Ross Kean

I don't really know where this should be posted (kit, speed, engines...) but I thought I would try this forum. I have a kit-built US 40 that I bought used and I want to get it into the air. (This is the older style Ultrasport with conventional gear, taildragger)

I am looking for the best (although reasonably inexpensive) power choice. I am looking for pretty good speed, good throttle response and reliability. I have read that a "normal" 46-size (i.e. TT Pro, OS AX etc) will power the plane adequately but more power is needed for a little more excitement. I would like to keep it to a 2-stroke for now. I have a Magnum .61 that isn't doing anything currently and I might give it a try. The Magnum is reliable but not a powerhouse. Other suggestions for engines that won't break the bank? How would you prop the Magnum for speed; 10x10, 11x8? (no pipe). How about for normal aerobatic flying; 12x6, 13x4?

Also, The plane is built with a single aileron servo. I was thinking about either making it into a two servo wing for flapperon capability or even splitting the ailerons for full flap capability (3 servos). Would you recommend this modification and where would you put the outboard servos? Thought about 4 servos but it gets a little heavy and complicated.

Thanks

Ross

britbrat

I'm envious -- my old Ultra Sport finally broke up in flight from accumulated fatigue & insane speeds after ten yrs of very violent flying. Mine had a TT.46 Pro with a Tower/Hobbico/GMS tuned muffler, & it blew around the sky at a very satisfying rate. An OS 50 SX would be even better if you want to spend the extra cash.

Put the dual aileron servos on the underside at mid panel. I prefer to mount them on their sides, on removable hatch doors, with only the servo arm protruding out through a slot in the hatch.

The .61 is not a great choice for the US 40 -- in general 61-size motors are heavy & bulky for their output (often as large and heavy as 75's, or even some 90's). I put a LEO .61 in mine with an APC 10-9 prop & was trying for 100+ mph when it broke-up. It didn't like the weight of the .61 very much -- landing speeds increased noticeably & agility fell off somewhat.

fredscz

My Feedback: (47)

If your US was built for a 46 you might have a time trying to fit the 61 in it. Also you will have to add a lot of tail weight. I looked at putting a ST75 in mine after a mid-air but I went back to the OS50SX. My US is as fast if not faster that a clubmate's Kougar with a Mag61.
The easiest way to use two servos on the ailerons is to mount them side by side in the center of the wing. Mine will land very slow so I do not see any need for flaps other than the novelty of them. If you decide to go with a 61 and flaps be sure and post how you did it and how it worked.
Fred

MinnFlyer

My Feedback: (4)

Believe me, a hot 46 is all this plane needs!

As for flaps, Don't go with Flapperons. This is a very easy mod to make and words can't describe how well it works.

You can do a 2 or 3 servo setup (So far, I have only used the 2 servo setup - it doesn't need 3 servos, but you just can't tell that to some people)

Cut the flaps so they are about 1/3 of the total aileron length.

PS, your Aileron roll rate won't suffer from losing the internal 1/3. Mine still rolls very fast with very little movement.

Ross Kean

I guess I'll start out with the 46 for now and see if I need more speed. The previous owner only flew it a couple of times and had a YS 45 in it (no pipe). Unfortunately, with the way the nose is built up, it may be a problem fitting any engine with physical dimensions that differ very much from the one in the original build.

Minn
I like your solution for the aileron/flap setup. The two servo plan is neat - I assume that the flexible nyrod doesn't flex enough to cause flutter? How would you fix it in place? I really don't want to strip the covering off the wing for the installation but I do think this plane "needs" flaps. Retracts would be nice too but I would rather avoid the cost for now. Maybe I'll try it in its current configuration first and see how I like it. It was very well built and covered and the only thing it needs after 5+ years of sitting in a dry basement is a little re-shrinking of the covering in a few spots.

Thanks for all the tips.

Ross

hotshabit

My Feedback: (1)

My flying field is at about 5000 foot, I run a picco .60 redhead engine with a tuned pipe @15,000 rpm on mine. It did require a half ounce of weight on the tail but it flies at well over 130 mph.......very fast. This plane also has retracts which adds to the weight. It does like to be landed hot but it flies like its on a rail even on very windy days. If I built another one I would put a hot piped 60 on it also.

MinnFlyer

My Feedback: (4)

Ross, You WOULD have to remove the bottom covering (Or at least remove a portion of it) but it's worth it.

For the flexrod exit, replace about the last 2" of cap strip on the two ribs where the exit will be, and replace them with a piece of 3/32" sheeting (Which is the same thickness as the cap strip)

I have used this setup on 4 US 40s so far. It works like a charm and I've never had any problems whatsoever.

Ross Kean

Minn

Do you use the Sullivan red-yellow stuff or is the color in your diagram for illustration? Didn't know whether to use it or possibly the heavier blue-yellow (maybe not flexible enough)? Other choices?

Ross

jzinckgra

My Feedback: (11)

anyone know what the chord length of the ailerons are supposed to be? mine are 1". just curious as I lost the plans for the wings.

MinnFlyer

My Feedback: (4)

Ross, yes, use the red/yellow stuff.

jz, I don't have one right here to measure, but 1" sounds about right.

happyal

If you realy want to get above 100mph with a 40 sized engine get a Rossi or MVVS Q500 engine.

I've got one on a small Pattern style plane and it revving to 17,500 with a 9 * 6 (On a full pipe), and unloading a lot more in the air.

Loads and loads of fun.