Great work, looks really good.

Thats awsome ....your a fast worker

Heres a couple more photos with the model on its wheels

looks good ...totally different airfoil on the "beak". i guess that is a good thing as i've herd that the full scale foil does'nt work well on models
it is really looking the part,cant wait to see it all painted up.

Wow, looks great standing on her own!

It's looking really good and I do like the engine nacelles, nice improvement.
I've just maidened my 5 foot version with pretty bad results. Maybe the scaling down doesn't work. Pretty heavy with an all up weight inc batteries 7lbs. By my calcs (which may be wrong) 30 oz per square foot wing loading Reasonable power of about 1200 Watts.
I did a nice straight taxi run, no noticeable yaw and what I thought was a relatively gentle lift-off. A roll to the left immediately followed which showed no sign of correction by putting in right stick. She rolled over and landed vertically on the nose. Damage wasn't as bad as it could have been so we bodged the nose up and a very experienced turbine pilot had a go. Almost identical results and more damage to the nose. I'll try and upload a video. Wing and washout is symetrical (although the washout does look quite significant), weight is laterally even, drag rudders matched. One theory is that the ramps for the exhausts are vectoring the thrust which could cause a roll if uneven and cause the nose to rise. C of G wrong ? (exactly on the plan position). I'd be grateful for any thoughts on the cause. Hopefully you'll have better "luck". Cheers Keith

Keith,

Bit of a bummer that, hope you can fix it. If you have been through this and have the Chris Golds plan (and QEFI article) the 8ft span model came in at 10lbs and I am aiming for closer to 8lbs. On a square basis a 5ft span should be aiming for 4lbs to be comparable to 10lb at 8ft. The weight may have something to do with it.

One area I would check is differential thrust, I can not see how many fans you have in there, maybe 4. Have you checked both sides produce the same or similar thrust levels either using a test stand and scales or even fan rpms. Do you have a single power bus, i.e. if you have batteries in parallel are they connected together or does one battery feed one side and a second abttery feed the other side. On the Banana hobby B2 I have heard people note that assymetric thrust has been problem. Are the inlets to both sides exactly the same, to avoid the risk of starving one side or the other. The exhaust ramps is a good thing to check. If you had badly asymmetric thrust I would have expected some yaw on the take off run.

Simple things like have you double checked the elevon directions and have the same elevator action on both sides of the plane, did you couple some drag rudder with the aileron as per the build notes, have you checked that both sides of the plane have the same incidence, if I understand correctly you have checked this but worth asking again as it would be quite easy to get a warp into the body section.

Mounting the motors

Been away with work for a while so little progress until today when I have got round to mounting the motors into all of the fans, so far I had only test run one. I have put little spacers into the back of the motor tubes for some extra support. Next job will be to run all four units on the test stand to check they all have similar rpm and thrust and to balance the fans.

Hi Peter,
I'm running on 4 4200Kv motors on two 4s 3300mAh batteries. Inners on one and outers on the other. I'm sure weight is an issue. All surfaces are operating in the correct directions and I coupled in about 20% of drag rudder with the aileron function. Also had about 25% differential. I tried hanging the B2 from the central axis and seeing if I got a turning torque but the results were inconclusive. I'm going to try and balance it longitudinally and put a balance under one wing tip and see if I get any downforce. Also going to try my pitot tube in each engine exhaust and see if I get any significant speed variation. I do wonder if the downthrust caused too high an angle of incidence coupled with low air speed and resulted in a stall. I have a video of the crash but don't know how to get it down to a small enough size to post on this site. By the way (grandmothers and sucking eggs!) my satellite Rx was very well screened by the batteries until I re-sited it in the tail! I read somewhere that a very high percentage of the bananahobby B2s crash on their maiden ! Any advice gratefully received, Keith

Keith, The BH B2 seems to have got a reputation as a bit of a widowmaker. The other thought on the inlets is to do with rounding of lips. The difference between having a direct inlet to a fan compared to one with a rounded inlet lip is significant, with the rounded lip giving measurably higher thrust - could you have some variation on the inlet areas where one is more rounded, again clutching at straws.

I post my vids on Youtube and link to them, less issue with video size.

Here is my fan balancing check, MMA7361 3 axis accelerometer hooked up to an AC voltmeter. The Z axis (least sensetive) is in line with the fans axis to the X & Y axes (most sensetive) pick up the key vibration directions. These fans were delivered balanced with a match mark on the adapter and one on the fan hub. I am not sure if the balacning was just static or dynamic, but I will find out.

Nice looking fans x 4!!

Hi Peter, finally pursuaded my antivirus software to let me upload tp youtube. A couple of clips of the finished plane

b2longerclip (0 min 28 sec)

(These are max control throws, I used about half for the flight) and of the final unsuccessful "flight"

B2crash2 (1 min 1 sec)

. It's a bit wide angle but I'd be very interested if you have any theories about the roll. I get the impression that you have taken a much more analytical route to your aircraft and hopefully this will pay off. I'll know better next time!http://www.youtube.com/watch?v=GyvDUf6dsIQ&feature=youtu.be

Take your incidence meter and check that each wingtip is the same. Do this also with all the control surfaces faired and at full deflection. Also balance at centerline to see if one wing is heavier than the other.

Keith, I have watched it several times. First thought was it looked like when I hauled my 2m wingspan DC-3 into the air too early, tip stall, roll over and nose in but I am not sure if this is the case here. Keep checking everything out as has been said and you might spot something.