Jerry,
Thanks for your reply on general engine mounting. I'm familiar with the process of installing engines in glass models but the Magic is a little different as the original 60 size (well, Hanno's competition second version) used an inverted configuration with an S-shaped header to bring the pipe to the top. Speaking of which...
I was about to reply with some pictures of the Magic 60 you just posted. I believe those pics might be from a build that Rob started some time back when QLK were first brought back. He has a thread started on the forum here:
http://www.rcuniverse.com/forum/clas...742-magic.html
The photos you've just posted appear to be of the same model a little more advanced. What was missing from Rob's photo posts was seeing the underside which now reveals that he made a cutout large enough to pass the engine through there. Not having seen it until now, and with the somewhat different front end of the M60 vs M40, I was wondering if Rob was actually able to pass the engine through the opening in the nose of the model. Because of the design, it looked like it almost might have been doable but I wasn't sure if the engine mounting tabs would have passed through the nose ring when canting the engine forward. Now, it is more obvious that the cutout is large enough to install and remove the engine from the underside - thanks!
That said, the M40 appears to have a slightly different front shape with the "carburetor chin" curved up toward the nose ring of the fuse. Maybe it's just an illusion and if the front were opened entirely as in the M60, it would look more or less the same. Anyhow, I'm really thinking about the logistics of getting a 45 size engine installed inverted in the model and other implications related to the air baffle, fuel tank and nose retract gear.
At this point, thinking aloud, I would ideally like to use a YS 45FR engine as they are "short and pumped" allowing for a more compact FW to Spinner distance and a fuel tank positioned above the front part of the wing with the radio behind it. I would also install a lite ply plate in the wing LE to FW area to mount the NG (with adequate ply reinforcement) and keep it separated from the rest of the components. The plate could also house two servos on either side of the wheel when retracted - one for the throttle and the other for NG steering. I'd probably try my luck with electric retracts using 3.5 mm struts - a little on the light side but they should be sturdy enough. The good news is the air baffle would provide some additional support for the NG/servo plate in the front and act as a "strut" of sorts.
The main drawback of using a "non Rossi" engine (i.e., the YS) is that a custom header would likely have to be made as there are no S-shaped standard headers for this engine. One of the great benefits of the NR Speed/13 engine that Rob used in the M60 is that NR makes three different header "rises" providing a perfect header for the inverted installation. I happen to have a Rossi 45 RE engine which uses the same headers as the NR Speed/13 so that would be an easy solution but my main concern is the reliability of engine operation with an inverted mount and a non metered engine like the YS. But like I said, I'm mainly thinking aloud if I am to build one of these M40's...
I'm not personally interested in an upright mount for this design although I can see the appeal as it makes the whole engine install dilemma much easier. An upright OS 46 VF or even the Rossi 45 RE would probably work well in that configuration assuming one could get the fuel tank high enough in the model since the carb would likely be at the level of the tuned pipe. Naturally, the easiest install of all would probably be a side mounted engine but this would break with my concept of the Magic and its concealed pipe and deck.
It might just be that anyone wanting to build an M40 might have to order a custom header specific to their engine. Even an engine like the OS 55AX could be used mounted inverted with a wrap around rise header. The header would exit and re-enter the fuse (either in front or behind the FW) and rise up to the pipe deck. At this point, I'm inclined toward using the YS FR but I'm just wondering if the project will give me more grief than I desire. Then again, a compact 40 size Prettner design is always a unique project!
Thanks again for your ongoing posts. If you have pics of an upright (and inverted for that matter) engine install on the M40, I'd be most interested in seeing them. Of course, if you have any further advice or suggestions on the topic, I'm all ears!
David
P.S. Giving it a little further thought, I'm wondering if the best solution would be to have a Rossi header adapter made for the 45 FR. It would likely be easier than a custom header and allows a Speed/13 header to be more easily installed and removed with the spring retention system. A part like the one shown below.