DB Sport And Scale - Cirrus Moth

[Martyn Johnston]

I'll probably stick to the very-stand-off scale.

The rudder control holes are 50mm apart.

If you have a rudder-bar extending through the fuselage, the holes will be farther apart than 50mm. Doesn't that cause problems?  Think I saw a picture somewhere of someone using two rudder servos, each with their controls sticking though either side of the fuselage.

[Eddie Stocker - Formerly, DB Sport and Scale]

You can use two 90 degree bellcranks, one each side of the fuselage with one end of each sticking through the sides and the other ends connected with a trackrod type of arrangement as the steering under a car. This way it is easier to correct any length difference between horn length on the rudder (centre to clevis point) and the same at the bellcrank (swivel point to clevis point).

[Former Member]

[This posting has been removed]

[Eddie Stocker - Formerly, DB Sport and Scale]

Regarding the forced on prop, If it has been forced so tight onto its shaft that it needs some kind of puller to remove it, it needs cutting off anyway. This is because the forces induced on the material that the prop is made from will inevitably have developed hairline fractures within, and are very likely to increase resulting in prop breakage which in turn becomes dangerous to borh yourself and anyone with you while the engine is running.

 Advice, cut the prop off, ream out a new one to fit correctly and be safe to all around you!!!

[Martyn Johnston]

I'll try a jar-opener first; - but unfortunately that seems like good advice from Eddie.

[Bob Cotsford]

"

The rudder control holes are 50mm apart.

If you have a rudder-bar extending through the fuselage, the holes will be farther apart than 50mm. Doesn't that cause problems? "

it will not be a problem in practise if the actuating bar and rudder horn spacing are different - as long as they each have the connection holes and pivot hole lined up, and the distance from the pivot to the connector hole is the same for left and right.   For instance if your rudder connection spacing is 25mm each side of the hingeline and the actuator arm  ends up as 50mm each side of it's pivot, it just means  that the actuator turns through a smaller angle than the rudder - like gearing up the movement.  

[Danny Fenton]

I am just helping a friend renovate an early version of the Cirrus, re-covering, removing warps, converting to electric etc to fit a remote controlled camera in the front seat. Very interesting to hear how you are getting on. Keep up the great work

Danny

[Martyn Johnston]

Work on the Moth is having to slow down I'm afraid. Just in the middle of moving house. Haven't yet got a shed at the new place, so nowhere to work.   And the missus seems to think I've got other priorities at the moment.

Unfortunatelly the (beautifully) covered tail plane got a hole pocked in it during the move. Can't recover it because I've now got the hinges glued in place.  What's the best recommendation for patching holes? 

[Danny Fenton]

Any of you that are doing the DB Cirrus Moth, can you let me know the recomended C of G position. I am getting close to having to bear that in mind as I start to position the A123 pack and leccy motor

I have repaired and redecked the fus, repaired the top wing and am just redoing the lower wing, then its recover and spray

Cheers

Danny

[Steve Wheeler]

The Plan gives a balance point just to the rear of the top wing mainspar; ie the rear edge of the leading edge sheeting. This comes out at  73mm  from the  L/E.

The Kit instructions advise that this aircraft be flown in an appropriate scale manner; attempts to perform modern extreme manoeuvres could well end in tears!

Regards... Steve.

[Danny Fenton]

Thanks Steve,

Extreme manouvres? what me???...... what have you heard

Cheers

Danny

[Martyn Johnston]

Danny,

Why 'cover and spray'?  Why not just cover in a colour you want?

[Danny Fenton]

Hi Martyn, The wings I am indeed covering in silver solartex, the fuselage is a shade of blue that isn't available, also spraying means I can match everything up, cowl, struts, etc. Just a light coat also helps to hide the film join lines too

Cheers

Danny

[Martyn Johnston]

Sounds wise.

What sort of paint? How does it bond to the Solartex? Do you treat the surface first? etc?

[Danny Fenton]

Hi Martyn, The paint I am using is Halfords Acrylic, seems they don't do celulose any more I covered the rudder with white solartex and blew a very light coat of blue on and it was great, I then blew a coat of silver on to see how it would look and to be honest it was a bit too shiny, hence the silver solartex.

I cut my own self adhesive vinyl stencils or masks to spray registrations etc, so I tried sticking some tape scraps to the fresh paint to see if it lifted as that would obviously be no good and the acrylic has bonded really weel to the solartex.

You have to be careful to only use a light touch, the aerosol cans put out a lot of paint and it runs fairly easily so gently does it.

I have attached the test shots of blue over white solartex, the camera flash has made it look less solid than it actually is, but another very light coat would do it. The rudder wasn't fully covered as it is to be binned due to being badly warped and the main upright cracked. I will use it as a template to make another.

[Danny Fenton]

This is the Shuttleworth Cirrus it is to be loosely based on if you are interested.

Cheers

Danny

[Danny Fenton]

Anybody with a plan of the Cirrus, can you tell me whether the longer struts go at the front or rear of the wings??

Cheers

[Eddie Stocker - Formerly, DB Sport and Scale]

Hi Danny,

 Longer strut to the rear (it has further to reach due to the upper surface of the lower wing dropping away with the taper).

Hope it helps,

Eddie

[Danny Fenton]

Thanks Eddie, yes thats great, nottifications have stopped so sorry for not acknowledging sooner.

more or less finished, just some detailing to do, I will wait until after the maiden flight. Both wings are badly twisted, and the fus is more akin to a banana than a finely tuned flying machine. Better remember to take a large black bag to the flying field for this one

C of G with an 800 watt TP motor and 6 A123 cells is spot on with no messing around or additional weight. AUW 5lb 15oz but that is with pack, so equates to fully fuelled.

Not sure if this is heavy as it is a repaired/restored old Cirrus kit, with solid tail surfaces. I had to rebuild/replace lots of the model, including making a new rudder and ailerons, also all the 64th ply was removed and replaced.

Sorry to hijack the thread but there seems litlle activity at the moment? can't all be flying the weather is rubbish!!

Danny

[Eddie Stocker - Formerly, DB Sport and Scale]

Hi Dan,

Worry not about the Hi-jack, good to see others taking part. Regarding your prospective flying Banana on corkscrew wings, a bit of positive thinking is required. Forget the bin bag, that is ultrasonic negative thinking, just neutralise all control surfaces for the maiden and be immediatly ready to correct any initial flight adversities.

I have flown some quite badly deformed airframes, and from experience, their flight is correctable with trim & adjustment.

So chin up, forget the bag, she will fly, paint a smile on the ol face & do it.

 Kind ones,

Eddie

[Martyn Johnston]

Thread's all about building DB S&S Moths.

Mine's paused while I'm moving house, and building a new workshop to put it in.

So anybody else feel free to add stuff.

(esoecially if it helps me when I get back to mine!)

[Danny Fenton]

I must just clarify, in case you think I built a banana shaped model, twas not me (though I have in my youth)  I volunteered to restore the model for a friend who is a bit short of time at the moment, and I love a challenge. He has restored a 58" DB Tiger Moth, and we thought it would be fun to fly them together.

Anyway my friend was given the model as a freebie, it was in a very sorry state. But looks much happier now, though I couldn't correct all the errors, ie wings attached crooked.

Anyway as Eddie says, it will trim out hopefully. What he hasn't mentioned though is that the trim will only be valid for one flying speed - alter the throttle and the trim will probably change.

Anyway as I said I like a challenge.  My friend went a little white around the gills at the prospect of the test flight so I volunteered to do it, I like test flights, its the unknown. But with this one I know it will pull to the left because of the top wing warps, and I know it will pull to the right because of the bottom wing warps. What I don't know is will they cancel each other out LOLOL

Tally Ho

[Eddie Stocker - Formerly, DB Sport and Scale]

Well, at least you have the right attitude to it, you might like to try putting the wing under purgatory in the opposite twist and then applying some gentle sweeping heat strokes to re-set the covering tension. also if you fit fully working rigging, it is easy enough to pull out the twists to a fair degree, espescially with the cross wires between the struts, and then compensated with the flying & landing wires.

I realise that the rigging is a bit of a job, but the moth is small enough to fit into a larger rigged.

Never had a problem with speed changes on trim, but that's perhaps due to being trained the good ol fashioned way to fly by looking at the aircraft and feeding in what's required (it comes naturally after a while)

Happy corkscrewing,

Eddie

[Danny Fenton]

Thx Eddie if it were the panels that were twisted then some heat and and a twist might well have worked but unfortunately the fellow that put the wings together glued the panels to the centre sections with differing incidences, so a bit much to ask the poor covering to resolve. We will just have to wait and see. Yes I had thought as a last resort I could use real rigging. But after fitting the struts they have eased the differences enough to make me want to try it.

Fingers crossed

[Danny Fenton]

well it was a bit of  a blustery evening in the end to test fly, but it coped okay. The takeoff was pretty uneventful, I increased the power slowly concentrating on keeping straight into wind, the starboard wing lifted slight before the port, easily caught with a bit of aileron to keep the wings level. I climbed away slowly at about half throttle to a safe height before turning left (often an easier turn than right ) There was no crabbing so the rudder looked about right. Eight clicks of right aileron, four clicks of down elevator had it flying hands free at third throttle. but the gusts meant you had to keep on top of it. The turns were initiated with the aileron but then controlled with the rudder. opposit eaileron was required at times to9 stop to much angle of bank. If you have never used the rudder as a primary control you are in for a bit of a shock. you need to use the rudder to turn

I think the swept wings of the tiger are a little more forgiving than the straight wings of the Cirrus. At one point I hit full aileron to correct a dropping wing. the landing was really nice and the model can be slowed right down, though just like the full size, the Moth will reward an accurate landing, and punish innacuracy with a bounce.

Anyway I was a little sad to hand her back over to her owner, but I think I will get to fly her now and again when he wants the Tiger and the Cirrus up together.

Martyn get on and finish yours its a nice model for lazy flying.