yeah mate good questions. i'v also got an ibeam trailcraft and would also like to add second axle, drop down spare and maybe a longer draw bar.

will be interesting to see what comments you get - just to see if its worthwhile and what sort of cost it could be.

I think the 2nd axle will give peace of mind not only on the tracks but also when burning up the highways.

imo i dont think it would be wise to modify a i beam single to a dual and add a longer draw bar they have a fair amount of flex and would need to be desighned with the above features before building and i would be asking around if a i beam can be made for off road fitting a treg hitch would be a start but the flex may be a issue

profish , i dont know how far you want to go , i dropped off the twin slippers and installed h duty dual leaf springs and counter lever arms.  my original springs were rated to 2 tonne and my boat and trailer actually weighed in at 2 tonnes so there was no leeway , i installed 3 tonne springs with counter leaver arms and the ride improved, we have been into gnaraloo with it several times and it certainly handles the extra weight better, if i went another step you could look at putting shockies on as extra softning or go independant suspension,  but IMO i dont like the i beam trailer which came with my trailly boat , i think there is to much flex and twist, iif you need a hand or got any ideas PM me , more than willing to help

chop the old leafs and put some bigger ones in to accomodate larger tyres 28-31 would be ideal. i had a sort of tradie trailer a while back i used for camping and did this and worked well, sat better behind a higher towball. althou you dont want to be towing a boat over to much rough stuff where you will need the clearance and flexing up the trailer.

could also get a greasable suspension set up so you can maintain it better and maybe  larger hubs so you have bigger bearings, bigger=less stress and that means improved life expectancy.

aaaaand a strip of rubber behind the tow car as a giant mudflat to stop the pesky rocks.

Years back we had a trailer modded with independent suspension arms, coil springs and air shocks. Be really careful with beefing up springs etc. Ours ended up too heavy for the load and really bounced the boat round, and needed further tweaking.

Thanks for the comments.

I will be putting hangers on for sure with greasable points.The trailys are already set up to take the second axel it is a option that i didnt get but the single slipper springs are poxy.

I have decided on not going any bigger that 15" so that i dont have to drown the 4b when putting it in on low tide.

Has any one set up a stone gaurd that dosn't get in the way of the winch?

Before I bought the 590 Trailblazer, I was looking at a second hand version (2006 model 570) that came with a single axle trailer. When I asked at the boat yard about wanting a tandem axle trailer, I was told to take it to a trailer place and have them install a second axle, etc. I went thru the exercise of getting it priced...about half the cost of a new tandem.

Anyway, when I bought the new boat, I insisted on a tandem axle trailer...I asked someone else at the same boat yard if the single axle and tandem axle trailers were the same trailer with just a second axle fitted and was told that they are completely different trailers. The tandem axle trailer sure looks bigger, stronger, etc. 

This doesn't mean that all single axle trailers can't be converted to tandem axle, but this is just my experience.

regards
rusty...

Has anyone had experience with tandem of road trailers ? I havent seen many myself. JMO but if you were driving over hills would you have problems with one set of tyres hanging of the ground ?

Some one might have more insight into this. There might be a good reason you dont see many 4x4 trailers with two axles.

Cheers Grant .

Probably expense more than anything.

I used to work for an ag business and we made boomsprayers, and they're not really about their on-road use.

Up to a point pretty much every big load was on dual axle trailers with rocker arms between the springs. They used 4WD tyres, right up to 4 super singles.

Grantartic  what you have probably seen is a standard tandem setup with slippers which dont allow difference in road height and when going over different terrain one set looses contact with the road because there not enough travel in the swing arm,  installing counter lever arms and leaf springs will prevent this and does allow both sets of wheels to do their  of travel and distibute all of the load evenly

Yes, on a different trailer, but similar size boat. Sorry for the motley collection of pics but they're all cropped out of others as they weren't specifically of the stone guard. Although it looks crowded, the (manual) winch is still easy to access and not interfered with. There's also a drop-down spare wheel, and a drawbar extension in there. The only thing that did get crowded was the jockey wheel, or more specifically the handle on top when the jockey is in the vertical position, so that was fixed with a velcro-opening panel in the mesh (last pic shows it a bit).

Afterthought, a stone guard on a camper trailer is usually straight, but on a boat trailer it has to be a lot further forward on the draw bar; so the sides have to be angled back pretty dramatically to allow clearance in tight turns (the kind you might get when reversing). You might not think it to look at, but I can still (just) crunch the outer edge reversing it into the shed.

Cheers Hal i like your work.

Great idea with the rubber flaps that you have attached on the bottom of the gaurd.

Also thanks to Just dhu it for your great advice in your pm i am now thinking of going with the single axel option.