The Smaragd would be fine with the SAP180. The RX handled these just fine. The Partner is probably a little on the large side for the SAP180 and might not be as good of a match.

You're welcome Dave, but really, you would want to try it first. And when you do get some results, please report back.

Besides Bob and me, I don't know if anyone else has their pattern models flying yet. There's a ton of flying info on the sport thread for the SAP with sport models on mufflers and small props, but very little flying experience on pattern models on piped set-ups with pattern sized props.

I dabbled a bit with the EF Extra/SAP/pipe. This plane is much larger, heavier and draggier than anything pattern related. I found that a pattern prop on that plane was not as effective as a larger diameter lower pitch like a 19x8....allowed higher spool up and better thrust (but noisier too)

Matt,

Reality has imposed itself on my plans to build the Pentathlon Evo this summer.

But when I do finally start on it I plan to keep it as light as possible, hopefully a bit under 10 lbs but more than likely a bit over because of the pipe tunnel.

PS I have a package with the props inside ready to mail, just PM your addy.

So the Focus II would be too big for the Syssa and the Focus Sport might be a better choice. 

No, the SAP180 is fine for the Focus II and too large for the Focus Sport. The SAP180 will haul an 11 lb 2M airplane just fine, with caveats. Earlier comments in this thread about suitability for upper classes and draggier airframes have nothing to do with its top end power, which is adequate. It has to do with torque and the way it behaves when responding to requests for power NOW.

For example, in the 5th corner of the Masters class hourglass (going from level heading up to the final leg) you can not expect it to respond with great authority when you roll (not slam) power in to carve the corner and establish the line, all the while trying to maintain the same airspeed as you had on the bottom line (or for that matter, on the line coming down and the corner heading into the level segment). You need to give it a bit of a running start when entering the corner, and consequently you have to anticipate handling increased airspeed in the start of the corner. In addition, since it will scrub energy while in the corner, you also have to wait a bit for it to build speed back up while exiting the corner into the first part of the leg upwards. Especially in windy conditions, this just makes it harder to establish the line the way you want to.

It's not that a maneuver like that can't be flown well with this or another 2C engine, but it increases the pilot workload as compared to an engine that gives you the exact change when you request it. It's just a 4C vs 2C behavior, and in the case of the SAP180, since it has a high exhaust timing as compared to, say, an OS 140RX, you have to lead it slightly more than you would with the RX. However, when propped correctly, the SAP180 will put out more top end power than the RX.

BTW, until switching away from 2C glow earlier this year, I didn't fully appreciate how much difference it makes to have a powerplant that behaves as described. You can go a long way with the SAP180, but just understand that you need to factor the lower midrange torque into how you fly it in a Pattern application. It's happiest when it's reving in the low to high 8K range, not so much when it is still trying to get there. Make sense?

No, the Focus II is a good match as long as the final package weighs in at about 10.5 lbs. The SAP would be way too big for a Focus Sport (which is no longer being sold as far as I know).

But it took some effort to keep the weight of the Focus II around 10.5 lbs. The big factors that kept the weight down were getting rid of the fiberglass pipe tunnel (which won't fit the ES pipe anyway) and making a balsa-lined pipe tunnel (see page 12 this thread), using much lighter control horns and linkages than the stock ones, using CF landing gear and wing tube, using the Syssa Ultra IBEC (Tech-Aero) and the Tech-Aero failsafe switch/reg.

[link=http://www.rcuniverse.com/forum/fb.asp?m=9794144]Post #1071[/link] of this thread contains the cookbook list compiled by Matt and me (with contributions from several others) for the SAP in a pattern application. I have close to a couple hundred flights on mine and it is still working well.

Agree with Bob. My Temptress airframe is similar to a FocusII in shape (drag). SAP has no problem in my set up....I don't have as many flights as Bob on my set-up but I have enough to know that it flies Temptress pretty much the same as glow 2 strokes (I've run Temptress with OS140RX, Webra 145 and 160 and Mintor 170).

It does things differently than something powered by a YS170 or electric. Ed listed the main difference in his post. We have said over and over the YS170 is no comparison for the SAP. If you want YS170 performance, there's only one way to get that. I hope people have gotten that much from these 40 odd pages of postings. I've tried to be as truthful and forthcoming as I could be with the findings

As stated many times now, the SAP is a 2 stroke sport engine adapted to pattern use. It is designed to rev up so it should be propped accordingly. The 17x12 apc is the "largest" prop we can run effectively in a Pattern application (Largest in quotes because the engine turns larger diameters but needs lower pitch, which is of little use in pattern).

Simply stretching the pipe doesn't get you more mid range torque as it does with glow 2 strokes. It's a CDI set-up which doesn't need mixture and pipe length to establish ignition timing as does a glow 2 stroke.

To me, *powerplant offerings for pattern* is about options. The SAP is an option that did not exist 7 months ago. It offers 2meter pattern flying on a budget. Maybe, at the end of the day, if one wants to fly a lot and doesn't want to break the bank, this is the best approach. Inexpensive to own and operate compared to all the other offerings. The caveat is that it will not suit every flying style desired. Could it win? In the lower classes, definitely. In Masters and F3A, it may not, at least not in my hands (he, he, he)

The other key thing with the SAP180 is that it is very low maintenance and also has a fairly easy learning curve, especially if you follow the cookbook that Matt & Bob came up with. You can expect hundreds flights without needing to take it apart, which is generally not the case for anything glow powered. Everything is a tradeoff.

Understood.  Thanks guys.

Hi, Ed:

I have had limited access to the computer the last few days so I didn't see your response that was posted while I was composing mine.

You explanation of the midrange torque characteristics and resultant pilot workload is excellent.

Even at my much lower level of experience, I realize that on a lot of maneuvers I have to throttle up and "get a run at it" before entering a vertical or a corner.

Bob, Anthony (Romano) and I got together at Stormville yesterday so I finally got to see the SAP180 in action. I was impressed with Bob's setup. It's pretty much like Ed described: Like all 2-strokes you need to anticipate your next action. That being said it looks to me as though this engine has every bit as much power as my OS160 / Aeroslave pipe setup does. Bob's Focus 2 and my Black Magic V2.2 both weigh about 10.5 lbs and it looked like we both had about the same amount of power in the verticals. The SAP180 started really easily and it sounded good in the air. Almost like a 140Rx - it only sounds like a gasser when it's idling.

As Bob pointed out however, his fuel only costs about $3.00 a gallon! This is something to consider.

John Pavlick
Team Black Magic

Wish there was a low weight (4 ozs) belt reduction unit available, designed specifically for the SAP. Take the 9K and make it 6.5 and then drive a 19x14. That could prove better than anything directly driven. Quiet too! I guess I may need to do this myself

Hi Matt,
Reading about the SAP 180 and digest the results, one thing comes too my mind re tuned pipe. As I understand you are now using a pipe for high revs? What comes to my mind are making a pipe that is especially tuned for low rev. so-called Enduropipe. This will have a different shape and maybe a larger diameter.
If it is possible to make such a pipe one will probably get a lot more grunt at low revs. Maybe this will solve your quest for power???????
However, do you know the timing of the exhaust port opening at dgree and the stroke? Rainy days maths maybe??????

Regards

Dag,

Exhaust duration is just about 170 degrees. It is very long duration that really takes advantage of lower loads in piped set-ups. Something like an 18x8 that is used in sport jobs extensively, will rev into 94-9500 or so on pipe. Same prop on muffler is 800 rpm less.

John, it was great to meet you and Barbara and to see your gorgeous Black Magic up close. Immaculate craftsmanship!

What prop are you using with the OS160 and what rpm's do you get? It was noticeably quieter than my set-up, that's for sure.

But in the air, it is hard to tell that the SAP is a gasser.

Bob,
Yeah it was a really nice day. I've been away from Pattern for too long. Thanks for the comments on my 'Magic. It was a labor of love and it was worth every minute of it.

My OS 160 is spinning an APC 18.1 x 10 at 7900-8000 RPM on the ground. With the pipe a little shorter I can get 8100-8200 but the midrange isn't as good. For Pattern we need more response in the midrange so we tend to run the pipe a bit on the "long" side. It took me a while to learn this but I'm really happy with how my OS160 runs now.

Your SAP180 has plenty of punch and it sounds great. Fly that ship fast and big (right over the poles) and you should score well. Are you planning on using the SAP180 in your new Pentathlon?

John Pavlick
Team Black Magic

I am planning to, but Matt keeps dangling new ideas in front of me.

Heres one to get your gears turning.
I didn't realize that reduction units were made for gassers.

Ahh the old Byro-drive.

Just a shame the drive unit weighs more than the engine in some cases!

A properly done belt reduction for the SAP will weigh no more than 4 ozs.

If you could convince him, Todd could make it an integral part of the CNC crankcase and prop thrust plate. It could be done with only the weight of another sprocket, bearing(s) and belt.

I forsee a redesigned crankcase with integral belt drive, not too dissimilar to the old geared 61's OS produced..

Matt,
Sorry to bother you, but can you give me the following measures:
1. From piston skirt to exhaust flange on engine( this to be subtracted from header lenght)
2. Port inside diameter

Raining heavely today, hehehe

Regards

Not to throw a wet blanket on the geared drive topic, but rather just asking...........

If a geared drive is used, of course the larger diameter/higher pitched prop will require significantly lower rpm's at the top end, but is the mid-range torque going to be increased?

Just trying to understand how the power curve is affected by the gearing.

And perhaps how much power is lost with a belt drive.

Geared drives are not really practical for this purpose. These need a dampener (and possibly some type of clutch) between the engine crankshaft or gear and the output gear it is driving. A certain (high) percent of the torque pulse needs to be damped.

Belt drives are more practical...the belt serves as its own dampener. What belt size, type (Vee, toothed, flat) and how many belts is the question.

I think that for transferring 4HP, two vee belts in tandem should be enough.

Higher torque is transferred everywhere in the rpm envelope, but max torque will always exist at the same rpm that the engine develops its max torque. For the SAP max torque will happen at around 8500 most likely.

Dag, I do not have the information you are asking for. I don't have an engine apart at the moment.