JP Large Scale Tiger Moth

[Dave Cooper]

Yes did away cross wire braceing, ie undercariage to rigged, replaced it with a very small key ring as a center for wire spring cross braceing, covered in heat shrink  the right diameter for springs, dont heat the tubeing. see picy in my gallary.

Dave. 

[David Monk]

Well, the SC 1.20 has just arrived so I have had a look at the engine mounting issue and the cowl 'droop' problem. It appears that with the SC 1.20 it is possible to use the 'wrong' side of the engine mounting lugs because there are  only vestigial crankcase gussets and there is still room to get the lugs flush on the bearers. The only problem is that the SC has a choke fitted with a 'lever' to control it which would foul the engine mounting. I intend to remove the lever as the choke has no function once the engine has started. I can start my Saito 62 OK without a choke so assume I will be able to start the SC as well.

So hopefully I will mount the engine the 'wrong' way (but as in the photo in the instructions) but with the thrust line about 19mm above that marked on the firewall (although the crankshaft thrustline will line up with the marking once it gets to the  'business' end of the engine, if you see what I mean). Russel, is that how your mounting will work out?

I also intend to cut out a duplicate firewall from 1/4in ply and epoxy it to the front of the existing firewall for a bit more strength. I'm not an experienced pilot and some heavy landings are inevitable. I'll also do something like Dave's undercarriage mod. 

Lastly, have to have a moan about the instructions:

throttle servo is shown in the wrong place in the photo- all three are actually in the same tray

Lower wing mounting is not by dowels as shown - plywood extensions from the inner wing ribs

Wing struts are not attached to the wings by bent bits of aluminium as shown, but by plywood pieces built into the wings

Two sets of flying wires are provided which are not shown in the instructions- I think they actually  form a cross between the wing braces

Wires are not held by 'fishing swivels' but by bits of aluminium

The former arrangement shown in the tank mounting diagram is wrong.

I realise you will, know this already, just felt like a moan! Pity to produce what looks like such a nicely built model, than spoil it with useless instructions!

David

[Russell Fletcher]

David,

 Yes, I made the 16 mm by measurng the centre line by eye but it should be 14 mm (the bearer thickness) + the crankcase lug thickness.

 I HAVE STARTED TO ASSEMBLE THE CLOSED-LOOP CONTROL WIRES AND HAVE DONE THE STANDARD TEST AFTER , BY HOLDING THE HORN WITH MY FINGERS AND PULLING ON THE CLEVIS END WITH A PAIR OF PLIERS.

 ******************HALF OF THEM HAVE FAILED!******************

i AM GOING TO REPLACE THE LOT.

DAVE (C) MIGHT BE WORTH DOING A TEST ON YOUR COMPLETED MODEL.

 Russ

[Dave Cooper]

Hi Russ

 SRY Forgot about that problem, i replaced all of mine at start of assembly over a year ago.

Dave.

[David Monk]

Russ, how did they fail? Did the wires break or did the clevis fail?

[Dave Cooper]

Hi David

On my rigging it was the brass threads to the clevices  that failed .

Dave.

[Dave Cooper]

Seems this may be a fault on all these tiger moths.

[Russell Fletcher]

It was caused by rubbish clevis ends where the internal thread had been made to fit by just flattening the tube. You only have to replace half the clevis/adusting rods as the other half can be soldered.

Oh, one more discovery :-

The ply rudder control bar is too short such that the cables to the rudder touch the fuz' sides and will cut into it.  Needs to be replaced with a longer one.

Gosh we are having fun!

Russ

[Dave Cooper]

Russ 

 i used the ply rudder bar suplyed with the model, i changed the control cables for nylon covered ones have had no problems with them cutting into the covering so far.

thats part 0 the fun solving some a the  design problems.

[David Monk]

That's  very helpful. Because of my hopalong status I havn't done much yet except begin to mount the engine, but at least I know the problems ahead. Thanks. Now I better get looking for some replacement clevises-everything I get has to be via the Internet and post at present so the postman is making a fortune out of me!

Thanks again

[Russell Fletcher]

Rudder bar/servo link :-

 I noticed that the thick bar with a clevis at each end for connecting the rudder servo had a problem. When tested the steel pin at one of the clevis ends pulled out because the angle prevents the clevis from locking properly.

I used the one supplied to get the length right and then replaced it with a piano wire link with Z bends. If you remove the horn from the servo and mount it on the wire you can get the whole lot back in by re-installing the ply rudder bar.

 Russ

[Dave Cooper]

What i did was cut off 1 arm off a spair servo horn, then bolted and cynoed it to the ply rudder arm see picy in my gallary. Sry picy slightly out off focus.

[Russell Fletcher]

Dave,

 Could you please help me out with the flying wires.

I can see how the four V shaped wires with three clevis' fit from top of rear centre strut and top front of lower wing root to outer struts, but I also have four single wires with a flat plate (not bent) on one end and a single clevis. Looking at your photos these seem to run from the tops of the four outer wing struts, but what do they attach to at the other end?  Is it somewhere on the fuselage? The front shot of your engine with extra weight shows what looks like some cables screwed to the fuselage top, but the front two would be under the cowling.

These four are not shown mounted in the instructions but are listed in the parts list.

By the way, what holds the top wings together, is it just the flying wires.

 Thanks

Russ

[Dave Cooper]

HI Russ

The 4 wires are for the wing outer struts, they slip on the strut connection bolts. See picys in my gallary. The front shot of eng, thats just a reflction of the caban struts on the covering. no wires attached to the fus. Yes the top wings are held in place by the rigging wires.

wish this crapy weather would get better im getting withdrawal simptoms.he he

Dave.

[Russell Fletcher]

Dave,

Thanks, that's very helpful, so they form a cross brace between the struts themselves.

 Yes, we could certainly do with an improvement in the weather, maybe later next week. I am retired and even with access during the week I have only managed about 6 sessions this year. But it will improve.

Russ

[Dave Cooper]

 Yep wire cross braceings, Snap! im retired as well.  Ive been out flying about the same so far. My flying fields 5mins from where i live, an its water logged at moment  itle take about 2 wks to dry out.

[David Monk]

Just to make you guys jealous, here in Spain I was able to fly on average three times a week in pretty calm conditions from September until I broke my ankle in February. Funnily enough since then its been quite windy, so I havn't actually missed that much flying!

David.

[Dave Cooper]

Hi David

Ive heard on the grapevine that spanyerds are flying nutters,that must be fun to wach, he he he.

Yes im jealous (BLOODY WEATHER HERES CRAP, ITS SNOWING AT MOM) still thats to be expected here in uk.

Dave

[David Monk]

Well, after a world record duration attempt for putting together an ARTF, I've almost finished mine. I've been checking the balance and reckon I will need 800g of lead if I attach it to the firewall or 550g if I can get it near the front of the cowl. I'm thinking of moulding a couple of pieces of lead and attaching them to the front ends of the engine mount lugs.

Dave, from your pics it looks like you have stuck lead to your crankcase?. Has that been secure, or caused any engine problems? Do you think that the engine mount (I've used the one supplied in the kit) will take the extra weight? Russel, how did you fix your lead?

David

[Dave Cooper]

Hi David

I used lead flashing, cut into 6No 2" 1/2 x 1" 5/8 pieces bolted  onto longer rear engine mounting bolts. After they have formed shape over crank case epoxy them together. (Not to the crank case.)

I also drilled 2 new holes thru at front of engine bearers. used stick on lead epoxyed together then bolted thru new holes

Ref to engine problems none, acts as extra cooling to crank case. Ive put another picy in my gallory      may help you.

Dave.

[David Monk]

Well, just to complete the story,  I finally had my first flight yesterday. Its been pretty windy here lately and the wind is usually across the runway so I've had to wait a while for the conditions to be suitable. It took me ages to get the plane ready to fly - getting the nose weight properly secured in the engine bay alone took me about two weeks- I always was a bit slow! I fitted mine (about 500g )pretty much like you did Dave, but as I had to use lead fishing weights melted and molded to shape I encased them in fibre glass  in an effort to stop the engine vibration beaking them up. This had the plane balancing exactly horizontally with the C of G 6.5 inches back from the top wing trailing edge. I then fitted another 60g to the bottom of the firewall outside the cowl, in the hope I would be able to remove it eventually.

I previously ran in the SC 1.20 for an hour or so but nevertheless couldn't really get a reliable tickover yesterday. I had lots of advice on hand from  people more experienced than me and we finally got the engine running reasonably well ,but had to have the tickover set quite fast. It may be that the engine is overheating so I'm making an additional hole at the front to get more air in, and a larger one on the underside of the cowl to get even more air out. Maybe not scale, but getting the engine to run reliably is more important. Then again maybe it just needs more running in time.

Anyway, I eventually took off successfuly, the only problem being a lurch to the left as I under compensated for the engine torque reaction. I gather I cleared  our windsock flagpole by 1 metre, but the flight after that was great. Just a few clicks of up elevator and a couple of left aileron to get it trimmed, and the C of G seems about right. My first impressions were that it is a really smooth and stable flyer, but I only did a  few circuits before making a pretty good (well, almost perfect by my standards!) landing . I was absolutely thrilled with it. Once I've got the engine running properly I think it will be a delight.

Many thanks Dave and Russel for your helpful advice,

 David

[Dave Cooper]

Hi Dave

Glad to here you have had successful maiden flight, my tigy is nearly 2 years old an still going.

Hope you have many more hours of fun flying your tigy.

Dave.

[Kit Davidson]

Hi Fellas,

 

I have just posted a review of my Super Tiger Moth build on this site. 

 

I have a query about the undercarriage. I note that Dave Cooper modified his to allow more shock absorption. Mine came out of the box without a central bolt to connect each leg by cross-bracing. There was a suitable short bolt and domed nut left over in one of the bags. I worked out that the cross-bracing had no effect without it, except visually. If I fitted the bolt, the undercarriage seemed very rigid. I flew without it but bounced on landing. I don't know whether to fit the bolt or not. Leaving it out allows the legs to momentarily splay and spring back. You have been flying yours for longer Dave. What do you recommend? Is your modification the definitive answer?

Edited By Tim Mackey - Administrator on 12/06/2011 18:45:47

[Tim Mackey]

Hello Kit - can you have a look at this please - ta