MacGregorSailors.com

Hello all and Happy New Year! Last year I noticed that when I pulled the boat out of the water after just putting it on the trailer that it would slide back on the trailer. When I bought it it had a rope on the winch and when I pulled my boat up to park it after loading it on the dock it was approx. 8 inches away away from where it was suppose to be at the nose of the trailer. After that I made sure the rope was very tight but it still did the same thing. I then replaced the rope for a belt or strap with a hook but this did not help either. It still did the same thing and the boat slides back approx 8 inches to a foot and then i have to figure out how to get it back to the front. Does anyone knows what causes this and how to fix it so when you do pull your boat out of the water your boat stays where it should be ? Thanx for your help

Try to use the trailer winch and give tension on the roap. Or give a controled break later

It depends how steep your ramp is. If you winch the boat all the way onto the trailer, the stern will be still floating. This means the angle of the boat will change as you pull it out and the boat is resting fully on the trailer. The bow will then again be at some distance from the rubber-stop. On my previous ramp that would be about 2'-3", on the steeper ramp I'm using now it's more like 4". Reason for developing the "Mac-Bump"

Obelix

This has been a much discussed issue over the years. Oblix's explanation is spot on. Several members have relocated /inverted the winch and mounted it on the opposite side of its current location. This lifts the bow somewhat and parallels the hull to the trailer. Those who remounted the winch on the opposite side of the support arm reported the gap being eliminated with no mac bump required. Needless to say the bump is a PIA and hard on the hitch and bottom gel coat. It scares the daylights on anyone around the ramp and gets plenty of WTF stares. My stearn bunks pads are white from years of mac bumps. I can only imagine how the gel coat and color coat have endured (not). This year I'm adding a winch on top to lift the bow. I'll use the old winch for travel as it pulls the bow down on the forward v-bunk.

Along this line, how often should the web strap from the winch to boat be replaced? Mine has been on since 2007.

Happy New Year---Chuck--owner of Lastchance

Chuck,

I was asking myself the same question, since the hook on my strap was showing some corrosion and issues with the spring loaded closure. I ordered a replacement strap from BWY before I would find out the hard way.

Obelix

Obelix wrote:It depends how steep your ramp is. If you winch the boat all the way onto the trailer, the stern will be still floating. This means the angle of the boat will change as you pull it out and the boat is resting fully on the trailer. The bow will then again be at some distance from the rubber-stop.... Reason for developing the "Mac-Bump"

+1

Just the way it is. Mac Bump (slam on the brakes) and it slides right into place.

Probably not a good idea to winch the boat back up. Especially with stock winch. Many have broken it this way.

--Russ

The slip is caused by the tightening of the strap under strain, and there's no way to avoid it. You don't have the force to completely tighten it on the ramp, and the amount it will allow the boat to settle back is a function of the length of the strap.

The "Mac Bump" is unfortunately necessary. Get up to 7mph, slam on brakes, get out and tighten the strap, and repeat until the bow is firmly in the rubber V-block. You do not want to trailer any significant distance without the bow firmly placed in the V because it keeps the trailer in tension with the hull of the boat, which reduces sidesway on the trailer.

I don't know about other trailers but the reason the boat sits back is the angle of the front bunks
The angle needs to be relieved a bit to allow the boat to sit further forward

Allan

I only got rid of my stock 26X trailer a couple years ago when I got a nice Aluminum Tandem, but I trailered on the stock trailer for more than 8 years and the Mac Bump is not necessary. I did it for the first couple years, but it scared everyone in the car and I figured it was putting too much load on the rusting trailer parts too. The key is that you get an idea for when the trailer geometry is starting to cause the bow bunk to seperate from the bow and you stop driving it up the ramp then (when it is like a third out of the water), put the parking brake on, get out and winch it a couple more times until it is snug, drive up another foot or two and it separates a bit further again, winch it again, drive up another foot or two and winch it again. It only takes a few times of extra winching and when you do it this way, the bow ends up all the way at the stop with no bump required. People do get a bit peturbed because it takes you 3 minutes to drive up the ramp instead of 30 seconds, but overall, it was a much more civilized solution than the bump to get the bow into the stop. No such nonsense with my new trailer of course..it is a tank in every respect and is what the boat always wanted.

The boat pulls away from the bow cushion as the back of the trailer rotates up to meet the hull as you pull out of the water.

Here's a quick and ugly sketch showing the trailer tilted on the ramp with the bow all the way in the cushion, the hull in the small forward bunk, and the winch line tight, then with the trailer rotated level and the boat stern on the bunks. I kept the winch line the same length in both sketches. You can see that the bow rotates away from the cushion, leaving a pretty big gap, requiring the 'Mac bump'.

I pull the trailer up the ramp a little, crank the winch a bit, pull out a little more, crank again, and so on, all the while the water is draining from the ballast tank. Don't have to do the bump if I crank it a few times while pulling up the ramp. Liquid Rollers probably helps a little, too, as I can pull it higher in the forward bunk with that stuff on the bunks than without.



Edit: Just read Dimitri's post more carefully, and he said the same thing.

Tomfoolery wrote:

Picture says it all. Excellent.

Don't know about others but because of the variability in the slip factor after being in different waters the "bump" was a bit of a problem with either not working to going too fast and bending the winch support forward even though ours is braced way more than standard, it may be that you can be more precise if in the same water all the time.
I will try it now but don't get excited if it doesn't work perfectly, I just tighten the winch up which as we have an electric winch now bends the whole structure back or moves the boat forward to usually less than 2" then get on the road and after a short drive winch it again but instead of relying just on the winch we have two chains which are hooked on to hold it once in position.
Mention was made of the bunks being White/Blue? from "mac bumping", I really don't think this is the case, it is more likely to be caused by just bounce especially if the boat is not tied down at least in the rear section, I am on my third set of carpets and second timbers and we also have an extra set between the two rear ones but our's get more work than most.
edit The support post is not very strong, even after more strengthening when we "modded" the trailer I still managed to bend it forward when driving the boat on at a fairly steep ramp (most our northern ramps are) and despite trying it stays that way.

Guess I'll put the money I was saving for a carbon mast towards a new tandem axle trailer!
Ix

K that all makes sense. I am doing and have done the Bump technique but that just didn't seem right so now I will do the extra roller tightening as I am bringing the boat out of the water. So instead of one episode of cranking I'll try 3 or 4 as I am moving it out. That has to be a lot easier on the boat and trailer versus driving down the road and locking up the brakes... Thanx for the pictures Tomfoolery. Out of everything your pictures say it all and explains it very well.