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Chris Foss Xtra Wot

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john stones 128/06/2020 22:27:34
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11546 forum posts
1517 photos

Oooh Jacinth, my favourite colour. rainbow

Gary Spicer 128/06/2020 22:51:53
46 forum posts
3 photos

Excellent Ron, the wings look great with that coveringyes Strange not seeing a Laser bolted on the front end!

Ron Gray28/06/2020 22:59:26
2186 forum posts
942 photos

Mine too John.

@Gary - yep, a bit of a departure from my normal!

Ron Gray30/06/2020 22:11:43
2186 forum posts
942 photos

Unfortunately I didn't hit my target of having the XW finished today, instead it looks like it's gong to be Thursday or Friday.

But lots of little jobs done, hard points fitted to rudder, elevator and ailerons. All hinge points slotted and hinges fitted. Elevator joining wire fitted. Rudder, elevators and ailerons covered. Fin and tailplane glued in place, for the latter I had to slightly trim one fuse tailplane slot as it was about 1/2 degrees out from level. I also spent a bit of time drawing and cutting out some letters for etc fuse and wings, for this I used the Silhouette Cameo to cut the letter from covering film.

Not many photos as the work was pretty basic and covering is covering! For eta hinges I'm using 'furry' plastic type glued into the control surfaces using medium, slow set cyano, then Gorilla Glue (white) to attach them to the wings etc,

Hinge slots cut using the slotting tool

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Most of the parts can be seen in this shot plus the lettering has been added to the fuse.

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Tim Flyer30/06/2020 22:14:31
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1290 forum posts
236 photos

Looks great Ron! Super Fast Build too!

Ron Gray30/06/2020 22:31:48
2186 forum posts
942 photos

Thanks Tim, it went together quite easily, really good instructions and sketches. Taking longer to finish bits off but me doing the fancy lettering hasn't helped! Hopefully it will look alright when it's all put together (got to paint the front deck and cowl first!)

Edited By Ron Gray on 30/06/2020 22:31:59

Gary Spicer 130/06/2020 23:15:49
46 forum posts
3 photos

I think it look great as well Ron, I,m very impressed with your lettering, I had know idea you could cut covering film with the Cameo.

Are you using the kit hardware pack for hinges clevis etc.?

Ron Gray01/07/2020 06:35:13
2186 forum posts
942 photos

Thanks Gary, I tried the Cameo as an experiment and am rather pleased with the results but wait until you see the wings!

I’m using the kit supplied hardware, apart from the hinge material which is smooth nylon but I prefer to use the ‘flocked’ nylon type for flat hinges.

flying pastor01/07/2020 12:43:59
24 forum posts

Excellent job Ron. This may be of interest regarding your power train. I am converting a Wot4 xl to electric using a Hyperion 4045/280 which is the forerunner of the 4045/12. On 8s and an 18*10 apc e I am getting 55 amps and about 1550 watts. This is with the cells on storage voltage. They are now on charge to see the results later today. The motor has a continuous current rating of 50amps and max 63 amps. Unless there is a significant difference between your motor and mine I think that you will need a smaller prop than the 19*10 than you intended to use. I'm sure that you will use a wattmeter to check and I look forward to seeing the results.

All the best...Chris.

Ron Gray01/07/2020 13:02:49
2186 forum posts
942 photos

Many thanks Chris and you are correct, I will be using a wattmeter to check it out before flying, I was basing mine on what another guy is using with the same motor plus what eCalc says (I know that is not always right!). Will be good to see your findings with fully charged cells.

flying pastor01/07/2020 19:46:01
24 forum posts

Ok Ron here we go. Fully charged my lipos and then left them for 3 hours to settle. Ran up motor at half throttle for 1 minute then went to full power and hastily shut down again as was seeing 75amps and over 2000 watts. Changed prop to 16*10 and saw 55 amps and 1650 watts which is fine for me. It could be that the type of wind/construction changed when the motor was updated. Will be interested in your results. Incidentally I reckon that you will finish your extrawot build before I finish my wot 4am assembly!

All the best...Chris.

Ron Gray01/07/2020 21:08:09
2186 forum posts
942 photos

Great info Chris, will probably have to re-think the prop then!

Peter Jenkins01/07/2020 23:41:58
1603 forum posts
266 photos

Some info on setting up electric motors guys. I bought a small on-board telemetry system sold by SM Modelbau called the UnisensE that can be made to talk to most types of radio system. (You can find an English translation here.) It is small and light yet provides real time readouts of the motor parameters as well as height and is pretty accurate.

I mention this as when doing a check on power output on two 2 mtr class aerobats I found that the static measurement was way out. I recorded 3600 watts at 98 amps on one motor/prop combo (10S pack with a 99 amp ESC) but never saw more than 2800 watts (the motor's limit) on more than one occasion and around 70 amps. Those figures were obtained from the UnisensE with the aircraft tethered and then at full throttle on a vertical climb.

I no longer rely on ground testing but on relying on airborne readings. For electrics, there is little point in doing a static full power check once you have sorted out the correct prop and, as you can see from the results I obtained, if you use the static power/current check to size the prop you will be well under that power/current in the air. Up to you how you go about this but for around Euro 70 (incl post) you have a piece of kit that can be moved from model to model to help check you are getting the maximum performance out of your equipment without overstressing it.

Ron Gray02/07/2020 06:21:37
2186 forum posts
942 photos

Peter, based on your comments about the UnisensE up at the field, I went ahead and bought one and will be using it in the Xtra Wot!

Bob Cotsford02/07/2020 09:11:46
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8597 forum posts
483 photos

The thing I like about the Unisens-E is that one unit can be swapped from model to model at the field. All you need is an SPort lead cable tied near your battery connectors. If you've got room for an extra 1 1/2" of connector they are a great upgrade.

Peter Jenkins02/07/2020 09:23:55
1603 forum posts
266 photos

Do you use the Max/Min function Bob? That needs a spare channel on the Rx though. You also get motor rpm if you connect to one of the 3 phase motor leads. If using a gearbox you can enter the gear ratio used to get prop rpm.

Ron Gray02/07/2020 10:37:47
2186 forum posts
942 photos

6 channel Rx should do it then in the XW.

Bob Cotsford02/07/2020 11:34:30
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8597 forum posts
483 photos
Posted by Peter Jenkins on 02/07/2020 09:23:55:

Do you use the Max/Min function Bob? That needs a spare channel on the Rx though. You also get motor rpm if you connect to one of the 3 phase motor leads. If using a gearbox you can enter the gear ratio used to get prop rpm.

Connecting to FrSky I just use consumption, pack voltage and altitude. I had to go away and check the manual to remind myself what's available on the Unisens-E and what you meant by min-max! I have set up telemetry displays to show max power, max height on my transmitters but I tend to forget they're there most of the time. I generally browse the logfiles at home out of curiosity or if there was an issue but I'm not chasing every watt so I only tend to monitor lowest cell voltage for warnings of poorly cells. Any value that needs warnings (pack voltage, altitude) are set up as logical switches triggering special function 'play track' warnings, all within OpenTX.

I think it's the Bolero that I set up a motor lead for RPM but I found it a bit unreliable - sometimes it triggers, more often not.  TBH unlike with IC I don't worry about the RPM of an electric motor, after all I set it up with a known kv and known battery voltage so it's not going to vary that much.

Edited By Bob Cotsford on 02/07/2020 11:37:29

Peter Jenkins02/07/2020 13:02:30
1603 forum posts
266 photos

Yes, I also rarely use the rpm figure as in my case I have a contra prop that is driven through an epicyclic gearbox so there's no telling what the individual prop rpm is! All I get is the calculated rpm on a 13.5:1 gear ratio! As you say, the key parameters are all covered by amps, volts and capacity remaining. I actually now only look at the max height reached as that tells me if I broke the 60 deg rule and ended outside the aerobatic box. Obviously, the further out you fly from the 150 m datum the higher you can be without going out of the 60 deg max angle! I also use the Tx (JR XG11) to alert on remaining capacity at 1,000 mah. Not usually a problem if I'm flying the schedule as I usually have between 1,500 and 1,800 mah remaining out of 4750 mah at start.

Ron Gray02/07/2020 20:29:17
2186 forum posts
942 photos

Today was quite productive.

Primer applied to the various bits that are white and need to be black

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I had already primed the fuse decking so I set about cutting teh front section out which will be the battery access hatch.

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Back to the outside spray booth and black topcoat applied.

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Control linkages fitted to the ailerons (I've already done the tail ones), using a Z bend for them servo end, keeping it nice and simple.

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Servo wiring sorted and for the wing I'm using Maxloc (Ashlock) connector, one plug instead of 2 to connect at the field.

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Other bits done, cowl mounting blocks fitted and cowl cut out for the motor shaft and the air intakes. U/C drilled and fitted along with wheels.

So I couldn't resist the temptation to see what it all looks like loosely assembled (I needed to get the fuse up to a position where I could check the C of G as that will determine where the battery pack goes and the support platform for them. Fortunately Chriss Foss gives a fuse only C of G and having checked it out, the batteries should fit into an easily accessible space. So that will be tomorrow's main job, build the platform then permanently fitting the top deck and making the battery hatch.

And this is what it looks like on the bench, 'posed' outside shots will be tomorrow. I am rather chuffed with the look.

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