Adding a tow attachment, pylon or tower. recommendations?

[tmh]

We will be using our 19' bowrider I/O for several watersports including skiing (NOT fancy stuff, just kids and out-of-shape adults), tubing and most importantly, Parasailing. Currently, the only spot to connect to is the two "U shaped" bolts midway down the Transom. Not sure what they are called, but was told in another thread they are plenty strong. The problem is, they are low and cause rope drag issues. This is especially a problem with parasailing as the rope really should be tight and out of the water at takeoff.

I've looked at various sites at pylons, towers and just simple ski rope fittings. I'd like a recommendation from anyone who knows this stuff. My preference would be something above the back of the boat, either attached on both sides with a harness or a single connection in the middle. I THINK the harness allows for better boat control when parasailing. I'd rather not spend the $1,000 plus I see the wakeboard towers going for. This will be a winter upgrade project so i'm gathering info now prior to purchase.

Just FYI, parasailing pulls about as hard as a fairly heavy waterskiier. However, it is critical that it withstand more pull because a "break" might severly injure or kill a parasailer. I think about 3-4,000 lbs is what my parasail rope is rated at, so that is a good guide.

Also, how would I best attach what you recommend to a fiberglass hull boat (1985)?

 

[deejaycee_2000]

Re: Adding a tow attachment, pylon or tower. recommendations?

I don't think a wakeboarding tower is to great for parasailing, just get a nice ski bar in the middle at the back, but for parasailing it needs to be extra reinforced ......

 

[tashasdaddy]

Re: Adding a tow attachment, pylon or tower. recommendations?

i personally don't like any attachment that is higher than the transom. even skiing a rope break can badly injure a passenger, as the rope usually snaps straight back toward the attachment point. you can attack a tow ring to the center of your transom above the outdrive.

 

[tmh]

Re: Adding a tow attachment, pylon or tower. recommendations?

t-daddy, good point on the rope breaking issue. Parasailing rope is heavy, 300 ft and would come down on the boat if it breaks, I assume.

How would you rattach the tow ring? Would it be from the top or out the back? Also, any thoughts on two tow rings in either side then using a ski tow bridle so the pull is distributed to two points? I have a high strength bridle that came with my parasail.

Can I attach the tow ring to the hull if I re-inforce with plywood and bolt through from the top?

Thanks

 

[tashasdaddy]

Re: Adding a tow attachment, pylon or tower. recommendations?

tow rings are usually attached to the rear side of the stearn above the outdrive, thru bolted and reinforced with plywood, if you are going to parasail, i would uses as largest piece you can fit on the inside, and maybe a steel plate , hull, plywood, steel plate. look in the iboats marine store to get an idea or tow rings.

 

[sport15]

Re: Adding a tow attachment, pylon or tower. recommendations?

In a previous life I was at Marine Hydraulic Engineering, the manufacturer of Hydroslave products to include parasail pumps, winches and controls.. That being the intro, we NEVER spec’ed out complete systems (power controls and towers etc. ) due to the liability. The whole “serious injury or death” thing is a real downer for the underwriters. So, what ever you do, if you do it yourself following the advice of some one on the forum you are setting yourself up for a litigation nightmare god forbid someone gets hurt.
Enough with the disclaimer..
The reason that you see parasail boats with attach points forward of the outdrive/rudder post/outboard is so they can steer the sail. This may be pointing out the obvious.. If you elect to use the transom eyes you are going to be severely limited in your maneuverability and will not have ultimate control over the sail and can end up at the mercy of the wind that just came up and end up getting dragged all over the bay.. With the sail mounted to hard points do you have a quick release in the event of trouble? Sorry to sound like and old worry wart but the potential for mischief seems really high. You can call John at Marine Hydraulic Engineering (web hydroslave.com) and ask him how to contact the folks at Premium Para Sail for professional guidance...

 

[tmh]

Re: Adding a tow attachment, pylon or tower. recommendations?

Well, I know that the "pros" use a big boat with a huge tower and winch to parasail. They send folks up right from the boat and pull them in to land on the boat. This is very different from what we do. We've done it before, just not with my boat. The boat we used had super re-inforced rear dock cleats (owner had it done this way for tubing) which we attached to.

I understand the liability and all, not done as a business, just with friends and family. However, I take all precautions I can which ver much minimizes the risk 9can't eliminate it completely). This is why I'm learning what folks think is best before setting up my boat.

As I said, the pull from the parasail is not what one might expect but I want a HUGE factor of safety built into the ski tow attachment I use. Tht's why I'm leaning to two attachment points rather than a pylon. The pylon would be great for getting the rope up and out of the water but seems kind of unstable to me.

We may wind up fabricating something with strong SS piping that sticks up a foot or so from the transom and is bolted n so as to never have a chance of coing loose unless the entire back end of the boat falls off! I have all winter to come up with something.

 

[sport15]

Re: Adding a tow attachment, pylon or tower. recommendations?

With the transom mount can you still steer ok? FYI the "pull" strength of the "smaller" ski tow post is from the guys that lead either forward or aft, depending on the installation. If you took some reasonable sized pipe from the top of the post and lead it to the stern you might be impressed how strong it was. The flying part sounds pretty cool, I just have this Funniest Home Vidios vision playing in my head of the guy that was dragged off a ladder then on his belly accross the beach into the water. It still cracks me up but it must have really sucked to be him!

Dave

 

[tmh]

Re: Adding a tow attachment, pylon or tower. recommendations?

Seaman, thanks for the help, but I'm not following what you're saying (I'm a bit slow of mind today, I guess). Are you referring to a ski pylon post supported bt the pipe? That may be one way to go. I guess. At www.bigairpylons.com they have a pylon system that uses cords to support the pole. Great reviews from users anywhere I looked.

As for the MANY parasailing blooper videos out tere....yeah, that's what I was afraid of also and why I looked into the sport very carefully before dropping $1400 for the equipment. It boils down to this: It a quite safe IF IF IF one only "flies" under optimum conditions. Winds under 15 mph and a large beach take-off area with NO obstacles around - no poles, rocks, wires, buildings, or people. Watch those videos and you'll see reckless operators following none of these rules!

Most accidents orrur when people start to bend the safety rules in order to "get in some flights". It's a bummer to get out to the lake and have someone make the "call" that the wind isn't just right and we won't be parasailing that day! BUT if you do follow those rules, it's not nearly as big a deal as you'd think. Very easy, actually.....and much more fun that commercial parasailing because you do it yourself!

It's also an all-day affair because each ride may only take 5-10 min. but the set-up, chute retrival, safety checks EACH launch, etc. take forever! We've done it with a large group and the kids need other activities to do while they wait for their turns. We also learned a ton from the 40+ flights we've launched, and one of those things is to get the 300 ft rope taut (sp?) and out of the water before the boat takes off. That's why I'm pretty particular about how my set-up winds up.

 

[sport15]

Re: Adding a tow attachment, pylon or tower. recommendations?

Look around at small comercial towing bits and you'll see what I am reffering to. The basic premise can be demo'ed by pushing on your keyboard with one hand, your index and middle fingers spread about two inches apart. Put a pencil vertically in between with the eraser on the desk top. This forms a three sided triangle (way strong). The keyboard represents the stern of the boat... If the distance from the top of the post to the braces going to the stern (guys) is kept short the majority of the pulling load is transfered back to the stern. The base plate that the post would sit on can be as small/big as you feel comfortable with, with multiple fasteners to spread out the load. This load would end up being mostly a shear load in the forward direction. The post only need to be tall enough to get the line over the obstructions in the stern. If the post is to tall you begin to have problems with the increased rolling moment that the sail will put on the boat.. How you solve the snap back problem in case of a line failure I haven't given thought to yet.

What acts as a hold back on the beach end when tensioning the bridle?

Dave

 

[tmh]

Re: Adding a tow attachment, pylon or tower. recommendations?

What acts as a hold back on the beach end when tensioning the bridle?
Dave

ME!!!!! Well, actually, anyone who gets the job of being the "beach captain" which is usually my job. When the rider(s) is ready, the beach captain signals the boat driver/spotter to take out the slack. he holds the rope with all his mite (or gets another person to help with this) while the slack is taken out. There are "tricks" to get this done a bit easier like keeping the rope fairly straight the entire time and shaking the rope to make waves as the boat pulls. As we fund out, 300 ft of wet, heavy rope doesn't pull tight so easily, especially when the water has a cross-current making it bow sideways!

Once the rope is tight and the chute is helped to fill with wind, the signal is given for the boat to take off. The rider walks/runs a bit in a "tug of war" with the boat, then 10-20 feet later, the rider is up in the air!

Anyways, back to your idea - yeah, now i get it. That would work fine, however, I do want to consider rope breakage also and where that might land the flying rope even though the rope we use is VERY unlikely to break as it is not your typical tow rope.

Thanks again.

 

[sport15]

Re: Adding a tow attachment, pylon or tower. recommendations?

A few more questions...

What type of I/O do you have, what’s the gear reduction and what size wheel is it swinging? I am interested in the numbers to get a swag on the thrust you can make...

You said that you can hold back the boat while the bridle goes taught and that the line has a rating of 3-4K lbs. Is the line rating the parting strength or the Safe Working Load (SWL)?

If you can't make enough thrust to part the line off (unless you are doing something really silly) there is the possibility that it may not be a really huge issue no matter where the line is tied off.

 

[tmh]

Re: Adding a tow attachment, pylon or tower. recommendations?

OK, it's a 1985 19' BR with a Mercruiser 200hp 5.0L 305 2bbl Alpha 1 . Right now it has a 3 blade 14? " 19 P. I THINK it's 1.62:1 ratio - close to that anyhow.

I'm trying a Piranha 4 blade 14 18P soon. I'm pretty sure the 4-blade will be better for water sports and likely better in general. Also adding Smart Tabs soon.

Not sure which type of rating it is for the line. Also, what does "part the line off" mean? Certainly, I don't hold the boat back under anything but minimal power before takeoff. Just enough to straighten the line as best we can.

 

[sport15]

Re: Adding a tow attachment, pylon or tower. recommendations?

Sorry, around the waterfront up here it means to break the line...

You don't get all 200 ponies at the wheel when you're doing the hole shot and the wheel will slip alot. The numbers you supplied, when put into the trust formula listed below produce a swag on the trust at about 2500lbs at low speed and high power setting. I am making no assumtions for the losses and have guessed at what the HP would be on a hole shot.
I will try and attach the work sheet. You just change the numbers in the yellow boxes.

From "The Propeller Handbook" by Dave Gerr (International Marine Publishing Camden, ME)

Formula is T=(326 x shp x e)/Va
T= thrust in pounds
Shp =shaft horse power at the propeller
e= Propeller efficiency (For your wheel assume about 70% and this is high.. )
Va= speed of the water at the propeller in kts (not boat speed)

 

[sport15]

Re: Adding a tow attachment, pylon or tower. recommendations?

DON'T OPEN THRUST TEST.XLS!!! I don't think I attached it correctly and something causes my browser to close when I try and open it. An "Unrecognizable format" error shows up.

My sincerest apologies. Dave

JB, How can I unattach it?