We all have had our ass handed to us out there buddy... Hell I, as a new TW student, ground looped twice in one day! (No better way to learn than THAT!!) Thanks for posting. This is a great reminder for everybody to review and think through.
Chart above is from CPS for the 912uls. Pretty flat curve! Looks like adding 400 static rpm would only add about 5 HP. But enough paper speculation!! Fly it and time a few runs from brake release to say 500 or 1000 agl. Then pitch for 5300 and see what the difference is in time to climb and also see if you notice better off the ground performance. In my O300 Maule (yeah I know, apples and oranges, but) I made a 300 rpm pitch increase and it was VERY noticeable!
The power curve of that motor would show if you would get better TO perf with more static rpm. Likely the engine will produce more HP (and thrust) at a higher static rpm. Problem obviously is the revs might be higher than you want in cruise when you set for optimal power during TO. My plan is to do some static thrust pulls at different pitch settings and get an idea of where my prop-engine combo will work best (also considering that rpm "ram" rise during the TO roll and in cruise) With a fixed pitch prop it obviously will end up being a comprise to a cetain degree
Easiest way is the "water trick". Essentially you fill the clutch bolt hole with water, then find another bolt that has threads that match the larger threads in the center of the clutch (get a flashlight and you'll see them), wrap teflon tape on those threads, and thread it in.... the hydro pressure forces off clutch. Here is a vid of one way to do it using a bolt from the sled. I would weld the hole on the end of the bolt closed if I used that bolt, wrap teflon, tip engine up, fill water, thread bolt in, pressurize water... off comes clutch. (And no that's not me in the video... I'm a hell of a lot uglier than that)
Wonder if that is a mechanical fuel injection? Kinda like my subaru which it is basically like a garden hose sprayer nozzle: as you push the throttle body plate open it also opens the fuel sprayer nozzle. That as opposed to a digital efi where it controls injectors via a computer, automatically adjusting for engine temp, air temp, and pressure alt, ect. The mechanical FI doesn't seem like too much of an advantage over carbs... except that you can incorporate a lean/rich mixture lever in there where it offsets the fuel nozzle position with respect to the throttle body as they move together. I really dont know much about it. Hopefully someone here who has tried it might chime in. But seems like tuning for all the carb ranges might be difficult (rich at a certain rpm, lean at another..) maybe more workable on a 4 stroke where a little lean here or there isn't as big of a deal.
Dang, no not able to make it to Anoka... but hopefully you can swing up north sometime and put another set of eyes on my work! Also, Matt Plante (Yam FB group) over in Stacy is halfway done with his Wild West Highlander. His FWF Apex is coming from Steve sometime later this year. So if you're looking to see how to do a Yamaha the right way, that'd be the one to look at!
Good thing is: Now you got someone to blame (me) if you are the first one that doesn't like it! LOL I'm not worried... I'm an expert at taking the blame for everything, but am sure you'll love it at first sight and first flight!
Hey Fred. I havent flown my Luga yet but did the same upgrade from a 72" warp, so FWIW my answer was "Go". And I've been in contact with a few people who have gone with Luga and I sure haven't heard anyone say they regretted it.
The EXUP exhaust valves have the same advantage in a snowmobile as do the RAVE variants in Ski doo sleds. They eliminate the comprimise between giving up low and midrange torque response for high rpm power. With the valves you can have the best of both worlds. If you dig deep in that article link it explains that better than I have but for an aircraft application the valves probably would not be necessary or easily feasible to work into a custom exhaust. That may leave someone with a slightly less responsive midrange but that is less of a neccesity for an aircraft application and the peak HP should still be achievable (with a proper intake and exhaust build) since the valves are in the wide open position at peak HP/RPM. Again the article explains how better breathing and a change in cam timing help account for the 150 - 162 difference. I also for sure want to clarify here that wheras the RX-1 adaptation has been out in numbers and proven through some time (the reason I chose it over the Apex), the Apex is just in it's infancy. Teal will be the first to tell you his prototype must be considered an unknown until it undergoes and passes extensive R&D. The wire harness on V1 motors has only been modified by a few and the V2 harness is more complex and on the "to do list" as Teal mentioned. Reality is that there are only a handful of Apexs out flying so far (most well known being Steve Henry in his "Yee-Haw 6" Highlander) but with guys as smart and capable as Teal, Steve, and Ian I for one have no doubt that any growing pains will be overcome and we will look back on 2018 as the big year for this great engine option becoming available as a well supported and "doable" conversion. And although this topic is specific to the Skytrax Apex adapter, it is only fair to recognize that this adapter is not the only way to connect a prop to the Apex. I believe Tango Gyro also makes an adapter and Steve Henry is flying his Apex with a Mohawk Areo (Greg Mills) adapter, Rotax C gearbox, and centrifugal clutch.
A few more details: Weight for entire gearbox/adapter (with oil) is projected at slightly under 19 lbs. Installed engine weight (total with everything fwf) falls in the 155-170 lb range. Final gear ratio is 3.83:1 with the broad powerband of the Apex in the 6200-8300 rpm band (pto) (approx 120-162 hp for the 2011+ Apex) The prop flange is designed considerably higher than the RX-1 w/ C box. This is a big improvement since with the RX-1 we had to make a bit of a compromise with regard to prop height (low if you try to tuck the motor under the cowl... or raise the motor for a better centered prop which would necessitate upper cowl mod)
Note: power chart below is pto rpm (after 1.23:1 internal reduction, so crankshaft rpm would be figures below x 1.23)
Not a lawyer here, but if the plane is not current on the CI then I think the next person that signs the CI takes a lot of responsibility. That is how it works with certified annuals and the AP / IA's carry insurance for it.... which sucks for all of us and I am in 1000% agreement with flywise on the tort reform subject! I haven't seen the EAA liability release but I bet it claims the seller provides no guarantees and calls for a thorough qualified inspection by the buyer before flying.
Hey Tony! Western or eastern Ontario? N central MN for me. And yeah I agree on the model 4 and above. I had a 2 but it was really a 2 stroke only plane. Ill get chewed out by a lot guys here for being anti 2 stroke (lol!) but after the motor seized on my KF2, after I watched another sieze after liftoff on a powered parachute, and after 6 others gave out on me and riding mates while out on the snow..... I'm personally done with them! They work well for people who they work well for, but for me they leave me puckering the whole time! Guess I never developed that "art" of flying behind a 2 smoke! So by my way of thinking, the KF 4 is a great option since it has more viable 4 stroke options, and I chose a model 5 to have a few hundred pounds more useful load. Welcome here! And good luck with your search! Brett (OK 2 stroke guys.... come tear me up now...)