Apogee Draco BG

[Rktman]

Really like the idea of using a Marco Polo GPS or other micro-tracking solution. This beautifully-crafted bird is definitely not one you'd be happy to lose.

 

[tab28682]

I have had good luck rubbing baby powder on painted sliding surfaces that have some faint stickiness, to make them slide freely. I never liked putting WD40 on my painted surfaces.

 

[neil_w]

I have had good luck rubbing baby powder on painted sliding surfaces that have some faint stickiness, to make them slide freely. I never liked putting WD40 on my painted surfaces.

WD40 is not really a lubricant (though it is often used that way), so it wouldn't be my choice in any case. I would think a silicone lubricant spray would work well; that's now my go-to for general-purpose slippery-ifying stuff.

 

[TXJeff]

Per the instructions, I'm testing opening and closing the wings looking for what they call "friction". Remember per my prior posts above I had some stiction from paint - but an even bigger question of the warping problem with the wing frame. Now the warping is a problem. When you remove the booster, the wings should immediately open themselves (if you haven't looked at the instructions, there is a rubber band inside to pull them open).
Here's a pic (look above the "O BG":
Note that I have loosened the screw to the upper left some, but that is not a solution. The solution will be to shave down the reinforcement on the wing frame a little bit and there is plenty of excess to allow this.
Taking one screw out twisted off it's head... this is an odd size at 4-40 x 1/2, but I found a replacement on Amazon, plus an assortment of M3 spacers in case some longer ones might be needed (read the instructions carefully - there are two different lengths of these and it is not especially apparent when you are looking thru parts. I noticed it and circled it in red as I read ahead in the instructions).
I hope my notes help the next builder! And I remain a big fan of this kit - it's brilliant. I'll be trim testing it this weekend. Then it's ready to fly under the right weather and field.

 

[Rktman]

Would some teflon tape help (applied either to the wing bottom or both the wing and frame where the problem area is)?

 

[TXJeff]

That's an idea.. I'm evaluating it. Thanks!
I hand-launched the glider out in my windy yard. Went 5 feet straight out, then curved straight down. I have a lot of trimming to do!
When the glider separates from the booster, the wings should immediately snap open from the pull of the rubber band opening them.
I am starting to wonder about what happens when this separates from the booster. The wrong separation angle and it won't be able to recover to fly right...
Seems like I should be flying some conventional boost gliders first to gain trimming and flight experience. I ordered two.

 

[TXJeff]

Looking at the friction problem and why the wings don't easily slide open.
I have found that the body tube is coming apart like so:

and then this (removed for the photo)

is not staying aligned on top of the tube as it slides forward and back. That is the friction. Now it wiggles and the spars are then not aligned in their proper position to themselves.
So the wings cannot slide back and open easily. A far stronger rubber band would power it thru despite the mis-alignment but that is not a solution.
However, I fab'd up a solution from cardboard with 4 alignment screws as shown here:

(all the way back)

(all the way forward).
This slides very easily (on the underside of the frame - not on the body tube)... in fact it might be a better design.
Note that some clearance will need to be cut in the spars so that the rearward screws (white) can fit inside the spars.
I have not cut anything yet... just contemplating. Note the rubber band is not connected yet but would connect the same way.
===
I'll contemplate this during the Super Bowl. Don't need to do anything today, and can continue flight trimming.
===
Meanwhile, I'd recommend considering coating the edges of the body tube with some CA to help preserve it. The body tube is extremely thin anyway.
And now I'm wondering why design-wise that big long hole needs to be there at all. It doesn't help aero. Use the above slider idea.. and all that is needed in the way of a hole is some way to mount the rubber band... maybe a narrow slot is enough.
Another thing I'd suggest in retrospect... make a very slight mod to make the entire frame removable. One screw each top and bottom to a reinforcement inside the body. Then if you dent the body tube in a crash (which seems likely), or decide on a different design like this, you can salvage the entire wing assembly and put it on a new body tube. The wing assembly is very desirable.
===
Anybody else building this kit yet?

 

[TXJeff]

So I tested the replacement with the cardboard prototype shown above, and have now made a plywood replacement. The screws face upward instead of downward where they would rub against the body. There is also a nut instead of just relying on the thread in the wood as before.
Next I will replace the spars... (adding clearance in the spar for the bolt as it slides forward) and instead of balsa/plywood it will be all plywood - but also narrower to keep the weight similar.
I've ordered a assortment of standoffs, screws, nuts and washers from Amazon - and found the same sizes as this came with this originally.
And I still recommend that you consider a modification to make the frame removable - anybody building this should think how that might be done. I think at some point I'd want to replace the entire body tube and wish I'd done this.
Anybody else building this kit? It's a brilliant design - I highly recommend it!
In the meantime I've build a small glider to fly on a 1/4A... but this Draco is going to be like an Eagle to a parakeet in comparison.

 

[Rktman]

So I tested the replacement with the cardboard prototype shown above, and have now made a plywood replacement. The screws face upward instead of downward where they would rub against the body. There is also a nut instead of just relying on the thread in the wood as before.
Next I will replace the spars... (adding clearance in the spar for the bolt as it slides forward) and instead of balsa/plywood it will be all plywood - but also narrower to keep the weight similar.
I've ordered a assortment of standoffs, screws, nuts and washers from Amazon - and found the same sizes as this came with this originally.
And I still recommend that you consider a modification to make the frame removable - anybody building this should think how that might be done. I think at some point I'd want to replace the entire body tube and wish I'd done this.
Anybody else building this kit? It's a brilliant design - I highly recommend it!
In the meantime I've build a small glider to fly on a 1/4A... but this Draco is going to be like an Eagle to a parakeet in comparison.

Great build thread, made even more valuable by pointing out the problem areas and your solutions so other builders will be aware of them beforehand and take appropriate action to address them.

I'm sure Tim Van Milligan at Apogee would appreciate your feedback so he can make/consider adjustments to any future production runs of the kit. I and a few others did that with eRocket's repro Scissor Wing Transport kit problems and Randy immediately made corrections to the affected components.