How should I mount my bunks?

[b.gagnon]

I have a 17' seanymph aluminum boat that I just got a used trailer for. I plan to put new bunks and rollers on but I question what position of bunk to use.
The old trailer (which I don't think was ever set up right) has vertically mounted bunks. What would be the reason for mounting them this way? Would it be ok to mount them flat?

 

[TruckDrivingFool]

Re: How should I mount my bunks?

I have seen them mounted vertically when the board is too wide to fit between the ribs (rakes?) in the bottom of the boat being trailered. I would think a wider surface area would be best and would definitely mount them flat if you can.

 

[reelfishin]

Re: How should I mount my bunks?

When mounted vertical the board has less flex and produces less drag when the boat has to slide on the bunks. I usually only flat mount the bunks if the boards need to conform to the hull a bit. I vertical mount them on a flat bottom boat.
On my 12' jon boat, I simply ran two 6' vertically mounted carpeted bunks and pushed the keel rollers all the way up. On a V hull, mounting them flat often works out better but it depends on the shape of the bottom of the boat. I have a 12' Duranautic that is pretty flat on the bottom and very light, I have those mounted vertical as well. With the bunks flat, the boat would stick the wet bunks and require me to winch it up out of the water the whole way, with the bunks vertical, I can slide it up by hand, making loading much faster.
I positioned the bunks directly under the main stringers in the hull, just to the outside of each outer strake.
If your boat has an extreme V shape at the rear, it may be necessary to mount the boards flat with a swivel top mount to get the proper angle.