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HelicopterBeginners Corner › Blade Woof
09-15-2007 08:56 PM  10 years agoPost 1
garaptor

rrApprentice

Atlanta,Ga,usa

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Raptor 30 v1 with Carbon Mavriks. Ok, I know all you old pros hate Mavriks, but I have flown them for a year and never had this happen so something else is CONTRIBUTING to the problem besides the blades.It woofed on me last weekend after going lean and hitting throttle hold from about 15 ft. Scared the crap out of me. So I found some slop and rebuilt new blade grips,bearings,feathering shaft and set the tracking. Today it did it again.What the hell is happening?

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09-15-2007 09:14 PM  10 years agoPost 2
ppridday

rrKey Veteran

Detroit Lakes MN

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Any slop at all in the linkages or any bent ball studs?

Paul

"There's someone in my head, but it's not me..."

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09-15-2007 09:54 PM  10 years agoPost 3
BarracudaHockey

rrMaster

Jacksonville FL

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Thrust bearings installed wrong or shot.

Radial bearings loose in the blade grips.

Slop in the collective system.

Blade grip ball screws bent or loose.

Mavrikk blades

Andy
AMA 77227
http://www.jaxrc.com

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09-15-2007 10:42 PM  10 years agoPost 4
garaptor

rrApprentice

Atlanta,Ga,usa

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New thrust bearings, I made sure the stackup was right,radial bearing tight fit,balls and joints tight,minimal vertical play in main. Uh-Oh... when I flex the blades up and down, I hear a popping noise seems like from inside the blade itself. I think maybe the layers inside the blades have broken loose??? Im gonna fly with some woodies tomorrow and see.

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09-16-2007 12:16 AM  10 years agoPost 5
Mark C

rrKey Veteran

Houston, TX - USA

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Hey... I flew a year on Mavrikks before I learned to hate them.

Let's go over the root cause of "Woofing" once more. I keep this paragraph handy. I seem to go over this often.

The woofing you are experiencing is caused by one (or possibly both) of the blades balancing toward the trailing edge of the blades too far.

When you take a wing, be it an airplane or helicopter blade, and balance it toward the trailing edge of the airfoil, it will tend to "balloon" as it reaches some critical speed. This is easily demonstrated on a 3D plank balanced toward the trailing edge.

The woofing condition occurs on a heli with such blades when they reach that critical speed and you pass the pitch through or around zero pitch. One or both blades balloon and when they do, the control arm anchored on the back side of the grip and forward of the center of the mast (this is called negative delta) causes the pitch to increase as the blade flies upward thereby exaggerating the condition. The blade continues it's track upward until it "bounces" off of the dampers and heads downward to then do the same thing only negative this time. All this time the opposite blade is heading the opposite direction. The woofing instantly becomes an oscillation of blades flying +/- to -/+ .

If you use leading edge blade grip control by flipping the grips, as the blade balloons upward, the stationary control link now on the front of the grip (this is called positive delta) tends to decrease the pitch of the blade thus dampening the effect.

So to sum it up: Woofing is an oscillation caused by reward chord-wise balanced blades reaching their critical ballooning speed and is amplified by the negative delta design of the raptor head.

The bottom line is that the Mavvrik blades are the root cause of the woofing you experienced. The CONTRIBUTING factor that triggered them into the woof was the excessively high head speed caused by your engine leaning out.

So here are your choices:
1. Change to blades such as SABs that are not aggressive on their chord-wise balancing.

2. Switch to positive delta - do the grip-flip modification to the rappy.

3. Keep your head speed low so you never hit the critical speed that triggers the condition.

It will help to upgrade your V1 head to a V2 head. If you find you need new thrust bearings you may as well make the jump since thy are most of the expense of the upgrade. The V2 head is a bit less prone to the condition and flys longer before it gets slop that tends to contribute to this condition.

You can either take some advice from some of us "old pros" (not really sure that I consider myself one) or you can be true to your signature and continue to learn the hard way.

Best of luck on your search for an answer.

Mark C.

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09-16-2007 01:55 AM  10 years agoPost 6
garaptor

rrApprentice

Atlanta,Ga,usa

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Thanks much Mark and Baracuda and everyone. I was mistaken about the popping coming from the blade itself but rather its coming form the blade/blade holder. I understand(have been told many times) that Mavriks are crap but I fly on a budget and, as I said, have never had a problem(loops,full fwd,stalls,wind,no wind,autorotations,overspeed,underspeed,lean,rich,etc)in about 250 flights untill now.The woof absolutly did occur around and thru zero pitch.Something has changed,however. I will fly some woodies to see if my Mavricks have somehow failed. 2)If the woodies still woof Ill change to positive delta.3) Trying to restrict it to a low rpm is not an option. I do know this, Im thru with carbon Mavricks.Thanks, any more advice is appreciated.

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09-16-2007 11:07 PM  10 years agoPost 7
garaptor

rrApprentice

Atlanta,Ga,usa

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This is what I found. According to Michael Prewitt, to check chordwise cg,hang the blade loose from a blade bolt. The blade should hang straight down. Mavriks do not.I ordered some Sab's as suggested. Found new feathering shaft bent(again).Found dampners too tight even greased. (Ordered new ones).Found slight loose bearings in blade grips.Found slight amount of wear(slop) in swash plate.The worst thing I found was the screw in the splined elevator control arm on the servo side was loose at least 1.5 turns allowing a huge amount of slop on the control arm links.I think this in itself would be the biggest contributer to the ocillation besides the blades.Thanks guys. It seems I have a slew of defects that all added up on me. Visit here for tracking troubleshooting http://www.raptortechnique.com/ts-blade-track.htm

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09-16-2007 11:19 PM  10 years agoPost 8
A. Bundy

rrElite Veteran

Aurora,IL. 30W/SW of Chicago

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That loose ball was probably it.I see that a lot.

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09-17-2007 02:50 AM  10 years agoPost 9
Mark C

rrKey Veteran

Houston, TX - USA

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That is excellent garaptor! You are gonna fall in love with the SABs. And you need to get yourself up to Mt. Plesant next weekend for what looks to be a HUGE funfly loaded with pro flyers and thank Michael in person. That is his home field.

I claim that if everyone that Michael ever helped would take him out to dinner that guy would not have to buy groceries for the next 5 years.

Good luck on the fix!

Mark C.

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09-17-2007 03:24 AM  10 years agoPost 10
Girard Ibanez

rrVeteran

Tucson, Arizona (formally from Guam)

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Try changing your collective servo.

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