Power Loading issue

[haulnazz15]

Re: Power Loading issue

May not be the weak link, but I can put my spare winch strap on in about 5 minutes. It's much more difficult (and expensive) to repair the boat. It's repetitive strain on the bow eye that can (and does) eventually weaken the pocket where the backing plate sits. I would never recommend "manhandling" the boat on the trailer with the bow eye....but of course to each his own.

I'm not advising that he winch 25' of boat onto the trailer. I am talking about less than 2ft, it's not a bunch of strain on anything. When you push a 4K lbs car on the road, it doesn't take 4K lbs of force, otherwise you'd never be able to move it. The same goes for pulling the boat across the bunks, it doesn't take even half of the weight of the boat to pull it across the bunks in order to overcome the friction of the bunks and the fiberglass.

Whichever method he uses, backing the trailer in further after initial winch or winching it all at once, will be fine.

Edit: Did some rough math. Assuming the full 7K lbs of boat has to be pulled (ignores any buoyancy from boat in the water) and a 12-degree incline with a friction coefficient of 0.2 (fiberglass over wood, so probably overstated), it comes up with 2,800 lbs of "weight" to move the boat. With a cable or HD winch strap, he would be well within the specs on his equipment with a 2-spd winch.

 

[JimS123]

Re: Power Loading issue

I'm not advising that he winch 25' of boat onto the trailer. I am talking about less than 2ft, it's not a bunch of strain on anything. When you push a 4K lbs car on the road, it doesn't take 4K lbs of force, otherwise you'd never be able to move it. The same goes for pulling the boat across the bunks, it doesn't take even half of the weight of the boat to pull it across the bunks in order to overcome the friction of the bunks and the fiberglass.

Whichever method he uses, backing the trailer in further after initial winch or winching it all at once, will be fine.

Edit: Did some rough math. Assuming the full 7K lbs of boat has to be pulled (ignores any buoyancy from boat in the water) and a 12-degree incline with a friction coefficient of 0.2 (fiberglass over wood, so probably overstated), it comes up with 2,800 lbs of "weight" to move the boat. With a cable or HD winch strap, he would be well within the specs on his equipment with a 2-spd winch.

Yeah right! There's always one in the crowd that has to cornfuse things with real Engineering calculations.....LOL.



(PS - good job)

 

[haulnazz15]

Re: Power Loading issue

Yeah right! There's always one in the crowd that has to cornfuse things with real Engineering calculations.....LOL.



(PS - good job)

Well don't let math/physics get in the way of a good debate! :happy:

 

[JASinIL2006]

Re: Power Loading issue

And silicone spray on bunks will help... it really reduces the friction of the boat sliding on the bunks.

 

[Maclin]

Re: Power Loading issue

Did some rough math. Assuming the full 7K lbs of boat has to be pulled (ignores any buoyancy from boat in the water) and a 12-degree incline with a friction coefficient of 0.2 (fiberglass over wood, so probably overstated), it comes up with 2,800 lbs of "weight" to move the boat. With a cable or HD winch strap, he would be well within the specs on his equipment with a 2-spd winch.

Ok, who invited Archimedes!

 

[Stamey]

Re: Power Loading issue

You could also get bunk slicks that cover the entire bunk surface, instead of carpet. That's what I did on mine. I have 24' of only about 3600 lbs though. I can easily pull the boat along the bunks when completely out of the water. Usually I don't even down shift the winch either.

Chris

 

[emilsr]

Re: Power Loading issue

I'm not advising that he winch 25' of boat onto the trailer. I am talking about less than 2ft, it's not a bunch of strain on anything. When you push a 4K lbs car on the road, it doesn't take 4K lbs of force, otherwise you'd never be able to move it. The same goes for pulling the boat across the bunks, it doesn't take even half of the weight of the boat to pull it across the bunks in order to overcome the friction of the bunks and the fiberglass.

Whichever method he uses, backing the trailer in further after initial winch or winching it all at once, will be fine.

Edit: Did some rough math. Assuming the full 7K lbs of boat has to be pulled (ignores any buoyancy from boat in the water) and a 12-degree incline with a friction coefficient of 0.2 (fiberglass over wood, so probably overstated), it comes up with 2,800 lbs of "weight" to move the boat. With a cable or HD winch strap, he would be well within the specs on his equipment with a 2-spd winch.

No problem with the winching power, and "theoretically" no problem with the bow eye as it, by design, should withstand half the weight of the boat (3,500lbs in your example). Your theory is factually correct, however here's where I have concerns:

Over time, the hardware holding everything tends to loosen up. On fiberglass boats there is some "give", and as the 'glass sandwiched in between the backing plates gets smaller the thing will start "wobbling" around a bit. The more this happens, the looser the assembly gets....and so on. This weakens the glass and, in effect reduces the amount of weight the bow eye will withstand. Rarely have I seen catastrophic failure where the whole assembly pulls out of the hull, but it does happen....more so with heavy (and wet) boats. Water intrusion is the main worry though.

That's why I wouldn't recommend putting too much load on the thing on a Bayliner pocket cruiser. If the boat was lighter, or a tinny, or had 6" of glass in the keel it may be different, but not on that boat. Not that it won't withstand the force, just that there are some second order consequences that I'd rather avoid if it were my own boat...and why when faced with that situation I just take the extra few seconds to back down another 3 or 4 feet.

As they say though, your mileage may vary.

 

[haulnazz15]

Re: Power Loading issue

Ok, who invited Archimedes!

I'm an accountant, no engineering degree required, lol. (although physics was always my favorite science)