Hi Mark,
Afraid I'm not too much of an expert on dart 18 vs 15 trailers - except to say that I have possibly the biggest trailer ever to convey a sprint 15 (it came with the boat, but could easily carry an F18 or bigger) and there's still plenty of clearance between the mudguards and inner hull - so I guess it just depends on the specific trailer design as much as the size of boat it was built for.
I prefer rope to ratchet straps, but I think I'm in the minority there. My reasoning is:
- Ratchet straps have metal buckles that can chip gelcoat
- If you don't arrange straps carefully (e.g. forget to put in half a twist where they span some distance) they can oscillate in the passing air and chafe themselves or parts of your boat.
- Ratchet straps can catastrophically fail with little warning when they age, usually at the stitching.
I tie one long length of rope right across the boat and back again between the rear supports (which sit 6-8 inches in front of the skegs). I have a loop (bowline) in one end and feed the other end through this to achieve some purchase and get things tight (without going mad). At the front, I have two shorter lengths that I take over each bow and tie down to the front supports - again with bowlines in each end to get some purchase. I have pieces of chopped-up Ikea doormat that I place under these ropes at corners to prevent chafing.
Finally, I have two separate ropes that I take from each side of the front beam forwards to the front trailer supports. These stop the boat sliding backwards. The shape of the hulls and the position of the other ties already ensure it can't slide forwards.
I rest my trolley upside down on top of the hulls, about half way between front beam and tip of the bow - directly over the front trailer supports. It sits at a slight angle, but once tied down to the trailer support it won't budge - not very aerodynamic though.
Another thing to think about is a sufficiently wide lighting board and means to mount it on the transoms (unless the trailer has its own mounting under the boat for this purpose). When sitting on a trailer, the transoms point upwards by 10-20 degrees, so your trailer lights will be optimised for low flying aircraft. If you can improvise a method to get the lighting board vertical (I have bodged some wedge-shaped wooden brackets) it makes best use of the slightly feeble light emitted by the average trailer light unit.
That's my 10p worth - others with more 15 towing experience may know better.
Cheers
David
