#18 Model Airplane Building Clinic >> Swanyshouse Primo 40 - Page 2 - RC Groups
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Nov 03, 2012, 11:39 PM
God is my pilot
JimTMich's Avatar
You are making quick work of this!
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Nov 04, 2012, 10:48 AM
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A bit more work this morning. At this point the framing is nearly complete, about all that's left is sheeting and rib/spar "capping" on the wing, and triangle stock applied to all control-surface hinge lines. All but a handful of the CNC-cut parts are incorporated into the build and accounted for.

Note in one of the pix the combination of glues used for the leading-edge sheeting -- as recommended in the instructions. The sheeting is glued to the sub-spar using medium CA, but wood glue is used on the ribs and leading edge. That gives you more time to tack things down and get it all right. I used Windex on the sheeting to help it bend.
Nov 09, 2012, 07:27 PM
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Very near the end of the framing here. The wing sheeting and rib/spar capping is done on one side -- the side you can't see. In the photo you see the wing center sheeting being clamped in place by a stack of heavy paper-bound books. Nice 'cuz they conform to the shape of the wing, if you lay 'em down the right way.

I don't trust myself to use CA in situations like this, preferring wood glue so that I can position things accurately before committing. It slows down the build, but who's in a hurry?

Did a preliminary weighing, and I'm guessing for now I might manage to get the all-up weight a bit over three pounds, which means I can use a 4S battery. Off to hunt for a motor... I may even spring for something other than generic, we'll see.
Nov 09, 2012, 11:41 PM
wood is good
loNslo's Avatar
Good idea: using flexible magazines as cauls. Could also be used with a few battens and some sandbags.
Nov 10, 2012, 09:30 AM
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Caul. Hmm. It's not every day that I have to look up a new word I first heard on RCGroups.
Nov 12, 2012, 07:51 PM
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Framing 99% done

Photos show present state of the build, with some details of the wing sheeting and rib and spar capping. Lots of cutting, fitting and sanding, but it's all simple, straight cuts for the most part.

Next step is a glue-less "final build." The goal is to have a somewhat sturdy in-the-bones version so that I can get an idea of how the plane will balance in its final form. Once battery position is known, I can rig something up to clamp and hold the battery in place.
Last edited by rafe_b; Nov 12, 2012 at 07:57 PM.
Nov 12, 2012, 08:24 PM
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JimTMich's Avatar
Good idea
Nov 13, 2012, 07:53 PM
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Generic motor it is. Hyperion and Scorpion way outta my range. Headsuprc PowerUp 32 Sport, 800W/50A, 800Kv, 7.5 oz. ESC is 45A with 6A switchmode BEC, 2.3 oz. I have a hunch this plane will need weight up front, so no real benefit from a super light motor. Battery will be 4S/2600, at least for starters.

Applied triangle stock to all hinged edges, using wood glue. Went all 'round the structure of all the parts, and applied fillets of medium CA to all accessible joints.

Need to pick up wheels, servo horns, pushrods and fittings at the LHS. (None of that comes with the kit.) Not to mention some covering and what-not.
Nov 14, 2012, 08:19 PM
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Servo Question

Just a question about wing servos , with the wing being 20% thinner than the MOJO will the servos be mounted on the outside of the wing ? I know with the MOJO hitec hs485,s barely fit under the hatch. I ask because I just ordered the Primo40. thanks Ron
Nov 14, 2012, 09:03 PM
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Here's your bones pix. Plane is hanging from a "Vanessa rig" (I have no idea where that name comes from.) The main components are held together with masking tape.

Physics says CG is directly below the hook (where the two loops of twine converge.) As expected, it just about works out when the battery is as far forward as it can get. It's not a perfect weight simulation by any means, but gets me in the ballpark.

To the query re: servo location, I didn't install wing hatches at all, I saw no point to them. The aileron servos install in a standard manner, such that the flange is even with the bottom surface of the wing. Wing thickness well exceeds the servo depth measured from the flange mounting surface.
Nov 15, 2012, 08:45 AM
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JimTMich's Avatar
I'm sure you are thinking of this......lots of covering behind the cog...
Nov 15, 2012, 09:55 AM
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Originally Posted by JimTMich
I'm sure you are thinking of this......lots of covering behind the cog...
Pretty much everything is behind the COG, except the power system. This simulation still lacks a tailwheel or tail skid, not to mention front LG wheels, aileron servos, propeller, etc.

I looked up weights of typical .40 sized 2-stroke engines, they seem to fall in around 1 lb. There would be a fuel tank up there as well, I dunno how many ounces there. I'm looking at 21 oz. for the power system, between motor, ESC and battery. Add another 1.5 oz. or so for the prop.

The motor itself can be pushed forward a bit, maybe an inch or so. I still need to cut a hunk of plywood for mounting it.
Nov 17, 2012, 09:39 AM
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All the bits are here

Finally managed a trip to LHS, and received the motor/ESC ordered from headsuprc. Did a quick little mod to the stock motor mount (pix.) So pretty much everything's on hand to get 'er done.

Maybe overkill, but I'm using ball-joint servo connectors and 0.93" wire all around for the servo linkages.

Covering will be Hangar 9 Ultracote dark yellow, maybe with white on certain parts or on underside. Just about ready for covering.
Nov 17, 2012, 04:29 PM
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Mock ups are useful for discovering little gotchas. This one necessitated a mod. The issue should be obvious. Will it look too weird if I don't make it symmetrical?

(In case it's not obvious: you're looking down the rudder hinge line. Without being cut away, the elevator will interfere with the rudder control horn.)
Nov 17, 2012, 09:05 PM
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JimTMich's Avatar
Good catch! Wouldn't have wanted to discover that while programming the radio.

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