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Old Dec 30, 2004, 03:05 PM
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Smooth Spanky's Avatar
Detroit, Michigan
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Maiden delayed, advice please

First of all, thanks to jlandis for starting this thread and for additional help offline!

I've decided to delay my maiden flight for one day because I'm running out of daylight and one detail is still nagging at me. At the risk of gaining a reputation for making the difficult out of the easy, I'm once again confused by the instructions for CofG placement.

Refer to the attached excerpt direct from the TM400 instructions. The instructions state "the C.G. is located 0-10mm from the leading edge of the under wing". I intrerpet this to mean that the CG is measured from the BOTTOM wing, not the top. As you can see in the picture, however, there is a red line drawn to the TOP wing.

Can someone confirm that the CG location is measured from the LE of the bottom wing?

Thanks as always for the feedback.

Smooth
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Old Dec 30, 2004, 04:17 PM
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Cg

Spankey-
As per my message, that is the exact point I used for the CG.
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Old Dec 30, 2004, 04:32 PM
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Tom Frank's Avatar
United States, MA, Walpole
Joined Dec 2003
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Quote:
Originally Posted by Smooth Spanky
... I'm once again confused by the instructions for CofG placement.

Refer to the attached excerpt direct from the TM400 instructions. The instructions state "the C.G. is located 0-10mm from the leading edge of the under wing". I intrerpet this to mean that the CG is measured from the BOTTOM wing, not the top. As you can see in the picture, however, there is a red line drawn to the TOP wing.

Can someone confirm that the CG location is measured from the LE of the bottom wing?

Thanks as always for the feedback.

Smooth
The arrow pointing to the top wing just indicates you need to support the plane by the upper wing to check balance, as it is top heavy if supported by the bottom wing and will try to flip inverted. You can set the plane so it is level (tail raised) on a flat surface, and use a square to indicate the point on the upper wing underside that corresponds to the balance location referenced on the bottom wing. Does this make sense?

I've found on a couple other GWS models I have that one of the "casting" circles on the underside of the upper wing corresponds very closely to the balance range, and makes a very handy reference point for balancing.

I have a TM400 under construction, and will be checking this out myself within a few days. Interestingly, the TM SG version in the photo is totally white... my TM SG has a black plastic cowl and brown plastic struts.

While on the subject of struts, a post above asks about gluing the inner struts to the wing. I may glue another plastic strip in the slot, and screw the inner strut to it instead of gluing. Has anyone done this?
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Old Dec 30, 2004, 05:33 PM
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Smooth Spanky's Avatar
Detroit, Michigan
Joined Oct 2004
371 Posts
Guys, thanks for the quick response - hopefully I'll get a chance to try this baby out tomorrow.

Tom, regarding the gluing of the inner struts, I debated this point myself. I thought it would be eashier to disassemble the model if I did not glue in this area. Ultimately I decided that strength should be paramount to serviceability, so I used some medium foam-safe CA. I'm very pleased with the outcome. As for disassembly, I simply unscrew the 4 outer struts at the lower connection point and the inner struts come apart with the upper wing. Easy.

Hoping for a calm day tomorrow....

S.S.
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Old Dec 30, 2004, 05:51 PM
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Quote:
Originally Posted by Smooth Spanky
Tom, regarding the gluing of the inner struts, I debated this point myself. I thought it would be eashier to disassemble the model if I did not glue in this area. Ultimately I decided that strength should be paramount to serviceability, so I used some medium foam-safe CA. I'm very pleased with the outcome. As for disassembly, I simply unscrew the 4 outer struts at the lower connection point and the inner struts come apart with the upper wing. Easy.

S.S.
Thanks, SS. I was thinking of the unlikely possibility that I crash and break or bend and weaken one of the inner struts. It would be much easier to repair if the struts were not glued in place. This is how my PT is put together, but the TM struts are much thicker and stiffer.

Did you use the plastic struts that come with the Kit? Mine are slightly curved, and they will not curve symmetrically when installed because of the way the struts were layed out on the plastic sheet. I'm trying to straighten them without bending or weakening them. I don't want to go to the third party wooden struts that are available.

Good luck on your maiden.. please post how your maiden goes and how the CG works out.

Tom
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Old Dec 30, 2004, 07:53 PM
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Struts

This is my 2nd TM and the struts that came with this kit were very curved. Tried a couple of different tricks to straighten them out and the trick that worked perfectly was placing them in a towel folded in half, getting the towel pretty wet and the carefully working it over with a hot iron. Worked great! But after I installed them and putting on wire braces they curved again. A quick fix for that was taping on some wooden dowels I had laying around. Straightened it out nicely and was able to tighten up the wires a bit. Now I can yank this plane around with nearly no flex and no worries of snapping off a wing.
I had a bit of an accident with it prior to these mods...think I had a loose wire and I lost control and shattered the cowling. My girlfriend brought me a plastic kool-aid container, "Will this work?" Turns out it did...and nicely. A bit heavier but helped balance the plane perfectly. Thought I'd share these little tidbits.... I'll include also some pix of the upper aileron mod I did. I have it set up so it flies scale on low rates....on high rates it turns into a yellos Pitts. LOL
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Old Dec 30, 2004, 08:02 PM
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Try the pics again

Ooops...pix were too big...
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Old Dec 30, 2004, 08:53 PM
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Huntsville, AL
Joined Mar 2004
396 Posts
Quote:
Originally Posted by mstrcntrlprgrm
I'm building my tiger moth 400. The field I fly in is uncut grass so I always hand launch. I'm a little worried about mounting the landing gear wheel on the tail. My instinct is it will rip off the rudder. Also, I'm not sure about the front landing gear either.

What's the best setup for landing in the grass?
I removed the main gear from my TM400 so I could belly land on grass too high for wheels. I left the tail wheel on and haven't had any problems so far. I put some clear packing tape on the leading edge of the lower wing and on the bottom of the fuselage from the cowl back a few inches to protect the finish from rough stuff in the grass.

Before removing the landing gear I had some nasty experiences landing on an unused roadway that had curbs. Almost everytime I'd ground loop and hit the curb on landing. Flights are much more enjoyable now knowing that I can just skid in on the grass and not whack a curb.

My TM is stock with a 3S 1500 Kokam LiPo. It is a very pleasant plane to fly and was easier to maiden than any of my other planes as the trim was dead-on first flight.

Rob
http://www.knology.net/~suggs/planes..._RC_hanger.htm
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Old Dec 30, 2004, 09:52 PM
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Quote:
Originally Posted by Awtoo
This is my 2nd TM and the struts that came with this kit were very curved. ...Tried a couple of different tricks to straighten them out and the trick that worked perfectly was placing them in a towel folded in half, getting the towel pretty wet and the carefully working it over with a hot iron. Worked great!

...I had a bit of an accident with it prior to these mods...think I had a loose wire and I lost control and shattered the cowling. My girlfriend brought me a plastic kool-aid container, "Will this work?" Turns out it did...and nicely. A bit heavier but helped balance the plane perfectly.
Thanks for the the pics and iron tip ... I was thinking of trying something like that if my attempt to straighten by taping them to a reverse curved can overnight doesn't do the trick. Great cowl rebuild, too! I did something similar with my PT17, only I used a plastic Pepsi bottle (with the 5-6 flutes on the bottom)... looks kind of like a radial engine!

I put carbon fiber tubes in both lower and upper wing of my Moth, and will try a different bracing method (plastic strip X-bracing on the outer pair of struts). I did this with my PT after snapping the upper wing in flight twice. It worked perfectly. I found the struts buckle if the upper wing can translate easily, and the x-bracing at each strut location prevents that. The outer Moth struts form a parallelogram with no bracing, so I know the ends can translte easily without the x-braces. The inner struts should be OK given they have one diagonal brace and are much more rigid than the PT struts.
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Old Dec 30, 2004, 09:56 PM
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Quote:
Originally Posted by Awtoo
... I'll include also some pix of the upper aileron mod I did. I have it set up so it flies scale on low rates....on high rates it turns into a yellos Pitts. LOL
How well do the upper ailerons improve the roll rate? My PT rolls very lazy, so I know about what to expect from the Moth with single ailerons, although I think the Moth is lighter with a little larger control surface area, so should perform a little better thean the PT.
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Old Dec 31, 2004, 06:21 AM
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Have ended up glueing them, wish GWS had thought a little more about this element though before releasing the kit, could easily however epoxy two plastic bits at either side, add some tiny screw holes, and use a bit of plastic over the two struts and screwed at either end.

Models all finished, tiny bit tail heavy with a 3s 1500mah installed, so a tiny bit of weight in the cowl may be necessary, or I'll just probably hollow out the battery bay a little more.

Exciting stuff, maidening today!
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Old Dec 31, 2004, 08:12 AM
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Smooth Spanky's Avatar
Detroit, Michigan
Joined Oct 2004
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Tom, just to follow up, I did use the struts included with the kit with no mods since my struts had no bending/warping at all. Had I seen a couple of these posts before finishing my kit, I probably would have beefed things up a bit. Particularly like the cowl replacements using bottles...very creative Awtoo! I'll probably add dowels to my outer struts in the near future because I don't even want to think of breaking anything in flight!

The wind here in Michigan this morning is strong enough to knock any park flyer out of the sky, so I'm waiting, but not very patiently. I'll let you know when I get my TM airborne.

Smooth
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Old Dec 31, 2004, 12:04 PM
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Quote:
Originally Posted by ashleyhall
...Models all finished, tiny bit tail heavy with a 3s 1500mah installed, so a tiny bit of weight in the cowl may be necessary, or I'll just probably hollow out the battery bay a little more.

Exciting stuff, maidening today!
re: tailheavy... so it won't even balance at 10 mm behind the lower leading edge? I'm using NiMH packs, so shouldn't have a balance problem like I did with the PT17. On that one I added real rubber wheels to help get some functional value out of the extra weight. Good luck on the maiden... let us know how it goes.
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Old Dec 31, 2004, 12:36 PM
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Quote:
Originally Posted by Tom Frank
How well do the upper ailerons improve the roll rate? My PT rolls very lazy, so I know about what to expect from the Moth with single ailerons, although I think the Moth is lighter with a little larger control surface area, so should perform a little better thean the PT.
They didn't improve the roll rate quite as much as I expected but there is definitely a difference. I didn't time a roll yet but I'm taking her out this afternoon and I will report back. I can say this....it's a lot snappier, especially with the rates maxed out. I only used one aileron servo but it's a HS-81MG medium size servo....plenty strong for this. I don't think one hs-55 would do as well.
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Old Jan 01, 2005, 08:19 AM
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Well maiden flew yesterday, a fair breeze but the little trooper took it easily!! Added big foam wheels (scale looking), it zoomed down the grass runway, took off within 10 metres (3s 1500mah onboard), and was incredibly easy to trim.

Love the little thing, very positive in flight, predictable, rolls nicely and looks great once airborne!!

It does however appear that GWS have changed their foam formula - I attempted to spray the model using the Acrylic based paints I have always used, and it started to disolve the foam!!! So word of caution, test before spraying, I took it for granted that it was the same foam as previous GWS models!!

Anyway, this is the third of the GWS models I've built, the first two had complications in terms of warping fuselage etc - this time it seems GWS have sharpened up their act, the kit's beautiful, and a pleasure to build!

Just need a little more power now, considering the Park 400 motor brushless as a replacement.
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