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DB Sport And Scale - Cirrus Moth
First 'Proper' kit build.
41 to 60 of 126 messages. Page: 1  2  3  4  5  6  7  To post a reply you need to be a member - Join now.

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Earlier post shows the cabane platform thing with lots of thread dangling down.

This was my attempt at attaching the ply platform to the wire 'U' shaped support struts, which I've also bound to the wooden 'legs'.

I drilled lots of holes in the platform, about 4mm apart. I then threaded some very, very strong thread (got it from the local cobblers). I left it very loose and dangly. Then I applied lots of thick Araldite, and then pulled the thread very tight. (very, very messy job).

Don't know if this is how you're supposed to do it, but I tried it and it seems to work.

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Hi martyn,

A little suggestion for your fuel tank, dont know if it suitable or not though. Over here on the Electric side of life we use velcrow bands to keep our batteries in place, might be a solution for your fuel tank

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Fuel tank is now araldited in place; never to be moved again !

Just hope I've pushed the fuel pipes on to the clonk thing hard enough. If not I can't imagine ever being able to get to it. 

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http://www.modelflying.co.uk/members/images/1860/Gallery/IMAG0035.jpg

These pictures show the wire undercarriage attached to the fuselage. Difficult and fiddly, but seems to work quite well. Thin peice of balsa araldited over the join has allowed me to sand it down smooth.


http://www.modelflying.co.uk/members/images/1860/Gallery/IMAG0036.jpg

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You've araldited in the fuel tank??!! Oh dear! You can guarantee the bit that you cannot get at will go wrong!

Silicone rubber would have been much better, becasue it will seal, but it can also be removed! 

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I posted here yesterday, but it hasn't shown up.

Eric 

Silicone rubber sealer's a good idea. Why didn't you tell me that two days ago ??? 

Anyway tank's in now. And I've put the ply top on the fuselage, so I'll never see the tank again anyway! 

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(cringes sympathetically) Oh dear, ah,well, here's hoping, but you can bet your life the fuel line will have a leak in it, or the clunk will fall off, or something!
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http://www.modelflying.co.uk/members/images/1860/Gallery/IMAG0037.jpg

Those little tiny clamps are really, really useful.

Not sure how I should have clamped the front half of the top ply. There' s quite a lot of glue escaped. Very thin ply (nice peice of ply Eddie) just overlapped onto the balsa sides. Difficult now to smooth down.

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The klunk is easy enough to access by removing the engine and withdrawing the end cap from the tank (yes its a bit fiddly) but at least it works.

 Tanks are usually installed surrounded in foam rubber to minimise fuel foaming, but I doubt it will come to any harm.

Edited: 22/04/08 08:54
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I did put some nut-lock stuff on the nut on the inside of the tank. But yes, I could get at it if needed. 

Anti-vibration foam rubber would have been a good idea, as well as the silicone sealant.

Must find a way of getting these good ideas just before each job I do, rather than just after !!! 

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It's the cowl next.

The instructions suggest glueing the two halves together, but I'm not sure what sort of glue to use. I think it's ABS plastic.

I though of just taping the two halves together and using them as a mould for making a fibreglass cowl. I've never done much fibreglassing but I've got a small kit, so that might be fun. 

What do people suggest? 

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Also, if I just glue the two halves together, as suggested, what would people suggest I use as a filler to smooth over the join?
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Put clear tape aka stickyback plastic aka sellotape over the join, on the outside, fold the two halves open, run a THIN thread of GORILLA glue along the edge, fold it shut, and wait three hours (+/-). Gorilla glue foams up as it cooks, so self-fills any gaps, (hence the clear tape on the outside!)

Gorilla glue sticks just about anything to anything, including fingers!, but doesn't attack plastics or foam. If you get a run, it can be scraped off with an old credit card or blunt knifeblade, before it goes off. 

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I've heard about this 'Gorilla Glue' stuff, but haven't got any.

StillI tempted to tape the two halves together and using them as a mould for making a fibreglass cowl. I've never done much fibreglassing but I've got a small kit.

What do people think of that idea? Would I need a releasing agent? Would I be able to buy a replacement cowl from DB if I screw up? 

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If the cowl IS ABS, the heat of the resin going off will distort the stuff. you would have to make a plaster-of-paris mould of the ABS, then take a 'negative' of the cast in grp, then use THAT as the mould for the cowl, a lot of work for a one-off. Yes, you will need release agent, and beeswax, or the items will not seperate!
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I followed the instructions, and glued the two halves of the cowl together, then reinforced with an extra strip of plastic on the inside of the join. I used some canopy glue I've got that says it's OK for ABS plastic. Looks good but I've got a bit of a seam down the middle that doesn't seem to want to sand out.

Just gone and bought an engine to put in it. I've treated myself to a Saito 72. Looks absolutely beautiful, but rather large (well, very large).

The instructions for the Moth just say something like 'Install the engine', and then elsewhere say something similarly unspecific like 'plan the servo layout'. I'd have liked a couple of pictures or ideas for servo layout. The rudder and elevator lie straight but the throttle one has to travel an awkward route. Don't know whether to lay the servo flat, and bend the wire, or lay the servo at an angle that allows a straight(ish) piece of wire.  But then, as I've said before, it's not a beginners model and I'm enjoying the challenge. It's all part of the fun. 

The kit includes all the parts for a closed-loop set-up for the throttle. I'd like to go down that route but can't quite picture what to do with it. If anyone has any links to any photos of what other people have done I'd be grateful.

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                               ?
For the Throttle

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'throttle' / 'rudder' . . .    near enough.

The closed loop stuff provided looks good stuff, so I want to make use of it.

I've seen some people have the closed loop cables go direct from the servo; and some go from a pivotted bar, which is actuated by the servo. Do you have a preference?

Also, I'm inclined (!) to angle the throttle servo (and reposition the throttle arm on the engne) to keep the wire straight(ish). What do you recommend.

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For the throttle, use a bowden cable, which is a length of flexi wire in a plastic tube, as a result it can go around corners! Glue the tube into place, and the wire can slide back and to inside it. Have a look at a bicycle brake cable or gearshift cable, that's the same idea, but thicker and heavier!

On each end of the cable you want a clevis. that's the forked bit with a cross pin that goes through the hole in the servo arm and the throttle arm. You can get a solder-on screw adjuster for each end, as well, if there is room, then you can make fine adjustments to the length. 

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I've now set the servos in place.

- First the throttle, set at an angle so the wire, running through a piece of plastic tube, goes in a straight line to the throttle arm, which I've turned 180deg.- Next the rudder, which actuates a small aluminium bar which pivots on a piece of ply just behind the servo.  This bar will, eventually, have the two wires attached for the closed-loop rudder control. If this doesnt work I can always rip it out and go direct from the servo!- Thirdly the elevator. This is likely to have a snake run down the fuselage, when I get one.I did take a photo but it didn't work, I'll take another tonight.  Q's.- Would you people still recommend a balsa push-rod for the elevator, or do you go for the more modern snakes?- If you like the snakes would you not also go for snakes for the rudder? Maybe two snakes for closed-loop control? - What about aileron control (months away at the snail-like speed I'm building at). The plans suggest a
 metal rod from a single, common servo. Would people use snakes here? - Eddie, would you suggest one servo in the middle, or two, one in each wing?  

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