Mac Bump

[cuisto]

Have seen reference to the "mac bump" but have not seen a description.
Can anyone tell me what this proceedure is and why it is done?
Thanks
S

[BK]

Some on this board can do this Mac bump and I have seen it done just right but it is hard to get the speed and braking distance right. Just do the Mac wiggle. Crank and push the bow back and forth at the same time and in a minute the boat will be in the snub. This is best done when the boat is wet and I put "Liquid Rollars" on the bed boards.

[Duane Dunn, Allegro]

The bump is a method for getting the boat all the way forward on the trailer. When backed down a ramp the trailer is at an angle under the boat which is level on the water. Even after you crank the bow tight to the bow stop when the boat is floating, you will find that after you pull up the ramp and the boat settles into the bunks as it comes out of the water, the nose of the boat is now 2"-4" away from the bow stop. How much depends on how steep the ramp is.

Usually there is too much friction to just winch the bow into the full forward position. That's where the bump comes in.

Once you have drained the ballast, pull up onto the level area of the ramp. Drive slowly forward, then apply the brakes fairly hard. The boat will slide forward into the bow stop. You don't have to fast, you don't have to slam the brakes on so hard the tires squeel. It just takes a firm application of the brakes.

The wiggle mentioned is another approach. Once on level ground, you crank on the winch while rocking the boat on the trailer.

I find applying a spray of liquid rollers to the bunks a couple times a year helps either of these methods for getting the boat all the way forward on the trailer.

[Catigale]

Im barely qualified to add anything to a 'Duane post' but offer the following on the bump.

I roll my Eurovan at idle speed (< 3mph) and then do a fairly hard stop (that you have to push against the steering wheel to hold your self straight) to move Catigale onto her trailer.

Watch out for hills, they add a lot of Force to the motion forward - I bent my trailer ladder doing this once.

Warn any passengers you will stop short - especially your date in the front seat.

[ralphk]

Two additions:

1) I usually derig, secure everything for the trip. Even though I'm getting faster with practice, it's likely near an hour, not 20 minutes as described by the Speedy Rigger guy. By then the pads are starting to dry, so I back up one more time to the ramp and soak the rear pads near the axle.

2) I prefer to do the Mac Bump on a little downhill slope near our local marina. Several times last year, I had her slip into the "Y" stop so smoothly that you couldn't feel it in our Pathfinder ie: sans bump.
Required speed is less and I'm convinced that there's less strain on the truck brakes.


MAKE SURE THAT THERE IS NO ONE BEHIND YOU!!

Ralph
Hakuna Matada '96

[Mark Prouty]

Liquid Rollers will lessen the need for the bump.



Available at West Marine.

[ALX357]

If you're not in a hurry to drive the boat up the ramp and others are not waiting for the ramp, you can avoid the "Mac Bump" by winching the boat up to the stop in the water as usual with the trailer underwater, and then pulling it out a bit, then winching up the slack, and pulling out some more, winching some more, etc. until the boat is all the way down onto the bunks and into the nose stop fully. Assures a good alignment and less wear on (all) the brakes, suspension, and hitch, plus not disturbing loose stuff in the cabin or cockpit... Although the 'Bump" is a good way to test whether everything is secured for travel.

[Sloop John B]

Once you try the bump, you will then know how to do it the next time. Start out being unsuccessful and work up to where the boat clunks into the V. Like Duane says, just ease along slow. I apply brake pressure and watch in the rear view mirror. I used to come to a stop, but now, just slowing down will bring the boat up. I use liquid rollers, and you can use any kind of soap, like Joy dishwashing liquid. Stuff smells a little weird though.

And like I mentioned a few days ago, make sure the inside vent is plugged up if you've still got tire bulging ballast in.

[Dave X2000 Jac]

Cuisto,
I regularly use "the bump". One time I "overbumped" - not enough to bend the ladder, but just enough to position the centerboard 1/4 inch past its support. I needed to wrap a dock line under the Mac - back and forth around the trailer beams to keep the centerboard from bouncing down near the pavement is I hauled the boat home. Making a longer centerboard support piece for the trailer is on my "to do" list, but it is way down on the list.
You'll get the hang of it,
Dave "Jac"

[Tahoe Jack]

Designed a mod on our trailer winch which appears to have ended the famous 'bump' issue. I have a mod drafted up that should be posted in about a week. My rig is a 2001 26X with OEM trailer. The winch was already rusted so I tossed it and added a similar but better one, on top vs. on the bottom of the strut. I tossed the cable and used a #2500 rated nylon strap...and cut a slot for the strap, into the steel channel strut, positioned to have the strap essentially horizontal-on the axis of
the trailer and hull. Seems to work much better, but haven't had it in the water since.

[Paul S]

Liquid Rollers will lessen the need for the bump.



Available at West Marine.

I have used plain ol dishwashing soap with great results. It usually lasts 2-3 launching/haulings. Best thing is it is next to free. I just squirt a fair amount on each board. Good to go.

I am sure LR works better..but in a pinch, dishwashing soap works well too

Paul

[NautiMoments]

I have waxed the bottom of the boat. I am reluctant to use dish soap on the bunks since I am worried it will wash dissolve the wax off. I know that if you wash your boat with a dish soap solution it takes the wax off. Does the Liquid Roller take the wax off as well?

[Paul S]

wax the bottom..wow...thats quite an undertaking, esp if it is still on the trailer. I don't think a few days at a time without wax will hurt anything. The bottom of our boat cleans up well after each outing with a long car wash brush and boat soap.

This is the reason I wanted a mac on a trailer, so I wouldn't have to deal with the bottom anymore. My days of painting a bottom are over. Never mind waxing it!

Paul

[ericorville]

ALX357 Has the same method that I use and it works a treat!! Try it before you bend something.
Eric

[jsserene]

I wonder how much speed you might loose with the soap on the bunks wearing off the wax. If it a blue hull, it might slow it down to a white hull.