tree2tree

There are build blogs on the Balsa USA SPAD XIII, but I have had a few folks ask me to post pictures of the mod’s I did that differ from the original plans. I hope it gives a few of you ideas for your own build. Although this SPAD was completed earlier this year and as of this post, has had about 70 flights, I’ll post the progress pic’s I took along the way, with comments. So here goes:
The main modifications I made are:
- Three-piece wings- top and bottom.
- Scale-like landing gear suspension
- Hidden aileron servos
There are also a few scale details added.

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Three-piece wings: The center sections and landing gear stay with the fuselage. The left and right wing pairs stay together with their rigging. They are removed as a two sets from the fus’ for transportation. Assembly at the field takes only about 10 minutes.

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I added joiners at the 28% span location and have the top wings separate at the cabane struts and the lower wings at the fuselage sides. This meant I needed to add ribs at those locations. These ribs had to carry load, so they and more ribs at the ends of the joiner are made from 1/16” ply. The joiner pockets are tied to the existing spars to spread the load to the spars. I built the wings as complete one-piece wings and then used a razor saw to separate them into the 3 pieces. The joiners are ¾” x 1/8” aluminum bar stock which slide into pockets made from 1/16 ply and 1/8x1/8 hardwood.

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The cabane brackets at the wing are made from brass plate and serve to hold the three sections together.
The lower wings are tied together using straps screwed to the landing gear blocks. If I was to do it again, I’d figure out a way to use the same size bolts as the upper wing – not wood screws.



I added shear webbing to the wings because it adds a lot of strength & rigidity for very little weight gain.

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The aileron servos are hidden by mounting them to access panels, but I did not take pictures of these during construction. Pretty straight forward though. The servo wires are routed through the “fuel supply pipe” as BUSA instructions suggest. I made custom servo extensions for this.

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I chose to wrap the struts with string to simulate the rope used on the full size that I was modeling. Here's a sequence of pic's showing how. The last (painted) one is viewed from the other side. This view is always to the wing tip, because it is seen more often than the side towards the fuselage.


Well that's it for this evening. If there is interest, I'll add the fuselage detail.

jwrich

My Feedback: (17)

Heck yes there is an interest. Great ideas, just finished my SPAD XIII, maiden it earlier this month.
Please show more of your build.

Thanks
Rich

foodstick

tree2tree , GREAT mods and nice work!

I have been experimenting with building a fuse that splits in half behind the cockpit. I install the tail servos in the back half of the fuse.. This allows only the removal of 4 screws, and then two wires need unplugged to haul a 1/4 scale in a van or pickup. I made the same plane break down even more but so far the split fuse has been the handiest mod on several occasions.

I am building a 1/3 triplane this winter and I will make it split this way as well. I am HOPING it can be hauled in my full sized van and setup in maybe 5 minutes.

keep on posting I like your build thread

redtail

My Feedback: (15)

What great ideas. Have one sitting in the queue to be built. Thanks. Chic

tree2tree

Thanks for the comments guys. I have thought of the fuselage split in the past and would be interested in how you did it Foodstick. With a plane like the SPAD (very short nose), I'd be concerned with it being tail heavy. As you will see in the fuselage posts as I get to them, I installed as much as far forward as I could. Interesting to see how the triplane works out.

OK - to the fuselage build: The start was pretty much to the plans although I did cut the clearance holes in the "cheeks" for the spark plug caps of Valley View RC 40 twin, that I am using for power. They are the round holes near the front in the picture and I figured they would be easier to drill while flat.
Then at the other end I started to allow for the tail skid with bungee suspension. (I used an elastic band during construction). The skid is hard wood and after staining it, I added a brass foot to protect it. The brass can be replaced if it wears out. The pivot brackets are aluminum L stock, and the pivot is a brass tube with a 2-56 bolt through it.

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For the main landing gear, I fixtured the wire as outlined in the instructions then added the small cross wire and bound it all. Using a 100 watt soldering iron (like used for stained glass work) I had no trouble with the soldering. Then came the balsa and ply strut parts, with slots cut as shown so the gear can "float". I will not need the couple of inches of wire that was intended to be the axle, so removed it with a Dremmel & cut-off wheel. The 3rd picture shows this and the new axle. Hair ties make good temporary bungees! I then added the spreader bar. To strengthen it, I drilled through the gear struts and into the spreader bar. Then glued dowels in those holes.

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I forgot to post this picture with the wing detail. It shows how the aileron servo leads enter the top wing. There are two layers of shrink tubing where the wires enter the wing, to prevent chafing.

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OK - so the main components are all built. Now comes all the detail stuff like adding the fus' front sheeting, the gun troughs etc. Mostly I just followed the good BUSA instructions. I made sure to paint the inside of the cheek area before adding the ply sheeting. It was time to fit the engine and fix the firewall location. The VVRC 40 is a tight fit between the fus' inner sides, but it does fit and the round clearance holes are barely noticed after the aircraft was covered and painted. After removing the engine, I started on shaping the cowl. A couple of ideas here: 1. I applied masking tape to any area I did not want the sanding to get to. 2. I glued sand paper to an empty Monocote tube which worked well for me.


That's it until next time . . . .

foodstick

Treetotree, I hear you on the tail heavy thing !

Lately I have been building an airfoil into the stab/elevator on some of my WW1 stuff to make it a lifting tail .. I always HOPE it offsets the bit of added weight in my builds.. especially when the weight is towards the back.

tree2tree

Interesting idea on the lifting tail, Foodstick. You a past free-flighter?
Things worked out well out on this SPAD. Only had to add about 3 oz of lead to the nose, although it is real neutral. If the CG was any further back, I think I'd be chasing it all over the sky. Final weight was about 18.5 lbs. BUSA specs called for 20 to 22 lbs, so I am happy.

foodstick

I don't have any expert free flight building background ... But I am willing to steal their tricks when it comes in handy !

tree2tree

A 1/4 scale model seems big until you lay out all the sh..... er stuff the has to go inside it. As much as possible was checked to make sure it all worked as intended, before getting installed where it might be difficult to get at.

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In these few pictures, the fuselage is inverted. The rudder and two elevator servos are mounted up against the firewall. The oval holes provide access to the servo screws and then the screws securing the tank platform that goes in next. The throttle servo is also on this tank platform, and lines up with the throttle arm on the other side of the firewall. A battery platform sits above the engine (picture is of the fus' still inverted). It hold two 1100 mAh A-123 receiver packs, the NiMH 700 mAh gun module pack, and the ignition module. Now all the heavy stuff has been accounted for and its either in front of the firewall or immediately behind it. The receiver is mounted behind all that.

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This is the only picture I took during the covering. I used natural color Solartex as I planned to paint the final colors. Nothing special about the way I covered the plane. Solartex just works great.

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A couple of our club members were on a team who constructed a full size SPAD XIII replica for the Selfridge museum. Through one of them, I was able to get access to take a lot of photos of the detail I needed. I planned on finishing the model in the same colors and markings as the SPADs that returned to Selfridge after WWI - which the replica also represents.

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One is the full scale snow owl emblem of the 17th Pursuit squadron and one is on the model. My good buddy Pete Rattlesnake M. cut the vinyl owl emblem for model - and spent a long time "weeding" the areas that were not needed.

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Some of the scale details added:
The leather cockpit coaming and instruments. The three levers are attached to hidden switches behind the panel. They are the 3 battery switches.


The guns, gun sight & fuel pipe


The leather maneuvering handle; tail skid and aluminum access panel for bungee maintenance - like the full scale SPAD.


Exhaust tail pipe and 2 assist steps. The tail pipe was 3-D printed by another club buddy.

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Nearing completion, it went for a visit to the Selfridge museum. It was a real honor to chat with some of the team that built the full-size replica; and to get a picture of the two SPAD XIIIs alongside each other.

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So that was the build. Time to wrap up the thread with the fun part - flying the maiden and then enjoying getting used to the SPAD. A few more things to do before we get there though.
Hanging a biplane (or parasol wing, or cabin style plane) from its top wing to check the CG, is not accurate. The plane will hang a bit like a pendulum. The SPAD was a classic example: I marked 4.25" back from the top wing LE (per the plans), placed my fingers there and it hung about level. Wow! No weight needed! 4.25" is 28%.
But like I said, I don't trust checking CG from the top wing. I made a couple of fixtures so that I could re-check nearer to the center of mass - Using these, the plane is supported on either side of the fus' about at the thrust line. This time the tail dropped. By the time I had it level, the balance point was at 4 5/8" which is about at 32%. That could have been disaster! Going back to using the top wing, I found I could hang the plane in about a 1/2 inch range with very little change in attitude.
So after all that, I needed to add about 5 oz to the cowl to get it to the 28%. Making the fixtures was worth the effort. They may have saved the plane.
The pilot was being painted and a few of the scale details had yet to be added when it flew for the first time. I was concerned that the short nose and forward landing gear location would make ground handling a problem, but it taxis just fine with no threat of ground looping. There is a tendency to swing left as it accelerates (you can see it in the video). The rudder can easily control it once you are ready for it though. It did need a few clicks of trim before it would fly hands-free. You'll see it does drop a wing in the stall, but there is plenty warning and it happens at a really slow speed. The landing at the end of a maiden always brings a bit of pucker factor - especially on a WWI bird. I'll let the video tell that story.......
https://youtu.be/lIxlYs1hDNc

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On the 5th flight, the engine went dead stick. I lucked out with enough altitude to get it down with a good landing. But not so lucky with the engine. A failed crankshaft! When I removed the mufflers you could see one piston up and one piston down!
Although it was disappointing, the folks at Valley View RC stood behind their product. They had me send it back for repair and kept me updated about progress. Seems they had a bad batch of crankshafts and one was installed in my engine.
I didn’t want to hangar the SPAD while waiting for the engine, so I installed an OS GT33.

It was a fairly painless conversion and I was soon flying the plane again. I particularly wanted to have it ready for Fond Du Lac. For anyone wondering if a 33cc is enough engine for the BUSA SPAD, here you go...

https://youtu.be/NlpSc3LLrB0

Anyone still reading this thread?