of power followed by glide. The battery can deliver more and can take the abuse. Just don't drain the 3520mAh of use that you have too quickly. You won't see any drop off till you are down to the last 1538mAh and your 20% cut off is 880mAh. You don't have to worry about how hard you push those batteries for that first 2.75 minutes because it can both take it and deliver. But they are heavier.
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Old Jan 08, 2013, 03:39 PM
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I'm on 8 channels and I have them active (though not using flaps), but you have an extra channel. What's your setup?
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Old Jan 08, 2013, 03:55 PM
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So i was just adjusting the CG on my Flanker and got hit by another lighting bolt...

I've been adjusting my CG with the gear extended. Should I be doing it with the gear retracted? I know the CG will shift forward after retraction, but the manual didn't elaborate on this. I figured it was best to adjust it with the gear extended to prevent exceeding the aft CG after extension.

Would anyone like to share their preferred CG measurements? I'm really interested to see if anyone has found their ideal spot aft of the manufacturer's limitation.
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Old Jan 08, 2013, 03:56 PM
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Too hard to draw my design up right now... but it is much better than a pair of 'little' pin hinges and alloy tubes. (though that level of strength might be just adequate anyway).
Made to a balance of 'never fail doing its required task' and as light as possible to achieve that.

Two vertical rails extened 20mm or so forwards of the airbrake - just like those tubes would. But they are 4mm plywood, width, and near 10mm in height. A pivot shaft goes across those.
The shafts ends go into 'bearings' immediately outboard of those rails. Those bearings, and similar on the rails onto the airbrake, are on plywood plate structure that use a fiar amount of the foam area on the hatch and airbrake, so they form their own structure and then the airbrake foam is just a 'shield' mainly, and the hatch side uses a lot of foam surface area, right up to, and including, the front bulkhead of it. So again, even the hatch side has almost made the forwards end of the hatch into a strong structure that effectively the foam 'sat on'.

Individual pin hinges can allow some flex across their pivot point.
I first had some CF squre tube 'rails' to test, but they are hard to make as nice a 'complex offset arm' from. That front arm extension needs to be flush to the foam on the outer side, and deeper into the plane on the inner side - not just a square/rectangle shape. To do it all best that is.
But I also don't like the 4mm ply rails.... because I do not have high quality 4mm ply, like my 5ply 2.5mm. So I have to laminate 2x 2.5mm, to make 5mm and then use that per rail.

I expect the total weight added to be between 50g to 100g. I have tons of AUW to spare still so I am not fussed over whatever it weighs. (though I must weigh it all up in total to see what it is at now)

Flight wise it has no issue so far. So assessment/measurement is done via:
1) Must fly well still
combined with:
2) Should land at fairly high AoA whilst having high angular forwards penetration due to mass/inertia. LOL. That means, a high AoA whilst it is really travelling along a negative decent angle. What you will see ALL real aircraft doing, especially fighters.

A "normal' foam plane can only do that by flying overly slow, relative to scale speeds it should be doing. And if you do any control motion it will still instantly react, whereas mass/inertias should impede that dramatically at those landing approach speed.
At 3.2Kg area before, it was still well short of that behaviour. I am expecting to settle for about 3.5Kg or so area.
I do this to ALL aircraft and my 1500mm Me-262 at 3.6Kg is on the verge of being perfect now. But I think (won't know till it is seen) the Su would need to be a bit lower mass, seeing it has higher wing loading anyway.

All I need is a 60m (or more) runway now...... LOL
The Me takes off within the 22m limit I have easily, but that is not with the full 'correct' roll out first portion, as it would need 20m more to do all that. It lands at a good 'correct' scale speed (flaps etc) and manner, pushing through the mass/inertia at high AoA like it should, but I land on grass and that ruins the landing run out result. But the plane itself is at its required mass.
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Old Jan 08, 2013, 03:59 PM
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The 9th channel is used for the seperated ailerons to allow flaperons. I suppose I can plug in some V-tail mixers for full time tailerons. But that'd call for 4 V-tail mixers just to prevent the flap input from transfering to the tailerons.
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Old Jan 08, 2013, 04:48 PM
Should've, Would've, Could've
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Pete,

Don't forget the chute
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Old Jan 08, 2013, 05:28 PM
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Where do you do most of your flying? That's what you CG to.
I do it with the gear up because all three retracts extend forward, I want the right CG not to effect my aerodynamic trims, and even though its more tail heavy on landing, I've slowed it down at that point to reduce any serious twitchy response.

It still depends on how stable you want it for what stage of flight. Up to you.
Quote:
Originally Posted by Whiskey Whiskey View Post
.....I've been adjusting my CG with the gear extended. Should I be doing it with the gear retracted? I know the CG will shift forward after retraction, but the manual didn't elaborate on this. I figured it was best to adjust it with the gear extended to prevent exceeding the aft CG after extension.....
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Old Jan 08, 2013, 05:29 PM
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A chute ??.... I don't want to have to fold something up every flight! LOL

That is an "After landing" thing... and I don't have that nice long and hard runway, so it would not be of use to me for now.
If I find a good road eventually, I will probably then want to do that - though I still don't like the 'packing it back up' idea. hehe

I guess it could be of some use to STOP on a 22m runway!! But I can't even land reliably on that with larger aircraft (2m wide runway approx), let alone assure the threshold point (umm, cricket stumps holes) is the touchdown point - to get use of the whole 22m anyway!
But if I could do that.... a chute would be of great help I guess!

My 1500mm Me262 typically stops within 10m of touchdown, on grass. But on a hard runway that would multiply out many times! (prob 30mm then). When landing it on my 'runway', the now and then times I can get it all aligned and right (!), it of course just scoots off the end into the grass anyway! And that is a 3.6Kg 'monster'... a reasonable amount bigger (half an illusion really) than the Su... though it lands a lot slower than the Su. (a more conventional wing, and thicker), and so it should in realism terms anyway.
The Su would have ZERO hope of stopping in time! (from a proper landing process).

I am getting eager to get the Su back into the air now... a bunch of other projects have been completed, and now my 90mm F-16 takes off from the 22m runway ok - JUST in time. That is a mix of "as realistic as I can get it" within the length limitation, and scarey because if it does NOT lift-off in time and hits grass then things go to crap!! A narrow stance and short wheelbase landing gear arrangement of an F-16 does NOT like powering across grass one little bit! It will just pull and 'angle roll' to one side on its nose quick smart then! Let alone the severe rearward longitudal stresses on the LG mountings - which has torn one of those off before, and on the F-22 also.

Now I have it that it is JUST rising off the ground with 1 to 3 metres of runway to go, and then I can just let it fly off at that low climb angle (5 deg? don't know for sure) merrily above the grass 'enemy' for a bit, before going to the higher climb rate (40deg?) maybe another 40m or so out - so it will clear the treeline out there.
As much as it is all a nuisance of limitations (short runway, then trees to clear etc) it actually works out just right for a realistic take-off process.

I guess half the "fun" of it all (hmmm, probably could do without that "fun" really!) is how it is all a very narrow margin of parameters to fit into! You MUST get them right - your process and control, and the aircraft set up - or else there fairly likely will be trouble!
I would prefer a nice and decent runway...... (they are actually very few and far between!!)
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