How far to move axle(s)

A forum for discussing issues relating to trailers and towing MacGregor sailboats.
wakataka
Chief Steward
Posts: 53
Joined: Mon Jul 06, 2015 10:06 pm
Sailboat: MacGregor 26X
Location: Redding California

Re: How far to move axle(s)

Post by wakataka »

My trailer does have an equalizer on the leaf springs to even out the load between the two axles. The weak spot on the factory trailer is the tongue, which I've reinforced.
Still, if I was going long distance (rather than just 20 minutes from lake to home) I would take weight off the boat and carry it in the truck. My truck doesn't balk at 600 pound tongue weight but the trailer eventually might.

Here's a photo of the reinforced tongue. The doubler extends back to the front cross member, same as the original tongue.

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Starscream
Admiral
Posts: 1388
Joined: Tue Nov 03, 2009 10:08 am
Sailboat: MacGregor 26X
Location: Montreal, Quebec. 2002 26X - Suzi DF90A

Re: How far to move axle(s)

Post by Starscream »

Russ wrote: Tue Jun 15, 2021 9:56 am I have the original factory aluminum trailer. I added another axle by moving the existing axle 16" forward and the new one 16" behind the original single axle.

Speeds over 65, the rig wants to dance (towing with 3/4 ton Duramax truck). Very aft heavy with 70hp motor and 2x 12gal fuel tanks. Even at lower speeds, it's clearly aft heavy and wants to wobble.

So I'm thinking it needs more tongue weight and I should move them both back. When I put a bunch of sand bags in the truck bed, it handled much nicer. Sorry, the boat is now floating in the slip and I can't get a reading on the existing tongue weight with boat on.

My question for the engineer types; how far would you move the axles back?
Before I upgraded my trailer, I added a second axle to the stock MacTrailer. The original axle stayed in the same place, and the new axle was added behind the original. This had the effect of adding an immense amount of tongue-weight, not determined by measurement, but by the new nose-up attitude of the truck. It was very stable when towing, but the modification had a severe negative effect on fuel economy, probably about 20%.

With the new trailer, the axles are moved to be centered around the original single Mac-Axle. Depending on where the boat ends up on the trailer (the MacBump doesn't work for me, previously due to the anti-fouling, now due to...not sure, maybe the structure and form of the new trailer), in can be a bit squirrely with light tongue-weight if the boat too far back. If the boat gets snugged up to the Vee, then the trailer is tongue heavy.

To make a long story longer, about 6" of boat location difference changes the trailer from tongue light to tongue heavy. It doesn't take much, but it makes a huge difference on the road. Even towing with gas in the tanks makes a difference that I THINK I can feel.

If I was in your position I wouldn't move the axles very much, but I would move them. I bet you would feel a huge difference with an 8" move-back. Zero calculations on that, just a bit of experience and a feeling.

The manufacturer of the new trailer built in multiple axle mounting points to make it easy to move them in the future, since they weren't entirely sure of the mounting location either. It feels like they got it right, though.
Sheppie62
First Officer
Posts: 351
Joined: Thu Sep 28, 2017 1:04 pm
Sailboat: MacGregor 26X
Location: Mission Bay San Diego

Re: How far to move axle(s)

Post by Sheppie62 »

I didn’t realize you had a balancer, must have been someone else. I found these sliding spring hanger/ fender brackets. I’m not sure exactly how they are used. But may make it easier to get balance right, instead of just guessing and welding new spring hangers. Maybe someone else has more info.
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I copied those but mine are not galvanized. I did this so I wasn’t trying to weld upside down (not good at that). I put 3 small bolts to hold until I’m sure balance is correct, then I will weld on permanent. I realize there can be an issue if water gets between frame and spring hanger/ fender slider bracket. I put marine sealant between metals before bolting, not sure how welding will effect sealant, but I’ll gob some more on later to seal completely.
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Image again I am no expert on trailers so do your own research/ get more advice.
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