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The Building of the BebBit

BebBit bit by bit

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Biggles' Elder Brother - Moderator11/06/2011 22:03:36
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OK the BebBit is finished!
 
At the beginning I said that this was going to be a "stick one piece of wood a day" sort of biuld. And boy was I right! Building the BebBit has coincided with one of the busiest periods at work I've known! I don't think any building session lasted more than 30mins and most were much shorter! So it does show that even if you're 'time poor' you can biuld! I don't normally have such a problem getting building time - but this one has been very much "snatched" time here and there.
 

The light was going but at least its in focus - unusual for me!
 

A younger female BEB modelling the BebBit!
 
So, just have to set the control throws, all the directions have been checked, and check out the CoG and we're ready for a maiden. Let's hope the weather is a bit better tomorrow!
 
BEB
Chris Bott - Moderator11/06/2011 22:24:05
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Looks great BEB. Good luck with the maiden.
David Gilder11/06/2011 23:10:04
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Great one BEB
 
Lookng forward to seeing it in person...
 
Not long now!!!!
 
Dave
 
Ian Jones11/06/2011 23:11:31
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Just seen the photos in the completed webbits thread too - looks great, good luck with the maiden (and the weather!).
 
Ian
Biggles' Elder Brother - Moderator11/06/2011 23:13:55
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Thanks Guys!
 
BEB
Tim Mackey12/06/2011 00:23:09
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Looks great BEB
Big Bandit12/06/2011 08:09:35
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Looks brilliant BEB like the use of the sticker and trim lines.

Chris.
Richard Harris12/06/2011 11:46:43
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That's nice BEB!
 
Good luck with the maiden, just hope this weather improves for you
 
Rich
Biggles' Elder Brother - Moderator12/06/2011 13:03:24
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Yep, you're right Richard, no chance today - its pouring down and quite blustery! I'm having a pottering round the workshop tidying up and getting ready to start the Extreme Flight Extra sort of day. Hoping I get a bit more concentrated building time on that one - at least its only ARTF so shouldn't take too long.
 
Chris - yes the sticker was a freebee from Webbies and the trim tape just seemed a quick and easy way to "set it off". I was originally going to add some matching white strips on the red upper surfaces - but I think it would look too fussy so I probably wont bother.
 
BEB
Biggles' Elder Brother - Moderator14/06/2011 21:09:44
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OK, I've taken advantage of what might be the only good day this week - and the BebBit has flown.
 
Fairly uneventful maiden, except quite a lot of downtrim was required. Put a bit of packing under the trailing edge for the second flight and that was a lot better. Plenty of power. Good aileron authority. Inverted needed a tad too much "down" elevator even with the packing in and the glide was rather too nose down, so she might be a tad nose heavy - which is no bad thing as it needed a fair bit of lead to get it too balance on the spar. Might remove a little and see how it is then.
 
BEB
Chris Bott - Moderator14/06/2011 21:17:29
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Nice one BEB well done.
Biggles' Elder Brother - Moderator15/06/2011 15:26:42
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Sad Tidings to Report...
 
I'm working at home today. Its raining here now. But before, at lunchtime. there was a nice break in the showers - so I thought I'd chuck the BebBit in the car with couple of batteries and take a quick run to the field. How I wish I hadn't had that idea
 
I'd removed one small piece of lead from the nose - couldn't really decern any movement in the balance point - 1/8" back at the very most.
 
Pre-flight checks OK - so off we go. The take-off was perfectly normal, as was the first 3-5 secs of flight in the climb out. Then the model suddenly reared its nose up at 60 degrees. It was under full power and climbing rapidly, I tried some down trim - zip. I throttled back to induce a stall. It stalled, recovered I eased the power back in - straight nose up again. By now I desperately needed to turn right - but any attempt at a turn was resisted or, if I was heavy handed, threatened the mother and father of a stall.
 
I powered down again, forced a turn whilst nose down, but as soon as I fed in any up elevator the nose just soared. It was like the model was increadably tail heavy - really massively so. I was now a long way to my left and heading away from myself - I needed another 90 degree right turn to get onto a downwing leg. The model was at about 200 feet by this point I would guess. Fed in right aileron - just a lot of wallowing. Added a touch of right rudder to try to encourage her round. The model immediately flicked onto its back then entered a near vertical spin. Interesting, I thought. Centred all controls, no recovery. Left rudder, no recovery. Left rudder and left aileron, no recovery. Thump! In she went, hard, nose first.
 


It repairable - but not without some major surgery
 
The obvious question is what the hell happened? It wasn't radio failure - control inputs were working. The only way I can decribe it is that it felt very tail heavy all of a sudden. It was unstable, wouldn't respond to aileron properly, pitching up, elevator sensitive. Its unlikely to be engine or wing incidence - they were OK yesterday - and symptomes persisted power on and off - though were less aggressive with the power off. The fact that I couldn't recover from the spin also suggests extreme tail heaviness.
 
But I swear I'd only removed about 1/2oz of lead out of about 5oz. The difference in balance point was miniscule.
 
When I recoved the wreakage the batterry was out of it compartment. It had been fixed in by a strip of velcro and a velco belt - there was no added packing/padding around it. It could have come free in the crash - though I would have thought that would tend to throw it forward into the battery compartment not out.
 
Has it broken loose on take off then slid backwards on climb out? I dunno - I just know I've now got a rather broken BebBit.
 
And to think, I was boasting the other day that I haven't had a major crash in over 12 months . Little bumps and the odd over heavy landing yes - but not a really scrunch job like this. Seems I spoke too soon.
 
BEB
 
Wingman15/06/2011 16:34:07
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Seems to me like it was probably the battery moving backwards because you say the battery was out but velcro usually has such a good grip, especially when it's wrapped round the battery like your strap, that a crash like that would tend to tear out the battery shelf and yours looks in perfect condition to me.
 
Anyway, looks like nice wintertime repair job

Edited By Wingman on 15/06/2011 16:35:58

Geoff Smith 115/06/2011 18:20:08
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Oh dear mate, what can I say except hard luck with the Webbit. Will it be ready for Greenacres? It would be interesting to find out what exactly happened so that the rest of us Webbiteers can watch out for similar symptoms. Cheers mate
 
Geoff
 
Nearly finished Webbit Builder No 20
Chris Bott - Moderator15/06/2011 19:09:04
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What rotten luck BEB. Your flight description certainly sounds like the battery shifted.
 
It does look repairable though like you say.
 
One thing to check now is the motor shaft, give it a run up with the prop off to make sure it still runs true.
David Gilder15/06/2011 19:15:36
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Very Bad Luck BEB
 
I agree, it sounds like a major shift in C of G (battery movement!).
 
I think I will be adding an Anti Battery Slip Plate to the rear of my battery tray!!
 
Hope it will be fixed in time for Greenacres!!
 
Dave
 
Big Bandit15/06/2011 19:22:26
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Dave, what can I say but bad luck mate.
 
I've taken to sticking some hook and loop to the under side of my lipo's (with double sided tape) and the battery plate. stops em moving about with the hook and loop tie down straps over the top of the lipo. I've started doing it to all of my models now, since I stuffed my Easy Cub. Can't imagine any other reason for the CG shift. Still trying to make it to Green Acres, but it's in the lap of the gods now.
 
Cheers,
 
Chris.
Tim Mackey15/06/2011 19:30:44
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Oh dear, bad luck Dave
I concur with the slipped battery theory - almost certainly it would have shoved forward in the crash you described. I assume there was enough lead length though to allow it to move back without disconnection - otherwise you would have had nothing power or radio.
For battery installation such as this one, I recommend you use a "proper" velcro strap such as that shown in the picture. It loops over the battery, and through the buckle - like a proper belt, and then back on itself to really grip very well indeed.
This - coupled with some velcro on the battery and tray should mean nothing shifts unless you want it to..

Bad luck mate.... now get the glue out....youve got a week and a half
Tim Mackey15/06/2011 19:33:38
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Heres a belt and braces version on my large PC9 - two straps for this big battery - and velcro on the tray / battery too
Big Bandit15/06/2011 20:04:54
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Hi Tim, Where are they on sale, I've been using the stuff from Asda.
 
Cheers,
 
Chris.

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