Forward sweeping tower owners please check your lock bolts

[swatski]

As some of you may have seen during this years Bimini Fling several 15+ AR owners had issues with their tower bolts backing out and or striping. When I put my boat In dry stack back in May I securely tightened mine but this issue made me think to check them today and glad I did. Just from regular use they had backed out almost a full 1 and 1/2 turn during this time. This will now be on my pre departure check list every time to put my hand on the bolts and tighten them if necessary as last thing I want is them to back out and the tower to fall.

Sorry guys, I am still catching up - just got back.

Here are my quick thoughts:

Yamaha should be filing the CG4917 forms, promptly.

My guess is they (or XTP) tested those towers for dynamic loads for towing (behind the boat) and static loads hanging off of a tower. I feel those towers are adequate (robust) for towing and wakesports. And I'm sure you can have two 300lbs guys doing pull-ups off of those all day long. But that is not the issue (those towers seem more than adequate for towing but not for safely passing in rough water).

The issue is harmonic resonance and hull flex when pounding waves.

A pin installed across (or perpendicular to) a base would be one solution, as it is done in LS/X models.

In this context, the sheeting material used on the sides of the AR tower leg base (encompassing/sliding over the solid aluminum base - bolted to the hull cap) is way too thin (IMO) to support the structure with a pin-through. Would need to be redesigned or modified with weld-on plates etc.



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[swatski]

My female base threads are stripped on both sides:


Bolt (knob) threads look better:


Here is the other one:



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[jcyamaharider]

I have a big problem with a stainless steel bolt into aluminum threads.
Dissimilar metals like these in a marine environment dont mix well.
They should have had a stainless nut in the housing

Stainless on stainless hardware can galled up. It sucks and you cannot get it apart without breaking. If I don't use anti-seize or Teflon paste they will do it in an instant.

 

[Neutron]

I would rather all stainless with anti seize than brittle aluminum female threads anyday. Way too easy to crossthread or strip..... as we have seen

 

[jcyamaharider]

It isn't the type of material but the quality of material. You can do a good 7075 aluminum and get it hard coat anodized and it would be stronger then the stainless threads. Why didn't they.......cost. Everything is made cheaper these days.

 

[swatski]

As some of you may have seen during this years Bimini Fling several 15+ AR owners had issues with their tower bolts backing out and or striping. When I put my boat In dry stack back in May I securely tightened mine but this issue made me think to check them today and glad I did. Just from regular use they had backed out almost a full 1 and 1/2 turn during this time. This will now be on my pre departure check list every time to put my hand on the bolts and tighten them if necessary as last thing I want is them to back out and the tower to fall.

A quick update:
We delivered the boat with all the parts to our dealer. We are currently waiting for Yamaha to perform their diagnostics. Their communication with us could be better at this point. But, I guess it is still early.

I believe this is an important issue for any owner of a 2015+ AR240 to follow up. I'm not a panicky type, but this is serious business and someone could die.


Also:
Regarding some of the questions we receive as far as the (possible) failure mode - while we wait for any official findings (Yamaha and our own) - it looks to be simply a pull-out by shearing of the female/internal threads (tapped inside the aluminum base).

I may at some point start a new thread here to discuss the potential redesign, as the design used for those AR towers is simply puzzling! For example, even though it is critical that things are tightened properly (the chance of pullout is way higher if the fit is sloppy) I could not find a torque spec so you don't damage the threads by over tightening which is always really easy with small stuff in aluminum, especially if the threads aren't cut really nicely. If they really worried about the tapped hole letting loose they could at least install a helicoil or something. (Helicoils and other types of thread inserts in aluminum through holes are common in aerospace, particularly where assemblies will be disassembled for maintenance.)

I also don’t believe they have thought much of forward forces associated with repetitive pounding in rough water. Which is fine if the boat is used exclusively for water sports. But not fine if you use the boat like I do, riding in chop on the big river (Mississippi) and in the ocean.

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[zipper]

A quick update:
We delivered the boat with all the parts to our dealer. We are currently waiting for Yamaha to perform their diagnostics. Their communication with us could be better at this point. But, I guess it is still early.

I also don’t believe they have thought much of forward forces associated with repetitive pounding in rough water. Which is fine if the boat is used exclusively for water sports. But not fine if you use the boat like I do, riding in chop on the big river (Mississippi) and in the ocean.
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I agree that those towers are designed to withstand forces from the aft, towing somebody, and by the looks of yours not designed strong enough to take forces from the other direction, those induced by pounding waves. I was going to post about this when it happened but figured it was too fresh, and I was not there. Those threads should not have sheared. They were either not deep enough or the bolt did not engage enough or the wrong dia. and pitch, all the above? A heli coil insert would certainly fix your tower. But I hope Yamaha realizes they need to do more than that.

 

[swatski]

To respond to some of the questions and comments on "tightening the lock-knob issue", Yamaha really does not give many specifics... Basically, this is what they tell you to do:


Here is the entirety of the 2015+ AR240 tower operation guidelines and warnings:



I have not used any tools and have hand tightened the lock knobs. Obviously, that did not work very well for me. But I am not endorsing using any tools. I believe the risk of stripping those coarse aluminum threads is just too great.
Some of the suggestions I received are kind of cool/entertaining, and may be useful - my favorite is a "towel wrench" method. But I'm not endorsing anything.
This tower needs a locking pin kit, IMO.


And for now it should come with a warning: "do not use for cruising in rough waters".


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[haknslash]

Yesterday I was out in the gulf and the winds picked up as I was making my way back in. As I approached the jetties the water conditions went to shit and it became a washing machine with waves seeming to come from every direction. Some waves I had no choice but to launch off them or take a shot over the bow if I dropped the throttle. The whole time I kept thinking about my tower bolts and the feeling of the tower slamming down on me. I wanted to bust out the GoPro but I was too busy sawing at the wheel to keep the boat from slamming into a roller. Once I got back to the dock I checked the tower bolts and they were snug and unscrewed fine despite lots of pounding. Granted this wasn't 6' waves but enough to launch the boat and pound the boat pretty good. I would love a locking pin and whatever is needed for enough support.

 

[eticket]

After reading about this problem I am not so unhappy anymore with the pre 2017 212x tower design...it is hard to collapse but it certainly missing the auto-collapse feature!

 

[swatski]

Yesterday I was out in the gulf and the winds picked up as I was making my way back in. As I approached the jetties the water conditions went to shit and it became a washing machine with waves seeming to come from every direction. Some waves I had no choice but to launch off them or take a shot over the bow if I dropped the throttles. The whole time I kept thinking about my tower bolts and the feeling of the tower slamming down on me. I wanted to bust out the GoPro but I was too busy sawing at the wheel to keep the boat from slamming into a roller. Once I got back to the dock I checked the tower bolts and they were snug and unscrewed fine despite lots of pounding. Granted this wasn't 6' waves but enough to launch the boat and pound the boat pretty good. I would love a locking pin and whatever is needed for enough support.

I know... it sucks some fun out of boating, doesn't it?...

Also makes you wonder: what does "check periodically" the lock knobs mean, exactly? Does that involve periodic checks while cruising?
Not always practical, or safe. Or even possible.

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[Neutron]

I think we are getting ahead of the issue. So far from this community we have one case out of how many ARs? I am not saying at all that this is user error on @swatski but this could be a defect on his mount. Lets be vigilant and check our tower screws as aregular pre launch item and wait for either Yamaha to give its input or (hopefully not) more failures.
I drive my boat and ski like i stole it when im alone and have jumped some serious waves. So lets hope its an isolated incident.

 

[swatski]

I think we are getting ahead of the issue. So far from this community we have one case out of how many ARs? I am not saying at all that this is user error on @swatski but this could be a defect on his mount. Lets be vigilant and check our tower screws as aregular pre launch item and wait for either Yamaha to give its input or (hopefully not) more failures.
I drive my boat and ski like i stole it when im alone and have jumped some serious waves. So lets hope its an isolated incident.

I certainly hope what happened to me is an isolated incident and hope it does not happen to anyone else with the AR tower.
I have also said the AR tower seems adequate for towing/water sports/general lake use.

Unfortunately, we already know of several cases where those same lock knobs have loosened up partially and in one case failed completely (on one side). So, if one considered this a sequence of causatively linked events, what would be the next?
(yes, the tower may collapse and hit you and/or a passenger on the head)


EDIT:

Here is an excerpt from a cocktail party conversation with a young mechanical engineer (my son's buddy):
"If I'm looking at it correctly the pin is definitely better because it looks like the load path for both has the fastener in shear, which pins are better at taking because they are a solid cylinder instead of having a bunch of sharp cutouts"

Does Yamaha know what they are doing?
Well, all 2015+ model big forward sweeping towers - LS/E/X - all have the pin kit. Not a bolt/knob.

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[swatski]

The whole time I kept thinking about my tower bolts and the feeling of the tower slamming down on me.

I think @haknslash kind of nailed that, as far as I'm concerned.

Do I want to run around and worry about a life threatening failure?
(One of my daughters could had been crippled or dead already - thank God her chair broke (!) and she was moved to the back of the boat just before the tower failed; I got pretty battered myself).


Regardless, I did not buy a new boat to ride it to the tune of:

"Did I tighten my knobs?"

"No, no, did I really tighten the knobs?"

"Is it time to re-tighten?"

"Wait, is it tight enough now - temperature just dropped and it got really cold?"

"Hope I don't get caught in this big storm ahead - can I drive the boat AND re-tighten the knobs at the same time?"

“Oh no, it suddenly got rough out here, hope the tower doesn’t fall on me and my crew”

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[eticket]

@swatski, the aluminum on the sides of the tower where it meets the base looks thin but, but no too thin. Just from eye balling your picture maybe 0.100" to 0.125". Perhaps a thru bolt/pin solution can work in combination with the existing bolt (once repaired and ideally with a helicoil) to share the load or at a minimum provide a back up load path. You could even put in two pins perhaps a few inches apart to share the load. The tower base fixed to the boat appears high enough to provide good edge margin for the holes. That could be a "do it yourself" solution, although it would require some very careful drilling if done on the boat. Of course Yamaha needs to address this and not leave it to customers to reinforce their towers to be safe, but as an interim fix it could provide some peace of mind that the tower is not going to break loose on you in rough water.

 

[swatski]

@swatski, the aluminum on the sides of the tower where it meets the base looks thin but, but no too thin. Just from eye balling your picture maybe 0.100" to 0.125". Perhaps a thru bolt/pin solution can work in combination with the existing bolt (once repaired and ideally with a helicoil) to share the load or at a minimum provide a back up load path. You could even put in two pins perhaps a few inches apart to share the load. The tower base fixed to the boat appears high enough to provide good edge margin for the holes. That could be a "do it yourself" solution, although it would require some very careful drilling if done on the boat. Of course Yamaha needs to address this and not leave it to customers to reinforce their towers to be safe, but as an interim fix it could provide some peace of mind that the tower is not going to break loose on you in rough water.

I agree.

I do think this particular tower has been very well designed - to support rearward loads. In that capacity it seems adequate. However, I believe those towers were not designed and rigorously tested with hard/repetitive/taxing forward forces in mind, especially such that involve harmonic resonance (not just static weight, or pulling loads from behind).

Had I known it beforehand, I would had bought a different boat/tower combo. The least that Yamaha can do is to provide adequate warnings of what the towers are and are not designed to perform.

Personally I think my tower should be able to survive any force in any direction that the hull can.

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[swatski]

Had an interesting conversation with another member here (a retired Boeing engineer). He is interested in this situation as he is considering an upgrade. His point was - that the hull (or hull/deck join) will usually be the weak point, under the circumstances. But the hull in my boat showed no signs of cracks.
I’m assuming Yamaha is looking at that in my boat, but I did not see any damage in the hull/cap, no hairline cracks in gelcoat or anything around the mounts.

So, maybe I did get a lemon and my boat had a defective mount(s), IDK.

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[Cobra Jet Steering LLC]

Having perused this thread without reading every word and not being familiar with the construction I keep thinking that an oversize insert made from stainless may be a way to reinforce the thread stripping issue if there is room for it. This sort of reminds me of the days of the clean out plugs blasting out the rear hatch and just missing crashing down on the heads of the occupants of the boat

 

[swatski]

Having perused this thread without reading every word and not being familiar with the construction I keep thinking that an oversize insert made from stainless may be a way to reinforce the thread stripping issue if there is room for it. This sort of reminds me of the days of the clean out plugs blasting out the rear hatch and just missing crashing down on the heads of the occupants of the boat

I totally agree and indeed has already been brought up. I think that is a REALLY good idea.

If they really worried about the tapped hole letting loose they could at least install a helicoil or something. (Helicoils and other types of thread inserts in aluminum through holes are common in aerospace, particularly where assemblies will be disassembled for maintenance.)

It's the least they could do.

Well, maybe also add a warning: a falling tower can hurt your rectum or vagina. In a big orange decal.

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[Cobra Jet Steering LLC]

So to build on that insert idea if the insert were long enough to protrude past the fiberglass material a large threaded piece could then be screwed on to it from underneath and further reinforce it.
If that is not practical perhaps a special nut and oversized washer that overlaps the threaded insert but goes on the center bolt if the bolt is long enough and the washer goes past the diameter of the insert to further back up the design