Boat Transom to Trailer Tiedowns??

[TREVELLY]

all things considered if I have a boat weighing 1.5t and 80% at back and a safety factor of 3 then 1.5x0.8x0.5x3=1.8tonne capacity to each of two straps but the boat trailer weighs only 0.5t but that is okay as with a safety factor of 3 then strap only needs to be 0.5x0.5x3=0.75t, but takes no breaking force into consideration - looks like 1.5 to 2t is something closer to right and only for swerving and braking not for sudden impact or crash.

I agree Darren, if we are just looking at uplift then trailer is the critical number as it is a lot lighter than the boat - but I am happy to have the bigger boat number as the governing value as we also need to include something for braking or sudden stop and not to count wholy on the front of the boat fixing to post/drawbar to stop it.

Just thinking if the front fixing is totally secure at the draw bar - ie chained down and the post will fold as expected - then without good security at the back as it has broken from the braking and not the lifting - then nothing is there to stop it lifting so over the top it goes to stop upside down on the roof of the car - yep I will stick with the bigger straps at the back of the boat.

From my recollection in braking I think in wheels be it for cars or bikes they rely upon the breaks to be 80% front wheel and 20% back wheel.

Force goes to the stiffer element so if the front gives way then force goes to the back.

I like the "to be sure to be sure" approach in this case.

And just for the record I am not trying to bring poor ol ShyGuys boat into this - it was pure coincidence in timing that I get my boat back this coming Monday and it has had transom lugs added so i just want to know the best way to secure it.

Based on your advice i went for the Beaver ties rated 2.5t
http://www.ebay.com.au/itm/190718009...84.m1497.l2649

A great forum for advice - I even learnt the best way to shorten and finish the strap and of course will add rub pads to the strap to hull if necessary.

[TREVELLY]

You know in thinking about this it seems that the extra strap I have right across both sides of the transom and down to each side of the trailer might not be the best solution.

Ideally you want something that exerts no downward or inward compressing force but that stops the boat lifting off rollers after road bumps.

A solid brace with adjustable height and a padded c shaped collar for going over transom would be ideal... One for each side. Bottom of brace has hook for the eye welded on trailer.

It would absolutely resist upward movement because it's a solid piece and yet place no force on the boat hull.

Seen anything like that?

I had a home made jobbie like you describe on my 10 foot fibreglass boat 33 years ago

[Fed]

Pulled this up from an old googleboot post.
The parts that count are bolded.

What ever you do, do not rely on the winch post, there are all to many instances of winch post failure, ya just have to look at all the pictures ya see posted with this particular failure.

Anything that moves arround on a trailer is going to get damaged one way or another.

Have a look at the National transport "load restraint guide" ( google will find it), and it will show you the minimum requirements.

Its a good read, and it raises a number if issues, you may not have thaught about.


Breifly
Minimum you must provide resraint as a persentage of the loads mass, to prevent movement in that direction.
80% forward
50% sideways
50% to the rear
20% upward
The rest of this is typical googleboot blah blah blah.
and that is an expectation for a relativly smooth road and to prevent loss of the load not movement that may cause damage.

remember you can not rely on any friction on a boat trailer and many of the lashings we use do not act directly so their lashing capaity has to be worked out...... those straps may easily be overloaded

So many boats we see being dragged arround rely on the winch strap and a single strap over the thwarts......anybody who has thaught about it will realise that this is hoplessly inadequate.

remember each end of the boat has to be held down seperately and if the thwart strap fails to do its job the boat can simply ride up over the winch post unless the front is held down and secured toward the rear.

Remember too that trailer flex, some quite a lot......ya need the boat tied down to the trailer so the whole thing rides a 1 rigid mass.

cheers

I've seen a few broken winch posts and every time it was caused by the winch post/winch not being adjusted properly to suit the position of the boat bow eye.

I'm happy to rely on my winch post (and safety chain) plus a strap at the back. I even trust my winch post alone when I take off up the ramp and I think most people do the same.

I'm sure none of the restraint guidelines even consider trying to stop a boat in a crash, let's face it a 1000Kg boat could turn into a 10,000Kg boat when you crash into a brick wall.

[cormorant]

"I even learnt the best way to shorten and finish the strap and of course will add rub pads to the strap to hull if necessary"

That would be a unofficial way and I'm sure there is a special official machine. Email beaver as they will probably tell ya the propper way. I have also "borrowed " the hot knife at the friendly chandlers just like you do with synthetic ropes. Don't trim em off too short too early as you may need extra length to tie em off to stop em flogging in the wind and also they are better with at least 2-3 winds on the spindle as that gives a bit of shock absorbtion. You'll then have a couple of great furniture removalist straps left over.

This style of hook may be better? http://www.tiedownsdirect.com.au/pro...le-J-Hook.html

The ones you bought will have 2 yellow thinish abrasion rub pads included and you can move em to the where you need them or do like we did and pull them inside each other to double em up. Depending on where your points are on trailer and boat you may have a issue with the actual ratched rubbing on the boat- we just used a old bit of tyre under it on the glass boat before we tensioned it up. You have lots of leverage with ratchets so they only need to be firm.

You have to consider accident forces / emergency braking in securing stuff so that the load doesn't move and wag the dog- totally different dynamic. Just using the trailer weight as the max working load totally ignores the fact of the forward momentum under braking or sudden stop as mentioned. Straps over the top of things lashing them totally rely on friction and huge tension to prevent movement and that is not good for boats on trailers.

Just about all the big offs you see in the horrible photos like Shyguys and the boats at intersections show that in some way the forces were bloody huge or the straps weren't adequate ,or tiedown points failed. Be interested to hear what was still attached to the bow and if the shackle, the tow point, cable or chain gave way or was the complete winch post still attached ? Either way whatever holding the stern and bow to the trailer in some way didn't work. In reality the failures absorbed a hell of a lot of force and may have stopped a worse situation or created one. Just glad it wasn't me and all are OK.

[terryc]

I must be unlucky but i have had 2 occasions where the stainless bow eye snapped off inside the fibreglass, 2 different boats, upon inspection rust was the factor but you would never see it until it happens. Each time it happened it was the main over the hull strap towards rear that saved the day.