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Author Topic: Spin-Up 42 (Design of Mark Benns)  (Read 3423 times)
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deltabravo
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« on: March 22, 2010, 03:39:35 AM »

Hello everybody,

Last year we started to fly TLGs here in the South of Germany. For this reason we ordered about ten Spin-Up 42 kits from Peck Polymers. Two Spin-Ups are now flying. See below some pictures of the first. It is built exactly as given in the kit/plan. After the first attempts to fly that thing, we found out, that the model has a strong tendency to roll left during launch. This leads the model very quickly back to the dust. Later we found out, that Mark Benns modified his original design: His left wing is now about 5cm longer than the right one. Knowing this, a friend of mine (he built the first model) built a wing like this. Unfortunately this wing is untested till now. In the meantime, I finished building the second Spin-Up with some different modifications to solve the roll-left problems. Observations of the flying behavior of model #1 showed clearly, that the dihedral is too big. It showed the typical swinging flying attitude. Hence I built the center section flat. Additionally, I added a little bit of sweep angle to increase the directional stability. See below some details of the second Spin-Up.


deltabravo
Attached files Thumbnail(s):
Spin-Up 42 (Design of Mark Benns)
Spin-Up 42 (Design of Mark Benns)
Spin-Up 42 (Design of Mark Benns)
Spin-Up 42 (Design of Mark Benns)
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deltabravo
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« Reply #1 on: March 22, 2010, 04:10:24 AM »

me again,

First flying attempts of model #2 showed clearly, that the modifications helped to prevent letal rolling during launch. The possibility to launch without fear is a essential basis for competitive flights.

Another thing came up: the right gliding curve was to wide. To tighten it, we simply added some tip wight on the right wing. We found out, that it is crucial only to add very little weight, because to much of tip weight on the right wing spoils the transition.

A experienced CLG-flyer told me to improve performance by simply grinding the first 10mm of the wings upper nose surface. Done this, the gliding performance went up a little bit. On the other hand, we observed an unexpected change in flight-behavior. We are not sure, if this is caused by the roughend nose.

(1) The Spin-Up #2 tends to tighten the gliding circle when encountering thermal

(2) the launch is not as simple as before. After several successful launches, #2 suddenly dived... ok, it is repairable.

any comments and especially tips are welcome, as we are interested in understanding what happened and to improve performance. By the way, best flying times are about 45s without thermal influence.

deltabravo
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MarkCovington
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« Reply #2 on: March 22, 2010, 10:30:22 AM »

 Hello Deltabravo,

I had a period of time where my gliders exhibited a strong left roll tendency. Tried everything imaginable with the gliders but finally determined I stopped rotating my body too soon on launch and was bringing my launch arm too far in front of me before release. This resulted in the model hooking around in front of me with extreme left roll. As it bled off speed it pitched up severely into a massive stall. Just remember to rotate through and release to your side.

 MC
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deltabravo
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« Reply #3 on: March 22, 2010, 11:07:32 AM »

MC,

thanks for sharing your thoughts on the launch. I am quite aware of the strong influence of the throwing technique. As I converted to freeflight from RC, I took a lot of DLG-experience with me. By bringing the launch arm to the front, it is possible to control the left starting curve. But releasing too late causes a lethal left roll. May be you are right and my crash was simply caused by releasing the plane too late. I don't feel that this is the cause. But I must admit, it happened too quick and it seemed to me as if #2 just dived only slightly banked left. Some days earlier, I deliberately tried some "late releases" just to test the reactions of #2 and had no problem. Man, I was glad! Then I added the rough upper nose surface....the problem occurred....now I am wondering why. OK maybe just a misfortune during the launch...

deltabravo
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JetPlaneFlyer
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« Reply #4 on: March 22, 2010, 02:51:51 PM »

It seams odd that there should be anything fundamentally wrong with the design that would prevent it launching, like too much dihedral or needing to adjust wing length. Mark proves all his models in contest flying and generally does very well. I'm sure this model will like all his other designs be comprehensively flight tested.

i suspect it's down to launch technique, but i guess everyone needs to adapt their glider to best suit their individual style, what works for Mark may not work for you.

More vertical stab area may help reduce roll off launch by reducing yaw???

Steve
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Rewinged
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« Reply #5 on: March 22, 2010, 04:15:16 PM »

Deltabravo, you have described a common problem! However, it is not hard to solve. This has been pretty well covered in other threads, but I'll summarize a few things here.

All tip launch gliders tend to have a rolling moment at launch, because of the differential in wing speed. A right-handed launcher will cause a left-rolling moment, and vice versa. Two key concepts, of which Mark already covered one a bit.

1. The throwing motion can have a big impact on wingtip speed differential.
2. Because the portions of the wing farthest from the axis of rotation (fuselage) have the greatest impact on roll, the span also has a big impact on wingtip speed differential.

Depending on the throwing motion and glider span, (and launcher's shoulder width and arm length) some simple math shows that the outer wingtip will be flying at 1.5 to 3 times the speed of the inner wingtip!

Smaller gliders are easier to learn on. But a little more math shows that the throwing motion has a bigger impact. The best advice I can give--which really came to me from Stan Buddenbohm--was to think of throwing toward a target on the horizon. Reach out toward the target on your follow-through. This will help lengthen your throwing stroke, in effect increasing the radius, help the timing of the release, and keep you from throwing upward too much. Later, with more experience and practice, you will be able to throw more upward, but these gliders climb pretty well with an almost horizontal launch anyway.

So, reach out toward your target on the follow-through to help keep your elbow from bending prematurely, and keep your arm lagging behind your shoulder on the launch, as Mark said.

Good luck!
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MarkCovington
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« Reply #6 on: March 22, 2010, 06:57:25 PM »

I agree with Steve`s comment about more vertical helping the situation,but... Adding enough to correct a hooked launch will present it`s own set of issues I believe. At the very least it will keep it from turning into any lift it encounters.

 MC
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deltabravo
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« Reply #7 on: March 23, 2010, 03:15:30 AM »

hi folks,

thanks very much for your input. As I wrote above, I am quite aware about a proper launching technique. This is for sure not an issue, as I know quite well how to do it.

I don't think that it is odd to modify Marks original design: increasing the left wing span in relation to the right wasn't my idea. the same thing with the dihedral. This are - as far as I know - all Marks thoughts. Less dihedral is definitely better. this is flight tested. As written above, we have two models, one with the original dihedral, one with a flat center section.

I am wondering why #2 tends to dive not to roll. Maybe I didn' t pointed that out clearly.

deltabravo

PS. I hope you all can read my poor english - it is hard for me to express my thoughts exactly
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JetPlaneFlyer
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« Reply #8 on: March 23, 2010, 09:03:17 AM »

Sorry perhaps my post was not clear. I don't think it's 'odd' to experiment with a modified design.

What i thought was odd was that you found that Mark's original design would not launch without rolling into the ground. I know Mark tests all of his designs in competition so i would be pretty sure that his model must not have had such a severe problem. I'd be very surprised if he would have put his name to a design that was incapable of launching properly. This is not to say that the design cant be improved........

As for the diving... what about increasing the decalage (i.e. adding some negative incidence on the tail)?
« Last Edit: March 23, 2010, 09:34:05 AM by JetPlaneFlyer » Logged
deltabravo
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« Reply #9 on: March 23, 2010, 09:23:35 AM »

Steve,

You are right. Marks original design works. The only thing, I wanted to say is that the original amount of dihedral is more critical during launch - no big problem if launched by an experienced modeler. I am sorry about this misunderstanding....for me #2 works safer & more simple.
 
deltabravo
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Randy Reynolds
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« Reply #10 on: March 23, 2010, 10:54:57 AM »

I would first examine the dihedral breaks to see if they are equal on both wings. This may sound too simplistic but if you take a tri-square and line it up at the TE on each break you may see some differential that causes launch problems. This is extremely easy to incorporate during the building phase and not enough has been written about it. Further, take a small straight edge and inspect the flatness of the wing undersurface critically. Equally easy for very small warps to creep in and at the speeds the wings travel these tiny differences become exaggerated. Sighting along the TE will often reveal a wavy edge and each "wave" indicates a warp. In this vein is the wood up to snuff as far as the ability to snap back to original shape after launch? We have found the balsa with good light weight to stiffness ratios are less of a problem.

I would check to see if any finish applied to the flying surfaces are warping when out doors especially if there is any asymmetrical color applied to the top vs. the bottom. All of the above comments apply to stab and rudder equally.

Finally, check the stability of the boom pivot area to see if anything is movable, loose or sloppy under launch stress. As I recall our original Spin-up models this was a suspicious matter in the design. Could be wrong with recent models however.

Good luck solving your problem and you're welcome to look back on this site to find a similar topic I started some time ago. There are many issues to look into to be sure.
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iflyhlg
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« Reply #11 on: March 23, 2010, 11:02:28 AM »

Delta Bravo, where are you located in Germany. I will be living in Luzern, Switzerland for about two months starting the end of April and staying until the 12th of July and I would love to get together with other free flighters.

Bruce Kimball
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sweepettelee
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« Reply #12 on: March 23, 2010, 11:56:59 AM »

Deltabravo,

Have you seen the video of Stan Buddenbohm's record-setting IHLG flight?

It might be helpful to absorb it thoroughly. Notice especially his initial wrist back setup and the fact he keeps his arm straight.
The video [plus many pix] is here:

 http://www.picturejoe.com/tustin/

Keep at it!

Leeper
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Leeper
deltabravo
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« Reply #13 on: March 25, 2010, 04:07:59 AM »

Delta Bravo, where are you located in Germany. I will be living in Luzern, Switzerland for about two months starting the end of April and staying until the 12th of July and I would love to get together with other free flighters.

Bruce, you have pm

deltabravo
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deltabravo
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« Reply #14 on: March 25, 2010, 09:13:08 AM »

Leeper,

Thanks for that link!!! Very impressive - this video makes it very hard to stay at work and not go to the flying field for launch-practicing.

deltabravo
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johnlaudenslager
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« Reply #15 on: March 25, 2010, 10:06:44 AM »

By the way, just what degree of dihedral are the winning TLGs using? Benns's, Batiuk's, Buddenbohm's, etc? Indoors and outdoors any different?

The only plans which I have been able to check are of Ishii's Cat 4 and Cat 3 winning gliders. The Cat 4 is his earlier glider and has 19-20 degrees average under its asymmetric wings. The Cat 3 is a later design and has 13 degrees.

John L
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Tmat
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« Reply #16 on: March 25, 2010, 01:23:14 PM »

I checked Tim B's Turn-up and Maxine, and both use an EDA of about 20 degrees. Similar to Leeper's SW36D and Bruce Kimball's Hoosier Daddy. Jim Buxton's Nat's winning TLG Amalgam used 20 degrees as well. Not sure about Stan's record setter, but IIRC it is a little bit less at 18 degrees or so (indoors remember).

Tony
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Mark Benns
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« Reply #17 on: May 06, 2010, 03:08:45 PM »

Hi Guys

A good friend suggested I subscribe and try and put you out of your misery.... However good instructions and your build skills are it is common that some trimming will be required. With the assumption you have built the model to plan and you have no warps I suspect it is one of the following that could require some adjustment.

The CofG if this is too far back the models will have a tendency to fly flatter & faster thus increasing the chance of it rolling to the left

The boom is too flexible... it shouldn’t be if it is the correct supplied tube but it has been proved that the more flexible the tube is the greater the tendency to barrel left. In fact a too stiff a tube can lead to right launches which is not what you want.

The final and most likely cause is as Steve said ... launch technique. If you release the model very late it can zoom left on launch, I use this technique in competition to plug the model in downwind lift, especially good in a breeze!... try and relax and not to throw the model too hard, the technique is to fast rotate and release.

I hope this helps...

FYI…. the larger inboard wing certainly helps especially indoors when I use very stiff lightweight (5gram) tubes, it is also good outdoors but not really required once the launch technique is perfected. The only other benefit is the 2" moment you gain for the launch phase.

Mark
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deltabravo
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« Reply #18 on: May 07, 2010, 02:42:40 AM »

Mark,

thanks for your comments. I really like your Spin-Up. It is great fun to fly it. Rolling left during launch is no issue anymore. The tailboom quality is really good and definitely not to weak. The wing has no warps. The reason why my Spin-Up dived during launch was found during repair: the screw for adjusting decalage has been "nailed" into the wood for some unknown reason.... this resulted in no or negative decalage during launch....

I am trying to improve launch height. It is a hard task. My personal best time is 61s with no thermals, but I am not able to do this repeatable. Average times are about 45 to 50s. What is your best time without thermal influence?

Could you please write something about trimming? I tried several positions for CG and observed the reactions but I could not find the ideal balance between good transition and good glide.

BTW. I personally still prefer the wing with less dihedral - much easier to launch.

best regards

Dieter
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Mark Benns
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« Reply #19 on: May 27, 2010, 03:45:11 PM »

Hi Delta

All of my latest models have been adapted slightly to improve the performance for me… this will not suit everyone therefore caution should be exercised and when adjusting take small steps as going too far usually ends in tears.. or balsa dust!

My improvements to the Spin up’s as kitted are:
1.  Slight reduction of dihedral try removing outer & mid tip angles by 3-5mm in mid & 7-10mm in outer. – I strongly urge you not to reduce centre section angles!
2.  For a light wind model the angle of the `V’ tail can be reduced quite dramatically but take note that this should be done in graduations of no more than 5mm either side. The model will tend to drift further left on launch the more you reduce the angle. Again too far and crunch!.. Be warned in stronger winds the trim may be far more temperamental.
3.  Make the wing as stiff as you can… I vacuum bag mine in carbon cloth to stop torsion and stiffen spanwise with a spar.
4.  The CofG is a bit of a `red herring’ as I have never really found moving it has made any performance difference except the launch consistency. I would trial & error with moving no more that 5% forward or aft and see how you get on.

The launch technique is the greatest way to improve times, the best way I find is to try and launch as flat as possible ensuring you have a great delayed 'unwind' which really accelerates the launch. This often takes me a good dozen throws to get back on song.

British Nationals in a couple of days and I haven't practiced for ages so just dusting the models down ready.

Enjoy them thermals

Mark
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sweepettelee
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« Reply #20 on: May 27, 2010, 05:23:21 PM »

Quote
....and I havent practiced for ages........

Hi Mark, When I read those words my immediate thought was: your mentor, Mick Page must be cringing! Roll Eyes

Yes, I have read his AeroModeller 'Butterfly' article.

Let us hope muscle memory instincts come to your rescue in time! Grin  I am sure they will, but just saw a good opportunity to have a bit of fun with you.

Good Luck at your NATS!

Ciao,
Leeper
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Mark Benns
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« Reply #21 on: May 28, 2010, 02:57:40 PM »

Lee as you are the HLG god... comments from you always make me smile.... Mick will be trying to wind me up this weekend to gain any advantage, I am used to it after 30 years!..

I hope the muscles remember also... otherwise it will be a long weekend especially as strong winds forecast.

Thermals

Mark
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glidermaster
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« Reply #22 on: May 28, 2010, 04:04:34 PM »

Strong winds on Nats Weekend, Mark, surely you jest..............

John
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« Reply #23 on: May 28, 2010, 09:59:32 PM »

Hello Mark,

Thanks for the work you all in the UK did to get us into the wing tip launch era! It has made glider flying much more
fun, rewarding and forgiving. I do not know the full history as prior to 2008 it was unknown to me that this was worked out for HLG's.

Have a successful Nationals!

John AMA 906929
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Mark Benns
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« Reply #24 on: May 31, 2010, 03:36:29 PM »

Dear Johns

Thank you for the good wishes and yes John B the winds were (as usual) higher than expected... all day Sunday the winds were mid 20's gusting to what must have been 30's... anyhow we all survived it and were thankful it didn't rain until 15 mins before the end of the comp.

M'
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