>On a similar note, I just bought an OS20 of a similar
>crossflow nature as the OS35 along with a Fox19 at a bargain
>price.
>
>What are the chances of these motors dragging a slow combat
>model around at 75mph on 5 or 10% nitro?
If it's a small enough plane, the various Fox 19's were powerful for their size, and not total slouches for some decent rpm's. But on a regular prop, 70 mph is probably the max. A Wooten Demon is about right, and if you build a VooDoo from plans, that is also small enough to go that slow with a Fox 19 swinging an 8-6. There might be a bit more speed with a 7-6 and the higher nitro (incidentally, the Fox 19 wasn't as happy with 5% fuel as it was with 15%).
The older steelfin Max-I through Max-III OS 19's were higher rpm engines than the 20 with a drop-in liner that replaced the steelfin. I don't think you can get it going as fast as that 70 mph I named without a lot of Nitro and a skinny toothpick of a prop.
The stoutest baffle piston 19's were Veco, particularly the Series 200. Those will spin up fast enough to pull a VooDoo around at the same sort of 80-85 mph speeds that were prevalent when the VooDoo was first designed (1960 +/-). If you want to go 75 without high nitro fuels, you need to move into the more modern engine era, or use the Veco I've named. I suspect that the Torp 19 GH has the guts to do the job also.
There were bunches of OS Max FP 20's/25's sold, and those are still available with low time on them. They work nicely. Finding usable 15's as reasonable prices to use is somewhat more difficult, although there have been a good many of several brands that will still run fast, such as the Cox Conquests, Fox 15BB's, Super Tigre 15's, etc.
.
Kiwi
Steve