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Competition News / Re: Leicester BMFA Open competition 21st July 2019
« Last Post by Rookie Jim on Today at 09:42:42 am »
Chris
I am afraid I am going to have to withdraw from the competition as I will not have a plane ready in time
Jim
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Construction & Finishing / Re: Lepton EVO
« Last Post by Adrian Mansell on Today at 07:50:31 am »
Hi Steve,


My wing, tail and motor are all on the same centre line with 0 degrees incidence.  The canalisers are equidistant from the wing and also at 0 degrees incidence.  This setup works because the model is trimmed for "neutral gravity"; I'm not sure it would work for a traditional trim.


If you are going to move the wing, you need to consider:
  • The vertical relationship between the wing and tail affects how locked in the model feels in pitch.  Typically 20mm - 30mm seems a common offset;  your numbers for the Invitation are higher but then I think the Invitation has an anhedral tail (?) so on average it is probably close.
  • The dihedral may need to change; the position of the wing, vertical CoG position and dihedral all contribute to the how the model rolls when side-slipping in knife edge i.e., whether it needs rudder-aileron mix for knife edge.
Cheers, A.
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New in the bag a pair of Mythos 125 Or Mythos Pro Wheel Spats.  These are the same as the items supplied in the kits.
Looking for £20 posted.
Contact me on 07510143584 if your interested .
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Electric Power / Re: XT60 Connectors
« Last Post by Mike Wood on Yesterday at 06:47:41 pm »
Sounds good.

Taping the "permanent" connection between the packs prevents pulling the wrong connector, but allows you to separate
the packs for any reason that may come up; of course you could just de-solder the connection too.

I've heard some people like to swap each 5s to the other side from time to time ??

Mike


p.s. I might look to do the same going forward as a solder joint will have less resistance albeit small ... ooooh and save some weight ... and use less bullet connectors .... nice
... thanks!
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Electric Power / Re: XT60 Connectors
« Last Post by AW2 on Yesterday at 10:30:52 am »
+1 more here for 5.5mm bullets.
I gave up using two 5S packs connected  in series via the bullets some time ago (the theory of that being that you could continue to utilise one 5S if the other failed prematurely).
Now I just solder the two packs together to make one 10S.
When I started with electric F3A, by far the most common accident with the packs was the black hand syndrome ,caused by shorting the positive and negative bullets.
I avoided this by having both leads female from the battery (and averted the chance of wrong polarity to the ESC by other methods).
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General Aeromodelling / Re: Chip Hyde Cap x
« Last Post by Gary Peachey on Yesterday at 08:13:53 am »
3-3.5” back from the leading edge at tip of wing
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Electric Power / Re: XT60 Connectors
« Last Post by Mike Wood on 18, June 2019, 08:52:00 pm »
Hi Keith

I standardised on 5.5mm bullets as mentioned by Bob because that's what's on Zippy Compacts but I like:

    . Soldering is easy as you are only dealing with one pole at a time.

    . Each pole bullet has it's own insulating cover which are easy to make from heat shrink or come supplied.

    . I can fit an anti spark connector.

    . They can handle the current with spare.

    . I can charge a 10s pack (2 x 5S) as a single pack without any other wires (I don't separate them for charging)
      The bullets which join the two packs have insulating tape over them to prevent me accidentally disconnecting
      them when in the model.

Hope it helps.

Mike
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Electric Power / Re: XT60 Connectors
« Last Post by Phil Lewis on 18, June 2019, 05:04:45 pm »
Hi Keith,


Nothing wrong with using XT90's should be fine for the job, personally I would make up some of these for the board but that's just a personal view neither is right or wrong, all down to personal preference really, whichever way you do it though you are going to need an adaptor to the charge board, using XT90's you could just get some of these.


Phil








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Electric Power / Re: XT60 Connectors
« Last Post by Bob Wasson on 18, June 2019, 02:36:47 pm »
XT60’s do not seem popular for F3A.  I believe there are numerous reasons to avoid them:


  • 60A continuous rating seems marginal for 2 metre F3A.  You could probably get away with it for most of the time but why take the risk.  If you must use XT’s I would use an XT 90.
  • Many of the XT connectors that are advertised are of dubious quality.  If you decide to use them, make sure you use a top quality make such as Amass.
  • Once connected, the male and female parts are a devil to separate.  This is the last thing you want if you need to disconnect a 10S battery in an emergency.  In separating them, it is all too easy to pull off the shroud part of the connector.  Do this a few times and the little plastic keys/protrusions which keep it affixed to the main connector will wear and the protective shroud will become permanently detached.  [EC double pole connectors (used by Hacker on some of their 5S batteries) are a bit easier to separate.  Deans can also be difficult.]
  • On any double pole connector, XT, EC or Deans, the male and the female poles are in very close proximity.  The greatest possible care needs to be taken in soldering the connections onto a live 10S battery.  As a minimum, goggles and full face protection should be worn. Even if the right soldering iron is used, it is also all too easy to melt the plastic part of the connector when soldering on heavy duty wire.  Even if you manage to do this successfully, it is vitally important to ensure that the exposed (bare) parts of the male and female connectors are fully insulated, right up close to the plastic parts of the connector.  Even with heat shrink tubing, this is easier said than done.  If the insulation ever slips, there is a real danger of short circuiting the male and female poles with any stray conductor.


All that begs the question about what connector(s) should be used.  For 10S use I would always advocate single pole connectors in preference to double pole.  I have used 5.5 mms gold plated slotted connectors with great success and have never had to replace one, even after 10 years of use.  However, I would accept that they are marginally heavier than 4 mms bullets and at 130A continuous they may be regarded by some as overkill. 4 mms “spring” style bullets are popular but the spring tension eventually relaxes requiring the connectors to be replaced.  If the lower weight of 4 mms bullets is a must have, I would personally use the slotted type in preference to the sprung variety.  In summary, if overall model weight was an issue, I would look to other solutions in preference to the use of XT60s.


Bob
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Electric Power / Re: XT60 Connectors
« Last Post by Keith Jackson on 18, June 2019, 02:30:04 pm »
Hi Phil,

I did wonder and have decided to try the XT90 connectors instead which are 5mm. It is as you say more complicated as you need a Y lead for use. However I charge my Lipos using a 6 pack balance board, which is now fitted with XT connectors (the older balance boards got melted in the recent fire and were fitted with 4mm bullets) and it should ease the connecting / disconnecting process during charging.

In addition the LPD 5500 mAh cells that Bondaero market can come fitted with connectors of your choice meaning if ordered with XT90's, then you can use them straight out of the box instead of spending half a day soldering.

Thanks

Keith

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