ORIGINAL: rambler53
Have any moderators or other pillars in the forum tried 4 stroke for speed and what speed plane, prop, and fuel did you use? I see videos on Tower suggesting 4 stroke for speed but never gave Tower much credit for any recommendations. I'd really like to know to get motivated to experiment with one, for speed. Generally I over power the faster 2 stroke planes, which is why .51 and .75 are for my .40 and .60 size planes. I wouldn't want to cut up a cowl for a 4 stroke just to pull it off again after one flight, so I'm asking for someone with experience doing this.
4 strokes I could prop are Saito 72, Saito 100 or Surpass 91, if you had experience with these, that would be most helpful in your reply.
ARFs at my disposal are GP Minnow, Revolver 60, World Models Midget Mustang 60, and I'm ready to throw one of these together but wanted to get input for a 4 stroke engine.
Rambler,
If you look at the majority of the scale racing eventsout there right now, the vast majority of the racers in the faster Silver and Gold classes are using YS 4 stroke engines. Theengine/plane/prop/fuel combinations vary somewhat, but probably the most common that I see is as follows:
[*]YS 110 or YS 110S 4stroke engine (which will likely soon to be superceded by the new YS 115) we findYS engines handle the higher nitro levels a bit better than the other 4 strokes[*]World Models P-51 seems to be the most common choice (Kyosho's Spitfire, Hein, & P-40 are also excellent choices)[*]APC props: if running 20-30% nitro, a 13 X 13N runs well and easily gets mein the 120mph range; if running higher nitro, some of theother racers say they are using 14" props. (But I've only been in the 120 - 125 mph range, so I haven't personally experimented with the 14" props. To go Gold speeds . . . in the 165 mph realm . . . most of these guys are either kicking up the nitro to 55 - 65% &/or modifying the wing with a thinner, specialized racing airfoil.)[/list]To see for yourself, or do some extra research, check out the threads in that forum at the link, below:
http://www.rcuniverse.com/forum/forumid_183/tt.htm
If you go back into that forum (another page or two), you'll find other threads where those interested in getting started have asked the questions you've asked above. Some of these threads are dedicated to specifically answering those questions. Others are threads about specific races, and throughout many of the guys are talking about the plane/engine/etc. combos they are using, and often discuss how these combos have been working for them. Furthermore, if you want to hunt for them, on some of the SAM Warbird Series races, TommyGun often posts videos of some of the races, so you can see these planes in action.
If you just want to get an existing ARF from your stable in the air to just start getting a feel for it, forget the Saito 72, and use either the Saito 100 or OS 91. I don't think these engines are going to be as consistent running using higher nitro levels, so my advice is stick to 20%, for now. But, this will give you a "taste" of speed; and just as importantly, flying with the oversized-engine will give you experience flying with the heavier wing loadings that your future racers will force you to deal with, too. My advice: Keep the landing speed up a bit more than you are used to, or may feel initially comfortable with. . . fly them down and land a bit "hot", otherwise, they stall all too easily with the higher wing loadings!!! (Trust me, I've learned this the hard way!)
Speed is addicting . . . have fun!