Aluminum Trailer - Need help

A forum for discussing topics relating to MacGregor Powersailor Sailboats
User avatar
kurz
Admiral
Posts: 1165
Joined: Mon Dec 06, 2010 9:07 am
Sailboat: MacGregor 26M
Location: Zürich, Switzerland, Europe

Re: Aluminum Trailer - Need help

Post by kurz »

Neo wrote: Wed Dec 23, 2020 2:53 am
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.
OH well the typically VW Van is a bigger an stronger sort of car, goes more to a truck. The VW Sharan is smaller and belongs to the limousine comfort style. So if you was a boat service I would not by the Sharan for every day towing an slipping heavy boats. But as I do just sometimes a year it works more than perfect for me. You see the sharan all time here, families love it (sliding doors...). And it's the only one of this kind of car you get big towing weight (max 2400kg). So boaters and caravans often use it. I still hope the modern stile of automatic gear (here called DSG) will hold long)...
User avatar
Neo
Admiral
Posts: 1093
Joined: Fri Jan 30, 2015 4:29 pm
Sailboat: MacGregor 26M
Location: Central Coast, NSW, Australia

Re: Aluminum Trailer - Need help

Post by Neo »

Tomfoolery wrote: Wed Dec 23, 2020 12:37 pm 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.
Ok just to clarify...
I thought your diagram is for just the old trailer without a boat .... In reality the old trailer still has my Mac on it, so I can't measure the unloaded ball weight.
But I just measured the new trailer unloaded weight and it's 66Kgs.
Hope this helps in some way :?:
All the best.
:macm: Neo
"Whatever floats ya boat" 8)
User avatar
Tomfoolery
Admiral
Posts: 6135
Joined: Tue Jul 05, 2011 7:42 am
Sailboat: MacGregor 26X
Location: Rochester, NY '99X BF50 'Tomfoolery'

Re: Aluminum Trailer - Need help

Post by Tomfoolery »

Neo wrote: Tue Dec 22, 2020 4:37 pm ... 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.
So, if I'm reading this right, your boat weighs 2334 - 480 = 1854 Kg {4079 lb]?
Tom
Be seeing you . . .
User avatar
Tomfoolery
Admiral
Posts: 6135
Joined: Tue Jul 05, 2011 7:42 am
Sailboat: MacGregor 26X
Location: Rochester, NY '99X BF50 'Tomfoolery'

Re: Aluminum Trailer - Need help

Post by Tomfoolery »

Here's what I think you have, followed by what you would have with the new trailer. These figures are based in large part on the existing tongue weight, which can vary with trailer tilt when using two torsion axles, so the margin of error can be relatively large. I had to calculate the CG of the boat based on the trailer + boat weight and tongue weight, so if the tongue weight is off, the CG location of the boat won't be right.

But having said that, I don't think it's too far off. The CG of my X boat is just a hair behind the front axle center, and yours calculates to just behind the midpoint between the two axles. That makes for a pretty light tongue load, given the location of the axles to the boat's CG, and my best guess as to the trailer's CG location.

Image

Image

Oh, and here's my boat on the trailer, with the boat's CG location, for reference.


Image
Tom
Be seeing you . . .
User avatar
Neo
Admiral
Posts: 1093
Joined: Fri Jan 30, 2015 4:29 pm
Sailboat: MacGregor 26M
Location: Central Coast, NSW, Australia

Re: Aluminum Trailer - Need help

Post by Neo »

Oh wow Tom that's a worry :? .... Does that take into consideration the 300pds (136Kgs) of permanent ballast? .... I can't recall if it's just back from the dagger board?... I know I had a picture with it's position somewhere but I can't find it.
All the best.
:macm: Neo
"Whatever floats ya boat" 8)
User avatar
kurz
Admiral
Posts: 1165
Joined: Mon Dec 06, 2010 9:07 am
Sailboat: MacGregor 26M
Location: Zürich, Switzerland, Europe

Re: Aluminum Trailer - Need help

Post by kurz »

We put the dual axle as far as possible on the factory alu frame.
Then test with the 26m on it.
Had luck...

As far as I know you have to test it out.
User avatar
Tomfoolery
Admiral
Posts: 6135
Joined: Tue Jul 05, 2011 7:42 am
Sailboat: MacGregor 26X
Location: Rochester, NY '99X BF50 'Tomfoolery'

Re: Aluminum Trailer - Need help

Post by Tomfoolery »

Neo wrote: Wed Dec 23, 2020 11:21 pm Oh wow Tom that's a worry :? .... Does that take into consideration the 300pds (136Kgs) of permanent ballast? .... I can't recall if it's just back from the dagger board?... I know I had a picture with it's position somewhere but I can't find it.
My estimate is based on the trailer dimensions, including axle locations, for the boat and trailer as you reported above. That presumably includes the ballast. If any of the first trailer weight and balance is wrong, everything that follows is also wrong.

But being that the axles are closer to the vee block at the bow than the old trailer, and being that trailer weight isn’t going to change much compared to the boat weight, it’s reasonable that the axle location will make a relatively large difference in the tongue weight. Since the axles are so much farther forward, the tongue weight will be greatly reduced.

That doesn’t mean you can’t roll with it, but I would make sure the coupler is adjusted so it’s just snug on the ball to minimize the chances of it pulling off the ball, as uplift is going to happen (happens even with the correct tongue weight on certain bumps and road wows). Just don’t go highway speeds. And move as much stuff in the cabin as you can to the bow, especially the heavy stuff.

Get accurate weight at a weigh station, like CAT scales (Edit: not in NSW, but I’m sure there are weigh bridges you can use), with the tow vehicle on the front platform and the trailer on the middle one, then at home get an accurate tongue weight. From that, it’s easy to calculate how much to move the axles to get the desired tongue weight.
Tom
Be seeing you . . .
User avatar
Neo
Admiral
Posts: 1093
Joined: Fri Jan 30, 2015 4:29 pm
Sailboat: MacGregor 26M
Location: Central Coast, NSW, Australia

Re: Aluminum Trailer - Need help

Post by Neo »

Ok thanks Tom ... This will really help me plan what I'll do at the swap-over. 8)
I have a couple of holdups at the moment but it should take place in two weeks time.
All the best.
:macm: Neo
"Whatever floats ya boat" 8)
User avatar
Neo
Admiral
Posts: 1093
Joined: Fri Jan 30, 2015 4:29 pm
Sailboat: MacGregor 26M
Location: Central Coast, NSW, Australia

Re: Aluminum Trailer - Need help

Post by Neo »

Hi Tom,

Could you please run your calculations again with the V-Block (and Mac) moved 450mm forward?... Everything else remains the same.
All the best.
:macm: Neo
"Whatever floats ya boat" 8)
User avatar
Tomfoolery
Admiral
Posts: 6135
Joined: Tue Jul 05, 2011 7:42 am
Sailboat: MacGregor 26X
Location: Rochester, NY '99X BF50 'Tomfoolery'

Re: Aluminum Trailer - Need help

Post by Tomfoolery »

I’ll do that tomorrow morning, as it’s on my work machine. :wink:
Tom
Be seeing you . . .
User avatar
Neo
Admiral
Posts: 1093
Joined: Fri Jan 30, 2015 4:29 pm
Sailboat: MacGregor 26M
Location: Central Coast, NSW, Australia

Re: Aluminum Trailer - Need help

Post by Neo »

Thanks Tom :wink:
All the best.
:macm: Neo
"Whatever floats ya boat" 8)
User avatar
Tomfoolery
Admiral
Posts: 6135
Joined: Tue Jul 05, 2011 7:42 am
Sailboat: MacGregor 26X
Location: Rochester, NY '99X BF50 'Tomfoolery'

Re: Aluminum Trailer - Need help

Post by Tomfoolery »

Here's what I get, given what I understand the weight and balance situation to be - 353 kg at the ball. Still rather light, but much better than before.

Image

Consider instead removing the front axle and moving to a new location behind the rear axle. That puts the tongue weight at about 11%, which is very reasonable, with the caveat that I had to 'guess' where the trailer's center of mass would be with the axle moved.

Image

But having said that, take a look at this photo, which has been circulating for at least a few years. It lines up very closely with the last sketch I posted. The most relevant dimension is the boat bow block to the mid-point between the axles. 4.7m for my last sketch, and 4.8m in the photo. That photo also shows a sagged tow vehicle, so presumably there is substantial load on the ball, which of course you do want. It makes sense, FWIW.

Image

Just some stuff to consider.
Tom
Be seeing you . . .
User avatar
Neo
Admiral
Posts: 1093
Joined: Fri Jan 30, 2015 4:29 pm
Sailboat: MacGregor 26M
Location: Central Coast, NSW, Australia

Re: Aluminum Trailer - Need help

Post by Neo »

Tomfoolery wrote: Mon Jan 11, 2021 9:30 am Here's what I get, given what I understand the weight and balance situation to be - 353 kg at the ball. Still rather light, but much better than before.
Image
353lb = 160Kg ... I might be able to live with that. :)
Tomfoolery wrote: Mon Jan 11, 2021 9:30 amConsider instead removing the front axle and moving to a new location behind the rear axle. That puts the tongue weight at about 11%, which is very reasonable, with the caveat that I had to 'guess' where the trailer's center of mass would be with the axle moved.
The axles are mounted on two hot dip galvanized subframes (which align and hold the mudguards) and it's all bolted to the I-Beams flanges with 20 large bolts. The subframes will rust if I drill holes in them so (keeping the subframes intact) if I jump the front axle back to the "back axle holes" that requires only 10 additional holes to be drilled in the I-Beam for the rear axle. But it also leaves 10 vacant holes (Swiss cheese I-Beam!!) and I worry what this will do to the structural integrity of the I-Beam :o ... Worse than that the axles are 860mm apart so the jump back would be 860mm which would most likely result in an excessive tongue weight.
What I'm trying to do (moving my :macm: forward on the trailer) also has it's drawbacks because I'm running out of drawbar length :? ... The winch post will be closer to the back of the car than before ... Which also means I will have to reverse my car closer (or further into) the seawater :cry:

Tomfoolery wrote: Mon Jan 11, 2021 9:30 amBut having said that, take a look at this photo, which has been circulating for at least a few years. It lines up very closely with the last sketch I posted. The most relevant dimension is the boat bow block to the mid-point between the axles. 4.7m for my last sketch, and 4.8m in the photo. That photo also shows a sagged tow vehicle, so presumably there is substantial load on the ball, which of course you do want. It makes sense, FWIW.
Yep will do some comparisons measurements today... But do we actually know if that rig had a good tongue weight? :|
All the best.
:macm: Neo
"Whatever floats ya boat" 8)
User avatar
Tomfoolery
Admiral
Posts: 6135
Joined: Tue Jul 05, 2011 7:42 am
Sailboat: MacGregor 26X
Location: Rochester, NY '99X BF50 'Tomfoolery'

Re: Aluminum Trailer - Need help

Post by Tomfoolery »

Neo wrote: Mon Jan 11, 2021 12:20 pmYep will do some comparisons measurements today... But do we actually know if that rig had a good tongue weight? :|
Actually, no I don't. But it belongs, or belonged, to a member here, who speaks metric as a first language. Kurz maybe? One of our friends in Australia or NZ perhaps? With any luck, the owner will unmask him- or herself and shed some light. 8)

Since the tongue is steel, perhaps it's easier to simply replace that with a longer one after moving the boat forward. What my sketch shows is only half a meter closer to the coupler, so an extra meter of steel tube isn't a big deal. Unless all that stuff is welded to it, but you're talking about moving it anyway.

And remember also that my I did is based on what I believe you have. If any of my assumptions or interpretations are off, the results will be off.
Tom
Be seeing you . . .
User avatar
Neo
Admiral
Posts: 1093
Joined: Fri Jan 30, 2015 4:29 pm
Sailboat: MacGregor 26M
Location: Central Coast, NSW, Australia

Re: Aluminum Trailer - Need help

Post by Neo »

Tomfoolery wrote: Mon Jan 11, 2021 1:42 pmAnd remember also that my I did is based on what I believe you have. If any of my assumptions or interpretations are off, the results will be off.
Fully understand Tom ..... Only my :macm: on my trailer will tell the full story ... but your calculations are a great indicator and a big help at this time.
Tomfoolery wrote: Mon Jan 11, 2021 1:42 pmSince the tongue is steel, perhaps it's easier to simply replace that with a longer one after moving the boat forward. What my sketch shows is only half a meter closer to the coupler, so an extra meter of steel tube isn't a big deal. Unless all that stuff is welded to it, but you're talking about moving it anyway.
Yes that's my last resort ... but if it has to be done it has to be done... It mainly bolts on too.
Having said this, with the winch post in its new position I just measured from the Bow V-block to the centre point of the two axles and it's 4.77m .... Which compared to the picture is reassuring 8)
All the best.
:macm: Neo
"Whatever floats ya boat" 8)
Post Reply