Kit Review and Flight Report: Dynaflite 80" Spitfire

My father with the finished model (he's 5'10"!)

Summary

Wingspan	81 inches
Length	65 inches
Wing Area	1150 square inches
Recommended Engine	.90-1.20 2C, 1.20-1.50 4C
Engine Used	Zenoah G-23
Spec. Weight	10-11 pounds
Actual Weight	13 pounds
Kit Cost	US $135
Hits	Excellent value for the money. Good quality components for the price. Very easy to build considering the subject. Flys beautifully! The more I fly it the more I like it.
Misses	Flat-bottom airfoil will require some adjustment for those used to warbirds with higher wingloading. It has a tendency to balloon on landing, especially in windy conditions. Templates for markings missing from kit. Instructions a bit too sketchy considering this may be a first-time scale kit for many.

Opening the Box

The kit is well packaged, and I found the quality of wood and die-cutting to be average. Some of the die-cut wing skin panel sheets were really hard, but nothing to get too worked up about. Minimal hardware is included, although I don't think I used any of it. The plans are good quality. A vacuformed canopy and ABS exhaust stacks are included, but no decals. The instruction sheet mentioned a template sheet for cutting the markings, but I never found one in my kit. The markings are pretty trivial anyway, all you need is a good drawing compass and a ruler. It would have been nice if they had drawn the markings in dotted lines on the plans, though.

The tail is built-up from 3/8 x 3/4" sticks. The curved pieces are built up from 3 layers of die-cut 1/8 balsa. This works out OK, it's probably a bit stronger and maybe a bit heavier than solid stock. I didn't want to cover the fuse with film, so I sheeted over this framework with 1/16" sheet.

The Fuselage

The fuse uses familiar die-cut lite ply tab-lock construction. It goes together quickly and easily, it really does build like a sport plane. The finished fuse is very strong. There is ample room for all the gear inside. I managed to install everything and still leave plenty of room for a scale cockpit (if I ever get around to it).

Since I planned to sand the fuse smooth and paint it, I left the side knockouts in and glued them in place.

The fuselage calls for a good amount of downthrust. It is very effective at preventing trim changes at different throttle settings. The airfoil shape makes this mandatory - don't take it out.

Considering my choice of engine (the 3.5 pound G-23) I thought I would need tail ballast, so I planned to install three servos in the tail, one for each elevator half and one for the rudder. This turned out not to be the case. With the servos in the tail the plane was decidedly tail heavy. I moved the servos to the mid-fuselage and it then balanced about right. I have since added about 8 ounces of lead to the nose just behind the firewall. With this configuration it flies very nicely. I still use one servo for each elevator half, so there are three pushrods going to the tail.

The Wing

The wing spar arrangement is a bit unusual. Two 1/8" x 3/8" spruce sticks are laminated together to form each spar. This double lamination only goes out to rib #9, from there to the wingtip the spar is just a single 1/8" x 3/8" spruce stick.

None of the ribs are symmetrical, so be careful. The wingtip rib looks symmetrical at first glance, but it's not. The retract installation shown on the plans is fine, although I replaced the light ply rib doublers with 1/8" aircraft grade plywood. I don't think the lite ply would withstand too many hard landings. I also added a 1/16" aircraft ply spar web behind the retract rails, and some 1/2" balsa triangle stock at the rib/spar web joint. My experience has shown that a little beefing up here pays big dividends, unless you're one of those ace pilots who never has a hard landing. (yeah right!)

Covering & Finishing

Canopy Area

I had a brainstorm for blending the canopy area. The usual problem is that the edges of the canopy stick up above the level of the surrounding balsa when it is glued on. So to fill it in and blend it, you have to build up a layer of filler surrounding the canopy, which results in a bulged look and alot of extra weight in filler.

So, I thought, why not try to bring the canopy down to the level of the balsa? Unfortunately the canopy is at least 1/32" thick, and the sheeting in this area is only 3/32", but I went ahead with my plan. I placed the canopy on the model and positioned it just the way I wanted it, then drew a line around the edges on the balsa. I then went around and scored the balsa with a #11 X-acto to about 1/16" depth. I then used a woodworking chisel to carve away the balsa where the canopy would contact it, about 1-1/2" or so all the way around the inside of the line. This only leaves 1/16", but with the canopy glued on the area is strengthened again.

I then used PFM to glue the canopy down, using masking tape to hold it while the glue dries. After that dried I lightly sanded the canopy on the areas that would be painted near the seam and applied epoxy/microballoons around the seam. After sanding that down, I used a product called "Mask it Easy" available from Micro Mark. It is a white-glue like product that you brush on. After it dries (translucent) you cut around the canopy frames with a NEW #11 X-acto blade (no, I don't work for X-acto :-) and peel off the part that is to be painted. The results, as you can see, are perfect!

The Dynaflite Spit is designed to be film-covered, so it has open bays on the wing and tail. I sheeted over the stab and fin, and then went directly to a filler coat and sanded... If I had it to do over again I would have used glass cloth and resin on the fuse. My thinking was that it didn't need any more structural strength and that was true. The problem is that the balsa areas where the seam is a bit weak tend to crack without the glass cloth to bind it together. I'm now getting alot of cracks. They're minor, but annoying. I don't think I saved more than a few ounces by skipping the cloth and resin anyway.

One filler that I discovered on this project was paint and talcum powder (baby powder). I had some light blue that I wasn't going to use, so I mixed some of it with baby powder until it got pretty thick, almost like a paste. You then brush it on and when it dries it sands "like butta" :-) You can add more and more powder to get a thicker paste if you have larger holes/voids to fill in. It's not as strong as epoxy/microballoons, but it's alot easier to sand and a bit lighter. A classic filler is nitrate dope and baby powder, mine is just a variation.

I built the wing to plan and covered it with "Micafilm". This is a film covering but it is backed with mica fibers which add alot of strength. It is probably about the same weight as monokote, but it is stronger and easier to paint. It comes pre-primed in light gray. I like the stuff alot. You have to use an adhesive with it, I used SIG "Stix-IT" with good results.

Next came the color coats. I don't use alot of primer to save weight. For the color coats I used Testor's "Model Master" enamels for plastic models. These are not fuel-proof, so I used Chevron "Perfect Paint" Dead Flat Clear over for fuel-proofing. I've used this method before with good results. I find the paints for plastic models have more accurate colors than any of the stuff available for R/C. They have pre-mixed colors for RAF, Luftwaffe, USAAF, etc. including interior colors. I use a Paache H-1 airbrush with the largest point they make.

* The "Roundel Red" is a dull red, close to "rust". I mixed it from Insignia Red (FS 31136), Dark Green (FS 34079) and Flat Black.

Forward Fuselage Compartment

The Graupner 24oz fuel tank I selected fits perfectly in the forward fuselage compartment which is just forward of the CG. The tank is close enough to the CG here that the CG change from empty to full is negligible.

Aft Fuselage Compartment

On my FW 190, I hid the air & radio switches and hookups in various places such as wheel wells and air scoops. This kept them out of sight, but they were less than convenient to reach. I decided to try a hatched compartment this time and I am very pleased with the results.

This view shows the hatch from the outside of the fuse. Inside the compartment, from left to right, are the Dubro fuel filler valve, the Robart retract air fill valve, the Futaba radio on/off switch, and a mini phono plug for charging and checking the radio batteries.

The Zenoah G-23 fits this plane pretty well. It makes it easy to balance, since it usually requires a pound or more of lead in the nose with a lighter 2 or 4 stroke glow engine.

Close-up of carburetor, kill switch, and throttle bellcrank mounting screw.

The Spitfire flew better than I expected. It has alot of wing and so with a relatively light wing loading it flies very gently. I was especially pleased with the performance. Even with the gear down it scooted around pretty well with the G-23. It was way too pitch-sensitive on the first flight, a combination of slight tail-heaviness and too much elevator throw. I put some lead in the nose and took the elevator throw down by about 1/2! The next flight was much better, although the landing wasn't too great. With the flat-bottomed airfoil, it tends to float on landing if you don't let it slow down enough. It will take some adjustment from my FW-190, which has a pretty high sink rate once you cut the power. On the second flight I came in too fast and it ballooned on landing. I made the mistake of trying to mush it on in. It hit the mains pretty hard and tore out one of them. I could have prevented the whole thing if I had just hit the power and gone around. Oh well, it was an easy repair. I always expect that landing gear are going to get a bit of abuse :-)

Update: 11/4/96

I have nine flights on it now and I like it more and more as I get used to it. The landings are no problem once you start treating it more like a sport plane and less like a warbird! The approach needs to be fairly long and shallow, leave on a bit of power until you're over the numbers and then cut back to idle and let her sink in and flare, gently!

Update: 11/17/96

On Nov. 14, I went out on a windy afternoon. I have decided this is not a plane for flying on windy days. A gust of wind on landing is almost guaranteed to cause it to balloon. This might be less of a problem if it weren't for the fact that the G-23 doesn't respond instantly when you gun it. There is about a 2-second delay before it revs up to full throttle from idle. In a ballooning situation, that two seconds can be fatal.

On the first flight of the day, the landing went well initially until about halfway down the runway when it ballooned. I hit the throttle, and by the time it got up to speed, I missed hitting the runway be mere inches.

I decided I just needed more landing practice, so I fueled it up, took off, and immediately prepared to land again. The first landing went OK, if a little shaky. On the second try, it ballooned again. This time I decided it was too low to try to gun it and go around, so I let it sink back down. It didn't hit all that hard, but it broke out BOTH retracts, including ripping out the front support rail on both units. Clearly I have to re-engineer the nylon bolt situation, as the 8-32s are too strong for the support structure. So now I have some repair work to do. The weather is turning here anyway. It's raining this weekend.

Three generations of Hethcoat men :-) Clockwise from left, me, my father Jerry, and my son Jeff.

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