Bixler 2 COG

[Brian Dorricott 1]

hi guys I've just put together a Bixler 2 and apart from the decals coming off so easily quite pleased with it but the COG is way off the suggested figure. I am putting 85 gram of lead in the nose to balance at the correct point ? About 60mm back from leading edge and a 2200 3s , 85g seems a lot considering the overall weight ? Anyone else got similar weight ? It will alter when I fit FPV gear of course but I'm finding it hard to hide in the nose without impeding the battery .

[John Robertson 3]

I will give a decent reply tomorrow morning. My Bix2 is out in the camper and I'll get you some figures in the morning as I don't fancy going out into the sub-zero windy night.

My last recorded weight was on 31st January, at 1006 grams, with the stock motor and a larger-than-yours 2600 MAh 3S. This is somewhat portly, as I have also done some extra reinforcement work behind the CG. It includes the HobbyKing ply FPV platform, as the original canopy disappeared over the sea after a fuselage-bending unintended part-loop during a gusty session.

On a 7 x 6 prop (rather than the original 7 x 5) it produced 171W @ 15.2A. This gives a figure of 170W/Kg and flies fairly sedately on this.

More tomorrow.

[Denis Watkins]

In the Bixler 2 C of G YouTube videos, the measurement is 348mm from the nose

[John Robertson 3]

"348 mm from the nose". As is the "User Manual", + or - 6mm.

I will measure my actual CG point with reference to the leading edge, as that is what the OP mentions. Additionally, I will weigh both the original Turnigy 3S 2200 pack and the currently-installed 3s 2600 pack so that Brian has as much information as possible. With the smaller pack, I had quite a bit of noseweight too, mounted externally, and I'll check some photographs to try to work out how much.

Normally, I have a complete record of my planes weights etc, but I disliked the Bixler SO much when I was putting it together that I just couldn't be bothered. I had bought it as more-or-less a throwaway item to get me back into the hobby and expected to write it off pretty quickly, but it HAS grown on me. Now I'm using it to buddy-box teach a beginner, to wean him away from a SAFE-equipped Rudder/Elevator job, and to teach myself how to manually cope with the "down" elevator required when the flaps are deployed rather than simply going over to one my 3 computer-radios and mixing stuff in.

All-in-all, I'm now happy I bought it!

[John Robertson 3]

Here we go:

My original 3S 2200 pack weighed 192 grams.

I don't have the original canopy - it was lost in space during a flight on 20 December last, so no weight figure.

Looking at video footage and a couple of stills, I think my original nose weight, taped on externally, was in the order of 55-60g.

I was going to run the CG at the recommended figure, which was measured from the nose and translates to about 70mm back from the leading edge, or 35% of chord - but I ended up being cautious and running at 50mm back (25%) to start with, then moving the battery back to get the CG at 61.2mm, 31.3% as I gained confidence.

The following relates to the current situation, with a bigger battery pack, the FPV mount in place with elastic bands and NO additional nose weight (i.e. the aforementioned 55-60g removed):

The new 3S 2600 cell weighs 230g.

The FPV platform, Mobius 3D-printed mount, liteply packing to get the mount level, Velcro and elastic bands weighs 55g.

The CG is 57mm back from the leading edge. That represents 28.5% of the chord.

The plane flies nicely at this setting. I have it set up without large throws and don't want it to be too twitchy, bearing in mind that I am a re-learner myself, that I have a learner buddy-boxing with me, that I am learning to cope manually with 4-step flap balancing and that I have plenty other planes either up-and-running or almost ready to maiden.

When I attach my Mobius to the FPV canopy, this has a noticeable effect on the handling, but it is perfectly fine - just a little more sluggish. That suits me for steadier filming. The Mobius plus mounting cage plus Velcro weighs 55g.

When I fly without the FPV mount fitted - just to see, with the fuselage now open to the elements - the handling is a bit livelier as the CG moves back. Again, no problems - quite enjoyable to get the sharper handling.

So you can see that when I vary the nose weight from an ADDITIONAL 55gms (the Mobius) to a REDUCTION of 55gms (the FPV platform) the plane doesn't exactly become unmanageable!

When I fitted the original 55-60gms of nose weight, I used these 5/10g flat strips of metal which have double-sided tape already attached which are sold for that very job. I simply attached them temporarily with fibreglass reinforced tape to the top side of the nose, above where the battery sits, and they never moved a millimetre. Ugly, yes - but they did the job and the plane survived those first few flights without incident.

I hope this helps.

[Brian Dorricott 1]

So basically not unheard of to have a little nose weight that's what I was looking for , mine I hammered the lead flat and put it under battery and hold the battery with foam to stop it moving . Not much room for sausage fingers in that nose so velcro was out. I'll get it airborne soon as the wind dies down a bit but as I have only just passed the A may get someone else to maiden it. 2600 mAh batteries are a thought as they are little heavier not keen on passengers even if it is lead , prefer to balance with battery if possible. On another note how are they on hand launch and landing as I'm still a bit nervous nelly with something new ( give me ePioneer or Apprentice I'm great - guess what I learned on ?)

[Denis Watkins]

Having flown your other 2 models Brian, you will have no problem flying the Bixler

Just a note on your receiver aerials

With the lead sheet and battery, make sure your aerials are diverse so as one or other or both are available for the signal

[John Robertson 3]

Hand launch? Fine, but I make sure I give mine a good, flat heave with full power and get my hand back on the (Mode 2) stick sharpish as there's not an excess of power.

If I have the DX5e to myself I have the use of 4-step flaps on the instantaneous/bind/trainer button and I use the first stage, 25% (of a maximum of 45 degrees, so about 11 degrees) and the climb-out is fine.

If I am wired- buddy-boxing to a slave DX4e I don't have the use of the flaps on that button and so make sure I don't climb-out too soon, letting a little speed build up first.

When I had the flaps on the Channel 5 3-position switch, I found that there was too much drag on the first setting above zero (0 - 22.5 degrees - 45 degrees) for comfort at take-off and didn't use them except for landing.

Flaps or no flaps, hand launches cause me no bother - I just ensure she is flat for a short time to get moving through the air.

Landings - flaps or not - are no problem so long as the speed is kept up, Greaser landings are the norm - just get it lined up well out until you're used to it and don't try to drag her along with the motor keeping it just above the stall. Remember - she's basically a glider and is best viewed that way at first.

[Brian Dorricott 1]

It flew a treat today club chairman took it off for me and trimmed it then I flew it for 6/7 minutes and manage to slightly overshoot field as it didn't want to come down and i wasn't man enough to engage flaps yet as I've not done the elevator mix yet. Otherwise superb and docile and pleasure to fly with no particular vices other than a bit floaty , excellent at the price .

[John Robertson 3]

That's good. I, too, was flying today both with buddy-box and no flap availability and without buddy-box and full flap choices. There's quite a difference in the landings because, as you describe, she floats on a bit without flaps and doesn't want to drop those last six inches.

I wouldn't be afraid to engage the flaps - you really DON'T need an elevator mix - you can do it all with your thumbs. Just practice some fly-bys at a safe height and distance and you can gauge how she reacts. To start with, I would arrange the geometry or travel such that there is a reduced level of flap deployment available, say 30 degrees maximum at the full setting, and you'll get the benefits of some increased lift without a huge amount of ballooning.

I fly mine quite comfortably on a DX5e, which is very basic and has no mixing facility. After a little practice, it's easy enough to hold in a little down elevator to compensate for the ballooning on deployment and you soon get used to driving her down onto the ground where you want her to land. It helps you with overall control of the model to be less reliant on computer tricks and to know that YOU are the pilot, not the transmitter.

I also have other models on my two DX6 Txs - some have flap/elevator mixes, some not, and I'm comfortable with either.

[Dave Bran]

Having flown a number of Bixlers 1-3 since they first appeared and owning two 2's currently, one of which is used primarily for student flying:-

1. Flaps are totally unnecessary, our field is tight, has mature trees, and the patch length is short with very short grass, but there are NO issues with landing smoothly and on spot at feet consistently. If you are "driving her down" you need to slow it up, I assume you have properly tested at height how slow it CAN go??!!

2. Just do not understand all this effort and paranoia over CG. Both my 2's fly perfectly well with a "normal" 2200mAH 3S (Nano-Tech, Zippy, Turnigy) inserted all way in nose (held in by a compressed lump of foam) and no other balancing effort at all. This is true for all orientations and aero, not just beginner circuits. It rolls acceptably axially, flies inverted with a little elevator, and stall turns well despite the tiny rudder.

3. Ballooning? Really? The 2's I have exhibit very little, far FAR less than an old RET control Mpx EasyStar.

4. Hand Launching in Mode 2. A simple slightly elevated lob with the left hand under Fus is all that is required, leaving in my case the right hand to hold the Tx (no strap) and operate the Ail/Ele stick thumb immediately. Throttle opened about 3/4 with chin or mouth, no more than that needed to climb out quite well snough to avoid close trees (!), all this with std supplied setup, no mods AT ALL. Full throttle after launch and ground clearance allows better than 45 degree climb out if really needed.

[Brian Dorricott 1]

Had a go at launching the Bixler today while I won't win any prizes it goes fine from hand launch both left and right handed so no problems . The cover on the wing started to come loose so had to abort just needs at bit more UHU and I have taken the precaution of taping over everything with glass reinforced tape. Still think the decals are rubbish have taken most of them off before they fall off but overall still a good buy and lots of fun.

[Denis Watkins]

Brian, always take UHU with you flying foamies,

also dont forget that everything that you stick on adds weight

[John Robertson 3]

Well done - you survived the "paranoia" then?

[Dave Bran]

Posted by Brian Dorricott 1 on 09/03/2018 15:47:31:

Had a go at launching the Bixler today while I won't win any prizes it goes fine from hand launch both left and right handed so no problems .

Excellent!

[Brian Dorricott 1]

I went to the field by myself just in case I made a total arse of it but as suggested it was a piece of cake . As I only passed my A a few weeks ago im very pleased to get my first handlaunch and fly under my belt. Thanks for help and encouragement guys.