YT International 120 Spitfire build.

[Tim Campling]

Hi all,

this is the one!! Since I started flying 5 or 6 years ago I've had one goal in mind. I know it's not original and probably a bit of a cliche but for as long as I can remember I've been in love with the Spitfire. The Mk 9 is easily my favourite but I've settled on the YT Mk X1V. In fact what really clinched it was meeting the guys from YT at Weston Park last month. They were helpful and keen with the offer of as much support as I needed.

Anyway, here goes with as many pics as I can. If anyone else has experience of this model and any tips to pass on, please feel free.

[Tim Campling]

The instructions first. These are adequate at describing the stages of the assembly process. However Hangar 9 they are not! These are much improved (I am told) from the first editions but be aware that they don't hold your hand through every last step. There are discrepencies and generic pictures but if you have put together a few ARTFs then there is nothing that can't be overcome with some thought. Even the amendment sheet that I was given has the flap servo hatch measurements wrong!

However, overall I think they are fine and I'm enjoying putting some thought and creativity into the process.

[Danny Fenton]

Hi Tim, I look forward to seeing your pics, I have a friend that has put together the early YT version and the newer one, and they both fly really well.

The only thing I would say, and this goes for any ARTF with retracts, paint a slightly thinned coating of pva over all the ribs and spars that you can access in and around the retract mounts.

 

Cheers

Danny

[Tim Campling]

First steps, the wings. These are beautifully painted as is the whole 'plane and very light. The first steps are to hinge the ailerons and flaps.

The ailerons use the usual cyano wafers, the cuts are accurate and just require a 2mm hole adding to allow the glue to wick in. I always add a few strips of masking tape to catch any drips and to prevent the fumes depositing white clouds on the wing.

The aileron control horn is a substantial bolt through the control surface. There is a countersunk washer on the top surface with a flat washer and nyloc nut underneath. The nylon pivot fittings are well up to the job and provide a slop free connection.

I've opted for Futaba S3010 servos for ailerons and flaps running at 6V. These fit under servo hatches as usual but take note that you will need long servo horns to get full movement. The control linkage is quite long but the supplied rods are substantial enough. A long servo extension lead is needed but I prefer to solder extension cable into the original so nothing can come apart. From my experience in the car audio business these cables should always be twisted to improve interference rejection.

The flaps use flat pin hinges that are let into the flap slightly. These need to be epoxied in so take care to cover the pin in vasaline to prevent it seizing. It's easy enough getting epoxy into the slots but of course any excess has a tendency to push out over the hinge and pin. I want to provide a big flap angle and these hinges and geometry will easily allow 90 degrees.

First problem here was that the flap control system was the same as for the aileron and there was no way the bulky washer and bolt would fit under the split flaps. After a bit of thought I hit on the idea of using a standard horn mounted from inside the flap. This meant letting the base into the flap but I think gives a very neat solution.

I should have mentioned that the wing comes without any of the servo hatches or wheel well cut outs. These have to be located and cut into the painted solartex covering (scary!). The servo hatches are supplied pre covered and are a perfect fit. There is a sheet giving locations but the flap one has the measurements reversed so take care and feel carefully before cutting! I would advise cutting everything out straight away as it helps with threading the servo leads. Also keep the cut outs as these will come in handy if you need to patch anything but also as covering for the undercarriage gear covers (not my idea but I pass it on).

I mounted the flap servos symetrically without thinking so that means they work in opposite directions (like the ailerons). It would be simple to mount them in the same direction but it's too late now so I'm using a servo reversing lead.

So far i am really impressed with the quality of the hardware and the construction of the model. The retract bearers appear substantial and the load bearers more than adequate. Most people recommend packing the aft bearer to angle the undercarriage forward to help ground handling. I've still to decide on the retract system yet but I'm swaying towards the Lado Tech electric system as it is lighter and simpler than air.

Anyway, that's all for now. I think I'll tackle the engine installation next.

[Tim Campling]

Hi Danny,

Is that to add strength?

[Tim Campling]

I did consider running in resin to the bay but i don't want to add the weight really. I did that to my Hangar 9 P-51 but like I said it was heavy.

[Danny Fenton]

Hi Tim, yes, to add strength. They are notoriously weak as the mounts are simply laminations of weak ply. I did this on my YT Hurricane and it strengthened it right up. a few brushfulls of thinned pva are not going to add a significant amount of weight, you only put it on the load bearing areas.

 

Cheers

Danny

[Tim Mackey]

Watching with interest Tim.

[Tim Campling]

Cheers Danny

That 's a good tip, thank you.

[Tim Campling]

Managed a couple of hours last night and started the engine install. I'd already read the forums through and had read this location method but it is also provided in the manual amendment sheet.

Instead of locating the engine and then fitting the cowl around it the process is reversed. The gorgeous cowl is located onto the fuselage for the best fit. Then measure the distance from the front to the firewall. By drawing this measurement on paper the engine can be assembled onto the mounts.

Now the clever bit! The mount can be screwed to a piece of 3mm ply (making sure that the screws do not stick through the ply). This is then offered up to the fuselage and a screw and big washer (bigger than the tank hole) is used to sandwich the firewall. By tightning up this screw just enough the mount assemply is held firmly but can be moved around for alignment. This is standing in a box and that is why I chose to do this now before any of the tail feathers are on.

The cowl can then be reintroduced and the engine/mount moved around to centralise it. At this point I discovered that I would need to cut the cowl which is a job I never look forward to! I chose to remove as little as possible for now and as soon as I started to cut it was obvious how substantial and well made this cowl was. This bird is well known for needing a lot of nose weight so there is no need to skimp on the glass fibre. I had thought to reinforce it but I really do not think I'll need to.

So with the cowl cut all that is needed is to adjust the motor for the centre line (bearing in mind that it is 3mm too far forward). Having the spinner helps of course!

With the cowl off again, remove the engine mount from the ply plate and mark the mounting holes on the firewall, easy!

[Tim Campling]

As you can see I've yet to complete this last step as there is something I'd like an answer to regarding thrust angles.

There is no side or down thrust built into the firewall. My question is, how is this likely to affect flight, particularly take off and landing? There is mention of thrust angles in the amendment sheet but also of mixing rudder/elevator to throttle.

I'm prepared to accept a slightly offset spinner/cowl interface if that means an easier flight characteristic. This could also be altered once I'm familiar with the 'plane.

Personally I am more comfortable flying without mixes and honestly haven't had a lot of experience with them apart from a little down elevator on flaps.

What do you lot think?

[Olly Giles]

I am green with envy tim. Id reccomend following the instructions on the thrust angles (im guessing its down and right thrust) as you will fid that opening the throttle will cause a climb and probably a yaw. Mixing this out is possible but not really the done thing. The yaw effect will be exadurated on the ground too. Id also fit an anti vibration mount for that size of motor, looks like a lazer 120?

[Tim Campling]

Hi Olly

Thanks for that. You've reinforced what I was thinking. Yes the notes mention a couple of degrees right and down and as I said, I can live witha bit of spinner offset.

It's a Laser 150 actually and when I ran it up on the bench there was a fair amount of vibration (not surprising really for a 25cc single pot). I've not come across anti vibration mounts but it sounds like a good idea. Any recommendations?

[Olly Giles]

These Hyde mounts work fantastically well but are specifically designed for YS engines but there is no reason why you couldnt bolt your lazer in. But they are hugely expensive. I have used one of these mounts before and worked well but the rubbers do eventually start to wear. Probably this would me most suitable for your project. Im not sure what prop you're using but these xoar props are second to none.

[Tim Campling]

Oh and congratulations on your success Olly. I saw your pic in the BMFA News. Well done mate.

[Alan Cantwell]

the standard mount is fine, but you have a lack of decent size washers, bolted as it comes to the bulkhead will be also fine, mine is the early version, and the mount is just whacked on the bulkhead, as are my other YT birds,

[Tim Campling]

Cheers Alan. Crikey those anti vibe mounts are expensive! I think I'll try the standard way first.

[Tim Campling]

Ok. I've spent a pleasant afternoon playing with the engine mounting. I've opted to apply a couple of degrees of down and right. I've just put some strips of liteply between the firewall and the mount to build up the required offset.

This of course means moving the mount position off centre and by drawing the angle against the firewall to prop driver line the offset can be easily measured and applied.

 

The result is more than acceptable to me. (The 'backplate' is fashioned from hardboard! I must order a real one).

I saw in another forum that people were fitting the throttle servo in the cowl to help the weight distribution. There's plenty of room so I thought I'd give it a go.

First I produced a ply mount, shaped to the contours of the nose piece.

A simple job then of mounting the servo and working out the linkage. Adjust the travel on the radio and it all worked a treat.

I stepped back to admire my handywork and then realised what would happen the first time the 'plane nosed over. Not to mention how awkward needle adjustment would be under the cowl.

School boy error! Luckily by reversing the servo position I could mount the carb in a near perfect position!

This all fits perfectly inside the cowl. I'll also build some sort of barrier around the servo to keep any stray gunge off it.

Once satisfied that everything fitted and moved correctly I stripped it all down and applied copious amounts of threadlock and fuelproofer.

I've decided on the Lado Tech 95 degree 333 retracts which should give a straight oleo without splaying. Better start saving up (no birthdays imminent).

Tail feathers next I think.

[Tim Campling]

I must also say that this is such great fun. Having to think about solutions and putting a little of myself into this project is brilliant. The product is fantastic, all the hardware is spot on. Love it!

[Alan Cantwell]

I have never used any packing on any of mine, if you just mount the engine to the bulkhead so the spinner is in line, all will be well,

 

just a point, are your brass eyelets the wrong way round? the top hat bit is sposed to be under the servo, or are me eyes failing me

[Danny Fenton]

I went with the bulkhead offsets on my 70" YT Hurricane and it is fine. I doubt you need to increase the thrust angles. My Hurricane was using a 20 x 10 innitially.

 

Cheers

Danny

[Tim Campling]

Well spotted Alan, you win the spot my other mistake prize!

No seriously though, do you think there's no need for offset thrust? A couple of years ago I had one go in on the maiden through torque roll. I was probably too slow at rotation but it still worries me. That Laser 150 should be swinging a 16x8.

[Tim Campling]

Got a bit more done over the weekend. The Lado retracts arrived but the Unitracts oleos won't be here for another week. A quick mock up and it was obvious that the supplied plastic wheel wells would not be deep enough (I was expecting that). Other modellers had lined the wells so, one sheet of loose grained 1/16th sheet of balsa in hand away we go.

I had chosen the least grained sheet that I could. This was lightest and bent easily. In fact it was bendy enough to naturally follow the well but after cutting I held it over a boiling kettle and it curled itself away from the steam.

This meant that it was not trying to pull away and thin cyano held it perfectly.

It was quite quick to work all the way round just leaving a gap at the back for the retract cable. After it had all dried I coated the entire structure with slightly thinned PVA (cheers Danny) and it feels really quite substantial. With the grain running vertically between the wing skins I think it has added significant stiffness.

Finally just for the look, a coat of silver paint and fuel proofer.

I'm very impressed with the Lado retract units so far. At 6V they deploy really slowly. They have an overcurrent shut off so no flat batteries allthough I'll still have a seperate battery for retracts and flaps. I'm looking forward to the Unitracts, I didn't realise they were made to order.

The next challenge will be the horizontal stabiliser. There is no key to ensure they are actually horizontal so I will build a jig. But before I do that I want the wings complete, I'm not very good at jumping around the build process!

'Till next time.

[Alan Cantwell]

just to tee you off, YT are switching to a new design of retract for the range, and they are--electronic, but they wont be available until next season, ah, the joy of it, fit, connect battery, and forget, no leaking air, no pumps, HOLD ON!! ive just spent 35quid on a 18volt compressor, DOH!!

[Tim Mackey]

I hear from a reliable source that YT are also going to bringing in a range of rather tasty gliders?