Take the old ones off and use them as a pattern to shape the new ones.
Then just carpet them and bolt them in place on the trailer.
I did mine a few years ago and it was pretty easy. Even for a knucklehead like me.
I need to replace the bunks but, a new piece of lumber obviously isn't going to match the hull contours. Does it even matter or over time will they mold to the correct shape. I 'd rather not screw up the hull because of two new sticks of lumber. Any advice? Thanks
PS- Just got the seats back from the uph shop, looks sweat!!!!!!!! Will post pics soon.
Take the old ones off and use them as a pattern to shape the new ones.
Then just carpet them and bolt them in place on the trailer.
I did mine a few years ago and it was pretty easy. Even for a knucklehead like me.
If they happen to be straight, we use that heavy duty plastic, cutting board material for the aluminum jet boats. I think the stuff is kind of expensive but a guy at the ramp the other day recommended those new synthetc boards that people are using for decks, should last awhile and be relatively cheap. No idea if they are difficult to shape. I wish I thought of good ideas-Aluminum Squirt
Cabelas has a conversion you can get too. It converts your bunks into rollers, looks like they would work great. They come in two sizes 4' and 5' @ 2,500 and 3,000 lbs. capacity respectively. Never have to worry about the carpet or the wood again.
70 to 90 bucks each including the brackets.
Cabelas Trailer Bunks Page
I wouldn't feel real good about roller bunks. I can just see having my boat sit on it for a year and getting a nice ripple effect where it sat on a roller. I'd be really pissed if I spent the time and money to blueprint the hull, too. Who has experience with these on a fiberglass hull?
I think their supposed to be flat I cant remember seeing contoured ones before. Pressure treated 2x4"s and bunk carpet from Overtons.
KC
my 16 ft runabout has a roller trailer and it works great, but 40 hp outboard weighs lots less than an 18 ft jet and the layup on my Silverline is much thicker also. I have ash bunks, they are light and soft and after several soaking and sittings will conform more to the hull shape than a much harder wood would. Maybe someone who specializes in carpentry would have a better idea.
Good point on the rollers possibly causing damage to the hull, I had not thought of that possibility.
However as a observation I own a 19.5' Wellcraft (Fiberglass) I/O that is heavier than most jet boats including my Sleekcraft and it sits on an eazyload trailer (all rollers) and has been for 14 years without a hint of trouble with the hull.
Still you may have a point as most production jet boat hulls are built thinner and racing hulls are much thinner still than most production I/O hulls, Wellcraft builds them like a tank........
I have seen some new plastic stuff that is used instead of the carpet. It is made to allow the wood to dry and not rot. Alot of the new bunk trailers are using it. Wish I had a picture of it.
Fire on the water,
Go with pressure treated lumber for your bunks. Im not familiar with your setup but I really doubt that they are contoured. The whole purpose of a bunk is to hold and support the hull so the running surface stays straight. They best support a hull can get is in the water, so bunks are the next best thing. Dont even consider going with rollers. Rollers instead of bunks are only found on cheap trailers. Any good custom trailer will have bunks. Be sure to through bolt them with stainless steel carriage bolts and nuts (always use anti-seize on stainless bolts) and staple the new bunk carpeting on with stainless staples and youll be set for 10 years or more.
The stuff Dan is talking about sounds interesting, might be worth checking out.
Good Luck!