I flew a newly built Sig Shoestring for the first this evening and found that it seemed to like to turn in/roll at me on the launch.  I noted that this happened more when I was running higher speeds with a 7x6 APC prop than when I overloaded it with a Zinger 7.5x7 woody or with a Taipan 7x4 plastic.  The plane was flying on 52'x.015" lines with a Fox 15 for power and I have about 5/8 oz in the wingtip.  On landing I do not have any tension issues and the wings stay level.  I have balanced it by adding about 1/2 oz to the tail to keep it from diving towards the ground on the power off part of the flight (this seems to work fairly well).  I spoke with another flyer who has recently built one as well and he said that he has encountered a similar condition with his airplane, but only has one flight to base this on.  Any feedback would be greatly appreciated.

BTW this is for the Lansing leg of the Tour d'Michigan.  That area club thought that this would be a good entry level type airplane to run in a speed event where you are timed for 16 laps from take off.  Except for the 1/4 to 1/2 lap of freeflight this airplane seems to perform very well.
Thanks,
John Paris

There are lots of things that can contribute to this behavior.  

Before you start trying to change the model, how are you launching the model?  Many folks are flat-footed and relaxed, then signal the pitman for release and then try to catchup to the model on the takeoff roll.  That works for large slow models.  It doesn't work for fast models and definitely doesn't work for small fast models.

Hit You Tube and search for "F2C" and you'll find examples of what I'm describing in the next paragraph.

You want to be about 1/2 step in front of a line stretched from the model to the center of the circle.  Your body is facing in the direction you are going to be moving with your arm extended to the side toward the model an the lines tight.  You should be slightly crouched with a comfortable stance.  Your right foot is placed so you can push off with it like a runner would and your left foot slightly forward so you are balanced and ready for the first step. Forget signals, you want to pull the model out of your mechanic's hand as you step forward, pushing off with your right foot.  The mechanic releases as you pull.  The mechanic does not push or turn the model.  A one hand release by the mechanic is probably best. Once you start moving, keep going.  Then use the length of your arm to sweep the handle forward and perhaps slightly up (but not up over your head).  If the model is light on the lines pulling your arm into your body as you are stepping (smartly) around the pilot's circle should take care of the lightness and give you a good launch.

If that doesn't work, check that the wheels rotate freely and the LG placement.  Sig used to show the wheels way far forward which can cause the problem you've described.  For ideas on LG placement look at the pictures in this forum from the recent Dallas contest.  "2009 Charles Ash Memorial Racing Results" There are lots of pictures of Goodyear models to give you an idea for LG and wheel placement.  

If the LG/Wheels are right and you are still having problems then it is time to look at the leadout placement vs. the CG.  But I'll leave that until you've looked at the other possibilities.

Dave

More tip weight will  help. The British have a much better solution to the dreaded two-wheel turn-in problem. They use a mono-wheel gear. Presto, no more problems!

Doc,
One of the local guys has been getting some of the Fox 15s off of the bay to have ready for this event.  Unfortunately he was unable to attend due to a conflicting event with NASCAR.  In any case, I think that he was making the engines available for $20 or $25 if you did not want to get in on the bidding.  We had toyed around with letting it be open to to all plain bearing 15s but since there is a general difference in performace in what is available out there, we decided that there were enough Foxes available that we could give this thing a go and keep people on the same level.

As it turned out for this event there were only 2 entries, me and one other guy and we both had Shoestrings.  Although I know this is a racing forum when I asked the question I figured it would be the best place to get info on these type of airframes even though we ran the event a bit more like a speed run.  The airplanes were timed from take off to the end of 16 laps to get what I believe was a mile.  I watched his launch and it did turn in and the wing rolled a little bit toward the center of the circle, but it was back on the end of the lines by 1/3 of a lap or so.  Mine did much better with no additional changes other than taking off more downwind than during my practice session.  Interestingly his airplane was flying without tip weight and I had 5/8 ozs on mine and they looked about the same in level flight from what I could tell.  If I recall correctly there was no mention of tip weight on the plans either.

For what it is worth he finished the timed portion (16 laps) in 1:12 with an 8x7 MA and I finished in 0:55 with a 7x6 APC with both of us on 10% fuel.  For me it was a worthwhile project and I hope to see more pilots out there next year.
John

You have arrived at the ultimate in limited performance, not enough power to get off the ground.

Those engines went out of use for a reason.

How about putting a little deliberate drag (bind) on the outboard wheel?  It sure works to turn it in when it's on the inboard.

Dave, I guess I forgot to mention wingtip weight.  I still do that to all my racing planes even tho my son is pretty quick.  I think it helps in landing also. 

The one engine rule is great until someone figures it all out.  Or like now we someone that is blue printing engines for Class II Goodyear competition.  Or if you have the bucks to buy a half dozen and use the best one.  But, in reality it is not always the fastest planes that wins.  It takes practice and more  practice, besides reliable equipment.  Have fun,  DOC Holliday

Mark,
As soon as I get back from Brazil I will get some shots.  Basically it looks exactly like the one on the box except that I went for a white canopy instead of silver.  There is no rudder kick on this one as I was trying to get the max speed out of it.  The landing gear is in the stock place as well.
John

EDIT:  Here they are

Okey Doke,

First off.     Good looking plane.

As I am new..I have questions:

1) Do builders ever kick the rudder on racing planes?
2) Same question for the motor?
3) Off Topic.. They always call the color on the plane Chartruese.  Sorry.. but that is Green.. These planes are always Yellow. Photos I have found.. Are Yellow. I guess I dont need an answer on this.


Forget 3.. lets talk 1 and 2.

Nice Pics. Mark