Weston Capiche 50cc Build

[Gary Manuel]

Posted by iqon on 06/03/2018 15:38:57:

Youve put me off it now Gary, dont like pull pull and to put them elevator as well ..is there an alternative with this plane

Yes there is. There are cutouts at the rear under the covering for elevator servos if you need them.

I really hope I don't live to regret saying this, but pull-pull controls are nothing to be afraid of if you are careful and follow a few rules. Watch this space as I've just done the elevators and will be posting details later on.

[cymaz]

I did closed loop elevators on a DSM Aerostar. Worked well but I realise this is a different beast altogether. BTW, my General Western Meteor P-2-S has closed loop ailerons.

[Gary Manuel]

Closed loop controls is one of the reasons I chose this model. I fancied something a bit different and I've always liked the positive feel of closed loop controls.

[Gary Manuel]

Before I start on the elevator controls, here's an update of what little progress I've made while the brass monkeys were occupying my shed:

Fuel tank stripped down to see what's inside.

Looks to be a nice quality tank - about 650-700ml with a lip on the front.

Supplied as a 2 pipe system with bare tubing and no tee joints etc. The clunk is just a weight with no felt filter.

Converted to 3 pipe by adding a length of brass tubing and soldering a nipple onto each end.

The clunk was replaced with a filtered one and the 3rd pipe for filling / emptying via a fuel dot was fitted with a plain clunk.

Stopper replaced and pipes identified. The stopper is black but it's not a Dubro type intended for Glow fuel only, so I'm sure it will be OK for petrol.

[Gary Manuel]

AGM heavy duty dual switch / fuel dot with the second switch removed. I won't need this for the receiver as this uses a dedicated fail-safe switch. Input power socket replaced with an XT60 to suit the 2 cell LiFePO4 battery I'll be using for the ignition.

Blanking plate formed from glass fibre board and epoxied to cover the switch hole.

This is the receiver I'll be using. A JR RD922 PowerSafe system with 3 satellites and dual power supplies. The supplied sockets have been replaced by XT60's to suit the two 2 cell LiFePO4's I'll be using for powering the receiver / servos.

[cymaz]

It seems you have adopted belt and braces with added bicycle clips...liking it

[Gary Manuel]

Now onto the elevator pull-pull (closed loop) setup.

I'll spend a bit of time explaining how I set these up. I'm sure that there are other ways, but this way seams logical to me.

The first point to make, and perhaps the most important part of a closed loop system is to make sure that the control horns in the moving surface is symmetrical about the control surface centre lane and that the ball links are in direct alignment with the control surface hinge line. If this is not the case, you will finish up with wires that slacken too much, or over-tighten when the control is moved away from the neutral position (assuming that straight servo arms are used).

What I'm aiming to achieve with my way of setting them up is that the wires remain fairly tight throughout the full range of movement, as this should give the best performance.

First job is to temporary connect the power supplies up and bind the receiver and transmitter. The transmitter should initially be set up with no reduced rates / expo / differential / sub trims etc. i.e. sub trims at zero and all travel / end points at 100%. I connected the throttle and kill switch to check that they were working correctly too. Ailerons not connected yet.

This bit is a little over the top, but should illustrate, what I'm trying to achieve. It is assumed that the servo arms have been fitted to the splines which give the bet initial alignment. In my case, I am using HiTec servo's which have 24 splines which make NO DIFFERENCE which way round the arm is fitted. In the case of most other makes of servos, which have odd number of splines, it's worth playing and reversing the arms to get the best initial alignment. Silly oversight on the part of HiTec in my opinion as this is one feature of them that I think is lacking.

A large set square and a couple of blocks of wood were used to determine the exact perpendicular with respect to a line between the servo centre and the control horn. It can be done with reasonable accuracy by eye, but using a set square guarantees it.

The pencil line on the wooden blocks is directly above the servo centre. The set square is aligned with the edge of the wooden block and is pointing directly towards the control horn. Note that the control horn is on the opposite side to the servo, due to the wires crossing within the fuselage.

Once everything is in alignment, looking down the edge of the wooden block (with receiver on and everything centred) confirms whether the servo arm is aligned properly or not. In this case the arm is slightly out and needs rotating clockwise slightly......

...... like this - using the sub trims on the transmitter. Once the sub-trim is set up, the aim is to LEAVE IT alone as the servo is now at it's optimum setting. Adjustments from here on should be made mechanically by adjusting the wire lengths.

P.S. The red LED is the kill switch, which I was also checking at the same time.

It is worth marking the fuselage with the position of the edges of the wooden block, in case you want to go back and reset the geometry later. All three servo neutral positions have been marked. The marks may not look to be over the centre holes here, but that is just perspective distortion associated with using a wide angle lens (10mm).

Edited By Gary Manuel on 06/03/2018 19:40:32

[Gary Manuel]

Next job. with the servos in the neutral position, tape the first control surface into the neutral position to make sure that it's where you want it when you adjust and cut the first wire. This is most important if you want to avoid accidentally cutting a wire too short. Don't ask me how I know about this, but it's a lesson I've remembered from other models I've built. Once all of the wires have been cut the tape can be removed to allow the control surface to be adjusted.

All 4 elevator wire ends adjusted to give the required tension (fairly tight but not straining the servo bearings) .....

..... with the control surface in the correct neutral position.

If everything has gone to plan and the geometry is correct, it should be possible to move the servo (slowly does it, in case the geometry is wrong) to the full extremes with a reasonably even tension in the wires. Some slackening is acceptable, as the force of the forward moving model will hold the "pulling" wire tight against the airflow. Tightening is a no-no as it will eventually result in the wires becoming slack at the neutral position, which could result in control surface flutter.

I'm happy with this at one extreme .......

..... and the other. The wires remain fairly tight throughout with very little free play in the control surface at any point.

I haven't done the rudder yet because the longer metal servo arms I'll be using are still in the post. The method will be exactly the same though.

Edited By Gary Manuel on 06/03/2018 19:42:17

[Gary Manuel]

Posted by cymaz on 06/03/2018 18:28:52:

It seems you have adopted belt and braces with added bicycle clips...liking it

I like to keep a length of string handy too

[Gary Manuel]

I had a bit of spare time today, so I've got a bit more done.

Silencer re-fitted, cardboard cutout of desired hole shape cut and taped to the underside of the fuselage.

Silencer twisted so that I can fit the cowl on.

Cowl fitted under the cardboard template and shape transfered onto masking tape which I'd stuck to the cowl.

Silencer straightened up and cowl tested to see if I had got lucky. No chance!

As expected I would need to remove some more material from the cowl in order to get it over the silencer ports.

Edge of planned cutout extended.

I don't want to cut all the way to the edge as I want to keep as much "structural integrity" (private joke) in the cowl as possible.

Inner edge of the cutout also marked. I'm deliberately making the hole as small as possible to start with. I can always make it larger later if I think that it needs more cooling air outlet area.

Hole cut. I'll tidy it up later.

It's a tight fit but .......

..... it does go on.

[Gary Manuel]

Engine fitted to check that the cowl can still be fitted with the engine in place.

I needed to remove the prop bolts and prop washer to get the cowl on, but it does go on OK.

Choke rod marked to show where it is clear of the prop / spinner back plate.

Cowl marked for the planned position of the cutout for the cylinder head cooling hole.

I simply transferred measurements of the engine onto the cowl for this using a ruler and set square.

Hole cut out ......

..... and checked.

Looks OK. Note the choke rod now bent so I can push / ull it from the front of the plane. I'll be filling the cheek holes in later and cutting a hole for the choke rod to poke through.

Baffle box shaped and made from Darice Foamies 6mm sheet.

I would have preferred black but that's a long (and annoying) story.

It's a cosy fit around the cylinder head.

Baffle box taped to the cowl to allow a trial fit.

Edited By Gary Manuel on 09/03/2018 21:34:15

[Gary Manuel]

Spark plug and H.T. lead fitted to make sure I don't need any additional holes in the cowl.

Engine has now been fitted using thread lock on both ends of each stand-off.

Header is fitted using 5 minute epoxy at the engine / manifold joint as recommended by Weston UK. A Nordlock washer has been fitted to the front bolt. The rear one has minimal clearance due to the tight bend in the header pipe. The rear bolt has a thin hexagonal head, which is extremely difficult to access. I managed to tighten it up OK, but couldn't fot a Nordlock washer. I smeared some 5 minute epoxy on to prevent it working loose.

Header / manifold joint OK after needing a bit of heat and brute force to get it in place.

Baffle box is now glued onto the cowl, which can be fitted with the engine and exhaust in place.

The cooling holes still need some thought and I might add some internal baffling to steer the cooling air where I want it to go.

 

Edited By Gary Manuel on 09/03/2018 21:50:01

[cymaz]

Quality build

[Rich too]

excellent job on the baffle . You could probably close the holes in the cheeks?

[Gary Manuel]

Thanks chaps.

Yes Rich - that's the plan. I might open the rear of the cheeks as exit holes though. Might even put some Aluminium Mesh over the outlets to finish it off.

[Ron Gray]

You maybe better off opening up the hole you have made for the exhausts with a lip on the front edge. (Area for air out should, ideally, be 4x that of air in?)

Edited By Ron Gray on 10/03/2018 10:25:07

[Gary Manuel]

You might be right Ron.

Decisions, decisions.

[Gary Manuel]

After having a good look at the model again, I've decided that rear cheek holes is not the best place for the cooling outlets. This is because the cheeks are in the upper part of the cowl, whereas the cylinder head is in the lower part. The path of the air wouldn't be direct enough for my liking.

I've decided to go with plan A and increase the size of the existing exhaust port hole.

Marked out ready for cutting.

I shaped a piece of balsa for the lip, whilst the cowl was still solid.

Hole cut - too late to change my mind now.

Lip shaped, covered and taped in place while the epoxy is setting.

Finished hole, complete with lip.

I also blocked the front cheek holes and cut a small hole for the choke lever.

Edited By Gary Manuel on 10/03/2018 18:38:58

[Ron Gray]

That looks better!

[Gary Manuel]

I thought I'd put the wings on to check that they fit, set up the aileron servos and see where the CoG is before I decide where to put the batteries.

It's a lot bigger than I thought - it's got me wondering whether it'll fit in the car or whether it's a trailer job.

It's definitely not nose heavy, so having the servos in the canopy with closed loops is definitely the right way of building this. Looks like I'll need everything mounting as forwards as possible to get the CoG right. I'll leave that until I've fitted the undercarriage, canopy and cowl though.

Tail wheel assembly fitted with the axle directly on the rudder hinge line.

Pretty nice fittings.

One problem I had is that one of the holes where the spring attaches to on the rudder bracket hadn't been drilled out. I don't know what the bracket is made from, but it's not Aluminium. I broke several small drills whilst drilling a hole out.

Front undercarriage and trims fitted. I won't be fitting wheel spats as I fly from a grass field which is cut be the council and can sometimes get a bit long.

The carbon undercarriage is one of the nicest I've seen. The legs are aerofoil shaped.

Supplied pilot fitted. I fitted a couple of captive nuts inside the pilot. He's now held in place by two screws and a few squeezes of UHU Por.

Canopy glued on, taped up and left to dry for a couple of days.

Edited By Gary Manuel on 13/03/2018 17:27:24

[Peter Jenkins]

Gary - great work. At the risk of stating the obvious, in your photo of the assembled aircraft and adjacent to your comment on the CG, I note you do not have the cowl fitted. On my Capiche 140, the cowl weighed 8 ozs and is well forward. I would expect your cowl to be heavier than that so I hope you had the cowl attached (and prop and spinner) when doing your CG trial balance. At least it will move the CG forward if you didn't have it on. As you obviously know, CG optimisation can only really be carried out by flying and trying different CG locations until you find what suits you - which might not be the one selected by the designer.

[Gary Manuel]

Yes Peter.

I balanced all 3 batteries and the cowl on the engine box and it was still tail heavy. Didn't bother with prop, spinner, ignition unit or ignition switch, but I don't think they will make much difference.

I'll try again now that the undercarriage is fitted, but I reckon I'll be moving the receiver up front so that I can fit the receiver batteries inside the engine box with the ignition battery and ignition unit on the outside. I'm just hoping that this doesn't become the only model in my fleet with added lead.

P.S. Recommended CoG is 225 to 240mm (for experts) behind the leading edge. This is way behind the wing tube. Mine was balancing at about 260mm.

Edited By Gary Manuel on 13/03/2018 19:53:53

[cymaz]

What batteries are you using...sub-c on the ignition will help.

[Gary Manuel]

Posted by cymaz on 13/03/2018 20:28:45:

What batteries are you using...sub-c on the ignition will help.

LiFePO4's all round - ironically to save weight on using sub-c's for the receiver batteries, which is what I'd normally do. Lightness is what it's all about.

I've convinced myself that LiFePO4's are the future and am using them for the receiver for the first time. I've been using them for ignition for a while. I'm not going to say that I wish I had heavier batteries!!!!

[Adrian Smith 1]

Humour me a second, Gary. May I suggest you weigh the spinner, prop, ignition unit/switch separately as I think you might be surprised what they weigh (is it an alloy spinner?). I have had a couple of Weston 50cc cans and they are on the heavy side compared to say Hatori or Krumscheid, so that is a contributory factor I guess and may help explain the CoG dilemma. I am not suggesting you change it though! I know it is a pain, but when I measure the CoG everything is fitted to the plane so I am absolutely sure. Great build by the way and such neat and tidy work!