Unlimited - Double Positive Snap?

[Jim Woodward]

Hi Guys,

I've been thinking about this double-positive snap in the unlimited sequence and how I think it relates to my spinner coming off the backplate and doing a lot of damage to my plane. Has anyone else noticed "funny-stuff" happening to their plane after flying this sequence a few times? Anyone with wings that mysteriously bend a little more than they should or motors breaking parts? Is anyone doing this at full throttle (... I think not, but you never know)? I'm more than 1/2 throttle when I do it as for now. Should we offer a prize for the first plane to go "catastrophic" from this?

Bottom line, has anyone else noticed accelerated plane wear of any type? Totally unscientific, but just wondering.
Thanks,
Jim

[Flyfalcons]

From doing two snaps in a row? Sounds like you need a better plane.

[Rolling Thunder]

I don't think that any element is out of the ordinary. I don't like this sequence compared to past years. But that has nothing to do with high G's on the plane.

[Plane Wrappers]

Hmmm....That makes 2 that I have heard of flying Unlimited and throwing spinners.
you and Bryan Luckett @ Bay City.
I'm glad you where able to shut yours down before the spinner shook the plane up.
Bryan wasn't so lucky.

[Jim Woodward]

HI Monty,

In my situation, as soon as I hit the double positive and stopped - almost instantly - you could hear something bad growling, so I shut down and dead stick landed. As an aside, the cowl is ready for paint (again :( )tomorrow night.
Jim

[RightThrust]

Jimbo. My 5 season old 260 has been through I have no freakin' clue how many, not only 2 positive snap elements, but gyroscopic maneuvers way more aggressive than such. With how fast the prop is turning I'd imagine the spinner doesn't care much of anything about the roll rate of the airplane during a snapping maneuver. I didn't take much attention to your spinner pre-destruction but was it composite or metal? I've split several backplates on Mejzlik spinners because the cone was just barely out of balance. After putting a small piece of velcro inside the cone and soaking it with CA until it balanced perfectly did I stop tearing up backplates. I guess what I'm trying to say is that I wouldn't worry about flying the airplane any easier thinking it'll save your spinner. Fly it like you stole it!!!

-Kelly

[Jim Woodward]

Thanks Kelly, It was a cheap MPI AL spinner. However, saving the spinner is not the issue. When the spinner gets caught inbetween the backplate and the cowl, it becomes a more serious issue.

How did you balance the cone of your spinner?
Thanks,
Jim

[Wild Thang]

Try a True Turn.

[Ryans Rebel]

Interesting thread. I think this particular double snap puts more stress on a plane than most think. From upright into a cuban, most will carry a good bit of speed entering the snap. Also from upright, you have gravity adding to the stress. I also think that diung this particular double snap hundreds of times in a season will take its toll on a few planes out there. I would not be suprised if someone has a failure of some sort during this season doing the double snap.

[Danny Baker]

No spinner problems ever, no plane problems from flying unlimited for the last 8 years. At the Don Lowe we had 14.5 rotations of snaps in one known sequence. Plane did not care. I've always flown Dave Brown spinners with full backplates. I wear out servo gears more than anything these days.

Hope this helps, Dan

[McFueler]

Just but a GOOD spinner and don't worry about that anymore !

[Jim Woodward]

Just but a GOOD spinner and don't worry about that anymore !


Mark ..... guess which airplane I last had, had a spankin' new TT spinner on it???

[McFueler]

The one you crashes at Jax. last year ? Well it did not crash because of the spinner, that is why you need another one.

[JohnVH]

ever double check your screws? maintenance people....

/funny thread.

[as722]

Do a single snap instead, most judged whon't catch it anyway.


Albert

[Chris Puckett]

Just roll through it like some guys we know. Sorry I will stay out of the IMAC threads

[pcastine]

I'd be looking at the cheap spinner as the culprit more than the double snap.

Pete

[hovhas]

Better to use cheap spinners on this manouver if they (the spinners) are going to tear apart...:197:

[bodywerks]

Just roll through it like some guys we know. Sorry I will stay out of the IMAC threads
I definitely see a lot of "flying" through this double snap, and there are guys that usually snap pretty fast throughout the rest of the sequence snaps but slow down for this one so they can fly it instead of hoping to end up on track. The snaps do look nice this way, but if you can "fly" the snap (i.e. control the attitude of the plane as it rotates), is it really a snap?
I know, this is a whole other thread, but I love discussing it to see who gets all defensive, lol!

[McFueler]

Roll through one when I'm in the Judging chair and I will give you a Zero !!!! I like to give zeros to pilots that earn them !

[exeter_acres]

Yep...He does!

And this past weekend... I worked hard and was able to earn 2 zeros on one maneuver from Mark!

[NCFR!!]

Just roll through it like some guys we know. Sorry I will stay out of the IMAC threads


LOL!!! Remember guys - it only ticks you off if there is a little bit of truth in it!:200:

[McFueler]

Yea you zeroed the manuever 2 times before you started the next one ! Good thing I could only give you one zero !

[exeter_acres]

You mean I can't carry over scores??

Hmmm...

so if I'm judging someone and they have more than 10pts off in a maneuver.... I can't borrow points from the next maneuver??
;) ;)

[McFueler]

Yea and I'll bet that makes you very happy Too !

[RightThrust]

Jim, I just used my Dubro prop balancer and balanced it to where I could turn the spinner in any degree of rotation and it wouldn't move from there.

[ifly3d]

Jim, Is the backing plate lightened ? If so this can cause more flex in the backing plate and the spinner become loose.


Josh

[Jim Woodward]

The backplate was not lightened, but is thinnly machined and not as strong/solid as a Dave Brown or TT spinner.

Kelly - did you balance the spinner and cone put together and mouned horizontal, or just the cone hanging vertical?
Thanks,
Jim

[why_fly_high]

You mean I can't carry over scores??

Hmmm...

so if I'm judging someone and they have more than 10pts off in a maneuver.... I can't borrow points from the next maneuver??
;) ;)

No, it is not possible. He has not flown the maneuver yet so you have to start with a ten. You have to take it off the previous maneuver.

[exeter_acres]

OK....so I'll take the points off the previous maneuver!! I'll make the pilot "owe me!"

[40%plane]

Guys let me chime in here with a question to ask you all on this issue of the spinner coming apart on the two positive snaps.

If I am not mistaken the prop and spinner act as a gyroscope on the front of the plane, if I am wrong on this then disregard everything I wright after this.
If in fact it is acting like a gyroscope is the following not possible:

Scenario

A 32 plus inch propeller and roughly a 5 inch spinner, spinning together at between 5500 and 6000 RPM would present great gyroscopic forces on the crankshaft, hints the reason for the nicely designed crankshafts on the market today. The propellers of today have been designed to reduce as much flex as possible by bulking them up or changing the material they are made out of, or other various techniques. The spinners on the other hand have taken in my opinion a slightly different route where they are being built lighter and out of different materials. Neither a good or bad thing, just my opinion and I am willing to be informed better if I need to be.

Question
So after stating this, is the following a possible explanation to what might be occurring: In the design of the spinner the backplate being manufactured a little thinner to both save material, material cost and time to machine, could it have possibly been machined just thin enough for the following to occur. In the event of a plane flying at greater speeds, likely above half throttle, could the spinner backplate flex just enough to release the front portion of the spinner.

If you think about it the spinner backplates are not to thick, and the designs I have seen out there, the front part of the spinner has a lip on the back portion that would fit inside a lip on the backplate, and then an allyn bolt would hold it on. If you look at the path of an airplane in a snap, it travels across 4 axies (forward motion, lateral motion, a roll motion and a vertical motion i.e. pitch, yaw, roll, forward momentum) all these happen in a relatively short time span with a relatively high speed compared to normal flight paths and G loadings.

Is it possible that at a speed higher then normal flight, with the plane changing on all axies in rapid movement cause the 5-6 inch backplate to flex just enough to let the front portion and back portion flex enough that some seperation could occurr. Or is it possible that a small movement in this joint could occurr, resulting in an out of balance prop and spinner now turning about 5500 plus RPMs on the front of your plane. This in a sense would be a 32 inch and 5 inch gyroscope acting as one, to become unbalanced causing the entire spinner to seperat at high speed or could cause excess airframe wear and tear, resultign in a shorter life span for the airframe. This basically would be a 5 inch gyroscope placed within a 32 inch gyroscope, cause different forces on the entire front of the plane.

If this is possible it could offer an explaination to the issues few have been asking about.


Again this is not an opinion but reather a question to be asked to all of you out there who have more experience then me. I would love to hear some feedback as to what you all think about this.

[MattyMatt]

Jim,

I use the pete's spinners and have never had an issue and I like to snap the crap out of my planes at speed. I think that the single bolt along with the prop flexing, crank flexing... that little lip holding the back plate and the cone together may not be enough.

I see this issue with the new all carbon spinners with the single bolt being an issue.

[Plane Wrappers]

There you go,...Mikey cleared it right up...Geesh Architects!:199:

[40%plane]

LOL easy Monty...I was merly posing a certain scenario that I personally think could be possible. Would like to know if any body else has any comments on it.

Monty, brotha hows everything going up there. I am graduating here in 2 months and might be finding my way back up around october. Gonna have to hook up with you fellas again to do some flying you know.

[Pistolera]

Anyone have one of the single bolt CF spinners fail yet?

Earle

[sukhoi26]

You can fly with us and I will even build you a plane but leave all that mumbo jumbo stuff to the engineers and architects. Oh that's right, you went to school to be one. LOL

[Jim Woodward]

HI Guys,

I like all the suggestions - rolling through snaps, and the best one being "get a new plane" from early on in the thread :).

I do think it is possible for the backplate to bend if it was machined too thin like I think the MPI is. I see value in the thicker backplate TT or DB spinners, and also the Pete's spinner with periphial mounts deserves another look. Now, we are using higher HP motors with tuned pipes (more RPMS), so if there is any in-balance in the systems it stands to reason that fatigue will be induced faster.

Can someone describe (... like a 6 year old can understand it), how to balance a spinner? Do you balance the backplate and cone together, or are we primarily interested in the cone balance? -just to cover the bases.

Thanks,
Jim

[wc524]

Anyone have one of the single bolt CF spinners fail yet?


I have not heard of any of them failing yet. Azure Hobbies made some of the first and they are good.

I just threw my Dave Brown spinner last night which not only ruined the spinner but also my CF Mezjlik 3-Blade. :208: Thank God it didn't hit my airframe at all. :206:

The center through-bolt sheared which may have been caused by the lightened back plate flexing on the 3rd flight. It happened after a snap too no less. My fault, I should have checked/replaced the through bolt a while ago.

Lesson learned. No more spinner up front for me. Backplate ONLY from now on for IMAC. One less thing out of the equation to ruin an airframe and $100+ prop.

Can someone describe (... like a 6 year old can understand it), how to balance a spinner? Do you balance the backplate and cone together, or are we primarily interested in the cone balance? -just to cover the bases.

Lots of people use the Dubro Prop/Spinner balancer and mount the spinner on there. Use the Velcro and CA method. Of course please don't put the velcro on the outside Jim....LOL.....you should not need much though if the spinner is high quality, but MPI has been known for lesser quality spinners than a TT or Dave Brown (Not trying to offend anyone).

[Jim Woodward]

Parker - sorry to hear this! My spinner didn't last a total of 8 minutes in the air. I checked the prop bolts and spinner bolt before taking off, so on that flight, it lasted about 2-3 minutes. Basically the first double positive snap on the plane threw it.
Jim

[wc524]

Looks like I'm going to run like Luckett used to without a spinner for a while. Makes it easy to check the prop bolts and eliminates a catestrophic failure point if the spinner ever did fail.

Plus when I start getting in to my 40% having a spinner fail and destroying an airframe will be easily avoided without a spinner.

[Flyfalcons]

Jim, I don't want you attempting two snaps in a row and possibly endangering the lives of many spectators from such an extreme maneuver as two snaps in a row without your full confidence in your equipment. I think we all might be safer if you just opt out of that maneuver during your sequences. Thanks.

[sweetpea]

Just call a "Safety Break" for that part of the sequence.

[Jim Woodward]

Jim, I don't want you attempting two snaps in a row and possibly endangering the lives of many spectators from such an extreme maneuver as two snaps in a row without your full confidence in your equipment. I think we all might be safer if you just opt out of that maneuver during your sequences. Thanks.


.... did one of my unlimited class guys put you up to this? I was thinking to propose 3 positive snaps for the next 1/2 Cuban, with 1 1/2 opposite rolls on the 45 downlines, to create a tsunami-suicide-1/2-cuban. :)

[Flyfalcons]

Your unlimited class guys? No, I'm my own unlimited class guy. Fly safely. Peace be with you.

[sweetpea]

Seriously Jim.....I'm glad your plane is ok. I've only used TT spinners with light backplates and on my 50cc I've been using the Azure center bolt CF. I can't imagine that this particular maneuver is that aggressive compared to some of the 3-D flying out there where guys use full throttle. I think you just had a bit of bad luck due to an inferior spinner.

And for those opting to go without the cone. I now this changed the way my plane handles immensely from how my plane was trimmed out with one.

[Jim Woodward]

Ryan, I was thinking one of the South East unlimited guys but that didn't come through the keyboard. I think I just had some bad luck - but it did provide me a wonderful opportunity too learn to patch and fade a paint repair.
Jim

[Flyfalcons]

I think the IMAC board determined this year that a double positive snap would be required to straighten out all the planes that were bent doing the double negative snap from last year.

[wc524]

I think the IMAC board determined this year that a double positive snap would be required to straighten out all the planes that were bent doing the double negative snap from last year.

LMAO!!!!!!!!

And for those opting to go without the cone. I now this changed the way my plane handles immensely from how my plane was trimmed out with one.

My plane could use a little slowing down anyways. I could pylon race with that thing almost 120 mph+. :200:

[firemedic305]

You mean I can't carry over scores??

Hmmm...

so if I'm judging someone and they have more than 10pts off in a maneuver.... I can't borrow points from the next maneuver??
;) ;)

If this was how you did it I would end the day with a -200 or so. LOL

[MattyMatt]

Jim,

I was thinking about this... just go full throttle slam the sticks in the corners and if something flys off... then it probably shouldn't have been there in the first place.

Extra parts falling off is just weight savings.

[Jim Woodward]

Hi Matt,

I did a bunch of these double-positive thingy's this weekend and nothing but sweet success! The plane is proving out well and overall, flies magificently.
Thanks,
Jim

[wc524]

I did a bunch of these double-positive thingy's this weekend and nothing but sweet success! The plane is proving out well and overall, flies magificently.
Thanks,
Jim

You remove the spinner or put a new one on?

[Jim Woodward]

Parker - I currently have an old Pete's Models ligtened backplate on it. However today, I ordered a 5" Dave Brown P-51 type spinner. My plan is to use the heavier backplate for now.
Thanks,
Jim