Hacking a GP US40+ kit
 

A couple of years back I bought a GP UltraSport 40 plus kit (the one with the enlarged tail surfaces) as my first build. The way I built it (in the mistakes I made), it became a very fast flier and not suited to the sunday flying type airplane I needed. We flew it only a few times and when it nosed over on landing, it broke the LG block in the wing and I didnt repair if after, moved to other models. It also didnt have a good covering job as I had used some very old Oracover which was powdering and scrap quality.

This year I need a rough and cheap airplane for flying in the off-season and having crashed my trainer in the last season due to radio loss, I was thinking of resurrecting the US40+. I also need something to keep me occupied in the off-season. But I do want to make if fly slower and easier. I have already taken the old covering off. Should I take the balsa sheeting off the wings, add capstrips on the ribs and then re-sheet over the cap strips? This would make the wing fatter (increase camber) and fly slower. It will also increase wing area and cord marginally. I can do this in the entire wing except where it fits into the fuse

Otherwise, should I junk it all together and get a Extra 330 60 size and build that in the monsoon? I have old unused engines for both sizes

Ameyam

RE: Hacking a GP US40+ kit
 

30+ views and not a response? Anyway... the decision may be due to other factors finally

Ameyam

RE: Hacking a GP US40+ kit
 

Ameyam,
can you post some pics of the damage and exactly what you have, size motor would help me give you a clearanswer as to what I would do...

RE: Hacking a GP US40+ kit
 

The damage is minor- I just broke the hardwood block into which the landing gear sits. Its no big deal to repair and I will be flying without gear anyway. My real issue is that with a 55ax and 12x8 prop, this plane flies like a rocket. I really wanted it to be atleast sports (the box said it was 3d capable but I doubt) and a easy lander

I have flown faster airplanes since I flew this last but in the monsoon, our field will be covered with 4-5 feet of grass, so a handlaunch and a soft dunk into grass is the way to fly. Part of the field will also be a lake, so I need an airplane I can fly suitably close while dunking. Basically, I need to slow this airplane down....

Ameyam

RE: Hacking a GP US40+ kit
 

I would say that a smaller engine, a .40 or a .46 if you have one, would help.
I am still building my US 40+ so I don't have that experience but I do have an OS 55AX in another 40-size airplane and it is a pretty zippy powerplant. I would suggest propping down to a 12x6 or even a 12x4 to slow it down.

Ken

RE: Hacking a GP US40+ kit
 

Well, I dont have a smaller engine. I tried the smaller props on that engine- 12x4 and the engine just screams at 50% throttle.

Guys, wouldnt making the wing fatter make it a better handler?

Ameyam

RE: Hacking a GP US40+ kit
 

Try coming back on the power. That usually slows all sorts of types of vehicles down. Over the years as my age increased I found it is not necessary to have only one speed, wide open. Rebuild/replace the gear block in the wing, patch the covering and fly about half throttle. You will probably be amaized at how responsive th ultra sport will be.

RE: Hacking a GP US40+ kit
 

Well said.

RE: Hacking a GP US40+ kit
 

I don't think that is the answer, it would slow it down some but not a lot.. The work involved would be major as well. The wing fitting to the fuse would become and issue, you would have to fir out the Ail. as well. Just a lot of work for not quite the results you are after...

A suggestion based on your flying conditions (hand launching) and dunk back in to tall grass on landing.. Why not convert it to electric? I'm sure someone with more experience in electrics then mecould help you figure out the cost and how to goabout it...


Jimbo

RE: Hacking a GP US40+ kit
 

Do you know what it weighs (ready to fly) compared to the 5.3 - 5.7 pound [2400 - 2600g] estimate in the manual?
If it is heavy, are there any areas where you can remove wood or drill holes to make it lighter?
Since you will hand launch, ground clearance is not a problem. Maybe a 13x6 prop would help limit the speed and give some braking effect when landing.

RE: Hacking a GP US40+ kit
 

MinnFlyer was a strong advocate of flaps on these planes. They would probably help to slow it down for the flop into the tall grass.

Ken

RE: Hacking a GP US40+ kit
 

The US40 plus is a slightly different model than the original Ultra Sport that so many people love.

Ameyam is interested in 3d capability (the kit was advertised that way) so weight is an enemy to be avoided if possible. Adding additional servos, mounts, linkage, etc; adds weight. The flaps effect might, or might not, be enough to make up for it.

RE: Hacking a GP US40+ kit
 

Modifying the wing as suggested will have marginal if any "noticeable" effect. As said the US+ is not the US original in a number of ways. With that said.. the only way to slow a corvette is to take your foot of the throttle. Changing it's boddy style minimally as in the minimal changes on the wing will little to no effect.

RE: Hacking a GP US40+ kit
 

Since he is flying without landing gear and since he is over-powered, would the weight trade really be an issue?

RE: Hacking a GP US40+ kit
 

If hacking the throttle wont slow it down enough for him to control, then the bird is to much for his ability. What he needs is more air time in a primary trainer. Sorry to be so blunt, but facts is facts which you can't alter or change. Might get a simulator for more quick stick time.

RE: Hacking a GP US40+ kit
 

Check your C.G., mark it, and start moving it back in small increments. -SERIOUSLY, just do it- when you get it back to the perfect neutral, but still stable point, the airplanes slow flight and landing characteristics will be totally transformed. A properly balanced Ultra-Sport is one of the sweetest landing intermediate designs ever.

I've seen the situation over and over for decades, where guys are flying their airpains noseheavy and wonder why they land like homesick anvils.
(I was that guy once upon a time, until a very good friend was stubborn enough to get through to me, and get me off my butt finally to take the time to trim my own fleet's C.G. to bring out the flying qualities they were designed for) It was a revelation to me, just how wonderful they could have been flying all along.....

The suggested C.G., (or forward portion of stated C.G. range) in the instructions for the vast majority of kits AND arfs is just a safe, conservative starting point...

RE: Hacking a GP US40+ kit
 

C_Roundy,
I've seen this discussed before but never with this particular aircraft. I intend to experiment with this when I finish my own US40+. Can you tell me what you mean by "small increments"? 1/4"? 1/8"?

RE: Hacking a GP US40+ kit
 

C_Roundy,
I've seen this discussed before but never with this particular aircraft. I intend to experiment with this when I finish my own US40+. Can you tell me what you mean by ''small increments''? 1/4''? 1/8''?[/quote]
about 1/8th". Unless a wing has a much broader chord than your U.S. thats plenty to feel handling change with each push rearward.

Fully expect the elevator to be more effective as you go, and therefore require decreased deflection at full stick (this is a good thing) but anticipate that it will be the case.

The simplest procedure to find the sweet spot, is by continuing to push rearward until you feel a little twitchy-ness on the pitch axis.

MAKE SURE THAT YOU REMEMBER TO REDUCE ELEVATOR THROW PROGRESSIVELY AND REFLY UNTIL THE ELEVATOR THROW IS OPTIMIZED FOR THE C.G. UNDER TEST, BEFORE REACHING THE CONCLUSION THAT THE C.G. UNDER TEST IS TWITCHY.

When it finally actually does become inherently twitchy, pull it back forward from the last 1/8th" push you made. Your pretty much done at that point, although really discerning modelers will fine tune it down to 1/16th" or even further, tuning the last 1/16th" is as small an increment as you will probably be able to feel.

I guarantee once you've dialed the airplanes handling characteristics in this way, the pilot workload in slow flight will be waay less, the consistancy of the planes responses to your control inputs across the whole speed range will be greatly enhanced, landing aproaches, and especially the final flair to touchdown wil be so transformed that your buddies will all think you've mysteriously become a better pilot.

Almost forgot, use temporary weights (safely) to do the change increments, so you can get it all done in one afternoon, darn well mark that final magic spot accurately, then take all the temporary weight off the airplane and do WHATEVER IT TAKES to make a new permanent battery mount however the heck far back it has to go to make the plane balance on the mark. Done.

RE: Hacking a GP US40+ kit
 

Hmm... I asked for that, didnt I?

I dont think slowing down is dependant on engine size or power here. I recollect I used to fly on as low power as possible in tose days. The first time I took the airplane to the field, it was too fast for me to fly on my own. Subsequently I had engine issues and I didnt take that particular airplane for a few months. When I flew the airplane a second time, I had a 'restored' engine in it. I had a more experienced club member fly it and he reported it was a 'hot' lander. I recollect he used a lot of rudder at landing to keep it on track.

Those days, I didnt have as much experience flying faster airplanes, so they wouldnt let me take-off or land this one, just circuit it. But I do remember that it was fast enough that I couldnt relax on the downwind circuit (when I wouldnt loop or roll). In fact, I dont think I even rolled this airplane ever. I could do all the standard aerobatic moves with my trainer though.

So looks like its a consensus that thickening the wing is not going to help.

Like I said, this was my first build and I had used all my cheapest stuff on it... standard servos, y-harnesses, foam wheels, etc. I never took the next step though...and I dont intend to go any better now. Issue is that if I do deadstick into the water, I shouldnt lose any of my prized equipment. My 6EX didnt have flap mixing, my 9c does but I dont intend to make the setup more complicated by adding flaps to the mix. Its just want a cheap easy flying airplane thats 'disposable' if you dont mind the term

In those days, I wasnt much into detailed aircraft setups- so I didnt check the weight. I dont remember regarding the CG but it would have been in the ballpark as per the manual, I had added nose weight in the tank section to achieve that.

Right now, the airplane is stripped down to replace the covering. I need to take a call whether its worth re-covering or whether I should build the GP Extra 60 instead. The Extra gives me more options as it can serve as a home for my dle20 also

Ameyam

RE: Hacking a GP US40+ kit
 

Well, if you want a disposable cheap airplane to belly land on tall grass, you wouldn't want to get the 60-size and DLE20. For this one, who cares if it has bad covering. Just repair the wing, recover as necessary with leftover cover (make sure it is visible), balance the CG as mentioned, make sure the engine can idle down quite low (2500 rpm MAX), use a large diameter/low pitch prop like a 13x4 with the OS 55AX.

A large diameter/low pitch prop acts as a low gear in a car. It will brake the plane speed down for a landing when you cut the throttle, and it will also help pull the plane harder when you hand launch.

Post some pictures when you get it done, we are a curious bunch.