Trailer Setup

Mike B · 20 July 2010, 10:36

Morning all,

After adding a aux outboard to the Transom, not suprisingly, the already light nose weight of my trailer has become none existant.

I can see a couple of ways to correct this (NB there are already 2 anchors and 15m of chain in the bow and I don't particularly want to add any more weight)

Looking at how the boat is sat on the trailer I could move the winch post forward about a foot, shifting the boat further forward on the trailer, still keeping the stern on the last set of rollers.

or

Move the axel back to move the pivot point further aft. (presumably this would also make launching easier as effectively the trailer would be deeper for less distance into the water).

or

Combination of both.

The trailer is unbraked so either should be reasonably simple (allowing for stuck bolts!)

Has anyone got any suggestions on the best approach or anything I have missed?

Cheers

Mike

Into The Blue · 20 July 2010, 11:10

I had exactly the opposite issue earlier this year, too much nose weight. I took the view that moving the axle forward was the prefered route as I didn't want the boat to move either closer to the car or away from the rear most rollers - esp. given that that is where most of the weight is.

The trailer was a braked one but as I was going to overhaul the brakes at the same time it made no more work.

Took about an hour to lift the boat and supports up off the spine of the trailer and get out a hammer big enough to move the axle.

The only issue, if you can call it that, was that I had to replace the "U" bolts that connected the axle to the trailer. Damn things had rusted solid, fortunately I spotted this before I started work. Got them from Trailer Tek.

I think I moved it about 100mm, taking some 30-40kg off the nose weight. It's made a massive difference to towing. The only downside has been IF I go over 60mph, unintentionally of course, the nose weight does seem to reduce, possibly lift from the air flow under the boat? Some one will undoubtedly drop by and correct me.

Well worth it.

jyasaki · 20 July 2010, 15:20

Sounds like you have the physics down; it's just a matter of which method is preferable to you.

Given that the boat is already well situated on the rollers, I would personally go for moving the axle. If you go that route, try and mark the current position (so you know how far you've moved each side), and double check squareness against the frame after you've set based on previous position.

Rule of thumb for tongue weight (at least what I've always heard) is 7 to 10 percent of gross weight of boat and trailer. Too light and you may get trailer sway (sometimes really violent trailer sway); too heavy and you induce squat in the tow vehicle, which may affect steering.

Luck;

jky

Mike B · 21 July 2010, 09:12

Thanks both!

I will give an axle move a go on Friday.

Cheers

Mike

9D280 · 21 July 2010, 11:32

If you can launch / sling the boat out the way it makes the job soooooo much quicker & easier.

Into The Blue · 21 July 2010, 12:06

Oh a couple more thoughts.

Max nose weight will be in your Car user manual somewhere. On a VW Passat it was c.90kg max, and they recommended that you run it as close to that as possible and to check it, borrow the bathroom scales - just don't tell the missus.

jyasaki · 21 July 2010, 14:29

Quote:

Originally Posted by Into The Blue

Max nose weight will be in your Car user manual somewhere. On a VW Passat it was c.90kg max, and they recommended that you run it as close to that as possible

Huh? Why would they recommend you run whatever trailer you've got at 90kg? I can see the max value, but that's just what it says: a max value. Not a baseline for whatever you stick on the back. If you have no trailer, you're running with zero tongue weight, so should you add a 90kg weight to the back of the car?

Tongue weight should a function of trailer GVW. A 100 kg trailer should have 7 to 10 kg sitting on the tow vehicle. A 1000kg trailer should have ten times that, or 70 to 100 kg. (In truth, I've also heard people advocating as low as 5%. but 7-10 is the generally accepted number I think.)

jky

9D280 · 21 July 2010, 15:52

And on a continuing theme, for example, I'd have to almost fix my old laser dinghy vertically to get 90Kg on there - the boat weighs about 50Kg minus the foils (int the boot) and the trailer only weiged about 70 Kg, and most of that weight was the axle & wheels!

The useful nose weight will depend on a multitude of factors. I run mine at about 40-45Kg (depends on the fuel aboard), and my old SR4 was nearer 30Kg. Both tow(ed) straight and stable.

Ref. the Aerodynamics comment, that will also vary depending on the tow vehicle and the trailer behind it. My box trailer behaves a lot more "twichily" on the motorway when empty behind my current estate car (waggon for the non UK readers amongst us) than it used to behind the hatchback I had before. The air coming off the back of the estate (brick shaped) is a lot more turbulent than the nice downdraft that came off the back of the hatch.

Into The Blue · 21 July 2010, 21:24

Quote:

Originally Posted by jyasaki

Huh? Why would they recommend you run whatever trailer you've got at 90kg? I can see the max value, but that's just what it says: a max value. Not a baseline for whatever you stick on the back. If you have no trailer, you're running with zero tongue weight, so should you add a 90kg weight to the back of the car?

Tongue weight should a function of trailer GVW. A 100 kg trailer should have 7 to 10 kg sitting on the tow vehicle. A 1000kg trailer should have ten times that, or 70 to 100 kg. (In truth, I've also heard people advocating as low as 5%. but 7-10 is the generally accepted number I think.)

jky

Got me beat why the handbook specs it as it does, but just checked for my current car - BMW 520, from the Handbook - nose weight limit is 90kg, "The nose weight should be kept close to this limit". Goes on to say how this will reduce the max payload of the vehicle, how the minimum nose weight is 25kg, blah, blah. If someone really knows this subject please post, I'd hate to be running too heavy.

I get the %age calc, that makes sense, current trailer would be 1500kg, even running at 5% would be 75kg, 7% 105kg so I'm likely to be safe at 90kg for my set up.

For Mike B - at least check the minimum and maximum nose weights in the handbook of the car you'll be using

jyasaki · 21 July 2010, 23:03

Quote:

Originally Posted by Into The Blue

nose weight limit is 90kg, "The nose weight should be kept close to this limit". Goes on to say how this will reduce the max payload of the vehicle,

This part is easy. The car can safely carry "x" amount of weight (well, inthe manufacturers eyes, anyway). If you put a trailer on the back, the tongue weight of the trailer is a load on the car. Therefore, your new max luggage allowance becomes (x, less the tongue weight).

As to why there should be a minimum tongue weight, I have no idea. Certainly isn't one without a trailer attached...

jky

Chris · 22 July 2010, 06:42

If your Rib is hanging a foot off the back of the rear of the trailer then I would start by moving the boat forward as this is much easier than moving the axles.

Don't forget if your trailer is braked you will need to readjust your brakes after you move the axle.

If you can get the nose weight you need by moving the Rib Forward then great if not then you will need to look at the axles as wel.

Chris

DGR · 11 August 2010, 19:56

As I understand it, the lighter the nose weight is, the more likely it is to set off on a wobble when your towing it. The limit on the tow ball is just that - so for easy towing, the nearer you get to it, the more stable it is. Just don't exceed the maximum.