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Feb 11, 2015, 10:40 AM
Late for work again!
Gary Binnie's Avatar
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A worry with the engine mount (as the dimensions were not available) was whether it would be too long, no need to worry as it is slightly too short.

Another worry was whether the 'Pitts' style exhaust would clear the firewall, again it is well clear.

The instructions give a distance from the firewall to the front of the prop driver of 150 mm. I make it 139 mm with the 120AX and its dedicated mount so I need to make an 11 mm spacer.

A plastic sidethrust wedge is supplied, it is square with a moulded pin in the centre of the rear face. This pin fits into a blind pre-drilled hole in the firewall, this hole is offset 5 mm to port to account for the side thrust (the prop driver should end up on the centre line with any luck, clever stuff!).

The sidethrust wedge makes up part of the mount spacer distance so I probably need nearer 10 mm.

Off to the shed!!

GB
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Feb 11, 2015, 02:58 PM
Registered User
That's a nice engine. By mounting it sideways, with the exhaust exit pointing down, you won't have to cut away much cowl at all.
Feb 11, 2015, 03:07 PM
Late for work again!
Gary Binnie's Avatar
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It's certainly still chilly out in the shed!

I laminated some ply to make the 10 mm spacer, clamped the engine mount to it and drilled through the four holes, slightly tricky as the mount has to be reversed after drilling two holes because the bearers foul the chuck.

The next step was to draw reference lines on the packer, match them up to the firewall lines and drill through the firewall, all going well so far!

Drilled through the plastic thrust wedge while I was at it.

'T' nuts are supplied with the engine mount, I think there were some supplied with the kit as well. A problem (which I also had with the wing mount 'T' nuts) is that the firewall is not thick enough, the spikes and front part of the nut would not be flush. Easily fixed with two strips of 3 mm ply added to the rear of the firewall, I have a plan to use these for some kind of tank box or tank bay floor.

Better tidy up now before I get in trouble!!

GB
Feb 11, 2015, 03:17 PM
Late for work again!
Gary Binnie's Avatar
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Quote:
Originally Posted by abenn
That's a nice engine. By mounting it sideways, with the exhaust exit pointing down, you won't have to cut away much cowl at all.
Hopefully not, I've had a quick look at it. I think the cylinder head will fit in the cowl without any holes, I did think about drilling a small hole for the glow plug driver but it's a big nasty prop so I'll probably wire a remote to a socket in the undercarriage plate.

It's nice to be doing something constructive again, seemed to spend the whole of January waiting for the postman!!
Feb 11, 2015, 03:56 PM
Registered User
Yes, I didn't have to cut anything for the cylinder head, and I used a remote glow socket in the lower flat part of the side of the cowl -- easier than reaching under to the bottom plate. Trickiest bit was getting a hole in the right place for the slanted mixture needle.
Feb 11, 2015, 04:05 PM
Late for work again!
Gary Binnie's Avatar
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That's the fella.

I'm hoping (that word again!) that I will be able to leave the needle once it's adjusted.

The weight is creeping up, weighing all the bits comes to 9.6 lb with radio gear and finishing still to go.
Mar 02, 2015, 10:04 AM
Late for work again!
Gary Binnie's Avatar
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Well...I need to get a move on with this because winter is nearly over (ish!).

It's still quite chilly in the shed so I've been given permission (lol!) to finish off the glassing in the house.

I've only really got the fuselage to cover (both sides and the rear lower sheeting) and possibly a layer of finishing cloth over the wing bandage to smooth out the bumps.

The fuselage sides should be very easy to do (being flat) but the cloth is puckering at the edge where it overlaps onto the turtledeck, not sure what is going on. It's as if the cloth needs pulling tight but doing that causes the strands to tear, nicking it with scissors helps a bit as does rubbing it down when the resin has nearly gone off. Anyone experienced this?

GB
Mar 02, 2015, 03:37 PM
Registered User
How are you applying your resin? I use a brush to stipple it into the cloth, and don't have any problem at overlaps. I do get the occasional bubble where maybe the balsa has drawn all the resin out of the cloth while curing, but sanding and another localised dab of resin solves the problem.
Mar 02, 2015, 06:53 PM
Late for work again!
Gary Binnie's Avatar
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I pretty much follow the instructions (Z-Poxy) which says 'spread' resin on the wood (I trickle a thin line of resin out of the mixing cup and use a credit card) then lay the cloth over then spread more resin through (which it doesn't say in the the instructions but it would be dry as a bone without) then squeegee out all the excess resin (blotting isolated pools with paper towel).

I think the coat on the wood makes things too sticky, I'm going to try the other side just pushing resin through the cloth.

Thinning the resin is often mentioned, that would probably help, others say not to do it.

It's a black art for sure.
Mar 03, 2015, 06:22 PM
Late for work again!
Gary Binnie's Avatar
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The fuselage glassing is finished, seemed to go better today.

Could it be that I'm getting on to final assembly?!! Maybe!

The fibreglass fuselage top deck needed balsa strip adding for extra glueing area, five minute job.

I decided a while ago to have a steerable tail wheel, I hate the scraping noise a metal skid makes on tarmac!

At one time a tail wheel was an option for this model, it's been crossed out in the instructions. I think it was a 'Klett' unit originally, what I have is very similar and marketed under the 'Flightline' brand in the UK.

Because of the sharply angled rear fuselage the tail wheel bracket would not have sat correctly to have the steering pivot vertical which would have caused shimmy problems so I made a hardwood wedge to fix it.

GB
Mar 04, 2015, 03:37 AM
Registered User
Pity that tailwheel's "arm" couldn't have been straightened so you wouldn't need the triangular piece. We don't have the luxury of a concrete runway at our field, so the metal skid works nice for me
Mar 04, 2015, 04:56 AM
Late for work again!
Gary Binnie's Avatar
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Yep, it's glass-filled nylon so there was no way to change it.

We have grass and tarmac, an old airfield perimeter track. The surface is broken in places but it's usable.

Going to fix the tail feathers on today, glassing has left some 'gunge' in the tailplane slot and it's very tight!
Mar 04, 2015, 09:09 AM
Late for work again!
Gary Binnie's Avatar
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I'm always nervous when I start gluing big parts together!

The instructions say to use a reference point on the fuselage centreline to check that it is square (in plan view), I did that by measuring from the trailing edge tips to the centre stringer in the 'instrument panel', easy enough.

It's possible though that the wing might not be exactly square to the fuselage so I fitted the wing and measured tip to tip, all good. I drew a couple of pencil lines on the tailplane either side of the fuselage so that I could remove the tailplane, apply glue and refit it in the right place.

Also checked that the tailplane was level (viewed from the front), not an awful lot I could do about it at this stage but all was good.

If anyone follows this blog to build their own Xtra Wot please note that I'm not using the wire elevator joiner and my tailplane trailing edge is level with the fin trailing edge (it would be 5 mm further forward if using the joiner).

Added the fin next, easy enough, just had to make sure it was vertical.

Next step will be to check/dry fit the rudder hinges and then I'm not sure what!
Mar 05, 2015, 09:16 AM
Late for work again!
Gary Binnie's Avatar
Thread OP
A job that definitely needed doing was to cut the cowl to fit round the silencer, I used my best guess, cutting undersize initially, quite pleased with how it's come out.

As there is almost a complete aeroplane I was eager to weigh it and have a first look at the balance point. With five dead servos added it currently weighs around 4.3 kilos or 9.5 lb. A pound to go for finishing, receiver battery and bits and bobs.

The balance point (with a prop fitted) is around 90 mm, it is supposed to be 112 mm so it's nose heavy. This was with three servos in the forward slot of the servo tray, I will try them in the rear slot next. Hopefully I won't need to add any ballast anywhere.

GB
Mar 05, 2015, 03:29 PM
Registered User
The tail gains more weight relative to the rest of the aircraft when you cover or paint it, so I would expect the c of g to creep rearwards a little anyway. Mine certainly didn't need any ballast when it had the OS120AX in it -- and still doesn't, with electric power.

Not sure if I mentioned it earlier, but mine was 9lb 3oz with the OS120AX, ready to fly but empty fuel tank. It's covered in Solarfilm or SolarSpan -- can't remember which -- but no glassing.


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