400 Series Spitfire RC Conversion....

[Bill Gaylord]

What I would first do is check the wing saddle mount, and modify if necessary so that the flat bottom of the wing is level with the stab. This works well for r/c, reducing and possibly eliminating speed related pitch changes. Mine flew well with a higher than usual right-thrust figure of something around 3 degrees if not a bit more, but it also has a large 9" 3-blade prop, which exaggerates the torque problem. Spitfire models in general seem to call for a bit more right thrust than others. A 9" prop is really a bit large for this model, considering that they have less torque issues with smaller props, but I wanted the scale appearance. For a 2-blade prop of 7"-8", I'd probably just go with 2 degrees. The down thrust that we commonly see recommended is partly due to the excessive positive incidence that these models often have. I'd probably only use 0 to 1 degrees, with the wing flat bottom set level with the stab. The Guillows P51 is by far the best flying I've built, with the incidence correction. Offhand it has a very small down thrust angle.

Mounting an outrunner should be fairly straight forward, if that's what you're using. I used a geared setup years ago, where the cowl actually fastens into the front of the gearbox. Outrunners made things a lot easier. The geared setups also tended to move the battery rearward, making the model more difficult to balance.

[dashmatrix]

So far I've got most all the structure done. Wings, fuse, stabs, control surfaces. I did a bit of sheeting and reinforcement. Not a single piece of hardware yet, no gear and she's a plump 79g. Is that end of the world heavy ?

The reason I asked is because I have tried a new ultra light fiberglassing process so everything that has been sheeted is actually sheeted with balsa then glassed. She is a bit chunky, but she's bullet proof.

[Bill Gaylord]

The main concern I would have is building tail feathers from 1/16" frame construction, and using a lightweight covering such as Microlite or tissue. I built mine with solid 1/16" tail feathers, and ended up adding a significant amount of ballast. Probably more ballast than I've used on every build combined in the past 5 years, which is essentially none. The model still flies well at around 14 oz, but done again I would have it in the 12oz or under range, with a fully sheeted fuse using 1/32" contest balsa, and probably some sheeting or inset planking on the wing LE. If the rear fuse in not inset planked then it may not be an issue, but definitely something to keep checking on. Along the same lines, if I had a choice, I'd prefer to have a fully sheeted or inset planked fuse for scale appearance, if the added weight could be traded off for lighter tail feathers.

[davidchoate]

Just basic square measurements. I usually wait til I get an idea of what the AUW will be before choosing power combo options. The best thing I ever did was research Electric Motor setups on RC Groups. There is a lot of good info out there, and a lot of bad info too. I also have been cutting down the dihedral on aileron wings, and make the ailerons way larger than scale. I tried scale size on My 1st and had a very similar result as Bill, but I did not land in tall Grass. Unfortunately.

[dashmatrix]

So far so good ??? With everything I'm at 15.1 oz's. She is a tad NOSE heavy. I followed your advice Bill and ripped off my sheeted tail feathers. Rebuilt them as light as possible. Don't judge me on the crappy decal job. I was pretty high at that point from Laquer fumes or something... Never have done those before. Next time I will plan those out a little better.... I know it sounds heavy, but keep in mind the whole plane from the tail forward is inset planked, then fiberglassed, not to mention a first build. It's heavy yes, but should withstand my less than stellar landings a bit better than monocote or tissue. The tail is the lightened 3/32 frame with 1/16 stringers, and tissue. I was overall really happy with the fiberglass process from Deluxe. It was much easier to do than anything I've done before.

[davidchoate]

Nice paint job. You air Brush? I can not afford one Yet, and I've heard that the cheap ones give cheap results. Can You Go over Your AUW,Power combo , etc one more time
?

[Bill Gaylord]

Looks good. I flew this model at somewhere around 14-15oz if I remember correctly. Probably better than the 190 or Zero at 12oz. I'm not sure what CG measurement you're using, but I'll have to see what I used. 22-25% center chord is probably not nose heavy, which is the range I've flown most of these Guillow's warbirds in. The Spitfire is essentially a forward swept wing also, in terms of the area distribution, locating the CG further forward than a straight, constant chord wing.

[davidchoate]

Bill, do You remember the exact Wing Area of the 1/16 Spit. I got one I may do next after seeing how nice they look. It's an old die cut Kit, but I am using it for a practice build. I blew plans up to a 34"WS so I can try MPi Retracts with a little breathin' room, and the kit wood is HEAVY! anyway. I found a place that makes a 1/12 scalke Spit and the canopy from that is a chance. I am not scared of anything, but making a scale canopy. Never did it, but I have read about it. I'll cross that Bridge when it comes to Me. But That is a Pretty Warbird. I had The 18"BNF Spit IX "Gabby" Gabreski Horizon foam plane a while ago. It was pretty. And Faast for a little 4 ch ! I wrecked it.

[davidchoate]

I am all but done an RC superlight Plane, ande its give and take. Because it's so light; it's also not as strong. I must have done at least 50 repairs on things that broke while building.

[Bill Gaylord]

I went to some effort calculating the wing area of this model some years ago, and I believe it is almost exactly 1 sq-ft, maybe +/- 1 sq inch, as posted earlier in this thread. That includes accounting for the rounded tips and not squaring them off as some model manufacturers do, stating wing area that does not actually exist.

I checked the CG on my Spitfire and measured the CG mark placed on the wing bottom at 40mm from the leading edge at the center of the wing, which I believe it was at when I flew the model, and seemed to be a good setting. It's quite possible that a bit more forward would not be a problem, as I was trying to not add any more ballast than necessary.

[davidchoate]

I am a History Channel Addict, and recall a clipped wing "low altitude", and extended wing "high altitude" Versions of the Spitfire used in the battle of Britain.I think they were tinkering and tweaking at that point to gain any advantage to save their Society. The Merlin was not fuel injected if I remember, as the Germans had this. And in an ever changing altitude and G-Force the Fuel injection must have been a great advantage. Why did the Allies still have carburetors? Imagine the Merlin injected? I am an Engine Guy, and I always wondered why the Merlin was soo much better . What was the secret? It must have lied in the camshaft and valve timing for that stage of piston engine design. Yes the Supercharger came from aviation,but I thought the Allison was always a U.S. made Merlin. Too bad there's none around ,or even guys who knew about them left to find out.

[Bill Gaylord]

From what I understand Rolls Royce custom built each engine to precision specs, versus building to tolerance as the US did a that time. It slowed production and made parts non interchangeable, such as custom machined engine parts such as crank to rod journals, but was precise and probably holding .001" oil clearances. With modern machining engines now hold .001" oil clearances with something like +/- .0001 tolerance, and we see the difference it makes. Back then and not all that long ago, the US used .001"-.003" clearances on crankshafts. You really don't want a new engine with .003" oil clearance on crankshaft bearings.

[davidchoate]

The Metals, and Alloys Today play a role in a car easily going 250,000 without a major problem. I was wathching on TV a restoration of a ME -109, and they needed a crankshaft but could not achieve the same precision with CNC and laser compter robotic crap of today as a German machinist did with a lathe and micrometer in the 1930's.

[dashmatrix]

I am all but done an RC superlight Plane, ande its give and take. Because it's so light; it's also not as strong. I must have done at least 50 repairs on things that broke while building.

Well I feel your pain, that's why I built this one entirely using Duracoat with 1/2 oz Fiberglass. It is completely flush planked with fiberglass over that. You can literally beat this thing up. It's SOLID and comes in at 15 oz ready to fly.
I'm using the Suppo Park 400 from grayson with a 1000mAh pack and the usual sub micro servos. Nothing really fancy. The only exception is the tail feathers are built lighter. Stock plans with tissue, doped and painted. With the glassing it comes in a tad nose heavy like this and seems to be real easy to balance this way. We shall see. We are having an typically SUPER windy spring here in Central Texas so I'm not able to maiden for a while. I've started the LC 400 series Mustang while I wait.