Qwic Fly III Build
Kit by Home and Hobby Solutions
This is a supplemental build article of the reproduction kit of Phil Kraft's original Qwic Fly III by Home and Hobby Solutions. I purchased the full kit, which includes all the wood and hardware. They also offer a short and short plus kits for those that want to select their own balsa and hardware. Their instruction manual expects you have a few kits under your belt. They also include a good number of pictures. My goal is to supplement Jeff Petroski's pictures and on areas where I had questions, show some more detail and explain a few items that caused me to stop and think.
The kit is all laser cut and I found the wood quality to be that of AAA grade balsa. The hardware is all Dubro. As with the period of the original aircraft they supply 'pin" type hinges. What you need to supply is a 2.5" spinner, engine, wheels, fuel tank and plumbing, control rods and your radio. Oh and a good amount of CA, both thin and medium, 30 minute epoxy and some white glue (Pica Glue-it, Tightbond etc.). Be sure to have plenty of sand paper and it helps if you have a jig or scroll saw.
The tail is a built up frame that is sheeted with 1/16" balsa.
The fuselage is fairly conventional and has plywood doublers fore and aft to add stiffness. If you are going to use a modern engine, be ready to add on to the nose ring. While I had an old, but new, Super Tiger blue head .60, I wanted to use a Kraft .61 engine on a "Kraft" designed airplane. The old Super Tiger would have fit with some clearance to spare. The front of the case on the Kraft .61 was a half inch longer than the Tiger and would have put the spinner backplate well ahead of the nose bulkhead. All I did was to add balsa rings to the backside of the 2.5" ply nose ring. These rings were 1/4" thick and were wider than the plywood ring to allow for the taper. The balsa rings were attached to the fuselage side planks and then sanded to shape. The tank area is large enough for a 16 oz Sullivan slant tank.
The pictures below show the fuselage going together. I used epoxy on the parts that used plywood doublers and on the firewall. Pica Glue-it (white Glue) was used on the top block, fuselage bottom and other places that needed time to position. CA was used on the formers and most everything else. The only issues with the manual I found was on fuselage step 2, it said to glue in 3/16 X 1/2 longerons to the top and bottom of the fuselage sides. Only the bottom gets the 3/16 X 1/2 stock. Step 3 tells you to glue in 1/2 X 1/2 tri stock from the hatch cover back and that is correct. However, it also says to do that for the bottom stringer which is incorrect as you just glued in the 3/16 X 1/2. These errors have been corrected. It seems that Jeff must use the same file system that I do occasionally and included the old instructions in my kit. He assures me the new instructions will go out with all future shipments.
The instructions tell you to sheet the bottom of the fuselage and the picture in the instructions shows doing it with the grain length-wise. Since the top block grain is also runs that direction I cross planked the bottom which should resist twisting a little better, it is personal preference.
The pictures below show adding the bottom nose block, the top block (which, if you have a band saw, jigsaw or scroll saw it will be handy to cut it down to the fuselage taper before gluing) and bottom sheeting. On a side note there is a piece called F2A, you will find it on the print, but only in the cross section views to the left of the fuselage drawings. It goes in front of F2 and on the bottom. It is positioned so the dowel rests on the top of F2A. The first photo below shows how it actually hangs below F2 and notches are cut in the laser cut hatch longerons to fit the 45 degree cut on F2A. Once you see the parts and the picture here, it will make sense.
I used a pair of older Sig aluminum tee motor mounts and I drilled and tapped them for 6/32 cap screws. If you take a close look at the picture showing them you will see 4 dimples in the firewall. The Kraft engine is so tight I had to recess for the back plate screws! The picture of the tank hatch you will notice the plywood square dowel reinforcement. I installed mine when it said "to make a choice" and to do so before the formers were attached. I used a small |_ 90 degree gouge or toy makers chisel. Jeff also includes a plywood wing bolt plate for those that do not think rubber bands and dowels should be entrusted to hold a wing on. Me, I am using the dowels and rubber bands.
The wing uses a very different type of spar. It is laminated, but more interesting is the way it is laminated actually sets the dihedral.
The wing print has a special section on the right side that shows how the spar pieces are to be cut and how they go together. For this make sure you have a sharp razor saw. For the number of cuts called for it wouldn't hurt to make a small jig to do the scarf cuts. I have tried to get a number of picture to help visualize it. The directions call for 3/16 X 3/16 stock for the rear spar. It is actually 3/8 X 3/16 stock. You are making full span spars so leave a little material for trimming on the tip end.
After the spars are built, then comes the wing, which is standard construction. The difference for most builders is that you build the entire wing as one piece. The manual has you pin down one side, assemble and then move to the other side and do the same thing. Just one caution, be sure you pin the wing down both fore and aft as you could build in a twist at this point. I found using a 3/8 shim under the rear spar (pieces from the rear spar assembly, leftovers) work well and you are then not dependant on the rib tabs that split very easily.
I choose to put the servos (2) out at the aileron locations instead of using 1 servo and bell cranks which are provided too. The other change I made was to the control horns for the barn door ailerons. The prints have you make a horn out of 3/32 plywood and laminate it into the inboard end of the aileron. What I did was to add a plate of 3/32 plywood 1" wide and long enough to fit tight between the aileron end rib and the first inboard rib. I epoxied it to the lower sheeting and the two ribs. I also added 3/8" tri stock between the ribs and the plate. I drilled holes for Dubro L&R control horns and used CA to lock two 2-56 blind nuts to the plate and I will use short 2-56 cap screws to attach the horns. This makes it easy to cover and the Dubro horns wear and look better than a plywood horn in my opinion. Plus they are accurate from side to side. You do take a chance making the horns in that they may not be identical.
In the photo's below I have not finish sanded anything in the photos as it was not yet ready to cover. I also had not yet installed the rib cap strips.
I spent about 20-25 hours in building this airframe to this point. It was a lot of fun and with some of the old school ways it made it different enough that any kit basher would enjoy building it to the plans. The spars were a challenge to get them right. I made enough saw dust ,with all the blocks and radius that need to be sanded, to build another model!!! Not really, but there is enough to wear out your arm in an evening.
I took the frame to our last RC Club meeting and it created a lot of excitement, especially from the older members. You know, "I had one of them!" and "I saw Phil at the NATS the year he won........."
1-19-2007 addition
I did add a few more things. I added shear webs to the rear of the upper and lower spars out to rib 5 for a C spar. I also made covers for the aileron bay so covering could be attached. I installed the servo rails in the fuselage and servos. I made an 1/8" deep slot for the vertical fin to set in as it simply attaches to the top of the fuselage with no additional support.
As I was getting ready to cover, I had that last 10% of the build that takes 90% of the time to finish. Running all the control pushrod housings to the rear and flex cables to the front. I prepped this model a little different that those I had built in the past. First I sanded with 220 grit and a block. I had heard of using hair spray to seal the balsa. The first coat lifts a small amount of grain and then it is sanded with 320 wd (wet or dry) dry. Then apply a second light coat. Again sand, but use 400 wd and again dry sand. The final is to sand with 600 wd. It makes for a slick base to attach Monokote or in my case I prefer Ultracoat. I also coated the engine bay and fuel tank area with a thinned coat of finishing epoxy.
Please don't mind the background it was a cheap towel!
2-2-2007
Here are some photos of the mostly completed product. I only have a few things to finish and it will be ready for it's test flight. I chose to use a film covering as I am going to use this plane as a daily flyer and do not expect to "compete" as a vintage flyer. Using the hairspray method had two benefits, it helps make the covering stick like glue and the smell was pleasant too. I can only wait for the comments on a hot sunny summers day!
The covering is Ultracote, white and flame red are the solids on the top with the new 1" checkerboard as contrast on the wing and tail. The bottom was covered with Ultracote yellow and black 1" checkerboard with bright yellow on the fuselage bottom. The only thing I have yet to do is to apply the Qwic Fly III graphics to both sides of the fuselage and my AMA number to the wing.
As I write this it is 8 degrees outside with a wind chill index of 20 below zero. The current snow depth here is about 6".
As soon as its warm out, a flight test!
I have started on the Primus and in one night was able to get the tail completely built. To see pictures as they are posted please go to the Primus Build Page
