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Old Nov 25, 2012, 10:48 PM
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Australia, VIC, Melbourne
Joined Nov 2006
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Hehe, but "... it sure does fly well." is relative.... relative to if things are WORKING.
eg servo issue, TV friction/jamming issue, ESC issue, retract/oleo collapsed-pins lost (which then prevent it getting to fly), etc etc... all the typical foamie possibilities, seeing pretty well all are made marginal.
You only get "Assured does fly well" and "Keeps flying well" if you cover all those issue areas yourself. Pretty much as case of "Adequate aircraft upgrade and maintenance" if you do want it to be reliably flying.

URRL's video is great! Well filmed (zoomed etc... sort of like ReadyToFly's), so it shows how well it behaves, during that "But it sure does fly well" time frame. hehe
I am sure Freewing and their testing/optimising it all played a large part in how well it does fly. (Choices they made on what the model needs to fly well).
Though I have found that all of my EDF jets fly great anyway. I have not encountered any that are a 'dog' (well, all fly bar the F-22 so I don't know about that one yet!!). It is probably because they are faster aircraft, thus more 'fluent' than slower prop warbirds are.

I was thinking, after looking at some real Su pics and reading another article on them, that LEADING EDGE EXTENSIONS is what I probably need for the better take-off manner.
If you don't have them you have to make do with other available options, but it is possible they are something it needs to have to rotate cleanly and properly - rather than fighting the opposition to rotate just via cruder methods. I would do them as just a 'Fixed hinge drop' motion, as that is simple enough to do and would replicate the look fine anyway.
Once I do the next test runs, and see what I think of that all, I will do those anyway. It will need a bit of humming and harring over strengths, methods etc, and I still have a few spare RC channels anyway.

Idea 1:
1) Cut off the LEX strips.
2) Just a bevelled lower face on the wing and LEX - so they are equal angle and will close up to each other flush with the same face heights, at the maximum angle you require (30deg or so? 15deg each face).
3) Put a CF strip 'face' onto the LEX so it cannot bend 'vertically' lengthwise.
4) Lots of wide pinned hinges (eg 20mm).... probably 5 to 8
5) Then a full length tape hinge on the top (repaint etc) - part for a flush airtight surface, part for more strength. It may as well run from the top main wing area, overlapping the hinge joint, and wrap right around and under the LEX strip. That would give a cleaner finish.
6) Driven by one 17g MG servo each.
7) Separate channels so they can be perfectly 'tuned' but would also allow them to be used as an individual control surface too, if that seemed useful. eg mixed with aileron etc.

Hmmm, seeing I won't fly it at least until the weekend now (seeing I have a van full of other planes to test/fly for now anyway) I will cut them off tonight so I am FORCED to complete that by next weekend!
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Old Nov 25, 2012, 11:05 PM
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United States, AR, Jacksonville
Joined Jul 2004
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Having read this thread through, I had an idea of what I was getting into. I'll keep doing my pre and postflight inspections to ensure it continues to fly well.
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Old Nov 25, 2012, 11:08 PM
I did it...
av8ersteve's Avatar
Morganton, NC
Joined Jun 2005
756 Posts
Hey guys.I'm waiting on my Su to get here and I was just wondering something. If I use a 4 cell 1000 mah (nicad) battery, plugged it into the batt channel on my receiver and let it take care of ALL servos and the receiver it's self, would that not eliminate esc and bec from everything, and at that point, the only thing that could ever happen is I lost an esc and an engine but would still Always have flight controls? I think that's what I'm going to go with. I know it adds a little weight, and I have to keep up with the batt status of another smaller battery, but the most I fly is a couple times a day due to I'm having to charge the larger pacs to fly. I fly my nitro Raptor heli 5 or 6 times a day and all the servos and a hungry gyro are all powered by a 1100 mah nicad, along with the receiver.

Why can't we just do this? To many people are loosing planes. I use to charge overnight, and fly all day (nitro of course). Been doing that for 30 years, and I know those big old servos ate more juice than what we are using now. I still have my Kraft stuff.
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Old Nov 25, 2012, 11:25 PM
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4 cell ??? Into a BEC I assume then?
Otherwise use some Life 2 cell made for that job.
It should be totally fine, as long as you do make sure it is charged!!!

You ask "would that not eliminate esc and bec from everything?" and the outline you made means the answer to that is YES. BUT..... you are adding a different set of failures sources.
Flat RX battery... or one that drops a cell and fails.

Using the flight battery means you can't get it 'wrong' as it will never drop voltage so low as not to be able to power RC anyway. (but has the BEC issue). And if it is very discharged, you won't get to 'fly' anyway - thus no matter that the RC might not be powered well either.
I am not bothering, but if I was worried about it I would do a Dual BEC method instead.
Thus you have a power source (flight battery) that is near 100% reliable, and redundant BEC's. Totalling to a near bullet-proof system of RX power supply. (As good as you should ever need)
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Old Nov 26, 2012, 04:43 AM
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LEX Mod commenced.....

Seeing I have one damaged leading edge that needs repairing anyway, I decided to use that wing for the initial testing.
The markings (panel lines) on the FW Su-35 do not really match the real Su's LEX size and shape. But it still looked a good set of lines to use - I am not fussed if it is not true to scale as it is only a stand-off scale model anyway.

It looks like the real ones can travel 30deg to 40deg sort of range, so I aimed for 40deg. Less can be used via RC setup.

On the cutting the LEX off I found that the alloy spar makes it that far forward, just! So I ground that back after cutting off the LEX.
I decided to bevel only the LEX the whole amount required, so as not to stuff the wing side, because I will quite possibly replace the whole LEX with a balsa one anyway. Doing this means no need to put a CF face strip onto the foam LEX, as it will not be foam anymore anyway.
And after testing the bevel on the LEX side only I will decide if that is really the best way, or not.... as I had another thoiught on why to bevel only the LEX side.....

If you only bevel one side then the face will be 'wider' than the other piece's face. eg LEX wider than the wing face. I decided that might be better really, because I am going to be running a 'surface skin strip' across the LEX gap/joint. Because the LEX gap total has to be bevelled to the desired 40 degrees (whether all on one side or half on each side), when the LEX is 'retracted' there will be a notable gap on the wing underside. So I decided it will be best covered wth a 'strip/ (shown later). And this strip will be affixed to the LEX side, and slide over the lower main wing surface as a 'bridge' over that gap at all times.
If the LEX face is larger, when the LEX is out (down) its face is deeper downwards than the main wing's face, and that will make the strip form a nice curve to the wing, with more of a blending curve formed from that deeper LEX side 'step'.
So that should be a useful thing.

I just did the inboard 2/3 LEX piece, seeing my leading edge is damaged at that point, and I will fix it all up properly later on.
To do a quick test I used a tape hinge along the top joint. And stuck a paper 'strip' on the underside. Nothing too amazing... it did as planned, so that was just a simple 'nothing special but fun test'. It will be using X amount of flat pinned hinges for the real hinging strength. I have also thought about using my own custom made full length hinge.... so I will ponder on that one more over time.
The real underside 'cover strip' will be made of some plastic film, like maybe PET 3C, stuck fully for its width that is on the LEX side, and free 'running' over the main wing underside. Maybe approx 10mm overlap onto the main wing when the LEX is retracted. It needs to have enough overlap so it forms a flat surface to run across the wing, whereas too short an overlap would try to initially dig into the wing.

The drive servo will be, and drive, the LEX approx 1/3 of the way inboard, seeing the inboard end of the LEX is far larger than the outboard and thus will have far more load too. I should get the test LEX all fully working tonight.

The LEX face bevel will be made to the finally decided angle that forms a solid joint - gap closed - at the maximumused angle. eg not a 40deg angle but you only use 30deg max and leave a gap opening. This is the strength of the LEX when deployed is that solid face to face meeting.

.....
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Old Nov 26, 2012, 05:00 AM
Life begins at transition
Australia, VIC, Sale
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Minor point - they're LE flaps, not LEXs. The LEX is the highly swept extension from the LE to just under the cockpit.

As for making everything on the aircraft only just good enough to fly - that's what engineers are paid to do! I was told once any schmuck can make a bridge stand up. The engineer's job is to make it only just stand up!

I still reckon mains forward, nose back. LE flaps will actually reduce the amount of lift your wings create
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Old Nov 26, 2012, 05:45 AM
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Australia, NSW, Williamtown RAAF
Joined Aug 2008
2,477 Posts
Pete,

I had a Starmax F-16 with LE flaps like that (also linked to standard simple TE flaps). Not sure the LE flaps contributed much except drag - but I could be wrong.

Ensure the LE flap pushrod is carbon rod sleeved so it cannot bend under pressure. Happened to me and a few others.

Dans RC F-16 90mm Stumax Crash.wmv (1 min 45 sec)
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Old Nov 26, 2012, 07:44 AM
Let the hating begin
evalith8's Avatar
HAMPTON VA
Joined Dec 2009
873 Posts
So far mine has been a blast to fly with minimal issues(knocking on wood)I had a rear gear block crack on landing,the brass strut sleeve where the strut tightens split(I think I may have overtightened it)I ordered a new one from Banana hobby & that took care of it.I added a 2 degree mix of down elevator when the gear is down which made landing it a breeze.The nose on mine kicked up when the gear was lowered making landings a bit sensitive pitchwise.After a few trys I settled on 2 degrees which allows me the descend at 25% throttle slowly bleeding off airspeed.Once over the runway chop the throttle & the back wheels touch first,the nose wheel settles down & it rolls to a stop about 20-30 feet down the runway.Its very scale in its approach & landing.I leave the TV on at all times & with about 45% expo its not even noticable unless you lean on the sticks.So far this has been a suprisingly nice edf jet & if looks could kill,I mean I could just stare it on the ground for hours.Oh yeah,the nose wheel servo also took a crap the same time gear block cracked.I think it twisted the front gear a bit & burnt the servo.I replaced it with an hs55 & found out that it has to be reversed,cant be mounted on the opposite side either.
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Old Nov 26, 2012, 07:48 AM
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I had seen your F-16 crash before.
Don't worry, I foresee weakness a mile away so that would never happen here. It is a much stronger design than the Starmax woeful implemention they did.
I have already made most of it up, I always use 2mm SHORT pushrods. So they are impossible to bend/flex under any level of possible stress they will encounter. eg probably 4x stronger than required.
I am just uploading videos of it all now....

I guess it does look more like a Leading Edge Flap!
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Old Nov 26, 2012, 08:18 AM
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LEF's now... LOL

I used just 3 20mm flat pinned hinges for now. The spacing shows I will need another 2 between these ones, and a total of about 12 per LEF. They have knife slots cut diagonally 'down' into the wing and LEF so for eg with the LEF up the hinge looks like an inverted V shape. In the finished version they will of course get epoxied in. But for the tests the tape hinge over the top is holding it all togther fine.

I used the old removed Freewing elevator servos, which are close to the exact same size as the MG-16s is replaced them with, so I can change these back out of they don't operate properly in this job.

The pushrods are 2mm with threaded end, so one end uses a nylong clevis and the other an alloy 'infinitely adjustable' type. Over that short distance they are as solid as a rock, so with the clevis pins all being perfect fits to the servo and control horn ends, there is zero free play.
There is very slight 'end to end twist ability' if the LEF for now, but that is because of the very low hinge count it has now.

It is a pretty simple thing, so it operates perfectly.
I used stiff card for the underside 'slide cover' for now, but as mentioned the final version will use PET 3C. The stiff card does not maintain its shape, so it does not quite run a snug fit along the wing underside at all times.

Videos are still uploading to YouTube.... and they keep being rejected, sigh. Don't know why yet....

.....
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Old Nov 26, 2012, 12:04 PM
Flying Hazard
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Spain
Joined May 2006
3,046 Posts
A couple of things.

This plane mostly flies amazing because of russian aerodynamicists, more than because of Freewing. Although the profile is not the same, it's the shape of the whole plane that gives it its stunning features, don't get me wrong, but that has nothing to do with freewing employees.

Then I just laughed so hard when you said you don't mind if it's not scale after all the realistic take off discussion! I know you mean you want it to FLY realistic, rather than to look but it was funny anyway

About the LE Flaps, two things.

First, make sure you use great servos and linkages to control them or you could have very ugly surprises but since you love to use nice servos regardless of weight I guess you have already considered this.

Then LE Flaps are an incredible thing, it would be nice to link them automatically with airspeed using a microcontroller. I may do it in the future. But I don't think this is going to help at all on your roll outs. At least not in the sense that they are smoother. Anyway, don't use full deflection for take off, it will work better at a medium angle because of flow-attachment and drag.

Good luck with the mod, would love to see a video of it flying!
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Old Nov 26, 2012, 12:34 PM
Should've, Would've, Could've
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United States, CA
Joined Dec 2010
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Dro,

Nice video, besides the crash. That is one reason i don't want to add LEF to my plane. She fly's perfectly fine, takeoffs, and lands fine so that's just another thing that could happen. I really would love to add em and may do so on the spare set of wings that i have just to mess with em, but I let " Crash Test Pete" have a go 1st.
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Old Nov 26, 2012, 01:04 PM
Flying Hazard
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Spain
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Pete, we have our hopes set in you!

BTW, Urrl, just saw the last vid you posted, and have to say that Su looked amazing with the missiles!
Nice vid there!

Loved the T-shirts at the end too
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Old Nov 26, 2012, 04:53 PM
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Yeah, I liked those missiles too! It made it looked more complete... though there are so many airshow videos off it clean which look great anyway. But the missiles just add that bit more, hmmm, 'something', to it... aggressiveness?

YouTube hates my videos today, no matter what I reformat them to. Reject, reject... any.
So that needs further investigation.
But the fit and operation of the LEFs is perfect! The top is 100% flush, no gap... you can't even see they are cut almost, and that is just with clear tape on them now - so painted they will of course become 100% unseen.
The temporary stiff card underside 'cover strip' travels almost 100% perfectly too, but it is not even stuck down properly - just taped along the front edge - so a PET strip glued on will travel perfectly for sure. I have only 10mm of overlap, for this biggest gap on LEFs up, but there is room to have up to 20mm if that seems better. So I will start with it big and decide if I cut it down a bit if I see any reason/need to.

The hinges need some investigation, because one problem with 'flat pinned' hinges is that they are always very thin plates, which allows a bit of flex on them to their pin ends. With only three on the test setup, that allows a fraction of LEF twist end to end. More used will strengthen that, but I am not sure they can ever be fully rigid enough, even if a non-stop row of them are used. eg the 12 aimed to use.
The other commonly used type of "round pinned' hinges - that have a 'rod' type body to go into the foam - are rigid right across their pin width. But because the 'rod' is more like 3mm that means you can't get it right to an edge as well as a flat pinned hinge. This means the pivot point is about 1mm lower then at the very top edge - versus the flap pinned hinge getting that pivot right on the very top edge.
If not pivoted from the very top edge, a top gap opens... albeit it quite small (1mm?).... but ANY gap opening means the tape across the top cannot work properly. So it is important that the pivot IS right at the top edge!
Thus flat pinned hinges win the choice.... versus their bit of end flex and need to use a lot more.

Tonight I will do the good wing - complete length LEF. But a complete job on that.
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Old Nov 26, 2012, 05:53 PM
Life begins at transition
Australia, VIC, Sale
Joined May 2007
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Try silicone hinges. Flush with the top surface, sealed, rigid spanwise and strong as a mo'fo...
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