Well it's a truck and I put the planes in the rear of the cab. Have to get a cap for the bed or something. My 40's are Brodak 40's is anyone running one of those on a 700 sq in plane? I looked around the net for an OS 40/46 VF no joy. What makes them so different?
The 40VF uses a tuned pipe and is much more effective as a stunt engine than a Brodak 40. Derek will get irritated again, but if anyone asked me what engine to start with for a competition program, and they didn't have a lot of help, I would still recommend the 40VF, because the engines are all about the same and the setups available are the most bulletproof of all current engines no matter what or how much you spend on it. Other engines might have some better characteristics and certainly more power capability (which is why I don't use them anymore, either), but as far as reliable and repeatable, nothing has ever been much better.
I would not use a Brodak 40 in either an Impact or a Thundergazer. It has the power of a very strong old-style 35. That's why you can't use engine size alone to determine the type of airplane, i.e. you pick the engine first, then design the airplane to match. Of course you won't end up with a world-class competitive performance no matter what airplane you build for it (which is why others use other engines - the 40VF has won about 5-6 NATS and a WC and dozens and dozens of other contests against all comers). But you can certainly build a very nice and good-flying airplane with it, probably as good or better than anything before about 1988.
Instead of attempting to scale one or the other down, I would suggest something like the Vector 40 or something similar, which is closer to what you want already. Make it look like whichever you like using a different fin and turn the canopy around the right way instead of backwards, for goodness sake. The design differences between that and any other competent modern airplane are more a matter of preference. Recall the other discussion - the overall design makes MUCH less difference than the construction/workmanship/trim variations.
If you want to go further, extend the tail an inch, make the tail the same overall area but reduce the aspect ratio of the tail to about 4.5:1 with a 65-35 split. Make the tail airfoil a "arc" airfoil that is about 3/8" thick at the max, and a LE radius of about 1/16". Use a 4" bellcrank and geometrically corrected control horns, etc. Make the flaps removable. If you like the look, add a turtledeck like the Nobler/Impact/Infinity. There, you have an Infinity Jr, for the most part, and it will be close enough to an Impact to pass, if you shape the tips of everything accordingly. The only real remaining difference would be the flaps. The basic Vector 40 has partial-span flaps with more taper than I would use. The Impact flap area would be proportionally larger than the Infinity but we both have less taper. The Thundergazer flaps are much narrow than either (almost like the first Infinity which almost no one here saw) which in turn is more-or-less off the same setup sheet as the Imitation. I much prefer full-span flaps as far as performance goes, if not the appearance. It is much more effective in terms of lift generated per hinge moment to put narrower flaps across the full span than the same area with partial span flaps, and the differential interaction between the moving and fixed sections can sometimes cause difficult trim issues (particularly if you use them for ailerons).
The Impact, Thundergazer, Trivial Pursuit, and Infinity all use much lower aspect ratio stabilizers than the Vector/SV series, and I think that this is a big part of why they turn like they do. This is largely us copying or "becoming inspired by" Gid Adkisson's "Bud Light" Lazer, which always came out of corners like it was rolling across a pool table, and had a very thin (1/4") externally-braced flat stab with a very low aspect ratio. But plenty of people have used the high-aspect ratio tails with success.
There, that's a quick "core dump" of the approach I would take (and have taken, with the Infinity Jr that I have drawings for but have not built the airplane - for the last 14 years...).
Brett
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