cmoulder

First off, NO NEED TO YELL. If you do a lot of forum grazing, all caps is hard on the eyes!

Now, to your problem... before adding any lead to the tail, make sure all the electrical stuff -- which is mainly the battery, receiver and switch -- is as far back in the plane as you can get it. In some extreme cases (which yours may be) it is even possible to locate the battery near the tail of the airplane and run a long extension back to the receiver, through the switch, of course. You will have to cut the covering and make a special mount or hatch for it. If you need more weight, use a bigger battery or run two smaller ones in parallel. The idea is, if you have to add weight, at least make it useful weight. Maybe also put the rudder servo in the tail. Only add lead after you've tried everything else.

Knowing nothing about you and your flying skills, I can only say that if you don't have a good bit of experience you may find this model a handful to fly, especially with that engine and the additional wing loading. Perhaps put the .75 AX in it and get a seasoned aerobatic flier to maiden it for you and get his opinion. That configuration is definitely not for training.

Here is a picture of my electric components. As you can see, everything is pretty far back, and I had to make a special tray for the battery, which is located under the receiver in the floor of the fuse.

ronofnc

I have built this aircraft but have one problem which I am concearned about. I am new to the hobby and have yet to solo so I may not have a problem afterall? I put the plane together per instructions and have noticed that the two elevators seem to have quite a bit of movement in them in the nutural position with power on. I am using 2 Futaba servos BB 3004. The stock links that came with the kit seem to be firm and the movement seems to be in the 2 servos which are new. Question is will a small amount of movement approxmitally 1/8 inch matter. Or should I invest in new (better) servos? Thanks for any and all advice.

hamshog

Thanks for the reply. At 66 years old the eyes are not as good as they use to be so I use upper case letters. It keeps me from having to get so close to the monitor.

hamshog

I didn't mean that i am brand new to flying. I presently fly a Funtana 50X which I really enjoy. I got such a good deal on this plane I couldn't pass it up. When adding weight to the back how much is too much?

cmoulder

Well, you obviously have to have enough weight to achieve a good CG, but adding any dead weight should be done only as a last resort. Far better to move components around, even if it seems a bit extreme. Recently I saw a giant scale Extra (I think it was a 37% or 40%) that had almost everything in the tail, including a power panel, 2 receivers, batteries, regulators, switches -- the whole shebang -- in order to balance the airplane properly without adding any dead weight.

As long as an airplane has the correct CG, with few exceptions (extremely long servo leads can cause problems, for example), it doesn't matter where the electrical components end up. It is far better to do it this way than to add dead weight, which only increases your wing loading, reduces performance and degrades overall flight performance.

cmoulder

The weather was much better than had been expected a couple of days ago, so I got in my maiden today, plus a few more flights, for a total of six.

Very nice flying airplane, and at 7lb 6oz it is very light on the wing. With the CG at 125mm, I had zero aileron coupling in KE, and just a little pull to the belly, probably mixed out with about 4-5% elevator. The required push for inverted flight was spot-on for my taste. The wing airfoil is rather thick, so it slowed down very nice and floaty for landings.

The airplane is very well constructed for the price ($139 at Tower), but when putting the wings on at the field I noticed a MAJOR design flaw that should be considered seriously by anyone who likes to do hard snaps, parachutes, blenders, walls, etc. The problem is the shear web between the wing spars. The grain of the wood runs parallel to the wing spars, when it should run perpendicular.

This means that if the wing is repeatedly stressed hard, the shear web could split easily and lead to catastrophic failure. Remember, 7.5 lbs at 11 G's is 82.5 lbs![]

Also keep in mind that the wing tube goes in only to the 2nd rib past the root, as opposed to most wing tubes that go in at least to the 3rd rib, or even the 4th rib. I for one will definitely not be slamming the sticks into the corners on this one.

If anyone doesn't know what I'm talking about here, I'll post a picture of it later.

cmoulder

Ron, did you use Loctite on the little nuts and tighten them down against the clevises. It takes a very small amount of metal-on-metal movement to create the servo behavior you describe.

How do you have the servos set up -- i.e. are you running them through separate channels or are you using a Y-harness, a reversing Y-harness? Are all the connections secured with clips, heat-shrink or strings with glued knots?

Sounds to me like either metal-on-metal interference or a bad connection.

gdryer

Congratulations CMOULDER on the maiden flight.

I got a few more flights in today. I am still unsure of what changes to make to the CG.

A few minutes of video can be found at:

http://media.putfile.com/Phoenix-Extra-330-Electric

cmoulder

gdryer, your CG looks pretty good to me -- very smooth flying![8D]

Mine feels about right at 125mm. For me the two main criteria are inverted flight (not requiring too much push) and landing approaches with low fuel at the end of the flight, where I don't want a nose-high, tip-stall attitude. I find that if both those conditions exist, everything else pretty much sorts out nicely.

This is only the second plane I've ever had -- the GP Venus II being the first -- that honestly had no aileron coupling in KE. How interesting that they are both low-wing models!

cmoulder

As usual, the weather forecast was wrong (thankfully) so I got in about 8 more flights today.

I continue to be impressed with the flight characteristics, very light on the wing and not snappy at all. The only thing I noticed is that although my CG is perfect, the elevator still requires a lot of down trim for level flight. So I eyeballed it from the side about 20 feet away and it seems the wing could use a little less incidence, which doesn't look like too big of a project with this design. Also needs more right thrust in the engine.

This airplane does the best inverted flat spin I have ever seen. Very flat and rotates tightly right on the canopy. Upright needs more elevator throw, but that is not an option with the pre-pinned hinges, so maybe another project this winter.

ronofnc

Hi yes I am using a single Y connection as I only have 4 channels on my transmitter. I haven't tried any of the methods you described but I will double check the link connections to make sure they are tight however I think they are. I think I will also loosen the servo arm connection and see how hard it is to deflect the servo. Thanks for the suggestions I learn something everytime I visit RCuniverse.

gdryer

I did some thinking about the flights on the weekend. I noticed that it descends when I move the throttle forward. My past experiences leads me to beleive that I have a little too much down thrust in the motor. The 15x8 Propeller is also a bit noisy especially when I hover. I may try a 16x8 the next time out.

I also noticed that it pulls to the left in a vertical climb. I will remove the down thrust and change the propeller to see if it helps this issue.

srothsch

What prop size do you recomend for a ST90?

gdryer

I am running a Rimfire motor (electric). I will have to let someone familiar with gas motors answer that one.

cmoulder

I'm running an OS .91 and it seems pretty happy with a 13x8. I had tried a 15x6 and it was a bit too much, but an APC 14x6 would probably be just about right for 3D, with the smaller pitch. However, I am getting unlimited vertical with the 13x8 -- chugs on up but will not rocket out of hovers.

srothsch

Thank You.

cmoulder

gdryer, I also had quite a bit of left thrust, so today I made some spacers for the engine mount and gave it a lot more right thrust, about 2 degrees more.

On my Tx programming, it took a throttle-to-rudder mix of 7% right rudder to keep verticals straight.

I also reduced the wing incidence a little, raising the trailing edge of the wing (at the back edge of the main wing, not the aileron) by 1/8". This design lends iteslf to easy modification.

Upon further reflection, I realized that the problem was not the wing incidence (with the hatch line as the reference) but rather the stab and the way it is positioned in that little saddle in the tail. A slight fore or aft position can change the incidence. But it's a lot easier to adjust the wings, so that's what I did.

I hope to fly tomorrow morning and see if these changes did the trick!

checkmate91

There are loads of messages about props for the ST90 in the engines message board, just search on ST90 or Super Tigre 90, 13*6, 13*8, 14*6 are all featured. It's not as powerful an engine as the OS91FX and the 13*6 is one of the factory recommendations...

Regards,
Andy

P.S I'm trying to get mine running after 20 years (just acquired it from a friend). If I do, I'll post some outcomes in the engines board...

gdryer

Hello CMOULDER;

I just checked and I have just a touch of right thrust currently but it might need more. I will test out the change in downthrust and larger propeller before I make more changes. I have fond that changing too many things at once leads to more confusion!

cmoulder

gdryer, yep same here with the small amount of right thrust built in. The rudder correction suggested it needed a lot more, so I'll find out if I over cranked it.

Wish I could have test-flown it this morning because it was dead calm again.

Anyway, I zeroed the trims and mixes, so it shouldn't be too squirrelly on take-off!

Crashtruk

I had to get rid of some of the downthrust that was built in. I now have about 1/2 a degree. I still need some up elevator mixed in with the rudder. When I knife edged it would pull toward the belly.

srothsch

Thanks for the info.

cmoulder

Got in a few flights this morning (SPECTACULAR conditions!) and am happy to report that the changes I made worked out quite well.

I added a rather large amount of right thrust to the engine. I think I know a way to measure it exactly -- using a long CF rod and a protractor -- but suffice to say it's at least a couple of degrees. Full-throttle verticals were dead straight with absolutely neutral rudder, so my guess was pretty close! Problem is, it leans so far to the right that for a good fit in the cowl the engine mount needs to be moved left a few millimeters, so that is another project for later.

The wing incidence change worked out well, with the elevator now almost at neutral, with just a bit of down trim. Quite close, and I think I might tweak it just a smidge and raise that trailing wing edge by another 1/16". But it flies just great as is, so I may just leave it alone.

This is an excellent flying model. I had (and still have) a Fliton Extra Freestyle which I retired in favor of this model. I flew the Fliton quite a bit, and to me this is the superior model, not that the Fliton was a piece of junk, but IMHO this is a few notches better.

EDIT: I have added some pics to show the airplane and also the wing incidence change and the engine thrust spacers. The ply spacers are kinda rough, but then I didn't want to get too fancy in case they weren't right! I used a GP pilot that came with my Venus II. Much more to scale than the original pilot!

gdryer

I like the color you added to the bottom of the wing. I must do the same as the grey kind of blends in with a cloudy sky. I agree that that the original pilot is a little small (and ugly). It makes a big imporvement to the looks.

cmoulder

Thanks, "G"! Yeah, those wing bottoms really need some contrast.

I went ahead and did the engine mount shift this morning. After mucho eyeballing and measuring and re-measuring and re-eyeballing, to compensate for the additional right thrust I moved it left 7mm, or a smidge over 1/4". Now the prop shaft is in line with the fuse center.

That's it -- I ain't changin' nuthin' else for a while!!!