MacGregorSailors.com

Hi All,

Hope you're all well?

It's been far too long but it's looking like "I'm Back ".... and I'm hoping many (and most) of the guys (active members) are still on this forum and still having fun out there.

So a year and a half ago I desperately tried to get the I-Beams I needed to make this Trailer but unless I purchased a dozen the manufactures wouldn't supply. And that situation is even worse today.
So much time has gone by (life got in the way) and my steel trailer got to a point where the rust wasn't funny any more
But yesterday was a turning point because I put my deposit down on a new Aluminium Trailer. The diagrams we did have helped so much (thanks for all the info guys) and my supplier is now getting a good understanding of all the changes I need and why I (we) need them.
I have to do a few mods myself and one of those is to make up some Windy Poles (guide poles). I'd like to replicate the ones on the Aluminium Mac Trailer (simple and effective) and would like to get some dimensions for ....
> Length of the Aluminium Poles
> Tube diameter and wall thickness
> Bend Angle
> Relative dimensions for the positions of the two fixing bolts

Can anyone (Jimmy I'm hoping you're out there?!!!) help me with this?

I would not mount these until you have the boat on the new trailer. They need to be fitted with the boat in place - especially with a different trailer manufacturer.

They are aluminum tube, 48 inches long, 1-1/2 inch OD, 0.135 inch wall. The angle is about 33 degrees off straight, and the radius is about 18 inches. Bottom rail attachment points are 50 inches apart (bolt hole distance), and the tube makes a 45 degree angle with the rear cross-member.

You can make them taller using more aluminum, or a PVC outer sleeve. The PVC sleeve keeps from marring the hull, so you may want to do it even if you don't want taller posts.







Good luck, and glad you're back!

Great Jimmy,

Thanks so much for this.

Not sure if I ever shared my final drawing of the Alu Mac Trailer https://docs.google.com/presentation/d/ ... sp=sharing
Anyone can print (to pdf too) it from here.

Does anyone with a dual axle Aluminium Trailer happen to know what your Hitch/Coupling weight is? .... That is the downward loading at the top of the drawbar/weight onto the towing vehicle?

I've taken delivery of my new Dual Axle Aluminium Trailer (will post up some photo's) but because of the complexities of the hull I'm doing all the hardware configurations myself .... At the moment the axles look way too far forward and I'm worried it won't tow too well like that.

Neo wrote: ↑Tue Dec 22, 2020 12:49 amI've taken delivery of my new Dual Axle Aluminium Trailer (will post up some photo's) but because of the complexities of the hull I'm doing all the hardware configurations myself .... At the moment the axles look way too far forward and I'm worried it won't tow too well like that.

It should have 10-15% of the loaded trailer weight on the tongue. Since it’s bound to be at least 4000 lb, it should have at least 400 lb on the ball, and probably more.

Every photo I could find of a single-axle trailer with the Mac M on it shows the axle center directly, or very nearly so, under the tail of the lower raccoon stripe. A two-axle trailer will have the mid-point between the axles directly under that same point, assuming a similar trailer CG location, or further back to increase the tongue weight if desired.







Notice, for the record, that I posted both blue and white hulls, left and right side elevations, and mast up and mast down, so nobody feels slighted.

But the white hull is clearly faster with its streamlined mast position.

My coupling weight is 100kg to 120kg.

My VW Sharan (minivan) 2wd, is allowed to take 100kg. So go to as much you can with your car.

The VW just tows more than perfect. Couldn't be better on the road. Even at the ramp with 2wd front wd I had never had a problem so far. Ca 10 liter diesel for 100km with Mac 26 behind on dual axle stock trailer.

Neo wrote: ↑Tue Dec 22, 2020 12:49 am Does anyone with a dual axle Aluminium Trailer happen to know what your Hitch/Coupling weight is? .... That is the downward loading at the top of the drawbar/weight onto the towing vehicle?

I've taken delivery of my new Dual Axle Aluminium Trailer (will post up some photo's) but because of the complexities of the hull I'm doing all the hardware configurations myself .... At the moment the axles look way too far forward and I'm worried it won't tow too well like that.

I have a dual axle aluminum trailer. The rear axle is pretty much in line with the companionway. I've never measured the tongue weight but it is probably pretty close to the minimum recommended. If the boat is not completely forward on the trailer it will begin to get a little squirrelly around 50mph. When it is all the way forward it tows smoothly at 70.

Tomfoolery wrote: ↑Tue Dec 22, 2020 4:58 am It should have 10-15% of the loaded trailer weight on the tongue. Since it’s bound to be at least 4000 lb, it should have at least 400 lb on the ball, and probably more.

Absolutely Tom ... Yesterday I got one of those ball weight measuring (spring) sticks and the old steel Trailer weighs in at 198Kgs on my 2,334Kg rig.
Moving the two torsion axles on my new trailer is not easy. Axles are bolted to the I-Beam so lots of repositioning holes will need to be drilled (somewhere?) to move it .... I don't like to do that to a new trailer ... but if I need to do it I have to get it right first time.
So firstly I'm trying to work out if I can get away with not moving them before I do the trailer swap-over at the boat ramp. Because there's no way I'd make it home with a ball weight of 0Kgs ... or less!

Tom, I was wondering if you could use your Mastery and Wizardry to calculate the approximate change in ball/tongue weight (if possible considering the concrete ballast)?
# Both trailers have independent (non-load balancing) suspension and my Mac weight is 1,854Kgs
# In effect the axle position will shift of 490mm forward.
# Old trailer is 480Kg...Bow-V-Block back to Centre point of axle group is 4730mm ...Bow-V-Block forward to Towball is 1210mm ...Which is a measured ball weight of 198Kgs
# New Trailer weighs in at 460Kgs...Bow-V-Block back to Centre point of axle group is 4240mm...Bow-V-Block forward to Towball is 1420mm ...Which could equate to a ball weight of ???Kgs

kurz wrote: ↑Tue Dec 22, 2020 6:01 amMy coupling weight is 100kg to 120kg.
My VW Sharan (minivan) 2wd, is allowed to take 100kg. So go to as much you can with your car.
The VW just tows more than perfect. Couldn't be better on the road. Even at the ramp with 2wd front wd I had never had a problem so far. Ca 10 liter diesel for 100km with Mac 26 behind on dual axle stock trailer.

You tow with a VW Sharan minivan? ... That would be illegal in Australia
My 2002 Merc ML is only allowed 225Kgs .... Other years are just 185Kgs so I was lucky to get 225Kgs I guess ... Of course, we only discover these minor details after we've purchased our car

Be Free wrote: ↑Tue Dec 22, 2020 6:26 amIf the boat is not completely forward on the trailer it will begin to get a little squirrelly around 50mph

Now this is interesting.... and the kind of stuff that worries me

They give no towing for the VW SHARAN in Australia?
Here in EU you get 2200kg for 2wd and 2400kg for 4wd.

Works perfect. Plenty of room inside. 7 people to sit in. Super comfort...

kurz wrote: ↑Wed Dec 23, 2020 1:53 am They give no towing for the VW SHARAN in Australia?
Here in EU you get 2200kg for 2wd and 2400kg for 4wd.

No its not sold over here .... I had to Google a picture to see what it was. From what I can see it looks the same chassis as a VW Van (they sell here)? ... If I'm right I do not think anything that small would get a rating of 2200Kgs in Australia.
Many good cars are not sold here ... the market is too small for manufactures to offer their full range of cars.

Neo wrote: ↑Tue Dec 22, 2020 4:37 pmTom, I was wondering if you could use your Mastery and Wizardry to calculate the approximate change in ball/tongue weight . . .

Give me al little time on that. I have to draw it out to make sure I have the geometry accurately represented. The math is easy, which then makes it easy to give a very definitive-but-wrong answer to 12 decimals places if the 'givens' aren't right to start with.

Neo wrote: ↑Tue Dec 22, 2020 4:37 pm # Old trailer is 480Kg...Bow-V-Block back to Centre point of axle group is 4730mm ...Bow-V-Block forward to Towball is 1210mm ...Which is a measured ball weight of 198Kgs

Is this right? Empty trailer only. Or is the tongue weight with the boat on it?

Awesome Tom... that's great
Except the ball/tongue weight would not be 198Kgs without the Mac on the trailer.

Neo wrote: ↑Wed Dec 23, 2020 11:46 am Awesome Tom... that's great
Except the ball/tongue weight would not be 198Kgs without the Mac on the trailer.

Ooooh, then what is it without the boat? That CG looked awfully far forward for just an empty trailer, especially with two heavy axles and wheels.

Tomfoolery wrote: ↑Wed Dec 23, 2020 12:37 pm [quote=Neo post_id=346949 time=<a href="tel:1608752789">1608752789</a> user_id=16681]
Awesome Tom... that's great
Except the ball/tongue weight would not be 198Kgs without the Mac on the trailer.

Ooooh, then what is it without the boat? That CG looked awfully far forward for just an empty trailer, especially with two heavy axles and wheels.
[/quote]
I think he was trying to get you to tell him what the new ball weight would be due to the new position of the axles... maybe he hasn't picked up the trailer yet???

Unless the axles are matched and the trailer is perfectly level, could be tricky to get more than a decimal place or two.