Setting up and balancing a twin axle trailer for 23 foot inboard power boat

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JimJimney

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Hello,
I've a 23 foot inboard cuddy cabin weighing 1700kg dry. I carry minimal fuel and no water on the trailer and little gear so I think we're comfortably under 2000kgs.
I've a new 7m twin axle trailer weighing around 400kgs which is capable of 2700kgs (inc trailer)
I'm towing it with either a heavy Landrover coil sprung discovery 2 (heavy as its an expedition vehicle) or a standard air suspension discovery 3.

I've had some problems setting it up, had paid a 'marine mechanic ' to do this but it turns out it wasn't well done and I've basically redone it from scratch.
The winch was pulling at an angle so I've had a post extension fabricated to pull horizontally. The winch supplied is a little under powered, rated to 500kgs but as long as I'm careful (ie float it most of the way up the trailer) seems to be ok, will look to upgrade in due course. Or is it enough?
The keel rollers had hollow spindles and after a bad retrieval had bent a little so I've replaced with solid spindles. Much better.

My questions are.
It's only got 4 keel rollers and then 'wobble' rollers up the sides (no bunks), seems sensible to have the wobble wheels taking a bit of the load too so I've jacked them up till they all touch the hull, hard to say how much load they take, not too much I think. Make sense?

The tow bar nose weight ( tongue weight for Americans) is tough to get right, it's not heavy enough. I can't move the boat any further forward so I've been hammering the axles back. (Jacking boat up, hammering a couple of inches, lowering boat, re checking, repeat!). I'm aiming for 100kgs nose weight as that's 5% of the load and seems a minimum. But depending on which vehicle I'm towing with, the tow ball has a 10cm height difference, this affects the tongue weight quite a lot. So far I've got the tow ball weight to maximum 80kgs when about 45cms off the ground, you think that's enough? I've spent days messing about with the trailer and started to have had enough.
When I lower the jockey wheel fully the tow hitch will now sit on the ground. Is that normal? I don't want to put too much weight on either axle, but I assume by having a decent positive nose weight the axles will be balanced.
I think I'm doing this all ok, read a huge amount on line and watched lots of YouTube videos. Any ideas are welcome.
Thanks for reading!
James
 
Ideal nose weight is 7% of load. Rig should be horizontal at ideal weight.
Large 4x4 should take 100 - 150 kgs nose weight. I tow Fairline 21 Weekender no trouble, including to Med.
I had to replace removable tow hook on my D4 with a fixed tow bracket to get enough height on the tow ball to achieve
horizontal rig and to give enough clearance on jockey wheel.
 
KDee said:
Ideal nose weight is 7% of load. Rig should be horizontal at ideal weight.
Large 4x4 should take 100 - 150 kgs nose weight. I tow Fairline 21 Weekender no trouble, including to Med.
I had to replace removable tow hook on my D4 with a fixed tow bracket to get enough height on the tow ball to achieve
horizontal rig and to give enough clearance on jockey wheel.
Click to expand...

Hi, ok so ideally when horitontal its 7% and at that height it is also attached onto the tow car?
Jockey wheel clearance, you just mean when it's fully retracted? Thanks
 
Yes, that is what I am lead to believe from the various towing websites. On the D4, the removable tow hook was too low, so the trailer was angled down at the hitch end, leaving little clearance between the fully-retracted jockey wheel and the road.
Corrected with the (adjustable) fixed tow bracket.
 
I bought a 2.5 ton Power Boat which was too heavy for the trailer which the boat sat on and I had to balance it.
By standing back and looking at the tyres I noticed that the front tyres bulged more than the rear, so I moved both axles back by around 6" and that did the trick. also the front hitch was too heavy to lift by hand.
 
If the winch is rated 500kg pull, that should be OK to pull a 2T boat up the rollers.
If it's rated for a 500kg boat it will be no good.
You are not lifting the boat, you are pulling it up a slope.

The trailer must be very close to horizontal or you are wasting your time. The suspension won't share the weight between the axles otherwise.
You need to be doing this on pretty level ground.
Nose weight, mostly a case of see vehicle handbook. A lot of people tow great big caravans with only 70kg on the hitch. More is probably better if your vehicle is happy with it.

If you lift the loaded trailer with a couple of trolley jacks, and find the balance point, you can work out where the axles need to be, if you know the total weight well enough. But it's not too hard to do it by trial and error.
Don't forget to check all the tyre pressures first!
 
My experience of setting up my twin axle trailer (for a much lighter boat)

Get as many keel rollers as you can. I still find in practice I can't roll my boat, but now I crane in and out that is not an issue. The side rollers are there to stabilise the boat when towing, not to take much weight.

I got the nose weight right by doing as you did, move the axles further back.

You want the trailer to tow level. Anything else and you are transfering too much weight to one or other axle. Adjust your tow hitch to get it the correct height to tow the trailer level, and measure your nose weight at that height. In my case I did that with an "upside down" drop plate to get the tow ball high enough. With the correct nose weight, if I uncouple from the car with the jockey wheel up, the tow hitch will settle lower, but not on the ground, it will reach a new equlibrium with more weight on the front axle and settle at that

If you are recovering from a slipway, because of the angle, as you pull up the slipway, the boat will always settle further back than the winch post / bow support. So can you make the winch post adjustable so it's "too far" forward for recovery but will leave the boat settled in the right place. Then once recovered, move the post back so the bow sits in the support for towing. This will avoid the need to drag the boat up the rollers.
 
THANKS EVERYONE, I think I've answered ideas here:-

The winch has a total capacity of 500kg (I'm 99% sure it's not rated for a 500kg boat) ) it does move it depending on
the angle , but it's tough going. A two speed winch sounds a good plan, as does using a crane. But I'd like to be able to launch and retrieve myself from a ramp, if I can get it right.

I've moved the axles back about a foot and can't easily move them without moving the position on 2 wobble rollers. I've got the nose weight whilst level to be 100kg and did a test run last night round an very hilly industrial estate plus a short 45 mph burst. All seemed solid. It's a struggle up steep inclines but the balance seemed spot on. Even my wife agreed who was following me to keep an eye on things.
I can't move the winch post forward, it's as far as it'll go, so sadly cant temporarily move it for retrieval purposes. I will add some extra keel rollers and maybe the shared load will aid rolling resistance and help that final few inches to get it snug.

Im having some training by a local marine mechanic next week and we're just doing launch and retrievals, hes already suggested some 'guide ons' , additional rollers (or bunks) attached to each side low down at the back. Does anyone have any option in on these or 'guide posts' , they seem popular in the states and help reloading so you can see where the rear is, and drive / pull the boat between them.
Many thanks
Jim
 
JimJimney said:
I could have something fabricated (friends a welder) easy enough, or you think these are worth it?
Click to expand...
They have been for me, mainly launching into a creek off the beach - so fair tidal flow - once the bow's in between them you have time to hook on the winch rope..... Soft padding so don't damage the boat, but I'm sure your friend could make something up for you.
 
Redfox226 said:
They have been for me, mainly launching into a creek off the beach - so fair tidal flow - once the bow's in between them you have time to hook on the winch rope..... Soft padding so don't damage the boat, but I'm sure your friend could make something up for you.
Click to expand...

I'm very tempted, I've seen them on YouTube. Look great, I've emailed the company to check they'll fit my rig. What size boat do you use them on? Thanks
 
Guide posts can be really usefull. ie posts attached to the back corners of the trailer rising up above the height of the gunwhale. As said they help guide the boat onto the trailer. A seldom thought of other advantage is that when backing the empty trailer into the water you can see the trailer easily from the driver's seat. I can't see my trailer when empty especially when it is lower than the car on the ramp. I used to have guide posts back when I launched for every sail but they got lost in trailer rebuild.
I don't know much about dual axle trailers but obviously the trailer must be level with equal load on each axle. So raising or lowering the tow ball would be a priority. Certainly on a single axle trailer 10% is a better number for nose weight.
The handling difficulties with insufficient nose weight come at reasonable speed going down a hill with car power off. It can start to sway like crazy until you put power on the car which can be a bit frightening.
Persevere with the towing and launching and it will all come easily eventually. It is just so common around here with hundreds of trailers at our local (one of many) ramps with often very heavy boats. olewill
 
William_H said:
Guide posts can be really usefull. ie posts attached to the back corners of the trailer rising up above the height of the gunwhale. As said they help guide the boat onto the trailer. A seldom thought of other advantage is that when backing the empty trailer into the water you can see the trailer easily from the driver's seat. I can't see my trailer when empty especially when it is lower than the car on the ramp. I used to have guide posts back when I launched for every sail but they got lost in trailer rebuild.
I don't know much about dual axle trailers but obviously the trailer must be level with equal load on each axle. So raising or lowering the tow ball would be a priority. Certainly on a single axle trailer 10% is a better number for nose weight.
The handling difficulties with insufficient nose weight come at reasonable speed going down a hill with car power off. It can start to sway like crazy until you put power on the car which can be a bit frightening.
Persevere with the towing and launching and it will all come easily eventually. It is just so common around here with hundreds of trailers at our local (one of many) ramps with often very heavy boats. olewill
Click to expand...

Hi Will, I've emailed Floatem and they sent a very quick reply with a technical drawing of my trailer dimensions. What service! I think that alone (almost) deserves a purchase. I think the added visibility with the empty trailer is a great positive.
I've tried a steep downhill with the trailer now and seemed fine. I might change the brake calipers and pads in my Landie though but as its so heavy it handled the boat great. I'm not sure my tow bar(s) are adjustable so would have to add a kind of extension plate, but it seems to be riding pretty level. Many thanks Jim
 
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