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May 18, 2015, 03:51 AM
Diesel Danny
danny mz's Avatar
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Discussion

Big Tiger


I decided to build a new C/L stunt trainer. I need the practise.

Looking through ancient Aeromodeller magazines a free plan from February 1991 edition caught my eye. Big Tiger by C.Maikis.

Like any model,I like to build them straight so made a wing jig - it seems to have been a useful exercise.

After building the wings my attention turned to a bellcrank. Having a few slabs of 3mm Paxolin in the goody box I made one to the plan size but added a ball-race to the pivot (salvaged from am ancient hard-disk). Now should I bush the lead-out and control rod holes?

Motive power shall be a Merco .35 once I dump the r/c carby and make a proper C/L venturi.

Here are a few photos of progress so far.

Covering shall be silk and dope with a sprayed epoxy paint job (I am very old fashioned). I have about 80 cans of K&B SuperPoxy that I bought on the cheap ($50) from a closing down hobby shop so nitro-proofing is not a worry. I only use about 5% nitromethane anyway.

Don't expect any rapid progress as I am making this just for fun, but have already decided to make an adjustable lead-out gizmo and cap-strip the wing ribs.

* Danny M *
Last edited by danny mz; May 18, 2015 at 04:00 AM.
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May 19, 2015, 09:49 PM
Registered User
I really like the wing jig!

The big tiger is on my list of "to-do" builds
May 20, 2015, 12:24 AM
Detail Freak
target's Avatar
Yes, bush the lead outs at the bell crank, and also it's a good idea to have them easy to adjust at the tip to get the right relation to the cg.
If you move the cg, you'll likely need to move the leads at the tip also.
May 20, 2015, 03:21 AM
Diesel Danny
danny mz's Avatar
Thread OP
Wing is almost finished, joined the two halves.

Decided to sleeve the lead out wires with brass tube where they pass through the bellcrank.

Definately going to make the tip lead-out location adjustable to fine tune the trim.

Thanks for your input Azryl and target . Makes this worthwhile. Here is my latest progress.

Not a real pro but having a go.

* Danny M *
May 20, 2015, 08:02 PM
Detail Freak
target's Avatar
Here is a sample picture of an ARF Oriental I am re-working and assembling as an electric. Flipped the bell crank around, removed the non bushed stock lead out wire, added bushing and used copper instead of crimps. Added a longer bolt so I could support the top too (not yet done in this picture). Ball links for the pushrods.

R,
Target
May 21, 2015, 01:05 AM
Diesel Danny
danny mz's Avatar
Thread OP
I found some good quality ball links for the elevator & flap connections at the bellcrank and also decided to add a top plate to the bellcrank mount - I have never felt comfortable with the cantilever bottom only support.

The wing leading edge is a sheeted D-box - I decided to add cap strips to the remainder of the ribs. The spars that I used are from aircraft spruce, only a few grams heavier than hard balsa but a bit tougher.

The plan shows an aluminium elevator pushrod, I might try a carbon-fibre tube.

Next job in the workshop is to make a delrin venturi for the Merco .35, cut and braze up elevator and flap horns. I plan to use r/c type hinges (with a pin) for free moving controls.

* Danny M *
May 21, 2015, 08:45 AM
Detail Freak
target's Avatar
Sounds perfect. Should last a long time. I used a cf tube over the 4-40 all thread rod. Makes it really stiff. Bought mine from an online kite shop and it's sized to slip perfectly over the threaded rod.
You might want to put bearing tubes on the flap horns since you are bending your own. Especially if you drive the elevator from the flap horn, as I did.
Regards,
Target
Last edited by target; May 21, 2015 at 08:50 AM.
May 25, 2015, 04:46 AM
Diesel Danny
danny mz's Avatar
Thread OP
Did a bit more work on the bellcrank assembly.

Bushed the leadout holes with brass tubing and peened the ends with the tip of a centre punch to lock them in.

Then made some 0.047in wire links and turned some brass buttons for the leadouts - I found a stash of 100 lb nylon coated stranded wire which will fit in the groove in the buttons and then crimped.

Also fitted and lock-nutted some ball-link type connectors for the flap and elevator pushrod links (I added a small 'safety' washer to the top that is larger diameter than the hole in the spigot).

I plan to bind and solder the overlap of the wire links.

* Danny M *
May 25, 2015, 01:02 PM
Detail Freak
target's Avatar
Looks good.
A lot of separate connections to the bell crank, but they seem like they should all be secure and free moving, and that's what matters.
One of the best I have seen had ball links bolted to the bell crank ends and the wires went to them. Not sure how the wire lead outs connected to the ball link yokes though....
I'm enjoying seeing the details of your build, keep posting!
R,
Target
May 25, 2015, 02:08 PM
BWA
BWA
Registered User
Not sure I would trust ball links with that kind of load.........
May 25, 2015, 05:24 PM
Detail Freak
target's Avatar
Why? I'm not referring to 2-56 snap on Dubro cup style, but the 4-40 heavy duty style.
R,
Target
May 26, 2015, 12:42 AM
Registered User
Many of my local flyers use the 4-40 ball links on the bellcrank. 4-40 threaded rod into some carbon fibre tube for the control rod, works well on many stunters with la46 size motors etc

I have yet to see a good dubro fitting give way... >touch wood<
May 26, 2015, 12:44 AM
Registered User
Hey Danny M, keep up the build progress reports with pics... its like aeromodeller pr0n

oh, a few more pics of the wing jig, very interesting! so much so, might have to rip-off your design and make one of my own!!
May 26, 2015, 07:23 AM
BWA
BWA
Registered User
Yeah, I use them on the control rods too, just wouldn't feel comfortable using them for lead out connection.....
May 26, 2015, 10:31 AM
Detail Freak
target's Avatar
And again, why?


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