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Sep 24, 2014, 07:45 AM
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Gary Binnie's Avatar
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Build Log

Chris Foss Xtra Wot - Winter build


Hi folks, not sure if I've posted in this forum before?!

The Xtra Wot is a 120 glow sized sport model, loosely based on the Extra 300 (or similar!).

Balsa/ply fuselage and foam wings it is essentially an enlargement of the Acrowot from the same designer.

I had one before, ready built and powered by an ASP 120 two-stroke, a fantastic flyer until it got swatted by a radio problem, RIP!!

My build logs tend to be quite detailed, a record of what I've done and also might possibly help someone.

I'll start by describing the kit contents. Have attached a couple of photos of my first Xtra Wot to give an idea of the size.

Cheers

Gary
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Sep 24, 2014, 08:46 AM
Late for work again!
Gary Binnie's Avatar
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So...I was on holiday on the South coast of England last month, quite near a well known large model shop! Popped in and asked about the Xtra Wot, 'Yes, we've got one in stock' they said. Hoorah! 'Let's have a look at it then' says me.

Guy comes huffing and puffing down the stairs, opens the box and there it is. 'Thanks' I said, 'I'll think about it' and popped off for some more slope soaring, I cracked a few days later and after bartering the price down by a whole 4 it went in the car. As if I needed another big model!!!

Have been reading the instructions on and off for the last few weeks and I am quite familiar with Chris's construction methods.

Have tidied the shed workshop (a bit) from the last build project and I'm ready to do some kit bashing!

Have just emptied the kit contents out in the garden, enjoy!!

GB
Sep 25, 2014, 02:54 AM
Registered User
I've had an Xtra Wot ever since they first came out. It was originally powered by an OS120FS, but that was too noisy so an OS120AX went in it instead. The "pitts style" mounting option for the 120AX silencer fitted in the model nicely, and was quieter than the 4-stroke.

A couple, maybe three, years ago I converted to electric. It's now powered by a Hyperion ZS-4045/12 motor with 12S 3900mAh LiPo and 16x10 prop for 2000+ watts. Performance is better than it was with glow

Enjoy your build, and the flying
Sep 25, 2014, 04:12 AM
Late for work again!
Gary Binnie's Avatar
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Cheers!

Amazing that the four-stroke was louder than the two-stroke.

The OS120AX is the engine that I'm thinking of using. Have been looking at petrol (gas) engines as well (DLE 20RA and Evolution) as I've never owned one. I like the idea of less oily mess and cheap fuel but they can be quite loud.

I like to drill the engine mount holes in the firewall before I fit it but I'm just going to have to plod on until funds allow an engine purchase!

The ASP 120 two-stroke that was involved in the crash is apparently undamaged as I ran it afterwards on the test stand, could use it but I don't want to!! It was a pig to set up, no amount of high/low needle adjustment could get a nice pick up, I have an OS 90FSR (old school!) and stole the carb from that and it was transformed.

I am enjoying the build, very simple and everything is fitting nicely.

There are semi-rumours that the Xtra Wot will be the next Ripmax ARTF model in the line, we'll see.

GB
Sep 25, 2014, 10:13 PM
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kimchiyuk's Avatar
Neat plane. I'll be watching. You may get a better following by moving this thread to "Balsa Builders" forum. Good luck with the build.
Sep 26, 2014, 03:07 AM
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Gary Binnie's Avatar
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Thanks.

I'll look into moving it, was puzzled that there was no 'sport' category in 'Fuel planes'.

GB
Sep 26, 2014, 01:06 PM
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Gary Binnie's Avatar
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Wings


Making good progress on the wings.

Foam veneer cores are faced with balsa and a Liteply tip rib.

Won't be able to join them just yet as there is quite a bit of work on the ailerons which get cut out.

GB
Sep 28, 2014, 10:09 AM
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davidterrell80's Avatar
I am grateful for the chance to enjoy and learn during your build.
I'm drawing the plans for converting a 1941-era 41-inch diesel FF to a 50-inch RC; and, your work is good for stimulating my thinking about some of the changes I need to make to the airframe.

Thanks.
David
Sep 28, 2014, 02:18 PM
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Gary Binnie's Avatar
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Cheers!

I don't think there are many complicated techniques that I will use but I do try to pass on hints and tips that I've learned along the way.

There may be useful design features that give ideas, Chris Foss's methods are well tried and tested.

I got the urge last night to dust and clean my old Wots-Wot, a smaller two-winged Xtra Wot! ASP 61 power.

GB
Sep 29, 2014, 10:20 AM
Late for work again!
Gary Binnie's Avatar
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Back on it after a minor shoulder operation last Friday and two days at work!

I found sanding the trailing edges a bit tricky, the instructions don't give guidance on how thick the trailing edge should be but I've gone for about 3/32".

Interestingly (if you get interested by these things!) this kit is all metric, dimensions are given in millimetres and the balsa stock list is also metric. A departure from earlier kits and plans in this range. I tend to work in imperial units, or at least when I look at a piece of wood I would say it is 1/8" not 3 mm!

The Liteply tip ribs were only just big enough and a very slightly different section, in hindsight I would have been better off making my own.

The next job is to cut out and face the ailerons. Chris has pre-cut the ends and dimensions are given to cut two lines, one is the forward edge of the unfaced aileron and the other is the forward edge of the aileron cutout face.
Again with hindsight (and what I did on the second panel) the aileron line should be marked then use the two facing strips held together to mark the second line (the actual thickness of the material), this avoids a spanwise step along the trailing edge .

The facing strip width is marginal, on the second panel it wasn't deep enough so I laminated a strip of balsa on to it before fixing, no biggie.

Something I learned from my Phase 6 build is to sand the facing strips with the aileron in place, if it's not done this way the wing facing strip can get horrible dips in it!! It's not mentioned in the instructions, just something I learned the hard way.
Sep 29, 2014, 03:24 PM
Registered User
AA5BY's Avatar
Quote:
Originally Posted by Gary Binnie
Cheers!

Amazing that the four-stroke was louder than the two-stroke.

The OS120AX is the engine that I'm thinking of using. Have been looking at petrol (gas) engines as well (DLE 20RA and Evolution) as I've never owned one. I like the idea of less oily mess and cheap fuel but they can be quite loud.

I like to drill the engine mount holes in the firewall before I fit it but I'm just going to have to plod on until funds allow an engine purchase!

The ASP 120 two-stroke that was involved in the crash is apparently undamaged as I ran it afterwards on the test stand, could use it but I don't want to!! It was a pig to set up, no amount of high/low needle adjustment could get a nice pick up, I have an OS 90FSR (old school!) and stole the carb from that and it was transformed.

I am enjoying the build, very simple and everything is fitting nicely.

There are semi-rumours that the Xtra Wot will be the next Ripmax ARTF model in the line, we'll see.

GB
Try finding someone with an Evolution gas to compare the noise, the Evolutionss are considerably quieter than the DLE. The trade off is that an electric starter is appreciated with the Evo's whereas the DLE should require no starter.

I sometimes start my Evo's by hand, but other times find them wanting the starter. With a starter however, they start instantly and easily.

I like gas so much better than glow. The one drawback might be if the plane is stored in the house, mine all hanger in the garage. If a fuel leak happens, it can stink a house up rather quickly.
Sep 29, 2014, 05:54 PM
Late for work again!
Gary Binnie's Avatar
Thread OP
Thanks, I've got plenty of time to look at options as I can't afford a servo at the moment!

There is no noise problem where I fly but if it bothers me then it's no good!

The ailerons took a whole day, not in a rush but I'd like to move on tomorrow, might join the wing panels.
Sep 30, 2014, 11:57 AM
Late for work again!
Gary Binnie's Avatar
Thread OP
Been on my feet all day, overdoing it I think!

Have finished the ailerons as far as I want to go at the moment, ply plates gets let in for the control horns to screw to and the forward faces will need bevelling. I will probably cut all the hinge slots together, not sure if I will use the kit supplied flat pinned hinges or perhaps some nice Robart ones.

The construction order is planned to do as much work as possible to the wing halves before joining them as they are a fair size and things get much more awkward with a completed wing, only thing I've left is lining the aileron servo bays as I don't know exactly which servos I will be using yet.

I checked the wing panels prior to joining for fit at the roots (as suggested in the instructions), the sections match perfectly but the joining faces were not quite square to the leading edge (the leading edge is supposed to be straight across the span). It was only a small error so I didn't bother trying to correct it, will just make sure the wing is symmetrical when I drill the mounting holes.

A good coat of 30 minute epoxy was applied to both faces, taped together then left to set after scraping off the squeezed out excess.

A ply plate for the mounting bolts gets let in to the panel, a matching rectangular hole is cut right through the wing panels and this also gets epoxied in, filling the top with balsa.

Did some odd jobs while the epoxy was setting, added the tailskid ply plate, added triangular hardwood stock for the undercarriage plate and started sheeting the rear of the fuselage.

GB


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