Bixto Electric Glider

[Nightflyer]

I have started this thread as I wondered whether many other people have built this Traplet design from the early 00's (if I remember correctly) at all. So my teenage son who has been learning to fly wanted us to build this 60" electric glider for him as he has likes gliders. The original design used a geared Speed 400 and 7 NiCad or NiMH cells. My son wanted his to be brought up to date.

His glider has an Overlander 2822 1200kV Thumper Motor with XP2 20A ESC and using a 3S LiPo pack driving an 8x4.5 folding prop. I am not sure at this time whether to use 1300 or 1500mAh LiPo packs, or to use 2200mAh cells which I have lying around. I suspect that with the weight savings and using 9g servos and 2.4G receiver that even with the higher capacity cells that this will still be lighter than the original design set up.

I will post a couple of pics and flight performance when ready and wonder what others might have done and how theirs performed.

[Simon Chaddock]

Nightflyer

The issue is not really will it save weight but rather how much do you want save.

There may be a case for keeping the same all up weight but unless you are flying is seriously strong winds I would expect a weight saving will have an advantage.

As a rough guide a LiPo/brushless setup is about half the weight of NiMh/brushed combination of the same power and endurance.

Exactly how much more power and/or endurance you end up with really becomes a matter of preference.

[Nightflyer]

Simon

I am not too worried about the weight situation because of the use of brushless motor and LiPo as you rightly say. I might start off with the 2200 pack to see what performance is like.

To anyone else contemplating the same model I would say that for safety clearance sake I did remove a very small amount and it is small off the corner of the upper longerons in the vicinity of the motor rotor as it was almost in contact and I suspect could rub with vibration against the longeron otherwise.

[Nightflyer]

Ok so latest is that the glider has flown twice - briefly. Motor is more than adequate and even with 2200 LiPo I had to add weight to the nose to get C of G right, but still lighter than design weight by 60 grammes. Both flights were ended premature when a wing spar started to crack right where the centre wing joining dihedral brace ends.

After the first flight I replaced the brace with one that extended to the end of the next rib bay and next flight same thing happened. For simplicity am now adding a small carbon spar to strengthen the mainspar.

[Simon Chaddock]

Nightflyer

Unless you were doing some serious high "g" manoeuvres is a bit worrying that the spar "started to crack".

The simple test I use to judge if a wing has sufficient strength is to pick the plane up in a 'ready to fly' condition just by it wing tips.

This imposes a root bending stress equivalent to pulling at least 4 g. It may flex a bit but passing this test means it should easily handle a loop.

If the wing does break under test then it rather better than risking the electrics after the wing 'claps hands' in flight.

[Nightflyer]

Hi Simon.

No nothing extreme at all. Gently climbing away under only half throttle. Yes I have used the same test as you, and have from the outset had a slight concern as while it supported the weight - and my son's Bixto is significantly lighter than the original design auw (which means that original design concerned me slightly). Wood for spar is good quality. Weakness is at point where the brace ends. Original designspans the first rib bay and I have since first flight at great effort replaced the brace to one covering the first two bays from centre.

I was going to rebuild centre panels and use new spars, but am thinking I will just let in some 1/16 or 3/32 carbon rod full length of spar (quicker and possibly less hassle). Not a bad suggestion from my 14 yo son who is still learning to fly.