My only observation is that a a yacht, how did you come about the CoG? you are towing with the mast down, fuel / water tanks could be full / empty. If you based it on a maker's drawing have you more / thicker anchor chain i nthe forward locker, or changed the winch to a big powered thing form a simple light hand winch/ etc etc. Simply based o nthe yachts I see on stilts at the marina, your pic seems to show it peretty much dead centred over the axles. very few of the yachts Isee sit perfectly centred in their cradles / trailers.
OK, My rib is on a 2 axle so no load sharing issues, but it still took me 2 months of towing to get it set up & balanced perfectly.
FWIW let me take you down the size scale to a wooden bodied camping trailer I have been towing since it was behind my dad's Vauxhall Cavalier.....
This trailer was designed to carry a couple of laser dinghies "car top" style on a rack, and as a result has an extending drawbar (so it could be used as a more sensible box trailer when not being used to lug lasers about) and an old Bradley Doublock hitch.
Now, when I was first acquanited with it, the hitch sat atop a 2x2 section welded atop the drawbar. This made it all sit vaguely level with the road on the Vauxhall factory fit ball.
So, FF a few years and I own a Fiesta with a Witter bar on the back. I ground the jockey wheel on the first three speed humps, so I turn the drawbar over such that the 2" box section is now doing nothng more than hanging below the drawbar out the way. Entire front of the trailer has now lifted by 2" and I proceed to tow uneventfully using that car and a subsequent two more Fiestas (and they are diffenret models so different Witter metalwork) - the first I had to drill the boot floorpan, thee subsequent 2 used the C "approved fit points" which were law(?) by then).
I then get myself a Mk1 Focus. Again, Witter bar is fitted, and the trailer stays pretty much horizontal. FF a bit more and a MK2 focus is bought with a factory fit hitch. Trailer is now at a funny angle and I have to spin the drawbar round again. This is the car I first tow my "new" rib with, and even taking nto account I specified 10" wheels to make launching easier, on the "relatively high" ball it looked OK.
All through this time with the witter bars I then got a Laser combio trailer which sat perfectly level behind the witter bars, and sloped back with the Ford bar.
I now drive a Mondeo with a dealer fitted Towsure Hitch, complete with Plate specifying date of manufacture, part number and a warning to fit it to the correct vehicle. Guess what. It's at the same height relative to the road as my Fiesta & Mk1 Focus aftermarket bars put the ball. Thing is I could spin the drawbar round on the box trailer to loose the 2" "packing" under the hitch, but it's not an option on the rib trailer..... so, how do I jack up a jockey wheel?
Now, My memory (part agreed by the numbers being thrown around above) is that the hitch height on a car (as good as paraphrased) has to be something like 350>h>420mm from the road in the loaded condition - that's a 2.75" difference in altitude!
- Are we talking Max GVM - rear wheels scraping the mud out form under the wheel arches?
- Are we talking the Euro standard for emmissions testing of 3 nominal adults at 75Kg, all with a 6.5 Kg (? going form memory here so someone correct me if I'm talking rubbish) luggage item each in the centre of the load space?
I suspect it's done like that so that cars with big overhangs (some estates ) can be fully loaded, (bigger overhang = bigger drop when loaded ) and I would guess most manufacturers put the factory fit / OEM hitch at the top of the travel to make sure it's always in the height range when the vehicle is loaded.
Based on my sample of 4 bars / 2 suppliers / 3 cars I would guess the aftermarket dudes aim a little lower for whatever reason - remmeber to get their metalwork signed off since about 2006 (probably earlier) they have to go through much the same testing as the OEMs.....
"i have been told by Vossa and the VCA you are not allowed to fit anything to the vehicles tow bar other than what's been designed for that vehicle. So drop plates cannot be fitted at all!"
So surely I shouldn't see them on sale at every caravan / trailler place I go to?
You sure they werenlt meaning "type approved metalwork" as most of the hitches these days bolt on in place of a rear corss member, unlike 20 years ago when you had to drill the boot floor? The "type approved hitch" I totally agree with - but jack plates?