Originally Posted by
LSP972
I don't. Where do you get those three pounds from? The larger engines I am discussing are, at most, a half-pound heavier than an OS 91 Surpass (which I have, but in another model) and, I presume, a Saito 1.00.
But you're right, the 15"-16" props those engines require would simply not work with the stock LG. Which is what I suspected. Your information confirmed it; thanks.
Regarding the firewall… did you reinforce yours by adding a second thickness of real plywood, as detailed way back in this thread? I have no doubt that some additional fuel proofing will be needed, and perhaps some tri-stock here and there. But slapping on another firewall over the existing one is pretty… severe. Necessary, you think? Or not?
Off to check out the Saito 1.00...
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The 10 lbs was just a number off the top of my head, my point was that you would be making a good air frame heavier. That 1/2 lb would have to be counter balanced some how.
As for my firewall, I replaced it after about my 3rd or 4th flight when I tested the stall speed at 3 ft off the ground. It popped out clean with very minor damage to the fuselage. I replaced it with 1/4 aircraft ply at that time. BTW, I believe the Saito 1.00 is lighter than the OS 91 and has slightly more hp. My 7.5 lb Ultra Sport with a Saito 1.00 w/13.5X9 prop has enough power to hover, though not enough tail to hold it for long.