Modifying bunks for launch sling cutouts

[geekgiant]

I tried searching this forum and scouring the web. I can't find good information on how to convert by bunks to be the modified kind for accommodating a sling. I can add the second layer of wood and add a cutout, but how do I determine where the cutouts should be? I don't think I can tell where the boat's center of gravity is etc...

I have looked in the Trophy manuals for lift points, but it doesn't identify any of them. So, any how tos for this type of work? Any tips for identifying lift points?

Thanks!

 

[UncleWillie]

Re: Modifying bunks for launch sling cutouts

You do not want to sling it at the Center of Gravity. Way too Tippy!
You will want one sling as far aft as possible and the other one as far forward as is practical.
The CG is typically 20-35% forward of the transom.
It will be a little forward of the trailer's axle.
For a 30ft boat that places it at ~8-10 ft from the stern.
One strap 1-2 ft from the stern under the engines, and another near the middle (~15-18ft) should be relatively safe.

Be sure to also tie the straps together so the forward one can slip off the bow.

 

[geekgiant]

Re: Modifying bunks for launch sling cutouts

You're right on hoisting at the center of gravity. I wanted to use that to possibly find the lift points.

I have a pretty good idea of where the lift points are, but I've only done the sling launch once with the unmodifieds. My other option of course is to leave them unmodified and pay the $10 extra the once every other year I end up at a sling. That's where I'm leaning at this point.

 

[UncleWillie]

Re: Modifying bunks for launch sling cutouts

The CG is going to be just a little in front of the trailer axle or, just about centered between dual axles.
That is what sets the weight on the towing ball.

The other option is, the next time the boat is in the slings, mark the position on the slings on the hull with a grease pencil.
After the launch, measure the pencil marks and transfer them to the trailer for the cutouts.
Be sure to note the boats position on the trailer to adjust for any offset.

??? How do the get the slings underneath when the boat is flat on the bunks?

 

[smokeonthewater]

Re: Modifying bunks for launch sling cutouts

My other option of course is to leave them unmodified and pay the $10 extra the once every other year I end up at a sling. That's where I'm leaning at this point.

Seriously? 5/year and you are even THINKING about it?.... I guess MY vote is obvious.......

 

[geekgiant]

Re: Modifying bunks for launch sling cutouts

Seriously? 5/year and you are even THINKING about it?.... I guess MY vote is obvious.......

LOL, I am pretty sure my vote is aligned with yours. I was just looking for how tos should I go that route. Looks like the best how to is "go to rollers."

 

[JimS123]

Re: Modifying bunks for launch sling cutouts

I never knew how easy it was to back a trailer until I got my first SUV. With the tailgate up I can see the whole trailer, including both wheels. Seeing the ground is an improvement over looking out a window and seeing the trunk lid.

The guy at the ramp that causes the most trouble is the one bent over looking forward at the driver's side mirror. When the boat goes out from his vision by the time he hunkers over to look at the other mirror its already jacknifed.

 

[smokeonthewater]

Re: Modifying bunks for launch sling cutouts

Wrong thread Jim ;-)

 

[JimS123]

Re: Modifying bunks for launch sling cutouts

Wrong thread Jim ;-)

When I typed it I was reading the other thread. Don't know how it got here.

Funny thing, yesterday I was reading 2 other threads that had out-of-place replies.

Must be my XP running out of steam...or is it Y2K?

 

[smokeonthewater]

Re: Modifying bunks for launch sling cutouts

Y2K v14.4