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Timís Grumpy Tigercub

Build log- Electric and a smidge bigger...

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Peter Miller15/04/2018 18:04:31
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9007 forum posts
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And if it helps, my Sper 60 was totaled when the battery came loose on its second outing.

To quote the old expression, The more spectacular the finish, the more spectacular the finish.

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Tim Ballinger15/04/2018 19:00:41
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410 forum posts
195 photos

Guessing loose in this instance also resulted in Rx disconnection?

Tim

Peter Miller15/04/2018 19:05:34
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9007 forum posts
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Oh yes. There it was in a tight left hand turn and stick waggling did nothing, We never found the battery.

I had tried a rough field take off with those huge foam wheels which was rather bouncy but didn't get off this time,

Rob Ashley15/04/2018 19:51:22
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191 forum posts
68 photos

Tim, Peter,

Sorry to hear about your losses - especially from two great flying models. I hope you can rebuild them both.

Best,

Rob

Lucas Hofman16/04/2018 06:43:55
593 forum posts
315 photos
Posted by Tim Ballinger on 15/04/2018 17:26:46:

Ground was really soft, so much so that from nose to F2 was still buried in the earth, trouble was it was not attached to the rest of the fuze. That bit looks repairable. Rest is shall we say rapid deceleration damage. Front wing dowel broke out but took a chunk of Wing le with it. Awkward bit seems to be that a lot of the LE sheeting has come away along the glue line with the LE of one wing where the dowel burst out.. Only got up the steel to start examining things today but all electrics and powertrain & battery's seem fine.

suffice to say there is a bit of work to do before she flys again.

sorry to hear about the P40 Ron, that probably trumps my tale of woe.

Tim

Very irritating. You have not had that many hours flying time with the modell. The good this is that you know how everything fits together and have the drawing of all the parts.

Lucas

Tim Ballinger16/04/2018 08:51:35
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410 forum posts
195 photos

Very irritating indeed. I have little explanation for my brain fade; it seems like I switched off and started flying as though it was my standard aero hack the Riot XL which has oodles of power. Really gutted.

Tim

Geoff Sleath16/04/2018 11:45:52
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2552 forum posts
197 photos

I know how you feel, Tim, but it's part of the game. I lost my Ballerina on Saturday due to stupidity on my part. At least it's repairable once I get round to it. My ordinary Riot is my warm-up hack. I'll fly it in anything.

Geoff

Tim Ballinger20/04/2018 15:15:37
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410 forum posts
195 photos

GTC fuselage repaired and hanging on wall waiting ......

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... for the wing repairs.

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Today was too good to miss, flying wise, so took the Skywriter out. No mishaps today but I suspect I wa a little more cautious than last time !

Tim

Levanter20/04/2018 16:00:05
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706 forum posts
346 photos

Tim

​It looks like it might not be too long before you get back in the air.

​I would be very interested to see how you sort out the wing repair and a few photos and words would be great.

Levanter

Tim Ballinger20/04/2018 17:47:35
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410 forum posts
195 photos

Not sure anyone should be subjected to such gruesome detail but I’ll give it a go. I still have to cut out all of the splintered wood but from what I can see I will need to replace both front half’s of R1 and scarf in ( close as 20:1 as I can get) some new LE. Might laminate the new piece before insertion. Probably need a rebate to accept the replace top sheeting.

That’s about as far as I have planned atm .

Tim

Tim Ballinger28/04/2018 10:53:57
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410 forum posts
195 photos

Perhaps it's because I don't look but i have not seen any how to repair blogs. Anyway this is more of a reprise than a re-build log.

Despite a vertical arrival the soft ground prevented a complete bag of bits. In fact once I took a good look the damage was remarkably localised.

First up for me after a smash and before starting repairs is a close examination of the covering all over the model. Major breaks are obvious but opening up all the wrinkles in the covering can yield otherwise unseen issues. If the film has wrinkled its a good bet something has happened to the structure underneath. Most of these inspections revealed only cracks in sheeting adjacent to glue lines; easily fixed with thin cyano. One crease in the trailing edge revealed a crack right through upper and lower TE capping which when paired back revealed a partial fracture in the TE itself. Fracture was treated with Cyano and TE capping cut back top and bottom either side creating a good 4 cm overlap before replacing and gluing with aliphatic. No other dramas under the covering so onto the 2 major damage sites.

The nose fractured just behind F2 and had to be dug out of the ground. This was one of those fractures that left both sides pretty much intact and the break while ragged just slotted all the balsa fibres back together such that it actually held back in place by itself in the exact alignment of the original. This then was a case of trimming away the surrounding covering and treating with thin cyano to bond it back. While I was as neat as I could be I had to sacrifice the Marine corp logo on the port side which mercifully was the only decal to suffer.Once back together F2 was rebuilt & reinforced inside before replacing the battery tray which actually connects F!, F2 and the sides to midway between F2 and F3.:all these repairs with aliphatic resin. I was cracking on at this point and had forgotten to any pictures of the damage/repairs.

The remaining wing repairs I did get some pictures and they are next ....

Tim Ballinger28/04/2018 11:27:01
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410 forum posts
195 photos

The major damage mechanism was the inertia of the heavy wing disengaging from the fuselage. At the rear the 2 nylon bolts simply sheared and as the ing moved back it bashed the sloping former ( F5B I think) . A simple replacement as once cleaned away it slipped back inside the planking which had remained in tact.

The front looked at bit more of a mess ..

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Cutting back the damaged wood revealed much less trauma than i expected..

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The crushed LE was cut away on the longest scarf I could manage between R and the wing join at R1. In this case about 8:1. All this damage was basically caused by the wing dowel breaking out sideways as the wing travelled aft in the impact. I had thought I would need to rebuild all of the R1 ribs and section that housed the dowel. However the failure mode was to simply break out the lower quarter of the ribs enclosing the dowel and the dowel itself which had not broken had left a clean exit, seemingly the the glue only having found a bond at the front and very rear of the slot/hole. I always wandered just how much glue contact you achieved when pushing a dowel into hole. Now I know and the lack of all over bond worked in my favour. Upshot was that I could replace the dowel exactly as before giving me no realignment issues when piecing it back together .

So with new R! quarter rib slotted around the dowel and the top and bottom sheeting replaced ( supporting lips glued in first to achieve a as flush a finish as possible) all was back together and ready for covering.

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And after recovering..

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GTC is ready for flight once more.

While she flew pretty well on the pier set up I had I have taken the opportunity to install slightly more powerful motors which should give me more scope in the future; nothing I know can mitigate for pilot follies like that which caused the original accident, but it should help.

In any case I now have 3541 1270 motors which should up the power to 740W giving me @ 100W per lb. As soon as it stops rain I will check the actual current draw and then wait for decent weather before the test flight.

Tim

Peter Miller28/04/2018 11:33:23
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9007 forum posts
1040 photos
10 articles

Well Done Tim

Repairs are always a bit of a pain but it looks as if you got away quite lightly really

Nice job now. All you have to do is wait for the rain and wind to stop

Tim Ballinger28/04/2018 13:01:58
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410 forum posts
195 photos

Yes weather forecast does not make happy reading. Still plenty of time to continue with my Cessna 172 rennovation project. Bit of nostalgia really as I built it in 1973 but then went off to university and never flew it. Still that’s for another blog if I can find a suitable place on the forum...

Tim

Tim Ballinger05/05/2018 15:48:32
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410 forum posts
195 photos

Checked the current draw for the new motors. A disappointing 54A on anything from 10x6 to 9x5..... then the penny dropped the current sensor in my TM was only rated 50A . Put it in just one side and bingo 30 A at 10.8V on the 3 blade 10x6 props giving me 648W. Could go up to 33A for each motor but better to keep that in the tank for now.

So took her out to fly again today....

3 wonderful flights which with no pilot induced stupidity also produced 3 landings. OK one was a bit fast and rather too firm , other 2 very pleasing. GTC now has lots of power if needed but spent most of the time at 1/4 to 1/2 throttle meaning if I extrapolate the 6 mins per flight I kept to today and only used half the 3700Ah battery that I should get something like 8 min flights. Will go for 7 min next time out.

I had the cg at 25% root chord for the first flights and this is feeling a bit nose heavy so I have moved the eneloop Rx battery back to mid chord giving me a value of 29% root chord.

Weather looks good for Monday still so will let you know how the next session goes.

Still looks absolutely fabulous in the air !

A happy Tim once more.wink

Peter Miller05/05/2018 18:08:15
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9007 forum posts
1040 photos
10 articles

Glad to hear that she is back on the flight line

Tim Ballinger07/05/2018 18:26:49
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410 forum posts
195 photos

2 more flights today. All good but cg now too far aft. Will split the difference next time out. ie 27% root chord. Also bent my first retract pin today. It won't be the last I am sure.

Tim Ballinger13/05/2018 19:03:53
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410 forum posts
195 photos

2 more flights withe the GTC today. Trim/C.G bang on for me now. Now got that same fantastic feeling back I had after the first maiden. Beautiful ,graceful flyer and now with more power she pulls lovely large loops from level flight with ease. Not experimented too much with the flaps as yet but what I think atm is that they are not really needed with this model. Perhaps it’s the inherent drag of the large round tigercat nacelles but the glide slope was adequately steep with the power off and nil wind as was the case tonight. I will play further as I gain more confidence.

Tim

Levanter13/05/2018 20:04:15
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706 forum posts
346 photos

Tim
​So pleased you are back in the air and better than ever it seems. A great job!
Levanter

Steven Shaw13/05/2018 23:03:58
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218 forum posts
138 photos

Tim - I've been following your thread from the beginning as I am building a GTC similar to yours, 110%, 100mm longer nose and retractable landing gear in the nacels. I am finishing mine as a De Havilland Hornet [but with a very long nose]. I am interested in your CogG, did you end up with it at 27%? I'm adding flaps also and they may be needed as the Hornet has twin Merlin V12's in very sleek nacels. So - did you end up with the CofG at 27 or 29%?

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