bunks, on edge or flat?

[hipster dufus]

is there a reason to put bunks on edge? i have seen them flat on a lot of trailers. i have seen them on few trailers on edge. which is best? why?

 

[s freud]

Re: bunks, on edge or flat?

is there a reason to put bunks on edge? i have seen them flat on a lot of trailers. i have seen them on few trailers on edge. which is best? why?

My uneducated thought would be that placing them flat would provide more surface area and thus more support. Remember not to use treated wood if your boat is aluminum.

 

[dlngr]

Re: bunks, on edge or flat?

As I just posted on another thread,mine lay flat [2x4 about 5' long] Never had a problem. 14 foot Lund.

 

[mrdancer]

Re: bunks, on edge or flat?

is there a reason to put bunks on edge? i have seen them flat on a lot of trailers. i have seen them on few trailers on edge. which is best? why?

Only good reason is to get extra strength or less warpage out of a given size of board. I've seen some older trailers with heavy boats that had warped boards. If your boat isn't too heavy, it would be better to lay them flat (better support and easier launching/loading).

If you used composite wood, you would need to lay on edge as well as have extra supports, or lay flat with a LOT of supports.

 

[BRICH1260]

Re: bunks, on edge or flat?

I`ve got both on my trailer. I have two large cypress bunks in the rear turned on edge and up front have two 2x6`s lain flat. If your supports are spaced farther apart, turn the board on edge as it will carry more weight. When the bunk supports are closer together, lay them flat.

 

[oops!]

Re: bunks, on edge or flat?

the reason for laying the bunks on the flat....is because they have some flex.

the rigidity of a board on edge could easily cause stress cracks in the gellcoat if being trailered over less than ideal road conditions.

 

[foodfisher]

Re: bunks, on edge or flat?

Haven't figured out the on edge thing. I'd rather lay down on the flat of a, pick your big knife, machete?, than either edge.

 

[bonz_d]

Re: bunks, on edge or flat?

Sorry but I too am having difficulty wrapping my head around this "flat or on edge" debate. Rigid/flex, support/no support, easier to load. Seems to be the same debate as rollers or bunks and which is better or provides the proper support.

If a bunk flexes how can it provide even support to a flat surface it's entire length? By increasing contact area how would that make it easier to launch or load w/o floating on and off and if one is floating on and off what difference does it make? Add as many bunks as you like.

Sorry again but I use many ramps were it is impossible to float on or off so I truely do not know this issue.

 

[Thalasso]

Re: bunks, on edge or flat?

As said above. When you have long spans and a heavy boat with a wider beam ( more then 8Ft 6in ) you need strength. You cant get that laying them flat. My bunks are on edge but they are 12ft 6in long supporting 10500 lbs (dry weight) on a 10ft beam.Can you imagine how much bow there would be if laying flat.

 

[tboltmike]

Re: bunks, on edge or flat?

By increasing contact area how would that make it easier to launch or load w/o floating on and off and if one is floating on and off what difference does it make? Add as many bunks as you like.
.

According to the laws of physics, at least in theory, surface area has no affect of force needed to slide an object on a surface. It is stirctly a function of weight and coefficient of friction. There are products that reduce friction for that specific purpose and common lubes like silicone spray, vegitable oil, etc.

 

[bonz_d]

Re: bunks, on edge or flat?

According to the laws of physics, at least in theory, surface area has no affect of force needed to slide an object on a surface. It is stirctly a function of weight and coefficient of friction. There are products that reduce friction for that specific purpose and common lubes like silicone spray, vegitable oil, etc.

Understood. Have read of the Slick Stix for bunk but have yet to be able to try them as I'm currently using an all roller trailer.

 

[loose rivet]

Re: bunks, on edge or flat?

What it boils down to is which way the bunks fit the hull best. If your hull has sufficient flat area for it to 'nest' properly onto bunks laid flat, than I'd probably say lay them flat, if not, you may not have a choice but to stand the bunks up.
I've found that on some aluminum boats the only option is to stand the bunks on end to avoid the boat resting on a row of rivets.
One big advantage in laying the bunks flat is that it often allows you to get the boat lower on the trailer while still keeping the bunks under the strongest part of the boat, just below the stringers.