kamakasi

My Feedback: (3)

got over the full house dilemna going with the velvia-fc frm art hobbies.

right now i am flying a 2m spirit the problem i am having is when i launch the plane (i am using a heavy duty hi-start) after the plane climbs to 50-75 feet it makes a hard left.
i need to use full right to get back in line. once the plane gets to about 300 feet things settle down. i've checked to make sure the rudder/elevator is square and that the wings are on the same plane as the rudder. i've also checked the wings for a twist. the kicker is that once off the line the plane flies straight with only minimum trim. at first i thought there were some cheeky cross winds but this happens no matter what compass point or wind configuration i launch in. any suggestions? this is a serious left almost parallel to the ground.

evlwevl-RCU

Hello,

It sounds like you covered all the bases so far. I had the same problem with my plane. It always wanted to veer off to the left. My problem would only show up when the plane was at higher speeds like the first 75 feet of the launch. If you already havent done so, turn the plane upside down and hang a key ring on the tow hook and see if the plane hangs level. It doesnt take much for one wing to weigh slightly more then another, so I've always had to add a little weight to balance my wings once the plane is completed.

KJohn

One thing you can try is to introduce a little 'down' stick (or less 'up' if you are holding 'up' stick during the launch) just before that point where it would depart from a smooth launch arc. That will increase the flying speed at that point in the arc by decreasing the relative angle of attack of the wing thus moving the plane away from a potential stall. Once you pass that point in the arc release the 'down' you introduced and allow the plane to continue again climbing in a nice arc. In other words, try to eliminate the departure by flying faster at that point in the launch arc. If this helps then I would suggest that some type of stall was occuring at that critical point in the launch arc. The stall is probably occuring on the left wing compared to the right wing. There are many possible contributors to your problem. However if this simple act cleans up the launch and gives a nice high launch, you might just introduce the above 'down trim' fix for each launch and let it go at that since you are after a controlled yet high launch rather than a very stable but low launch.

Also keep in mind that during launch the wing is lifting at a point on the wing where IT wants to lift. It has excessive lift caused by the pull of the high start and thus speed of the plane. Your towhook is 'fixed' in one place on the fuselage. It may be that during the launch phase of flight the towhook is just a little too far back for a completely stable launch. Again this is not necessarily bad as long as the plane can be 'controlled' during that phase that gives trouble. In other words, if you move the towhook forward you may remove the stall at that one point in the launch arc but you might also find that the launch height is no longer maximized overall.

Check the leading edge of the left wing compared to the leading edge of the right wing. The left wing might have a sharper leading edge or maybe a different 'droop' at some point compared to the right wing. I assume the wing ribs are the same on both left and right wing panels and that both have been sanded to the same shape.

Look at the twist in each wing panel and make any twist exactly the same when comparing left wing half to right wing half. Especially make sure you have no 'washin' in any part of the wing. Washout (or lack of washout) should be checked every day before leaving for the flying field since generally it is easier to fix a washout problem in the shop rather than at the field.

I would also make sure to have about 1/8'' of washout in the outer panels to make sure tip stall is not a contributing problem. This can be removed if you find it does not help handling and if the plane is designed to have no washout. Generally I like SOME amount of washout compared to NO washout. I find that low speed handling is very dependable with some amount of washout existing in the outer panels.

The CG can be changed to see how that affects the launch. As long as it is CLOSE to the proper location I would think it should not be a large contributor to your problem but it will affect the overall normal flight handling once the plane releases from the towhook. During the launch phase I suspect that the location of the towhook compared to the point of maximum lift of the wing (during launch) would override a small change in CG made prior to the launch. If the CG is considerably different from that suggested on the plans then this may be contributing to the flight behavior you see as you would now have three items to contend with: the location of the tow hook, the location of maximum lift of the airfoil during launch and the CG point you have chosen.

Jack Hyde

My Feedback: (1)

When a plane veers consistently during launch, I move the hook forward 1/8" and see if that fixes it. I usually have an adjustable hook on my planes. I have a couple of planes that I dial in a little down elevator on the launch preset to keep the launch stable (the hook is screwed in and not convenient to adjust). Both work. The preset of down during launch requires a change during or just after launch that is a little more complicated than the fwd hook method that requires nothing.
My buddy has a Stork2 that veers wildly unless we throw it really hard, then it goes up straight. You can try throwing your plane level and hard. That may do it.
Does the plane have flaps? You can droop the flaps a tad on launch to encourage the wing to stall at the root first , but it will go up steeper , requiring some added down - maybe.
Launch setup is like cg location. Start safe and move carefully to a more aggressive setup, back off at the first sign of trouble.

jerry dotson

I have a 2 meter Spirit and it did the same thing. I give it 6 clicks of down trim before launch and when it gets about half way of the Hi-Start launch I pull back on the stick or retrim. If it is calm I retrim during the launch. I flew it several times today but had 10-15 mph wind and I flew the stick all the way. It was not a good day to soar.

kamakasi

My Feedback: (3)

thanks to all,

moved the tow hook foward and the left turn decreased. then backed off on the line tension and everything is working great. seems i was pushing the plane to hard for killer launches. i am still getting good height with no leaning on the stick with added body english to correct the now none existent left turn. again thanks to all.

why2cay

My Feedback: (8)

I have a Spirit ARF that I picked up inexpensively. one thing I noticed immediately is that when I weighed the wing panels the left panel was quite a heavier. This may be part of the problem. It seems that this is not the first site I have seen the comment of the Spirit going left on launch.This is my second arf and what I learned from all the people on this and other sites is being put to use building this plane. Just my 2cents


Steve