Been doing some work on the rear fuz, decided to deviate from Mick's suggestions about servos.

Firstly I've decided to use two servos for the elevator, and secondly I've decided to mount them on the side of a fuz rather than Micks fully internal linkages. Yeah I know it looks ugly and this is supposed to be a scale model etc, but once the tail is in place then they cannot be seen from most angles and yet it offers much better geometry which should lead to much more solid linkages. Plus I dont like the thought of just one servo for both elevators.

...Micks suggestion for the rudder is to butt the rudder directly onto the top of the servo. I um'd and er'd about this quite a bit before going for a more traditional torque rod approach.

What do people think of this pipe? It is supplied with the kit, but as you can see it is single walled. It is spot welded at the seem and when in the fuz has quite a lot of clearance from the sides of the fuz.

...note it doesnt have a funnel at the turbine end.

Should I bite the bullet and order a custom made double walled pipe, or is a dual walled pipe no less likely to fail?

I've got this Kevlar tank, but to be honest I was going to send it back and order a different one. The reason I wanted to go with a Kevlar tank is to minimise the risk of a post crash fire. But looking at the design of the tank the lid is just butt glued onto the rest of the tank and so doesnt really offer much strength.

...but, one possible counter argument is that its better for the tank to shatter and spray the fuel everywhere, this will then flash burn very quickly and cause little damage rather than a tank that survives most of the impact but then leaks a puddle of fuel in the plane which slow burns and destroys everything.

What do people think about turbine fuel tanks? Strong or weak?

Dont have on board gas, the gas can bursting is the no 1 cause of a fire not the fuel tank.

I am building his Lightning kit, similar thing, ignored Mick's design and have gone for traditional servo in the fin with direct pushrod to the rudder, it is not hidden scale like Mick's design but I trust it a heck of a lot more.


Again, same with the Lightning, no way am I using the MR pipe with its single row of welds some of which on your photo are split across the joint and therefore doing little in the way of bonding! Being single wall doesn't bother me, I have been using Wren's single wall pipes for many years. So for the Lightning I have just taken delivery of a pipe from Wren, single wall, double row of welds and Wren have lots of experience of making pipes, and most importantly it is Wren's divergent cone thrust enhancing pipe which allegedly runs cooler too, rather than the standard straight wall pipe that loses thrust. If I were you I would treat the MR pipe as spare metal for some other project and give Wren a call to order a pipe.

Harry

Dear Lord mate noooooooooooo! You keep saying what a good looking jet this is and then do that! Sacrilege

Can't you mount the servos inside the fuse so that just the output shaft/linkage is visible externally? Beats having those unsightly lumps of plastic stuck outside the model?? Might be a bit fiddly but you probably have enough access to do it?

Smaller servos would look better if you couldn't? Or is there any way you could side mount servos in the stab? Check out the Voltz (or Volz) servos.

M

I've selected the Futaba 9650 for the rudder of the Lightning, modest torque but is within the calculated requirement (see Oli's servo torque calculator spreadsheet) and is high speed so as to optimise the gyro that will be used to damp out the swept wing dutch roll. At 15mm thick it just fits inside the Lightning fin so that only the servo arm and pushrod are exposed through the hatch.
http://www2.ripmax.net/item.asp?item...ry=060-020-010

There is nothing wrong in the method of driving the rudder direct from the servo output shaft that MR shows on his plans for the Hunter, same for the way the elevators are driven. In fact they both provide slop free linkages, I've put two together now and there is no way I'd mount the servos externally or even buried into the tailplane, absolute sacrelige ! Regarding the supplied single wall pipe, there are many flying and I'm not aware of any issues to date.

Ian B

I have one of these built, RTF less turbine, with electronics installed if anyone is interested in one. It is a large impressive plane, with the lines of a pattern ship.

Ah, that sounds quite different then to the Lightning Ian.

Hi Harry, the rudder servo is fitted directly under the rudder with the output shaft on the hinge line. A servo output arm is glued and screwed to the underside of the rudder and drops directly into the servo output shaft when fitted. Not tricky to fit and align and very positive and slop free. One of those "why didn't I think of that" methods !

Ian B

I still would not use that pipe, look at the number of welds which are not fully on both layers, some are even mostly on just one layer and therefore doing barely anything to hold the pipe together

OK thanks, I have to say, the more I look at the servos on the outside of the tail the more I have to agree - they do look rubbish! ;-(

...I'm going to try and redo them so that the servos are internal, but just the horns and rods external. (ie like a typical aileron link)

To do this I'm going to have to try Mick's rudder servo suggestion as if the rudder uses a torque rod then the rod runs right through where I'd want to put an elevator servo.

And I think the general concesus seems to be that I'd do best to get a new pipe. Wren has been mentioned, are there any other companies that people can recommend for pipes?

Dave,

Wren is your best best from the UK. Otherwise, try TamJets, GBRJets, Turbo Didi....

Hi Dave,
have you considered putting a slim servo in each tailplane half? This way you have short direct linkages so less chance of slop. You do need to take care which servos to use of course, but I can recomend the MKS 6125 servo. 10mm thick and on 6 volts 8Kg of torque. Theu are metal geared, double ball raced and have a metal case.

Mick has been around a long time and there is not much he has'nt tried or knows about model aircraft at this stage.

If he suggests a method or supplies a product you can be fairly sure it will work or will do the job.

Everyone likes to do things their own way or have ideas of how they think it should be done, but you can go to far, just look at what has happened in the jet world regarding the size of servo's.

OK, I decided to change the way the tail servos are mounted.

I'm using Mick's rudder servo method, it wasn't easy to get the servo exactly lined up with the hinge line, but after quite a bit of faffing it did work and I have to admit it has resulted in a much more positive linkage than I thought it would.

This freed up enough room to mount the servos on hatches (ie like aileron servos) in the side of the tail.

...Still not 100% scale, but an improvement!

Nothing wrong with that, and I'd go with two elevator servos too over an OEM method that only uses one. I just think its more secure. Elevator is the one control, that if you run out of torque, is a disaster because when it happens, the nose is almost always already pointed at the ground...

Bob

Started planing the bits and bobs that will go in the fuz.

Batts will be right in the nose.

RX, switch, servos for all pneumatics, air gauge, air fill will all be on the tray at the bottom of the pic.

Airtanks just behind with airtrap on top (off set so that I can still get at the wing bolts).

Main tank just behind. (just ordered new one from Als Hobbies)

All turbine stuff (ECU, pump, solenoids etc) will be in the engine bay just in front of the turbine.

Dave,

On the rudder setup, I'm not sure if this works better but it's fine on a 3m Airworld MB339 and what I did on mine......

I have Proskin now on my big Spitfire and Hurricane models. No problems, quick, very tough.
Mick

OK, decided to chop the nose off and attach a plywood plate to the front former. This gives me enough space to mount two RX batts, the turbine batts and possibly some nose weight. (Does anyone know if these come out nose heavy or tail heavy?)

I've gone with smaller twin air tanks, only slightly more capacity than the single tank Mick suggests, but can be mounted low in the fuz giving good access to the wing bolts and the air trap which will be mounted on the ply plate on the right of the photo.

I managed to solve one Hunter related problem the other day. I was running out of room in the garage, but now I've got a space!

I've been thinking about how to layout the radio in the fuz. I've decided to mount the everything on a tray low down in the fuz, this allows me to route all the wires and pipes under the tray which should look neater, plus it keeps everything low in the fuz which allows space for a detailed cockpit.