Oracle,

I noticed that too. The Blue Bird BMS-303 servos that some of us use on the Apogee 400 are rated at 10 oz-in of torque (at 4.8 volts), and they have worked very well. This is what I will use on the prototype Apogee Sport.

I really don't know the minimum servo torque specification needed for the Apogee Sport.

Jack Stephens

Originally Posted by oracle_9

The blue arrow 2.5 gram servos states only 3.7oz-in torque for 6V, 3.5 oz-in for 4.8V, so 3.6V will probably be very little. I dont know how much torque is really necessary for such a small plane, but it may be too little, or at least on the launching part.

That's certainly enough torque for flying, even at the low voltage. A bigger unknown is if there's enough holding torque and gear strength for the rudder. With so little torque and weight, these sound like flimsy servos.

Reliability and resolution are also important, especially for the elevator. For example, the Dymond D3.7 has terrible resolution, which makes it almost impossible to set a trimmed flying speed.

Slightly OT:
On these small gliders, the current consumption is almost entirely determined by pushrod friction, since the servo airloads during glide are almost nil. It really pays to get the pushrod runs as straight as possible, and any required bends should be as gradual as possible. For example, the balsa ramp to the rudder horn should be made as long as is practical. The elevator horn ideally extends close to the boom, so the rear elevator pushrod can be straight, etc.

I wouldn't risk this (or any other plane) to Blue Arrow servos. I bought 4 of them a while back during a big Hoby Lobby sale. One was DOA, 1 died after I install (noticed before I flew it) in a DL50 and the other two had poor resolution and liked to jitter and tremble. I swapped them out for some little GWS Picos and they work fine with a very small weight penalty.

Keep up the good work on this little DLG, I need another one...o.k I really don't but I sure WANT another one

OhioPete.
I had the same experience with Blue Bird and came to same conclusions, but I only tested three which is not a very large number. However, it made me a firm believer in testing any servos to be used on elevator.

Back in October I posted a thread with simple, quick test set up. Hope it is of some value.
http://www.rcgroups.com/forums/showthread.php?t=581765
Regards,
John255

Blue Bird and Blue Arrow are two different brands, correct? I had heard better reports about Blue Bird and bad reports about Blue Arrow.

And am I correct in the Waypoint series being the same as the Blue Bird?

I'd still like to find reliable 4gm servos, but, haven't tried the BMS303's yet.

charlie

Personally I have used more than 16 different Blue Bird BMS303, and so far they have been very reliable. I have also sold many of these to Apogee 400 owners and I haven’t received a call or email about lack of performance.

The Blue Arrows are an entirely different brand; I did use them for a while, but stop because they didn’t perform well at all.

I recommend the BMS303, they are the best for that size and work very well with as little as 3.6 v.

Jose

Originally Posted by markdrela

....Reliability and resolution are also important, especially for the elevator. For example, the Dymond D3.7 has terrible resolution, which makes it almost impossible to set a trimmed flying speed....

Troubles with trimmed flying speed was driving me nuts on a new plane in dead air. That led to testing the servos which had to have an extension on the servo arm to really see that resolution was poor. However, the servos I rejected for elevator duty would probably work fine on the rudder.

To get back to the Apogee Sport, will there be enough room in the pod for using other small servos like HS-55's or GWS Pico BB's? Or, will only the 303's fit the designed space?
John255

John,

The Apogee Sport is not necessarily designed for any one servo, but for a size of servo that fits the design; you could use the Dymond 47 or any of the Ultra-Micro servos, probably a better fit than the HS-55 would be the HS-50.

Jose

The wing nut is affixed to the bottom of the wing bolt block using 5 minute epoxy. Be sure to ligntly sand the surfaces of the nylon nut to ensure a good grip for the epoxy.

The wing bolt is used to hold the nut in place. A small rectangular plywood piece will be provided in the kit to span the wing saddle.

Protect the bolt threads with Chapstick or a tiny bit of Vaseline, but take care not to get the greasy stuff on any of the surfaces to be glued.

Jack Stephens

Nice job Jack! that was some sanding you had to do in the pod/boom intersection. I adjusted the model, so people will only have to sand half as much in that area.

P.S. I sent you some building materials you are going to need.

Jose

Jose,

Thanks. I like your revision to the back of the pod. Making the pod sides converge to zero thickness at the boom was a lot of work. Your new version will be much easier to do.

Jack Stephens

Glue in the laminated 3/32" pod bottom pieces usng glue such as Ambroid or Titebond. Bevel the edges between the front and back pieces to ensure a tight joint.

Jack Stephens

Glue a small plywood tab to the bottom front of the hatch to engage the nose block. Round the back bottom edge of the hatch slightly to ease insertion past the second bulkhead.

Jack Stephens

In sanding the pod to its final shape, the builder will need to refer to the sectional views on the plans to check the desired profile at key points along the pod. Removing too much material at the "corners" could result in an embarrassing hole in the pod.

I still have a bit of sanding to do before glassing the pod, but I think it has a pleasing shape at this point.

I will not glass the pod until after the wing is fitted. As a prototype, with all hand cut parts, I need to be sure that the wing saddle is accurate before I commit to the glass.

Jack Stephens

Jack, I'm in awe! You are a true craftsman. That is a work of art you've got there. I might have to contract you to build me one!

War Eagle!

Andy