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Jabberwock RTS (ready To Skip)

or the tale of the suspect switch

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Bob Cotsford10/08/2015 13:38:13
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7963 forum posts
439 photos

Here you go:

exit jabberwok.jpg

jabberwok oopsy.jpg

Flying absolutely fine, midway round a turn upwind the turn became a roll, no throttle response, no elevator response and no aileron response - and more significantly, no failsafe either.

After retrieving the remains the switch was found to be 'off' - cause or effect of the impact? Switching on restored control movements, and switching off the Tx triggered the failsafe - low throttle, everything else to neutral, so I'm certain it was a loss of power somewhere along the line. The lead connections battery>switch and switch> Rx had leadlocks and wiggling them didn't indicate any poor connections so what does that leave? The switch.

It's one of those switches with a built-in charge socket and a sliding cover, one I had in stock when I built the model earlier this year but I don't recall whether it was branded or not.

The receiver (FrSky D8-II) joined the switch and airframe in a convenient skip. Not worth risking it after the impact it received.

RIP Jabberwock, now onto the nextsmiley

Edited By Bob Cotsford on 10/08/2015 13:44:32

Bob Cotsford10/08/2015 13:43:07
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7963 forum posts
439 photos

ps - the photos make the damage appear quite light - it's really more a case that the HK film covering is doing a good job of holding in the matchsticks! Upper wing LE pushed back crushing the ribs, all four wing fixing points ripped out or badly damaged, fuselage back to the U/C mount shredded, cowl split and cracked. Crankshaft bent, throttle arm broken off the carb, spinner split open - the skip was the kindest option in the circumstances as we aren't allowed funeral pyres at the field.

extra slim10/08/2015 13:44:01
448 forum posts
48 photos

Gutted for you Bob, looked lovely...is it too far gone to repair?...I've seen worse restored back to former glory. Its horrible when there is a cloud over what actually happened...

Onwards and upwards (not downwards)

Bob Cotsford10/08/2015 13:51:12
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7963 forum posts
439 photos

Anything (almost) is repairable but to me this didn't warrant the time and expense needed. There are too many designs I've not built or flown yet to go back over old ground. I've scratched the itch for a Jabberwock. It was a great design, full of character and pretty aerobatic with the tremendous bonus of being very quick to assemble at the field. I'd recommend it to anyone looking for a different style of bipe, but now I've been there, done that.

Paul Marsh10/08/2015 14:29:30
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3703 forum posts
1050 photos

Give the remains to someone at the field. I like repairing damaged models - much better than going in the skip. Reckon it'll be repaired in about 10-12 hours, as the wings look undamaged.

If you are going to the Nats - I would like it, if possible and do a "rebuild thread" here...

Bob Cotsford10/08/2015 14:57:43
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7963 forum posts
439 photos

Sorry Paul, no-one at the field wanted to rebuild it so it literally went car boot to skip (or as some less kind club members said - skip to skip). When I got home the builders working next door had left a suitable funereal carriage parked in a convenient spot, it's now under a layer of paving slab offcuts.

The wings were a very long way from undamaged, most of the ribs were concertina'd back to the spar, the mounting blocks were ripped out or loose, and the tips were very unstable under the covering - matchsticks held in loose formation by the HK filmlaugh.

The tailplane, fin and rudder were remarkably intact though.

ps - the impact was enough to bend the crank on an MVVS 90!

Edited By Bob Cotsford on 10/08/2015 14:59:49

Phil Green10/08/2015 16:51:05
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1515 forum posts
308 photos

You think the switch vibrated 'off' Bob?

Edited By Phil Green on 10/08/2015 16:53:36

ChrisB10/08/2015 17:43:35
1219 forum posts
34 photos

Sorry to see and read about the shredded Jabberwock Bob. I had a brand new switch disintergrated in me hands a few years ago and having never opened a switch up, I was shocked to see they were crimped and not soldered, similar to that of extension leads.

Vibration can be problem for leads and switched whether soldered or not, so I suppose there isn't really a perfect solution. For big models we're moving towards toggle switches rather than slide switches as these tend to be more secure.....Maybe

Bob Cotsford10/08/2015 18:39:23
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7963 forum posts
439 photos
Posted by Phil Green on 10/08/2015 16:51:05:

You think the switch vibrated 'off' Bob?

Edited By Phil Green on 10/08/2015 16:53:36

It's a strong possibility Phil, the rest of the power train seemed sound enough.

Chris - oddly enough I've just tried a toggle for the first time - or rather twin toggles with two batteries to two receiver sockets. I remember seeing this setup being recommended on RCMF a couple of years ago. The alternate approach is a failover 'soft' switch where the switch turns an FET or similar off, and any failure leaves the system live. I've got a few in use but you have to remember to disconnect the battery as they do have enough residual drain to kill a battery over a week or two.

You can see the bulk of the twin toggle unit on an Acrowot XL here:

Acro XL.jpg

Wish I'd had one on the Jabcrying

ps - the other switch in  the pic is a JR brand HD slide switch for ignition, so three switches on that one!

Edited By Bob Cotsford on 10/08/2015 18:41:17

Phil Green10/08/2015 19:41:21
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1515 forum posts
308 photos

I think it was Shaun who told me that full size practise is two toggles set at 90 degrees.

PowerFETs always fail short so a solid-state switch should be ok, theres no reason for them to leak badly though, I wanted a small toggle on my e-bike so it has a FET and when 'off' takes 80 microamps ie nothing 

Cheers
Phil

 

 

Edited By Phil Green on 10/08/2015 20:04:18

Percy Verance10/08/2015 20:28:17
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8108 forum posts
155 photos

Oh no, the crank on the MVVS .90 is bent? Not the MVVS .90 Bob? secret

Bob Cotsford10/08/2015 22:29:24
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7963 forum posts
439 photos

No Brian - a new one! Actually it looks to be just the thread that's bent so it may be salvageable, Otherwise MVVS spares really are cheap, and it would probably benefit from a new front bearing anyway after the thump it took.

Mark Stringer12/08/2015 22:22:06
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322 forum posts
209 photos
Be careful what you wish for. ..a guy called Baz gave me Jabberwock III at Green acres back in 1979 .. I refurbished it and loved it for ages until the aileron stuck one day and it spiraled to its demise.
Almost 20 years later I still loved it so much I bought Ratby Aeroplanes!!
I still love them and have several ...so any loss of a Jabberwock is a sad day. ...do build another
Bob Cotsford13/08/2015 12:00:13
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7963 forum posts
439 photos

Maybe one day Mark, but not yet. I did keep the transport jig I made to hold the wing panels aligned and assembled when off the fuselage. Did you ever think about getting the plans digitised for laser cutting? Maybe update it with some lightening holes for a lower AUW?

Mark Stringer13/08/2015 22:52:01
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322 forum posts
209 photos
Bob, that would be great one day - I have the plans all scanned so should be easy enough - I also thought of a Jabberwock Foam-e but the initial costs are huge - one day maybe
Anthony Pattison 101/12/2015 10:45:38
30 forum posts
7 photos

Hello Jabberwock fans

I have just bought a nice 66" Jiant Jabberwock from a chap on BMFA classifieds and need to decide on what engine is needed.....

I don't need massive performance as I have smaller/lighter models for high performance but I don't want to fit it all out and find it's underpowered for comfortable flight.

Currently I have a Moki 135 or OS FT160 twin sitting on the shelf. Would either of these be big enough to try or do I need more?

Tony

Percy Verance01/12/2015 14:52:23
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8108 forum posts
155 photos

Either would be good Anthony, but of course the c of g might determine which engine finds it's way into the cowl......

Just out of interest, how heavy is it?

Anthony Pattison 102/12/2015 08:04:32
30 forum posts
7 photos

Hi Percy

Weighed the airframe last night and it's a scarey 12.5lbs with no radio gear or engine. I imagine it will need as much weight forwards as possible so probably the FT160 is the way to go.

Claimed output for the FT160 is 2hp but not sure about the Moki.......

Tony

John Bransgrove 112/09/2019 13:09:04
3 forum posts

Hi Guys, I usually fly Jiant Jabberwocks on ST3000 or ST3250. So, any suitable similar engine will do the trick. I have a Moki 180 waiting to go in a JJ I'm refurbishing or maybe in one of two I'm building from the plans. I still have ST3000 and 3250 for the others. Also see http://fgnf.co.uk/ratbyaeroplanes/jabberwocks.htm the white/blue one was one I had ages ago but is sadly no longer with us! J

Edited By John Bransgrove 1 on 12/09/2019 13:10:38

Mark Stringer12/09/2019 13:29:43
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322 forum posts
209 photos
Posted by John Bransgrove 1 on 12/09/2019 13:09:04:

Hi Guys, I usually fly Jiant Jabberwocks on ST3000 or ST3250. So, any suitable similar engine will do the trick. I have a Moki 180 waiting to go in a JJ I'm refurbishing or maybe in one of two I'm building from the plans. I still have ST3000 and 3250 for the others. Also see http://fgnf.co.uk/ratbyaeroplanes/jabberwocks.htm the white/blue one was one I had ages ago but is sadly no longer with us! J

Edited By John Bransgrove 1 on 12/09/2019 13:10:38

John

I have seen your email - i have a "real" job these days so will check my stocks to see what parts i can help you with as soon as i get chance but i only have what was left in stock when Ratby became a hobby rather than a business.

Lovely to hear you are renovating these JJ's - do send pictures when they are done.

Be in touch soon

Mark

Edited By Mark Stringer on 12/09/2019 13:30:09

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