Rear Pilon Loose. Nut size? 06' 24Ve

[anhaney]

Good informaiton

Guys, I asked my brother in law a question about the force on our pylons. He holds a Doctorates Degree in Physics and teaches at a University in Missouri.

This was his reply to my question My question is at the end of his reply. I just copied the email that he sent back a reply on to me.

This is a lot more complex than it seems. The force on the rope is a result of the drag force between the tube of kids and the water. Imagine the tube at rest in the water. The bottom of the tube sits slightly below the surface. As the tube moves forward in the water, it must push the water in front of the tube out of the way. In effect, it is accelerating the water to the speed of the tube.

Assuming the tube is about 6 feet wide and 3 feet deep and weighs 350 lbs, the tube would sit about 3 inches deep in the water. If this condition remains while it is moving, the tension in the rope could be about 22 tons (44,000 lbs). However, I would expect that as the tube is moving the tension would pull the tube slightly out of the water to lessen this force. To completely pull the tube out of the water, would require the vertical component of the tension be equal to the weight of the tube. For a 75' rope attached about 4' above the water surface, this force would be 6500 lbs. The minimum tension that I would expect is a balance between these two possibilities. In this case, I would calculate the minimum tension to be about 2600 lbs.

In this calculation I assumed a uniform distribution in the tube. However, if I were in one half of the tube and my 30lbs daughter was in the other, the drag force on my side would be much greater than on hers, causing the tube to flip. Also, this assumes the water is smooth so that the tube is just skimming the top, the force would be greater if the water is choppy or the tube is bouncing around in the wake.

I really can't give you a better guess than this.

Michael


Mike, I am trying to figure out the force put on my ski pylon on my boat, If I have a 75' rope and I am going 25 MPH on the water pulling a tube of kids that weights 350lbs. What would the force be on my pylon where the rope attaches to the boat?

[Jason B]

2600#s isn't too far from 300#s...you'll be fine



All this debate is making me glad my boat is a 2002. My steel pylon cage could drag the Titanic from it's depths.

[dogbert]

I put up thread regarding how many skiers a 2007 20V could tow and after voicing my opinion I was told that I was being ridiculous.

I was worried that you'd shoot someone

Seriously, we were really just trying to reassure you that you'd made a good choice and suggested some alternatives that might work for you.

[talltigeguy]

[QUOTE=tessa;115603]As good as a Tige is built does nothing to alleviate my concern over what seems to be an under engineered pylon. I will not tow from the lift hooks because the harness and rope will snag on the platform. QUOTE]

I used to use a harness and had to watch it to make sure when starting it did not catch between the platform and the boat. It was not a big deal, but another issue to deal with along with watching to make sure the kids were seated and that a jetski wasn't zooming in front of me and the millions of other things you need to think of when boating. So that is one of the reasons I just went for my pylon, but certainly not a big deal.

Chpthrill - Part of me wants to see the full size pic that your avatar came from, and part of me is afraid.

My tube recommended a 4,000 pound break strength rope...I wonder why?

[talltigeguy]

I would emphasize to Tessa that despite all of the grumbling, no one has EVER posted a pic on this site of a damaged pylon. And I think we would find out about it if it has happened more than very rarely. I am the only one I know of who has even heard of it happening firsthand.

[dogbert]

I found a 1 inch gel coat crack next to my pylon a month ago. It is just a tiny gel coat crack, not anything structural, but nonetheless, I am concerned about it. I have never tightened the bolt, but to pull hard on it with my bare hands, it does not move. I will tighten it and see what I get.

I hope no one has called anyone ridiculous on the site. We try to remain civil for the most part, and I think I would still return to the site often, despite one time someone was having PMS. It is winter and we all are going through withdrawals a bit. So please forgive.

Ok, can I call you silly instead? You see, that's just a wrinkle, if you're worried about it, try some plastic surgery. Do they make Botox for gelcoat?

Seriously, tho. I understand your concern. While my pylon is like Moki's, completely overengineered to the point where I could parasail....I probably won't.

I do have some hairline gelcoat cracks in the same part of my boat in about the same spot as the pylon, but my pylon is attached to my engine mounts so I'm sure it's not caused by the pylon itself. It may have more to do with the fact that on a V-Drive, this area is essentially a cross-beam that may be under stress because there's always some amount of flex in an open-bow boat such as this.

It's hard to say without a structural engineer weighing in on the issue along with someone familiar with the hull design of our Tiges.

In the mean time, if you're overly worried about it, use the lift rings. If you don't want to do that, use the pylon and let us know how it works out. Given anhaney's analysis of the force a tube can put when submerged and the fact that we've had a rope snap due to this force, I'm attaching my tubes to the lift rings, which is one of the strongest points on my boat besides the bow eye.

[dogbert]

I used to use a harness and had to watch it to make sure when starting it did not catch between the platform and the boat. It was not a big deal, but another issue to deal with along with watching to make sure the kids were seated and that a jetski wasn't zooming in front of me and the millions of other things you need to think of when boating. So that is one of the reasons I just went for my pylon, but certainly not a big deal.

My tube recommended a 4,000 pound break strength rope...I wonder why?

For what it's worth, the pylon doesn't exactly prevent the rope catching on the platform.

As for the rope strength...now imagine breaking this. I was pretty torqued at my kids because they actually submarined the front of the tube on purpose as I began to accelerate. The broken end of the rope came flying into the cockpit. Had it been attached to the lift rings, it would have hit the transom. Luckily, no one got hurt.

[tarheeler]

if you look closely at the pylon mount you will see some penske composite inlaid into the fiberglass that goes from one side to the other.

[zad0030]

Is it possible someone screwed up and it should be 3000 lbs?

In all seriousness I, personally, would be more concerned about my gas gauge not functioning correctly then my pylon busting out of my new boat.

[Jason B]

I'm boggled why somebody from Tige hasn't chimed in here to clear up some confusion???????????

[chpthril]

Chpthrill - Part of me wants to see the full size pic that your avatar came from, and part of me is afraid.

If you're brave enough Tall

http://www.tigeowners.com/forum/show...0&postcount=25

[anhaney]

I know when I first bought my boat I pulled tubes from the pylon. Then I read the labels and the book that came with the boat after TIGE' sent it to me since my saleing dealer did not give me one. After that I started to pull from the handle. Being that my kids love to tube I have considered adding 6"X6" aluminum plates in place of the 2" stainless washers on all four mounting bolts they have holding the handle on now. The transom on the boat is 1 1/2 to 2" thick. and being that the handle runs such a long distance across the back of the transom I feel that there is plenty of strength there for a tube. Of course the driver pulling the tube makes a big difference.

Even when I did pull from the pylon I never had an issue.

[shake-n-bake]

I must be the tard with the bad luck, my pylon cracked the gel coat and a piece of it cracked off and you can see some of the fiberglass. The sticker on the pylon only says that I am responsible to keep it tight, but it doesn't say anything about pulling tubes or more than one skiier. I put a piece of plate steel about 3" wide and about 6" long on the bottom and top of where the pylon bolt goes through. I think that has strengthened it a little bit.

[chpthril]

I must be the tard with the bad luck, my pylon cracked the gel coat and a piece of it cracked off and you can see some of the fiberglass. The sticker on the pylon only says that I am responsible to keep it tight, but it doesn't say anything about pulling tubes or more than one skiier. I put a piece of plate steel about 3" wide and about 6" long on the bottom and top of where the pylon bolt goes through. I think that has strengthened it a little bit.

Can I ask, Had you ever checked/tightened the pylon before the crack/chip.

[talltigeguy]

For what it's worth, the pylon doesn't exactly prevent the rope catching on the platform.

With the rope attached to the lifting rings, whenever there is slack in the rope, it can sink down between the boat and the swim platform. So it happens all the time. With the rope attached to the pylon, it is immensely more difficult to make that happen, albeit possible.

I must be the tard with the bad luck, my pylon cracked the gel coat and a piece of it cracked off and you can see some of the fiberglass. The sticker on the pylon only says that I am responsible to keep it tight, but it doesn't say anything about pulling tubes or more than one skiier. I put a piece of plate steel about 3" wide and about 6" long on the bottom and top of where the pylon bolt goes through. I think that has strengthened it a little bit.

Do you have a picture? It would be the first documentation of this occurring on this discussion board.