The Snappy Building Page

The Snappy Building Page

As with all EPP kits, when you take the wings out of their beds you have to rub them with a spare piece
of EPP and then sand with 150 grit sandpaper. The Snappy is no different. The instructions mention
a cross marking 4.5" from the TE and 4" from the wingroot. That is the spot the servohorn should be.
No such mark was found on my wings, but no problem. It took all of 5 minutes to measure and mark.

I took a piece of paper and measured 4.5" and 4" from the corner. I used paper instead of a ruler
because the rigid ruler made it difficult to measure the right spot, and paper bends... I then placed
the marks on the TE and root, and marked the dot.

From that spot the servo should butt against the main spar. Since HS55's are recommended,
and I will use GWS Pico servos, I wanted to make sure I got the position right; it seems I did.

Only the main CF spar needs to be glued in place. The other two spars come pre-installed. First I
measured the center of the cf flatrod. Then I trial fitted the flatrod in the pre-cut cavity.
I found I had to deepen the cavity a few milimeters, to get the rod to be flush with the surface.
Once the fit was fine, I placed the rod in one wing, and let some thin CA soak in.

Then I taped of both the wings and sprayed 3M77 on both wingroots.
Placing the wing halves on a piece of greasproof paper, I carefully lined the main rod up with
the cavity, and slid the wing halves together. I then put some masking tape on both top and bottom
of the wing and put the wing on the flat table top with some weights on top, to let the spray glue cure.
Once that was done, I treated the other half of the main CF rod with some thin CA.

Oh horrors! With all that trial fitting, I still didn't get it right! One end of the main CF rod sticks about 1mm out above the surface...

Once all glue is cured I'll have to file it down.

Like most EPP wings I've seen, here and there I found some small "holes". I decided I will use a
little spackle to fill in the worst ones.

To keep the wing clean and undamaged while building, I taped the wingbeds together to store the wing.

Trial fitting the light-ply motormount, I found that there where some uneven patches.

So I decided to glue the light-ply part using Gorilla Glue. I rolled a wet Q-tip over the surface,
and then thinly spread some Gorilla Glue over the foam surface. I placed the light-ply part on
the glue, and then placed the wing on a sheet of greasproof paper, and covered it with another sheet
of greaseproof paper.

On top of that I put some weight, to keep the Gorilla Glue from foaming the light-ply out of place.

Before taping the TE I spackled the worst EPP holes.

After spackling I sanded the wing. I then taped of the wing so only just over 1" from the TE was
still uncovered. I sprayed the TE with 3M77, and while the glue was still tacky I fibertaped the TE.

These corners are likely to come under a lot of stress during negative altitude flying,
so some extra attention was given here.

I don't like making an EPP particle storm on our diningroom table (and my wife likes it even less...).
So instead of digging out pieces of EPP to make room for the servos, I decided to slice all the way through.

I will slice the bottom of the plug that I cut out, and CA it back in the bottom to make the servo fit slightly below flush level

The key to a straight, clean cut is "new knife blades". In general, while cutting EPP,
when you feel the knife "bumping" through the EPP balls it is time to replace the blade.
To cut the two servo holes I used 5 blades(!). EPP is a blade killer. When satisfied
with the fit, I CA'd the plugs in place, and lightly spackled the area. When cured I will sand
it with 400 grit sandpaper.

Once sanded, I taped and covered the rear end of the wing's underside. Now I'm ready to spray
the wing with 3M77.

Sprayed and taped. I used a creditcard key to smooth out each layer of tape. I started on top
of the main spar, and each next piece of tape overlapped the previous piece by half. The ends
at the LE where sliced of about 1/4" of the TE and folded over towards the top of the wing.

Trying to figure out where to place all the electrical bits. The wires of all components are too
short! There's a major soldering project here to extend all the wiring. And I hate soldering...

First I replaced the wires on the motor side of the ESC. The first inch or so was far too stiff
to be able to bend the wiring and make the ESC fit. I also soldered some dinky little 2.5mm goldplugs
from Aircraft-World to the wires for easy motor switches.

Here's a close up of the plugs.

Once that was done I attached two of the three capacitators. I'll see how it goes with two;
I can always add the third one later.

Ready for the water break in of the motor. All wiring attached as it should be, and a glass of
tapwater with a drop of washing-up liquid in it at the ready.

Going at three clicks of throttle...

...and going half throttle...

Just to make sure, I connected all components and checked that the servos moved in the right direction,
and that the motor turned in the right direction (reversed for a pusher).

Next, servo Channel2 wire needed extending.
I cut the wire in the middle, and soldered a piece of servo wire in between.

I'm getting quite good at this! Nice clean solder joints. Well, sort of.

I took the board with all components outside for some range tests. With the motor running,
and the Tx antenna in, I couldn't get more then a 10 meter range before the jitters started.
A quick phone consultation with a friend revealed my mistake. The capacitators were not connected
properly. First of all I should've used all three, and they should be connected as follows:
One connected to the (+) and the motor's body, one connected to the (-) and the motor's body,
and one between (+) and (-). Like so:

Another trip to the garden showed (with the Tx antenna in) absolutely no jitters uptill 20 meters,
with the motor off and any throttle setting. With the Tx antenna extended, the range easily went
to at least 200 meters (the end of the garden). So range seems ok.

Another problem popped up though. The JST connectors were realy hot after the range tests with
the motor running. I will have to change them to Mini Deans connectors. I've ordered some from
Bishop Power Products, and they should ship tomorrow (25 July). So until then there's not much I can do.

The connectors arrived (5 August)! Back to work...

After fitting all connectors to their respective wires, accompanied by some choice swear words
of me because of the relation between the size of the connectors and the size of my fingers (they're
not called micro deans for nothing...), it was time to fit all equipmentnin place, bury the wiring, and do another range test.

The range test was similar to the previous one with all equipment on the board, so covers were cut
for a snug, sleek, and flush fit. Only the servo covers have a small bead of Goop. I am tempted
to spackle here and there. But I'll first fibertape the equipment.