Bottom bunk (support) position

[sberl]

Hi all,
I've been around boats and fishing my entire life however just recently purchased a (project) boat of my own. A question I have on the trailer is this: are the bottom bunk boards supposed to support the hull the entire length of the bunk? The ones on my trailer only support the very aft end of the boat and do not even touch in any other place. I hope I'm even using the correct term - learning as I go haha.
They need to be replaced on my trailer because they are 30 years old and are completely rotten. Am I correct in assuming they are just treated 2x4's covered with bunk material?
Thanks for any guidance you can give this new boat owner!

 

[Ibl0wstuffup]

I used cedar. If it's an aluminum boat, don't use pressure treated.

 

[sberl]

Thanks! Good call on the treated - I knew not to use it for the flooring but for some reason that didn't cross my mind for the bunk.