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Jun 24, 2019, 12:02 AM
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Build Log

F-18C Hornet - Freewing 90mm EDF -Rating 6/10.


I always wanted an F-18....... so......

With Freewing bringing out an all-new F-18, after discontinuing their earlier version of one, I hummed and harred and then just decided to get one.
But I chose the ARF version so I can use a Jetfan/HET 8S setup in it. The full scale is after-all a FAST and powerful jet and a 6S setup is unlikely to match that.... the full scale being OVER 1:! Thrust to Weight ratio (not armed/loaded of course).
And the F-18 superceded the F-14 Tomcat..... so that is another 'vague' reason to have one.

I think it comes stock as a Stabilator setup - not Tailerons. But I will change it to have full span flaps... no Ailerons... and Tailerons.
I expect the Taileron Pivots will be the typical sloppy, poor tolerance. Freewing design so I will replace those if required - and I am sure they will need that.

I was happy enough with the Blue Angels scheme, rather than the all grey version. It helps it be something more "different" than other camo scheme aircraft.Plus it is a well known 'look'.
I also had (have) the Starmax 70mm F-18 Hornet 64mm jet, from about ten years back(!!)..... and, I still have it stashed in a corner somewhere and it has a 70mm EDF in it now, but it was still somewhat anemic in power, and nothing like the level of scale detail etc that a larger 90mm size can have. More of an "RC Toy"....

The F-18 is probably one of the cheapest of Freewing's 90mm jets - bar the DH-112 Sea Venom - seeing it has somewhat minimal "stuff" in it. Mechanical gear doors, no weapons set (no need on a Blue Angel), and not a complete lighting set.
It is on its way and should arrive in a few more days.....

....
Last edited by PeterVRC; Jul 28, 2019 at 03:08 AM.
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Jun 27, 2019, 11:18 PM
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The F-18 arrived "3.4 days" from order. eg ordered in evening.... arrived in a morning.... super fast!!
But it costs AUD$144 for shipping, so you would hope it was by AIR!! (No option but EMS)

Everything is perfectly intact, that is nice.

I am pretty sure I will make it Blue Angel #6.......but I have not fully decided.

It will get an 8S Jetfan/HET combo, HET650-1600kv 3000W and see how it goes to reproduce the over 1:1 Thrust to Weight 'required'.
2x 4S 5000mAH 60C and a 120A or 150A HV ESC.

And of course the standard WBPU coating - but in Gloss not Matte(!) - to make it High Gloss, as per the full scale ones are.

I will be bypassing the "Blue Box" and wiring ALL surfaces to their own Channels.
Jun 28, 2019, 12:00 AM
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Control Surface/Channel setup


It is a bit of a shortfall to not have Leading Edge Flaps on this.... Though an even bigger shortfall not to have a Fly-By-Wire system, LOL.
The F-18 has a quite intricate Control Surface setup that might be 'messy' to have for a NON FBW system - like a manual RC pilot....
But I will investigate all options....

Setup 1:
I will have Flight Modes to allow multiple setup systems. In Setup 1 it will be just Stabilators - not Tailerons - with Inboard Flaps only, plus Ailerons and Rudders.

Setup2:
This will be the 'full complexity' setup with a whole bunch of specialised functionality.
There will be a Take-off/Landing mode which alters the setups to suit. Also a High Alpha mode.

1) Ailerons and Flaps join to be Flaperons - ONLY when the Flaps are deployed. Ailerons as Ailerons if not in a Take-Off/Landing mode.
But also, in Flaperon mode the Ailerons still move BACK UPWARDS some amount (half way towards neutral?) as per Aileron/Roll functionality. (The full scale does this).

2) Flaps to be mixed to the Pitch control, only for Pitch Up, and not linear but on a curve only adding them for higher Pitch Up regions. This is when NOT in Take-Off/Landing mode, but can also be switched off if desired.

3) Rudders both inwards - again linked to Pitch Control, and again only for Pitch Up. Take-Off/Landing mode will enable this, and there will be a "High Alpha" mode where they get enabled also. The full scale moves both Rudders inboard automatically on take-off when the nose wheel lifts off - or some trigger like that. Specific details are unclear.

4) Tailerons, not Stabilators. In Take-off/Landing mode, where the Ailerons are just Flaps then, the Roll Rate will be increased a lot so the Tailerons have adequate Roll Authority then.

By using Flight Modes to separate the systems, I can test Setup2 bit by bit and switch back out to a docile/safer 'simple' mode of control.
I am actually worried a bit about WHAT some control surface uses will produce/create.
Why didn't Freewing make this as a Taileron control system as per the full scale? And so many other of their jets do use. That seems odd.
I have read that when the Flap(eron)s are deployed that the Tailerons get blanketed a bit and they then need larger throws to have adequate Pitch Authority. When you set up Tailerons you have to decide/compromise over having the full possible Pitch throws, or a lesser amount so that using Roll does not 'clip' out the travel range that using both at once (Pitch and Roll) would cause then. I would probably allow full Pitch travels because when the Flaps are NOT deployed the Ailerons are fully just Ailerons, and thus they will provide a lot of Roll Authority anyway.
eg Allow 100% Pitch range to Tailerons, but something like just 50% Roll - which means if both are used it 'clips' at 100% (not getting the 150% it could total to), but having Ailerons means you have plenty of Roll Authority anyway.

This will all likely need some detailed flight testing and tuning!!! Up high... safe.... and with that Setup1 (simple mode) fallback ability!
Jun 29, 2019, 06:50 AM
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Lots of issues to work out


I began the "ARF Construction" from the Friday night..... Construction means all the mods and alterations required to complete a well set up and safe, truly "fit for purpose" airframe. And there is a fair bit to do on this F-18 !!

Firstly, it is a little bit small for a "90mm" jet. It could have been 10% larger or so, to be a good size with presence then. Versus my lower scale number (eg 1/7th scale etc) FlyFly jets, like the BAE Hawk or F-86 Sabre, it is a lot smaller in "volume". This means its fuselage is small and narrow, and thus not a lot of room internally. It makes fitting 8S virtually impossible in its stock form, though a 6S setup would fit with space to spare.
I can see why MotionRC/Freewing say they are not going to release an 8S version.... as per they do with many of their other 90mm jets.

The Taileron assembly is quite impressive, with ball bearings and good tolerances on the shafts etc. It is very well done BUT it is let down by the plastic bearing housings that are sloppy fits for the bearings! You can wiggle the Tailerons and cause those bearings to rock and move inside the bearing housings! I tried shimming them up, in the bearing 'groove' but so far that has not worked better than approx a 50% slop improvement. I will look into that again later on....

LOTS of the things Freewing have done are EXCELLENT! A lot of thought into all the ways to achieve requirements! So even the Taileron end is all well thought out - all its other great design aspects are just let down by that sloppy bearing housing(!).
The DETAILS are amazing... so many... so intricate.... If you were only going to consider hanging this from the ceiling, to be more like a high scale detail plastic model, then it would even pass as a great job of that!

All in, when compared to the A-10 and the F-14, which are very complex and well thought out models, that are also that bit larger, the F-18 is more in the "league" of the smaller 80mm series jets. Just that bit less intricate/complex. Even a fractional amount simpler than the L-39 80mm.... and more like the quite simplistic Avanti 80mm.
But, the F-18 is that bit cheaper too... so its price point is in line with what you get.
It actually comes with EDF moldings to fit an 80mm EDF instead of 90mm..... so in many ways it makes me think this was really going to be just an 80mm series jet! But then they thought "Let's make it both 80mm and 90mm, to be high performance with a 90mm".

The Gear Doors all all operated by mechanical "levers" not servos - but they are designed and implemented really well and they work perfectly!! In some ways they are BETTER than using servos at all!

The Flaps are HUGE!! But they only use 9g servos !!! They have got to be joking as that has to be asking for big trouble!!
My LX 1550mm A-10 had a Flap servo STALL on its maiden flight, and spiralled into a crash.... as so has at least one stock F-18, and one or two others go out of control on Flap deployment! 9g is just ludicrous for these!!
But it cause a BIG problem, as the servo POCKETS are fixed in the Wing and it would be a fair amount of work, and mess up the awesome F-18 surface finish it comes with(!), to change those to be larger!!
Versus NOT using larger servos verges on assuring there is going to be a crash sooner or later!!! Probably sooner than later!!!
So they MUST be changed..... or, do not use the Flaps... or use only a very shallow Flap angle ever....

The full scale use Flaps down to around 45deg, and that is a huge angle for these large Flaps to be at, and then 9g servos are really going to be dangerous!
I can print some new servo pockets, and refinish the surface damage it will likely cause in fitting those, but that whole task will be quite a big one to do!! Annoying!!
They should have been 17g servos.... like the Tailerons use.

The first thing I did was WBPU the entire F-18 - all parts whilst separate still - in GLOSS WBPU. Seeing the full scale Blue Angels are super shiny polished up finishes! And I did three coats, to really smooth it out and get a deep shine. It looks fantastic.....

Due to the very limited space I had to ponder for AGES over how to fit everything... WHERE??? And for it all to be a 'NOT Crammed", clean wiring and access, manner! That verged on an impossible task..... but after a LOT of looking, checking, pondering, I got it worked out.
Dual batteries cannot fit side by side, so they have to go lengthwise and that is a LOT of length required then!
The final decision was that the HATCH had to be made much longer - just like for the Freewing Su-35 required to run 7S or 8S via dual batteries. But I had to be sure it would work and still be strong etc.

Once I cut open the rear upper deck to make that hatch opening longer, everything fell into place relatively easily!!
To run 7S or 8S, this longer hatch is a "Must-do" manner to achieve that!
Jun 29, 2019, 09:47 AM
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Back to 6S ??? 8S too heavy?


I loaded up all the items that the 8S setup would have in the F-18. It ended up at 4050g !!
For the size of this jet I think that is just too heavy. Or rather, it is somewhat 'situation dependant' and if you had a long hard runway, and flew strictly to a scale manner of a full scale, it would all probably be fine. Its lift to weight ratio would be a bit strained, but 'longer linear' paths can cope with that.

It is when you fly off grass, and need more thrust to offset the high drag that has.... and the problem of flying 'scale length and arc' paths with an RC model, as those are too large to have the room to do that, or to see it well at such distances..... plus the loads on the landing gear when on grass..... that a high AUW is un-viable in this jet.
If it had been 100mm larger wingspan, or more, then it would probably be OK with 8S......

I pondered over it all a lot, and then decided to CHECK the AUW of a "2500W" 6S setup, versus the "3000W" 8S setup.
The Jetfan/HET EDF and the associated HV ESC alone are almost 500g heavier than the 6S EDF and ESC! And then the 8S 5000mAH versus 6S 4500mAH are near 500g on top of that!!
The 6S setup with a 6S 4500mAH was an AUW of 3250g !!
You could probably run some setup/battery combo that ran out to 3600g OK, but I would not really want it to be more than that region.

The 8S setup is just too heavy.....
Possibly 8S 4000mAH would be OK in AUW, but I do not have 4000's and it would be a waste to buy them just for one jet.
There would be other 8S setups, such as the Freewing setups, that would be quite a bit lighter - possibly that 3600g AUW region. But I do not have one and it would not be worth the COST of buying that setup either.
The F-18 being that bit too small means an 8S setup is almost not worth using. Possibly a 7S (2700W) setup would be appropriate.... but I do not have stuff around here for that either.

Add in that I have a HSD 6S 10 blade EDF and ESC, from the first HSD ViperJet I had (crashed and gone now) - and is thus effectively "free" - so that is the best 6S option for me to use.
2500W..... which should be about 3300g of Thrust, on the bench..... so maybe 2700-2800g in the F-18(???)......

I will change it for this 6S HSD setup and use that first... then decide on any changes after flying it like that.
Jun 30, 2019, 11:55 PM
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6S HSD setup


I completed the wiring and setup changes to run the 6S HSD system. Basically the 8S setup can be put in, or the 6S setup. They are 'self contained' in all their own wiring so there is nothing to do but mount the bits in.....
But I can't see that I will use 8S 5000mAH.... too heavy.

Interestingly you can get 2x 6S 3300mAH 40C batteries, for 1.0Kg AUW versus 2x 4S 5000mAH 60C being close to 1200g AUW - but the ENERGY totals are the same! So a 12S setup, or 8S setup, giving the same outputs and flight time "fuel", the 12S is lighter. Of course that would need a 12S EDF setup and the different batteries, that I don't have, so that option is not much use to me anyway.

I have some Wemo EVO 90mm fans, and might have some motor that would get that suited to 7S... or I could get a motor....
Of all options, and costs, I like that idea the best. Aiming for 2700W or so, with 7S 5000mAH 60C. That should give an good AUW region, plus the Power to drive/fly that well.

But anyway for now it is the 6S HSD setup and I will fly it like that first....

I completed all the RC installation etc, plus the TX programming, so it is all ready to go now...
I am running a 5.8v SBEC, to have a higher servo Torque ability than that stock 5.0v SBEC would give.
I also have the Flap servos running from a closer in hole on the servo arm end, so that they have more leverage/power to drive the Flaps more assured. But I will still TEST them up HIGH first!! And give them some reasonably high speed checks up there too!
I am using the "Full" angle that the full scale F-18's use for the Flaps, so they are large Flaps going down at quite high angles!! They look evil/aggressive.... but it also a bit scarey due to the 9g servos!

I have done the "Dual" RC system control setup.... the "Simple" mode, and "Full Complexity" mode.
This uses a mixture of Flight Modes and other switches. The Flight Mode choice does the main changes, but some are just linked to the use of Flaps per Flight Mode used, and Rudder mode changes (Adding Pitch control, or Air Braking, to them) are via switches.
The OpenTX file is attached below - it is for a Horus X10S, but would not be too hard to convert to any OpenTX transmitter system. It is just the V1.0 of the system setup and things will need to be changed and tuned to the F-18 once flying it.
Last edited by PeterVRC; Jul 01, 2019 at 12:07 AM.
Jul 01, 2019, 07:26 PM
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OpenTX setup V2a


Reasonably major "Re-Writes" of the F-18 setups. And even this still needs a bit more tweaking and going over, to triple check it does all interactions correctly.
I added another Flight Mode, so now there are three:
1) Simple stock Freewing control mode
2) Full scale full complexity control mode
3) Full scale full complexity, with Fixed Full Inwards Rudder Pitch for Take-off

No.3 is of course for use on Take-Offs only and then you switch back to No.2 as it climbs out.

I still have to ponder over the "continual Flaps use" that the Blue Angels do. Almost all flight they are using a very low Flap angle (Flaps only, not Flaperons), but this is being controlled by the FBW thus it is not a constant angle or constant use. Though the angle is generally either 0 (retracted) or a low 7deg sort of thing. I am thinking I will just have to set a low "7deg" angle that you leave it set with.
It is sort of like they operate better with some Reflex, thus at lower to mid speeds it is almost a constant (the slight Flaps down angle).

I cannot use the Take-Off Flap setup for this as that also uses the Flaperons. It really needs a new/separate switch/setup.
And possibly linking it to the "Rudder Pitch" system it suitable - so that one on/off function sets 7deg Flap and enables the "V-Tail" Rudder to Pitch Mix at the same time. For now that is the idea I like best....

The reason they even use Rudder Pitch is that the canted/leaned Fins/Rudders are a V-Tail and at higher Angles Of Attack (AoA) the Tailerons can be partially blanketed by the Wings - more so if Flaps are in use. Thus the "V-Tail", used only for Pitch UP (it seems), gives another source of Pitch Up control, and is not impeded by the Wing/Flaps.
I would expect the full scale is run by the FBW system, so they only even operate when the AoA is higher (15deg or greater?). We cannot do that... it is a manual "have it on, or have it off" choice by the pilot.
Jul 01, 2019, 07:28 PM
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Hatch latch


For the extended hatch I added a new latch, and also some "lateral guide plates" that ensure the hatch closes centrally and is laterally supported.

I will fill in and paint the latch area once I get some paint matched up... one day....
I all also cut, fill in, the stock latch area too then.
Jul 01, 2019, 07:39 PM
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Blue Box, SBEC, RX


The BlueBox is at the rear end of the extended hatch, and under the battery/RX tray layer. Under the dedicated RX Tray.
I only use it to run the Lights and the Gear. Though I am going to bypass the gear to it also because they add a "Gear door delay" of about 2 to 3 seconds to the Gear operating after you change state at the TX Switch. It was just nice and easy to have connectors running from the BlueBox headers - but that delay is painful and a nuisance! I need to make up a appropriate length Two-Way Splitter for the gear channel leads.

The 6 Volt 7Amp SBEC is in the "bay" just ahead of the BlueBox bay. Thus it is under the Battery Tray.

The RX diversity aerials run as a "V" - one out each fuselage side at 45deg incline.
Jul 01, 2019, 07:51 PM
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Power and Telemetry


I have an AS150 Anti-Spark Connector in the Positive lead. I use them for anything 6S and above as those all spark notably and damage connector ends quite often. Technically it can't be good to have such a Current surge - which is caused by the ESC Capacitors "instantly" charging, thus at an "infinite" Current surge rate(!) - and a sharp fast rise in Current means the Voltage also does sharp sudden changes. This can't be good for any items on that Voltage Supply Bus (battery lead), so the ESC and SBEC have to deal with that.
Anti-Spark..... you are removing those above occurrences....

Tons of people do not add Anti-Spark, and things 'just keep working anyway'. So the percentage cases of failures is "low". It is just that you will never know what part your allowing things to spark helped, or caused, when things fail eventually.....
"Hmmm, my ESC died in flight... and I ceashed" - but the damages were done long long ago by all the sparking over the many arcing/sparking connections you made.
Like I said... it is technically (electrically/electronically) unsound to let anything spark!!

The Anti-Spark Connector/Adaptor also has the Unisense-E Telemetry sensor plugged in there. The wiring lengths and lays are made to have it all tuck in down past the side of the battery, to keep it a bit more 'trapped' so it won't flail around in flight.

Telemetry is another "must do" RC thing that I highly recommend - if you want to be able to maximise you flight times AND know the battery state at all times so you can be sure not to abuse it. Thus you have the longer flight times AND far longer battery lifespans too!
Jul 01, 2019, 08:09 PM
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7S setup


I realised 7S has some more plusses.....

A 3S and 4S 5000mAH 60C can go side-by-side, basically as per the 6S battery position/manner, but some amount more rearwards. Probably just short of reaching the current RX position.
Versus 2x 4S for 8S needs them nose to tail, and one then has to go WAY back into the rear fuselage area also!

I also have some Wemo EVO fans that would be a great fan type for the F-18 and its ducting.
I just need a suitable motor to drive that to 2700W/2800W region.... and I might have something for that, as I have some ChangeSun branded motors that are "low powered 6S", I am not sure of their KV. But maybe the rise to 7S would take them to the Power level required.
I need to check them out in more detail and get their specs.
Otherwise I would need to buy some other motor to suit.
I really want the greater AUW region for the F-18 (3700g or so), and an appropriate rise in Power/Thrust to match that. Plus longer flight times than for 6S. So I will be going to 7S at some stage.....

The pair were originally going to go into a twin 90mm Mig-29, but it got a different solution in the end.
I can't read the motor labels and am not sure if it had been going to run 6S or 7S. I think I was going to run them on 6S seeing the pair at a lower Power level would be fine for that Mig. Thus they could be a good Power level when used at 7S.
They are motors used for high load fans (like 12,13,14 blade types) - on 6S. So as a general rule you can use them in a low load fan type, on one cell higher. Thus 7S. I am just not sure what KV they are and thus what RM/Power level they will run at.
I will check and see.....
Last edited by PeterVRC; Jul 01, 2019 at 08:14 PM.
Jul 05, 2019, 08:08 AM
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2200g Thrust....


Well that is not good. A Thrust test showed I get 2200g of Thrust for 2300W from 100Amps of 6S.
It pretty well has to be the Ducting causing excessive restriction to the 10 blade fan.
3420g AUW, versus 2200g Thrust.... not a good Ratio! 0.59 : 1
Enough to fly, but it will not be any sports jet!

There are also no MOTORS of any useful KV to run the 7S setup. I need 1800-1850kv to get a worthwhile RPM./Thrust.

So the other option of the 8S Jetfan/HET, but the 1500kv version (2800W max), and then only using 4S 4000mAH batteries so it is lighter AUW, seems the better way to go now.
That would give an AUW of 3800-3900g
And 8S 4000mAh is still more Energy ("fuel") than 6S 5000mAh is. So flight times can be the same... but also have the higher Power/Thrust (~2700W) available too.

This HSD 6S setup it just not good for it.....
Jul 05, 2019, 08:29 AM
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Maiden it 6S anyway....


It was a good day to fly today! Sunny and dead calm!!
A good day to fly, and crash, an F-18.....

It flew "so-so".... only a part of that was it being underpowered in maximum thrust/speed.
It just does not fly nice as it has a few 'nuisance' quirks.
I took off in stock manual listed control mode (Simple Mode) and it had so much left Roll I ran out of trim to even get near close to right. But it was OK to fly on....

As it turns out, the first boo-boo idea was to test out Complex Mode in that same flight. That added a lot more to do, taking more time, and then I forgot I was even using it and that mode added some Flap/Flaperon 'negatives' - the Drag levels are huge!!
It was just a string of factors that added up to a crash when heading to land!

1) Forgot I was in Complex mode, which has much higher Drag for Flaps than Simple Mode
2) Used up more time checking things.. responses... controls.... and then got to "Time to Land" Capacity before I had really checked any form of landing manner.
3) The much higher Drag ate more Capacity FASTER than typical aircraft that use less then. The high Drag needs higher Throttle than typical.

So it went LVC just before I turned to final approach. And with Flaps out it does not fly very well at all with no Power/Thrust!!
If I had landed 10sec or so sooner it would probably have been ok. As long as I got to Final (coming straight-in towards me to land) it would have been ok.

4) I switched to Low Level Flaps (Full Span) when it went LVC - but should have RETRACTED them fully!

I tried to do a Descending Turn leftwards - most of my jets can go Dead Stick for that portion. Not the F-18....
It was slowing so fast it foundered to dive away so I quickly got back to Wings Level, but then it was flying almost straight AWAY from me.... 50m away or so.
I knew there was no way I could turn again..... and there was no way I could land in any decent manner at such a growing distance away from me!
You can't see airspeed....
You can't gauge the height to the ground very well at all....
So I knew it was just going to be an attempt to crash land the 'best' way possible.....

It seems it hit the ground (medium length grass) fractionally Left Wing down, and maybe 30deg or so nose down. Most impact on the nose wheel, so it tore the nose gear out, but that also snapped off the nose and split it at the joins too.
It was probably the best way to crash - whilst a fraction more luck could have had it 'land' even better.
All in all it was as good as could be expected, and could have been WAY worse too!!

I began a move towards landing as it crossed 3000mAH used. Going to Stage 1 Flaps used a bit of time.... then going to Full Flaps a bit more.... and how it needed more Power for those higher Drag level states - maybe 70% Throttle or more. SUPER DRAG from the Full Flaps. And with all the 'make it up as you go' pressure, I didn't even HEAR the Telemetry Speech to know it was eating up capacity FAST then. So it going to LVC was a surprise!

Yes, a whole string of factors.... that if any one of them was not there, it probably would have landed correctly and fine... bah.
I guess a very first factor is not to fly out to 3000MAH out of 5000mAH on a maiden!! Most aircraft it is ok.. but not on this one! Due to its 'special' differences versus most others.

I had a quick look at the damages at home.... it is worse than it looked on the ground. more to do, structurally to fix it up. It is all in the nose front 'half - but there is a lot of plane up there. (a long nose!)
And numerous plastic 'custom' Freewing parts broken. So it is not going to be a simple fix!
Jul 20, 2019, 04:44 AM
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Repaired...


I did a few changes to the F-18 when I repaired it after that Maiden Flight Crash Landing.
I put in a "Full Length Floor" for the battery area, and ALL the RC stuff..... the SBEC, BlueBlox and RX.... went under that. Plus the wiring for all that stuff was run out through a Channel I made in the rear hatch lower foam, so that no RC wiring is inside the hatch area at all. Thus only the Power wiring is in there with the battery.

I also added a internal Fuselage "Side Plate" in the forwards area of the Hatch - partly to strengthen the Nose end repairs, but also as it is just a very weak structure up there anyway. Once the floor is fit in tight and between those side plates, it all forms a quite strong "Box" that then stopped the flex that the nose end has. More so the Nose end can TWIST with reasonable ease in stock form, so the Box strengthens that a lot too.
It is not a "Must do" thing... it just makes it stronger and better,

The other reason for a Full Length Floor was to attach the Nose Retract Mount onto that also. Rather than it being just in its very weak "Not much foam" area that is glues into. So now it used three screws to secure it to the floor plate.

I also removed all the Nose Gear Door mechanics - Levers..... and added a servo so they doors are now servo operated. To Sequence those they run off their own RC Channel and that sequencing is done in the TX. The reason to do it that way is that the End Points can be set to have the doors open, and close, to exact positions. Plus they always remain 'tuneable' (in the TX) to make sure they are operating correctly no matter what happens.
Sequencers (most) just run the servo from one fixed point of travel, to another at the other end of travel.
The main reason for doing this is that once the Fuselage was a bit "Different" to how it comes stock - due to repairs - the mechanical door system was amiss. It has no tolerance for any change occurring up front here - not even a slightly bent retract pin.

So the F-18 was all ready to go out for its next Flight.....
Jul 20, 2019, 05:23 AM
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The F-18 flies..... many flights... from BAD to better... to good....


I headed out with the F-18 on a nice dead calm, sunny, not cold at all really, Winters day.....
Seeing I had flown it before I was not worried about flying it at all. I knew it would fly.

It had rained over night and the flying field was WET.... medium long grass....
This was a worry as the F-18 with its 6S HSD 10 Blade EDF is not overly good in Thrust numbers. Soggy grass was going to impede it notably! So whilst I was not worried about FLYING the F-18, I was worried it might never even LIFT OFF to get to fly!!
I like the 6S 5000mAH 60C batteries in it (I have 4 of those), but I had a TON of 6S 4500mAH 40C batteries also. The 5000mAh are 100g heavier, but also give a reasonable amount more Power out of the EDF too. So I decided to still use those first.

I also decided to begin flying right away with a 93mm CofG, seeing so many people (in Forums) "said" it flew well with that. A more rearwards CofG should also help it ROTATE easier for a take-off in the wet grass.....
In more usual terms, you would NOT want that to happen..... a jet that can't move across the ground truly fast enough (due to wet grass), MADE to Rotate and gain maximum Lift via a high Angle of Attack.... when it was not truly capable of 'flying' yet..... = asking for trouble!!
The F-18 has one 'special feature' in that it can cope with HIGH Angles of Attack, at Low Airspeeds, and not stall. So I had decided it SHOULD be fine to 'make'; it Lift Off even if it was too slow really.

Flight 1.... I tried that with NO Flaps used, and it did struggle to get into the air. I hunted out the best PATH to run across the LOWEST possible grass heights. The first run was just that... a run across the grass with it unable to Rotate into Flight.
So then I decided I would NEED the extra Lift of Take-Off Flaps, and the High Drag they add should easily be overcome by the Take-Off 100% Thrust level anyway.
And it did take-off..... not particularly 'easily', but I kicked in Full Pitch Up when it looked it was at Terminal velocity, and it did Rotate notably and into a 40deg climb.

This above process worked for all Flights... almost - Flight 6, and the battery it used, never got airborne at all. But changing that battery to the next one, had it Take-Off fine for all the remaining Flights too.


Flight 1... it flew like a PIG !!!
Due to a number of reasons.
1) Extremely sensitive in ROLL - even Low Rate was psycho sensitive.
2) Extremely sensitive in Pitch - again, even Low Rate was too much, but not "psycho''.
3) Floundery looking Flight - notably too Tail heavy.

I dialed down the Roll and Pitch travels quite a lot (for Low and mid Rates), and went to 90mm CofG for Flight 2. It was a lot better, but the Pitch and Roll Rates were still way too sensitive!! I was using well under the manual listed throws now! Well under their LOW Rate outlines!

I decided the Roll Rate 'problem' is due to the F-18 having extremely LOW ROLL INERTIA. It has no mass outside of the Fuselage bounds laterally, thus nothing to STOP it rolling with extreme ease. Nothing to cause a "slow" start to Roll - no MASS for it to overcome to begin Rolling.
This is not actually a CONTROL based issue - it just MAKES control hyper sensitive. But also, lower control Rates are not the true 'fix' for it either - they are just the band-aid way to fix it. But also, that is all you can do....
Well, you could add some lead weights onto the wing tips... LOL

The Pitch sensitivity is partly due to CofG = too rearwards, but also just that it has its Longitudinal Mass quite centered. This allows it, just as per the low Lateral Mass allowa Roll easily, to PITCH very easily.
In a Full Scale aircraft they would LOVE this..... as they fight to even achieve that. But in the model it is 'useless' and more detrimental than any good.
So again, you can only use RATES... Control Surface Throw angles... to 'fix' this.
It is a good enough band-aid fix....

By the time I got to 88mm CofG it was flying very nicely... plus with extremely low rates AND extremely HIGH EXPO settings!
I had to go out to 70% Expo.... because, for example, the Roll Rate was down at 25% for the TX setting. If you have extremely low travel ranges - like 25% - then the resultant effect Expo has is greatly masked/diminished, thus you need a huge value of Expo (like this 70%).
The proper solution is to alter the MECHANICAL throws, so that then the RC values needed are much greater - hopefully towards 100%. if that can be achieved - and then the Expo needed, for the same result, will be more like 30, 40,50% at most.
But that is a very messy task to do on-site, so I left that to do at home.......

By Flight 8 it was flying very well.
The one 'special' need was to have a Very Low Rate, to use for Landing only. With it being so Pitch Sensitive overall, it was very hard to keep it very stable at a Landing AoA (+10deg etc), in the 'Normal' Rate. It really needed a highly reduced throw so you CAN'T over-control it!
After numerous Flights and other ideas/tests, this just remained as what had to be done/used.

The CofG at 93mm - the flight behaviours it causes - was a joke. I would say Freewing got the ideal CofG dead right for this - as per the manual says 88mm. All the typical 'tests' I do to show behaviours being 'right' were best with this 88mm. Plus it is possible that it might even be optimal a bit more forwards still. I did not try more forwards on the day.....

Flight 12.....
On Flight 12 I came down the Approach path to land.... I go to Dead Stick, for a very short period, as the Potential Energy of descent is more than enough to maintain a good approach airspeed anyway. The F-18 has quite a bit of Drag with Take-Off Flaps used to land, so that Dead Stick period is quite short - but the other good reason to go to zero Throttle is that it gives you a guaranteed base to COME BACK UP from. it is very easy to com up from ZERO to 10% (or whatever you know an aircraft type needs for its final flare etc), but not easy to get that accurate if coming DOWN from a higher unknown value.

I went through the typical motions, as per all prior landings were from good to excellent, but it came down and slammed into the deck like an Aircraft Carrier Landing!! At the time all I "saw" was that I added Throttle and Pitched Up to nose level - which it did... and then a bit more to go nose Up about +10deg - which it did.... so I saw the ATTITUDE changes, but I didn't recognise its true DESCENT path heading into the ground!
At approx the Nose UP motion point, it dipped the Left Wing and I thought "Oh Oh!!", corrected it, and it was in the ground in a split second.
I had no idea what had happened!! WHY????

Luckily it whacked into the ground on the Main Gear - except that it hit the Right gear first, which sharply rocked it into the Left Gear, which had it roll over leftwards to hit the Wingtip rail into the grass/Mud.... and that skewered in and made the F-18 fling around leftwards... and.... who knows, all over..... though still upright. The main damage was how the Nose Leg broke the Retract Mount out seeing it was moving Laterally when it hit the ground. BAH.
So that was the end of the flying for the day.....

All in all, I got it flying very well. But it needs a LOT of mechanical adjusting, and then re-tuning all the TX/RC stuff to suit that. But I know what the AIMS are, so that won't be too hard to do.
Plus.. it needs repairs now....


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