Originally Posted by SPR
can I ask what the reasoning of the front strap to rear, I though that is pulling Thr boat off the trailer ?
If you think of what would happen in the event of even a minor frontal collision, the boat, because of its inertia will naturally try to continue at the same speed as the trailer was traveling at prior to the sudden deceleration. Gwenn weigs in at just over 1600kgs which a lot of energy to try to stop. Without a front strap i would be concerned she would ride up and over the bow snubber eventually causing the winch strap to 'snap' tight again.
Shock loading any kind of strap or sling can impose a massive increase in the loading it experiences potentially causing a failure. (one of the reasons lifting slings have an inherent safety factor built in)
By pulling back on the bow against the winch strap you are effectively canceling any chance of the boat shooting forwards (obviously only to the UTS of the rear facing ratchet strap) The downward angle of the strap also causes a downward thrust on the bow should she get pushed forwards.
Because Gwenn overhangs the rear of the trailer by approx 500mm, the two rear straps are in effect putting a very slight forward thrust on the boat potentially helping her to ride forward and over the bow snubber. It also helps to reduce the chance of ripping the winch post of the front cross beam (although my winch post is held on quite well with 3x12mm high grade U bolts so in effect 6 1émm nuts to shear off)
I built the trailer with this in mind and for the cost of welding in a couple of pad eyes and a decent ratchet strap it's IMHO, money well spent.