Peter Rake's 36" WACO 9- prototype build - RC Groups
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Jan 28, 2012, 12:38 AM
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Peter Rake's 36" WACO 9- prototype build

This is a scaled down version of Peter's 1/8 WACO 9 which is being prototyped by hoffboy. Read about his adventures here:

The 9 doesn't have the looks or fame of the Taperwings and later cabin models but it was a sturdy workhorse and it should make for a model with pleasant flying characteristics.

This model is being built from a laser cut set of parts from Manzano Laser Works which is up to the usual high standard as their production kits. Span is 36" which makes it about 1/10 scale by my reckoning.

So, let's start with the tail. Since the tail outlines and wing tips are laminated I did them all together. A few laser cut parts and some 1/8 and 1/16 sticks were added and there you have it.

If you're like me, you'll be used to laminating everything with 3 layers of wood so make sure you follow the plan and do the wing tips with 4!
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Jan 28, 2012, 12:59 AM
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Not good for a prototype build but I deviated from the plan almost immediately. Peter calls for bass spars but I can't get bass or spruce so I substituted locally grown hoop pine. It's a good bit heavier than bass but also much stronger so I ripped the 3/32 thick spars from an 8mm thick pine batten faced with 1.5mm balsa to get the correct 9.5mm or 3/8" depth for the main spars. Despite being under-sized the spars are still far stronger than required.

The bottom wings are dead simple, the hardest part being in identifying the correct ribs. I notched the spars into the tip bows slightly for added strength although it's not really necessary.

Dihedral for the top wing is shown on the plan so I drew the angle and worked out how far to block the lower wing off the board. I think it worked out to about 1/4" under the tip rib. With the wing thus blocked up I set the root rib vertical with a square.
Jan 28, 2012, 01:24 AM
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The top wings are much the same but with ailerons. A bit of thought is required before gluing as the balsa facing on the rear of the rear spar and the aileron leading edge have to be accurately notched to fit over the tip bow and aileron tip respectively.

The ribs are a really tight fit which is great. No dodgy gaps to fill and if a part won't fit, chances are it's the wrong part... This is very evident with the ribs in front of the aileron cutout. All kits should be like this, and I wish my own hand-cut parts could be like this more often!

You can see the aileron mounting plates which are screwed to small ply rails in the wings.

I sanded the aileron false spars down to meet the tip bows and then shaped the aileron leading edges to match. At this stage I'm not sure if I did the right thing as it's hard to see how the covering will look on the aileron tips. Some remedial work may be needed prior to covering.

Not all aircraft had the large aileron balance areas so there's an option for a slightly different look if anyone feels the need.
Jan 28, 2012, 04:43 AM
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I visualised the balance as being flat, with the covering taking a very similar line to the lower tips. I couldn't see any other practical way to do it - short of chopping them off altogether.

Jan 28, 2012, 07:51 AM
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That makes sense. I might glue a false rib on top of the balance and feather it out to a triangular section so the covering attaches to the sheet wood along a hard edge, if you see what I mean.
Feb 01, 2012, 06:38 AM
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The fuselage is your basic sheet balsa box at the front with an open frame of 1/8Ē square sticks at the back. I think (and Iím not going out to the shed to check tonight) the plan specifies 1/8Ē square balsa but you could substitute bass with no significant weight penalty. Itís adequately strong with balsa.

Itís a bit unusual- or maybe not, but I havenít built one of Peteís ĎS400í sized models since a Nieuport 11 free plan back in the 90ís- in having horizontal ply plates to support the centre-section and undercarriage struts but it all makes complete sense. The N11 was terrific by the way, on eight AR600s and a geared Speed 400, and although itís no longer airworthy my 4 year old still flies it around the house!

I glued the strut plate to one side and the undercarriage plate to the other before joining the sides inverted over the plan. It helps to chamfer the fin posts BEFORE adding glue and pinning everything to the board. In my case it was pulled apart and the rear end sanded very quicklyÖ

At this point the centre-section struts really need to be made. Adjusting them would be a whole lot more complicated with any of the upper fuselage structure in place. Care is needed- with four separate struts you have a bit of leeway but with this arrangement it all has to be perfect. The good side of that is itís very stiff when the struts are joined at the centre. I bent the struts as per the plan and everything was OK for once. Bending piano wire isnít my strongest skill but Iím learning to embrace my fear!
Feb 01, 2012, 07:31 AM
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I am a bit variable on strut/u/c fixings. Sometimes I use large plates, other times smaller plates and sometimes just attach them to formers. Generally, if there's a large enough flat section I favour a single plate.
In this instance there was an ample flat area of lower fuselage, so the u/c plate looked as if it might also double as a handy place for the battery pack to sit. Even though I hedged my bets by making a large opening in the former immediately in front of the plate.
An added bonus of the larger style plates is that they help to stiffen the forward fuselage.

Feb 04, 2012, 07:29 PM
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No progress lately as we've been without power for a while due to wind storms.
I do have battery power though, so I gave the intended motor a try out.

It's a Turnigy C2409 1200kv (no longer available as far as I can see from the HK website) and it matches the motor on the drawing perfectly! On a slightly used 2S battery with a GWS 9047 prop it draws 15.5A at full throttle. My Emeter was indicating 115W.

On 3S it will rip the blades off the GWS prop at 3/4 throttle but the option is there, with a better prop, if needed. I think we'll be fine with 2S though.
Feb 06, 2012, 09:21 PM
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Power restored so I could do a bit of soldering. Usually I solder gear legs more or less in the air with the expected variable accuracy and burnt fingers. This time I made a simple jig from 3mm ply and wired the pieces in place. There's not much to say really- it's conventional, simple and strong.
Feb 07, 2012, 12:16 PM
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I used to suffer and solder the LG while on the plane. Ugly results.

I have also gone to simple jigs like yours. I will also add a couple of upright parts to hold them together. Clothespins work to hold the parts in position while I wrap the gear with copper wire (speaker wire strands).

Looks good!
Feb 07, 2012, 04:11 PM
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I just use a piece of 1 x 4 a couple feet long and use a square to draw lines the correct spread for the landing gear I`m making at that time.

Then I tape each side down over the lines, this has worked well for me, and I don`t worry about dripping hot solder on the plane.
Feb 07, 2012, 06:14 PM
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Copper wire is great, for really small stuff I strip the lacquer off the small gauge solid copper wire used for winding CD-ROM motors. It's a bit of a pain though, and anywhere a speck of lacquer remains, of course, the solder won't stick. For models like the WACO I use 5 amp fuse wire.

Bending and soldering a neat and accurate assembly is one of the modelling jobs I find most satisfying- probably because I'm not that good at wire bending and really have to work at it.

Soldering is easy, although it seems to confound many modellers...
Feb 08, 2012, 02:56 AM
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The fuselage is quickly taking shape. I attached the undercarriage before gluing to top sheeting on, while access to the top side of the undercarriage mounting plate was still easy. The undercarriage and strut tubes are bound to the ply with fuse wire and glued.

I couldn't do the top sheeting in one piece so short sections ahead of and behind that shown in the photo were done separately. Insert usual whine about locally available balsa here! With softer 1/16 it would be no trouble to do it with a single piece.

Almost all the kit parts are incorporated into the model now. Although it's taken me a couple of weeks to get this far the actual time spent building is remarkably brief. I estimate it's taken no more than 6 hours so far, and I spent at least an hour of that time bending wire.
Feb 19, 2012, 06:27 AM
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Slow progress over the last week- I'm very busy with work and that's a good thing!

The cowl is built up from sheet balsa which I achieved by bolting a ply disc of approximately the spinner diameter to the motor shaft and hacking big lumps of 1/2" balsa to fit (or near enough) behind it. When it emerged from the cloud of wood shavings and dust it looked fairly good.

With that done there was less chance of squeezing the rear deck stringers to breaking point so I added them. I cobbled up templates for the cockpit cutouts using the fuselage side view and they matched photos of the real thing rather well so I cut the holes.

The area between the lower stringer and the bottom wing roots is filled with a piece of sheet wood which is tapered towards the bottom to follow the shape of the fabric covering. This could have required a bit of fitting but it all went into place with no adjustment needed. From the tone of this post you may pick up that I'm very happy with the way this model is turning out. There's no reason why it shouldn't of course, but I was expecting to do more fitting and fiddling, especially with the cowl and lower wing roots.

That will probably be all until next weekend.
Feb 29, 2012, 08:09 AM
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Today I joined the top wing halves and put everything together to see how it looks.
With the centre-line strut attachment it's going to be pretty easy to line everything up. The top wing is slightly skewed so I need to tweak the struts a bit.

Also, because the struts lean back slightly, the whole cabane assembly tends to lean back further with the weight of the top wing on it. A couple of functional bracing wires seem the easiest way to make it rigid.

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