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Chris Foss Xtra Wot

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Ron Gray19/06/2020 07:07:01
2235 forum posts
978 photos

Having just finished the Lavochkin LA-7 my next project is the CF Xtra Wot so is anyone interested in seeing the build progress? I’m happy to record the progress with photos and videos but equally no problem if Forumulites think it is a bit of a boring subject!

Frank Skilbeck19/06/2020 08:24:43
4754 forum posts
104 photos

Is this the ARTB version, then I'll follow with interest.

Gary Spicer 119/06/2020 08:42:54
46 forum posts
3 photos

Hi Ron, I will follow it, I was thinking of building one myself, another Laser for power?


Bob Cotsford19/06/2020 09:02:59
8650 forum posts
483 photos

Be interesting to see how similar or otherwise it is to the ARTB AcroWot.

Paul Marsh19/06/2020 09:59:28
4072 forum posts
1225 photos

I have 2 Xtra Wots, good model. First one has a OS 120 FS Pump (originally has a Saito 180) and the other a OS 120 AX two stroke.

Ron Gray19/06/2020 09:59:35
2235 forum posts
978 photos

It is the kit version, not the Ripmax Acro Wot XL and it will be leccy powered! (shock, horror, not a Laser 155). I was going to go down the Laser route but I was 'challenged' by a colleague to 'lectrify it so it will be 10s. For the colour scheme I want to mimic the Hamilton orange and black so already have HK and Solarfilm covering film in stock for that. I also ordered it with the longer can of peas.

Edited By Ron Gray on 19/06/2020 10:00:40

Paul Marsh19/06/2020 10:05:10
4072 forum posts
1225 photos

The first one was one of the first that Chris Foss had off the production line. It was sold at a special price - abit like a prototype and test report, think I only paid £160 for it.

Ron Gray19/06/2020 10:47:04
2235 forum posts
978 photos

I first saw one, in the flesh, a couple of years ago and it was powered by a Laser. It flew really well and I was impressed although, at the time, didn’t like the tail skid in place of a wheel mainly because it made such a noise on our tarmac! So when lockdown arrived I decided to go ahead and get one and I even have plans for that tailskid.

Ron Gray19/06/2020 10:54:14
2235 forum posts
978 photos

The box of bits, excellent quality of balsa and ply, good CNC cutting and pretty good destructions too.


Edited By Ron Gray on 19/06/2020 10:55:46

Paul Marsh19/06/2020 11:29:06
4072 forum posts
1225 photos

How much are they now? Can't find a price anywhere...

Ron Gray19/06/2020 13:06:05
2235 forum posts
978 photos

I paid £270 with postage and the larger canopy.

Gary Spicer 119/06/2020 13:12:13
46 forum posts
3 photos

You did well to get it for that Ron. Leeds Model Shop have them for £299.99 and direct from Chris they are the same price, Leeds have them in stock just landed today!

Ron Gray19/06/2020 15:29:30
2235 forum posts
978 photos

I did think it was a competitive price from Chris, maybe he took sympathy with a lockdown build project!

Ron Gray19/06/2020 20:30:34
2235 forum posts
978 photos

And we're off!

Following the excellent instructions and sketches the fuse was first up on the agenda and joining the balsa outer pieces using masking tape over the joints, folded back, glued then pinned onto the workbench tape side down. I'm using Gorilla Glue White for most of this build as I find that it sets quite quickly is strong and dries clear, oh and it sands very well too.



Excellent quality cutting of the parts means very little sanding required to get a good fit.


Once the glue had set then it was fitting the ply doublers (yes making doubly sure that I had a left and right part!).


Balsa stiffeners and longhorns added together with the tail post.


Quickly progressed to the formers which have to be removed from their parent sheets but you can see the quality of the CNC routed parts


And this is the tool that I use on ply parts to cut them from their parent sheet


Engine bulkhead and first former fitted making sure that everything is lined up correctly, lots of clamping and good use of 6s batteries!


Opposite fuse side fitted with other formers temporarily fitted in position (the fuse has to be drawn in at the tail for these other formers to fit.


And to support the tail whilst the glue was drying an offcut from one of the parent sheets


I keep meaning to make myself a jig but progressed without one using set squares and front to back aligning to make sure everything was square. To be fair having made sure that the front end was square when I fitted the first 2 formers, very little adjustment was necessary to make sure the fuse wasn't twisted when it came round to pulling in the tail end but a jig would have made it easier (make one!!!!).


And then it was a matter of fitting the remaining 2 formers and the servo tray.


And that was the first day and a bit of work, coming along quite nicely.

Brian Cooper19/06/2020 23:10:53
567 forum posts
27 photos

The Xtra Wot is a great performer thumbs up but make sure the tailplane is "solid".

The tails have been known to fail during a bit of "spirited" flying. smile o

Ron Gray20/06/2020 06:47:53
2235 forum posts
978 photos

God point Brian, Chris Foss does say, in the instructions, that if a larger engine is to be used or if the proposed flying is to be somewhat spirited then the tail should be reinforced with carbon. The tailplane was redesigned so that the elevator counter balances were removed and those pieces stuck to the horizontal stab (sorry about the use of an Americanism) as I believe that was another weak point. Mine will be reinforced!

Engine Doctor20/06/2020 10:06:59
2540 forum posts
40 photos

If I remember correctly it wasn't just the tail plane that failed but also the fuselage just in front of the tail plane could break. I built one for a club mate some years ago with a YS 140 for power. Great plane and no vices to speak of. The rear the was strengthened with some thin doublers. The model is still around with a Moki 180 Glow in it now . Great model enjoy .

Ron Gray20/06/2020 14:54:20
2235 forum posts
978 photos

I just thought I'd weigh the powertrain I propose for this model and, with batteries (10s) it comes out at 2Kg. Now a Laser 155 weighs in at, say 1Kg and a full tank (500cc) weighs about 120g, that's a lot of difference! Am I missing something here?

Keith Berriman20/06/2020 15:26:37
756 forum posts
11 photos

Maybe worth a quick call to Chris' Foss Monday morning to check on electric set up ?? for that model before going much further

Ron Gray20/06/2020 16:02:06
2235 forum posts
978 photos

There's a chap on RC Groups with an almost identical setup to mine but he's running it on 12s and he changed his from IC to leccy so I've asked him what it's like.

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