I'm perplexed. I purchased a CG Ultimate Bipe ARF and purchased one of the recommended engines ie; OS .61FX to power the thing with. The manufacturers hype states .60 to .90 2 stroke. After reading the posts relative to this particular aircraft I think I made a mistake on that engine choice. Why do kit and arf manufacturers specify a certain engine group and when the smoke clears the general consenus is that the plane will barely fly with the lower end of that group? My gosh, I've read where some guys are putting ST 2300's under, over, or around the cowl of this bipe. Why don't they just tell it like it is and recommend an engine grouping that will realistically give reasonable performance?

I am new to RC power and therefore still pretty green, but this is just one of the many areas that has baffled me. Do I just op to buy the most powerful engine they recommend, or am I missing something? Thanks for listening to my rant.

Covering their butt. I wish they would recommend the right size engine, but if some guy who didn't know better, used the biggest on the box. And flew the wings off, and took out some little Lady's doggy they would get sued.[] Suxs but welcome to 2005

Ditto,
I understand your frustration over what the manufacturer's state in their documentation. But you also have to take into account that a lot of people in the RC world, and here on RCU, will over power a plane to suit their style of flying. So who's right? Both of them are? And both are wrong too. What you need to do is find out how you are going to fly, and then you can start figuring out where you power an aircraft. I consider myself a purely sport flyer. I like to perform aerobatic maneuvers with my planes, but I don't need to be able to do 3D. For myself I have always used the upper end of the manufacturer's recommendations and I have never been disappointed with a plane yet. While my choices suit my style of flying, they would be totally out of line for a 3D flyer.

It's been my experience that the recommendations by the manufacturers are there for the average pilot out there. I don't think that have under estimated any recommendations. For the average pilots the recommended motor will usually be just fine. But like I said above, you have to learn to adjust according to your flying styles.

Hope this helps

Ken

Unfortunately, I think you're right on....I hadn't thought of it with that slant but makes perfect sense. [>:]

Thanks for the reply RCKen, its tough being a newbie if for no other reason than ignorance is costly....oh well, onward and upward.

Something to realize is that there is such a wide range in performance that modelers are after these days. What used to be lots of power not so long ago, is barely enough to even think about doing modern 3D flying and such. For example, the Ultimate you mention will sport fly around the patch is a very traditional way with the recommended 60. The recommended 90 will give old stile pattern flying performance. But for today's 3D and such at least a 1.20. Basically lazy sport flying requires thrust to weight of about 75%. Traditional aerobatics about 1:1. But modern IMAC planes are running 1.5 and 2 to one. A very large spread almost unheard of not so many years ago. Like many ARFs, the Goldberg Ultimate is an older design that grew from the pattern flying days. My guess is that Goldberg never aimed the design at IMAC/3D flying, though many today are trying to do just that with it.

Multiflyer

I have never had a problem with flying a plane with the recommended engine on the nose. I think manufacturers follow their CAD designs to a tee to prevent some numb nuts from coming back with a law suit about how a set up was way over powered.

I never was into over powering a plane. I always thought why by an engine that you can only fly at half throttle with through the entire flight ?

Well after getting my OS .70fs and first putting it on a .40 trainer and then into a .46 CHIPMUNK , I have seen the light [sm=idea.gif].

I now think of over powering as an security blanket for not crashing.

It appears that this 3D thing definitely has an impact on engine selection. I have no idea what 3D is. I see guys at the field using their planes like helicopters which is of no interest to me. I fly a Senior Kadet (newbie)and the Ultimate was to be my 2nd r/c plane. I want to sport fly the Ultimate, gain some experience around the patch, as you say, so some loops and rolls in that type aircraft and pratice landings in something more than a floater. Now, based on what I have just described, will the OS .61 FX do the job for me or not? If I'm understanding Mutiflyer correctly, the .61 should at least accomplish that.

I would appreciate futher comment and I thank you guys for taking the time to answer my post.

Ditto, I hear ya.

Usually, the smallest engine recommended WILL fly the plane, but often just barely. Whenever I build a kit, I install the largest engine recommended. If I have too much power, I can either throttle back or use a larger prop to absorb the H.P. As you know by now, you should have installed, at least, the .90. If the engine you purchased is still unused, you may be able to return it. If not, keep it for a future project or sell it at your local club or on eBay. Personally, I would NOT attempt to fly that plane with that engine.

You state that you're still new to R/C power. Are your capabilities up to an Ultimate?

Dr.1

PS Next time, you might want to ask more experienced R/Cers first.

WOW, RC-Fiend you just threw a huge monkey wrench into the discussion........you're saying "overpowering is a security blanket against crashing?" You now have my attention and you're going to have to explain that to me because this is a brand-new slant on the subject. [X(]

Ditto,

Go with the .90. Remember that you can always throttle it down. It's hard to get extra power out of a .60 that's already going full bore just to keep the plane in the air. Been there.

papermache

You know what, maybe the Ultimate is not a good choice for a 2nd plane. I think I fly the Kadet well and I feel like I could handle it but there is always that unknown doubt. I think it is time to reconsider. Please advise as to which plane you all think would be a good choice for #2.

And your right next time, like right now, I'm asking for more experienced help.

Ditto,

A large engine MAY pull your plane out of a bad situation by pure power, especially at low speed. It MAY get you into that trouble to begin with, too. RC-Fiend is incorrect when he states, "overpowering is a security blanket against crashing". The only security blanket against crashing is the pilot's flying ability. Some planes ae designed to fly "on the wing". Some are designed to fly "on the prop". Some do both. Use a larger engine to improve flight characteristics, not to prevent crashes. It won't.

Dr.1

I say quit molling over your choice. The bells been rung. Put the 61 fx on it. Fly it. If you like it - GREAT! If you don't, then sell the 61 fx and buy something bigger. Sure you might have to do a little more work on the plane to rebalance it after putting another engine on it, but working on the plane is half the fun isn't it?

To modify a phrase I learned from amateur telescope making: Fly more - Worry less!

Enjoy.
Brad

Ditto,

If it were MY plane, I WOULD NOT fly it with that engine. Especially if you're a low-time pilot. Brad has little to lose with his cavalier attitude, "Fly it. If you like it..." It'll be more like "if it survives."

That plane has thin airfoils, large control surfaces, and a lot of drag (as do all bipes). It needs more power. PLEASE trust my experience on this.

Hey Brad, you can't crash a telescope, you know.

Dr.1

Here's the bottom line, I have the ability to fly a mid wing as I have flown, succesfully, a GP .60 Ugly Stik. The Stik was a lot of plane over what I'm used to and tons of fun. By the way it was configured with tail dragger gear and I have had 3 successful flights and landings. Not a lot of experience but enough that I thought I was was ready for a plane I love, the Ultimate.

The 90 is somewhat intimidating, as was the .60 when I first flew it, but as papermache said, it can be throttled back. The only way I'm going to find out is to bite the bullet, get a freakin .90, slam it in that puppy and do what all you have done in the past, go for it. It's pretty easy to get confused when you have many different opinions.

This is my first post and I appreciate the input.....thank you all....I'll let you know the outcome in a follow-up post.

PS: I will continue to ask for advice from more experienced R/C'ers.

I have had three of the GB bips. The first one had a .60 and would not do a loop without diving for speed first. The .90 is the least power i would use, I've used Webra 1.20 and had a lot of fun with it. Tried a YS 1.20 and found it made the plane heavy and landing had to be fast. Dennis

Cavalier? Nah. My understanding is that Carl Goldberg products are pretty well designed, and at a design weight of 7.5-8.5 lbs, the final thrust/weight ratio should end up being greater than 1, depending on prop selection. The engine recommendation from the CG website is a .60 two stroke or .90-1.20 four stroke. Admittedly the torque of the 4 strokes is better, but the final power rating of a .60 two stroke or the .90 four stroke are similar. The OS 60 fx is a ball bearing engine, and should have enough power to adequately fly the plane, although it might not be perfect for the extreme 3D maneuvers. The wing loading works out to about 20 oz/sq ft (assuming the 8.5 lbs final weight), which is not a floater, but pretty tame, so the OS 60 fx should be more than capable of generating enough ground speed for an easy takeoff. I've got a plane that weighs in at nearly 7 lbs, with wing loading at 22 oz/sq-ft, with a Thunder Tiger GP 61 (not nearly as much power as the OS 60 fx, and it flies quite nicely.

Consequenty, I don't consider my statement cavalier. Simply it means you don't need to second guess the designer. Would more power be good? Possibly, maybe even probably. But he has the designer recommended engine. Why not try it?

Brad

"Why not try it?"

Why risk the airplane? As for second guessing the designers, some need to be second guessed, as you know if you've been in R/C for very long. A designer's or factory's recommendation is NOT written in stone. How many times have I seen a wrong Center of Gravity recommended? A lot.

A 20 oz. loading on a draggy plane isn't "tame" in my book. Coupled with the high inherant drag of bipes, and the small engine recommended, it's a formula for disaster, in my book. An 8# stunt biplane like the Ultimate, with a .60, is probably underpowered. People are putting 1.20s in this plane, does that tell you something? A 1.20 may certainly be overpowering it, but if it flys without pulling the wings off, that might indicate the "designer's" recommended engine range may be wrong. Is the plane you mention in your post a biplane with a thin airfoil and large control surfaces?

I repeat: an 8# biplane with thin airfoil, high wing loading, and typical biplane drag needs more than a .60 for confident flying.

'nuff said...

Dr.1

Nope, it's absolutely not a good choice for a second plane. A fairly tame shoulder or low wing plane would be a better choice.

And adding to this, beginners would actually be better off learning with engines that are toward the lower range of the power requirements for their planes. Way to many trainers have engines with too much power. Some pilots learn to rely on using the engine to get out of bad situations rather than learning to never get in them in the first place.

Keep the 60 and keep the plane. Buy another plane (more suited to your flight level ) and put the 60 on it. Then when your flight level goes up buy a bigger eng. for the bipe. NUFF said !!! ENJOY !!! RED

Come-on guys, we're talking about a bipe with only a 54" wing span! When this airplane was designed, a .60 WAS the standard engine size! Let's look at this from the manufacturer's view point. Manufacturers care very deeply that a modeler be satisfied with the recommendations they make as they want your return business. They do testing to determine what suites there products best. The designers and testing folks have many, many years of experience in determining what is needed to fly their planes. So, they are not going to recommend an engine that will not adequatly power their products, as this doesn't make good business sense!

Ditto stated he is a competant sport flyer with a mid wing airplane. If he is not interested in 3D, he doesn't need high end power for this plane!

Mark DeSchane, AMA 59157

When did they release a mid wing version of the Kadet Senior? In one of his followup posts he asked if the Ultimate is a good choice for a second plane. I've already given my response.

Piper... right here



However on the other hand only 3 flights on that kind of plane would not be anywhere near enough experience for an Ultimate. I would say put the ultimate aside and get a Tiger or 4 Star 60. The 61 would be plenty of power and it would get you ready for that Ultimate.