buzzingb

My Feedback: (2)

I am flying an Ultra Sport 40 now and have tried several engines but something is lackig, Power, Real Power. I have tried the following engines OS 61FX, Saito 91, Saito 80. The airframe will handle all these engines easily. I believe it needs a 90 size engine to really show what it can do. The only problem I can see in doing this is installing a larger size fuel tank. How can I do this in this airplane. I am thinking of the Jett 90 or OS 91. If you know of other good engines in this size please reply. Any suggestions would be greatly appreciated.

Cyclic Hardover

My Feedback: (3)

Here is a close up of my 60 size Ultrasport with a Jett 90. Well go for it but if your going to use a 91fx your wasting your time. 1. What prop did you use on your 61 fx, 2. Is this the ARF version of the Ultra Sport or the kit? I would give it a shot here but your going to have to do a bit of rebuilding but its worth it to have something different.

You may have to rebuild the cowl area too and make sure that back end is solid and not some framed up surfaces. If you have never see a back end explode, it's a sight to see. Like shooting a pidgeon with a shotgun.

I have done similar, take a perfectly good plane and "bash " it into something useful. I have also dremeled out the bulkhead that allows the fuel tank through but then I run a bead of epoxy around it to compensate for what I took off.

bob27s

My Feedback: (19)

What props were you running on the 61FX ? That engine turns up fairly well.

If the plane was already set up for the OS 61FX, the Jett 90L will pretty much drop right in.

Bolt on a 10x10 prop and hang on to the sticks.

As snoop noted..... make sure the plane is structurally sound. Especailly if it is the ARF.

A few years ago I flew an UltraSport .40 with the Jett .50 up front. Weighed under 5 pounds, and with the gear up, it went like he_l

Bob

buzzingb

My Feedback: (2)

The OS 61FX was running 12X8 and the porting has been massaged a little to let it run in the higher rpm range. I am still using stock muffler since the engine isn't going to get into the higher rpm, I didn't want to waste money on pipe. I checked rpm last year and think it was about 12,000. In the air it did open up a considerable amount. The saito 91 was pulling a 13X10 APC. It loaded the engine a little on take off but it would pull it in the air well. The airplame ballanced quite will with all of these engines but flight time was short because of the samll tank. I know the Jett engines like to drink the fuel and it will need larger tank.

bob27s

My Feedback: (19)

Burning fuel = energy = hp + rpm and performance There is no way around that equation

The Jett engines do tend to burn a bit more fuel, but that is due to higher output per displacment.

The 90L burns a bit more than 1oz per min on average. Not an incredible amount more than most of the 60 size pattern engines did. Throttle back some of the time, and the fuel lasts quite a bit longer. Your OS61 turning at 12K consumed just a bit less than the SJ-90L will. If you were ok with those flight durations, you will probably be ok with the 90L.


Speed wise..... the 12x8 was WAY too big. Too much frontal area. Great take off and vertical, but definately not right if you want "fast". You want a smaller diameter, and bring the pitch up. Something more along the lines of an 11x8, 11x9 or 10x9 would be more suiting considering the engine and aircraft. 12K on the 12x8 and stock exhaust is pretty stout. Nothing to complain about there.

buzzingb

My Feedback: (2)

The OS 61 is a much better engine than I first thought it would be. In stock form it isn't much as far a power and rpm goes but ok. But with some work it will deliver adequate power for price since I only payed $90 in like new condition. What kind of rpm will the Jett 90 deliver? with say a 12X8?

bob27s

My Feedback: (19)

They typically turn an APC 12x6 somewhere around 14,500 rpm (sea level, 15% fuel, std jett stream muffler) on the ground once properly broken in. They do not leave the shop unless they comfortably turn up near 14K. Engine idle is set by Dub, and the transition is check before it leaves too.

With the 12x8, we usually see somewhere around 13-13.5K under the same conditions.

This is about the limit of the prop load. You want to keep the 90L ground rpm above 13K if at all possible. 12.5K is minimum - engine will be running off-the-pipe on the ground...which makes it harder to needle... but as long as its on a faster aircraft and can unload quickly above 13K in the air, its ok to prop down that low.

The muffler's tuning range is appx 13-15K rpm. With a full pipe, you can optimize the prop/rpm for what ever you wish.

I think you will see in Snoop's Ultrasport post he gets slightly differnt numbers at his Altitude (5000 feet or so), and what he described is the 'harder to needle' thing coming into play with the engine rpm. Just takes a bit of practice...but I believe he is getting pretty good performance under those conditions.

buzzingb

My Feedback: (2)

Many people don't realize how sweet these Ultra Sports are. They can fly as fast as greesed lightling or slow down and do 3d as well. Lands like a trainer. Very stable and tracks well in air at any speed. This plane will spin and tumble like a circus performer on high wire. However, it does need more porer than a meer 46-50 size engine to really shine.

buzzingb

My Feedback: (2)

Have you ever looked at the tailfeathers (control surface areas) or the Ultra Sport. It has pleanty to do mild 3D work. If you intend to go fast just switch to low rates with exponential.
A word of caution, If you intend to run a larger engine install larger blind nuts that is supplied with kit. I have seen these fail when using larger engines.

bob27s

My Feedback: (19)

Although there are possibilities,

there are other airframes better suited to speed applications. I wouldnt truely advise using a 90 engine on the UltraSport 40. In the long run, its just not worth it.

Ive owned and flown both the Ultrasport 40 and 60 airframes. I still have the 60 size one... its 12 years old now - probably has 50 hr of flight time on it. Excellent aircraft. They are based on the Bridi Kaos..... and use the Kaos wing. Although excellent aerobatic aircraft, the thick wing is not condusive to speed.

John A

Bob, the Ultra Sport has been changed to the US 40 Plus, which now uses a 14% thickness airfoil. Great Planes appears to think they can't have too many 3D planes in the inventory. If he has the new one, he isn't going to get the speed out of it the old Ultra Sport could.

http://www2.towerhobbies.com/cgi-bin...?&I=LXCZR8&P=7

buzzingb

My Feedback: (2)

Thanks John A and bob27, I think it is the newer one. I know it isn't a true speed plane but it can easily exceed 100mph in current configuration. But what true speed plane can 3D and flies well on Sunday afternoon??
To get into speed I am waiting on a warm weekend to launch a Patriot 40 with OS50SX. I don't consider the Patriot a true speed plane either but I am building up to that level. Eventually I want to design my own patriot based airplane with much thinner wing and fuse.
About how fast will the Patriot go with this engine? I bet not much faster than the Ultra Sport .