Trailer bunk replacement?

[buckaroo]

Hi, all -- I'm finally getting back to working on my CP16 after a few years of neglect, and have realized I need to replace the bunk boards on the trailer. To any of you who have done this - do I need to make sure the bunks are properly bowed to conform to the shape of the hull by installing with the boat on the trailer (a process which will take many steps) or is it ok to just screw the new bunks on with the boat off the trailer, leaving a straight-across board (I worry about oilcanning and the pressure of the weight of the hull stressing the screw holes as the board assumes the shape screwed-in)?

(Also: May I just vent for a moment about the terrible design of the bunk bolsters on these trailers. Once the 3.5 inch set screw has rusted, it's in there for good, and there is simply no lowering the bunks anymore. Arrrrggh. I'd like to swap out the screws, but the last time I tried (with the keel guide, thankfully, so not a critical part) the tack-welded "nut" in the bracket snapped right off. Unreplaceable, too, as near as I can tell.)

[Chris D]

Yeah, i've been eyeing up the rusty bolts on my trailer bunk guides. They don't look too friendly. I wonder if stainless steel bolts would last?
I thought I read somewhere on this forum that the boat will cause the bunks to form to it.  Maybe someone can back this up.

Chris

[Chris D]

Here is a post that may help.
http://cpyoa.geekworkshosting.com/forum/index.php?topic=6942.msg50315#msg50315

Chris

[JTMeissner]

buckaroo,

I just went straight across when I replaced bunk boards in 2011 (and all other wood on the trailer).  Two things, the first is that the majority of the weight of the boat is sitting on the keel on the rollers (in my case) or board, so there's a comparably smaller amount of force on the side bunks, and second, they are guides, not supports (see first thing).

After installing the straight pieces, I raised them until they were just touching the sides of the boat.  There is a gap along both the forward and aft portions of the guides (the wood does not conform to the shape all along the hull).  IMHO, if you tried to do that, you'd end up with the rear spacing being too skinny.  When the side guides conform too much, the fatter, middle part of the hull has problems fitting between the guides, which requires the trailer to be deeper so you can float over the rails.  It makes it a pain in launching as well. 

Once things are set, time will bend the boards a bit, so adjustments can be made, but I'd recommend more so in the front as you want to keep the stern end open to ease the boat in and out.  At the end of the day, you want the boards slightly vee-shaped so the boat gets guided in, sits on the keel and can get secured for travel.

As far as oil canning, where the bunks lie is where the foam is placed under the berths; it's pretty solid.  IIRC, one of the purposes of the foam there (not for floatation) is to keep the hull shape solid in case the boat was fork-lifted/stored.  Again, with most of the weight on the keel, you'd have to be trying to lift the boat by the side guides to start pressing that hard, not sure the wood/fasteners would hold.

And for the trailer, I have a Magic-Tilt from 1982, so I think a bit different.  I have a small bracket where nuts were inserted with machine screws running through.  These were rusty, and I had a heck of a time getting them out (grinder, cutter, torch, etc).  But, replaceable, and so we'll see how the stainless hardware holds out. 

I'll try and update with more photos once I recover from the Photobucket hostage situation.

The first picture shows what was replaced (square heads as well).  The second is the rear support, shows the bracket for adjusting the height of the bunk (used a jack like as per the other post).  The third is a shot from when I removed the bunk berths and shows the foam underneath. {OK, those got swapped around} Final photo shows the slight bend in the guide but that it's not flush along the sides.

-Justin

[buckaroo]

Thanks, everyone -- this is all great info. Looks like I'll just mount them flat and let time do the job for me. Justin, thanks for the photos -- my mount are a little different (my tailer isn't a Magic-Tilt). I think I've got photos around here somewhere -- I'll post them if I can find them.

[ameysails]

Buckaroo
Agree with reading Chris D's recommendations...I think we can make it more simple
and the review notes of JT Meissner
We have a 1989 16cb whose trailer spent too much time in the elements, so we DID NOT attempt to loosen the bolts that secure the vertical posts to their best height. Our total cost was less than $100. We use SS whenever possible for longer life.

Materials: (we leave the bolt dimensions to your situation. You can do this better than we since you are there )
1.)   Get some solid POLYWOOD  ...16 ft and 1 in think and 5+in wide. As it's plastic and used for decking, it is water adverse and needs no further treatment. BUT I urge you to get the proper carpet to enclose it so that this plastic bunk does not scratch your hull.
2.)   4 SS bolts to replace at the top of the vertical stanchions that go thru the "L" brackets  (see Lowes)
3.)   4 new "L" brackets (from any trailer place)
4.)   new ¾" long SS  bolt-screws to attach "L" bracket to the POLYWOOD  bunk board (see Lowes)
5.)   new carpeting (be sure that it's boat carpet! Be sure that it wraps over the edges of the new bunks...even at the end...you can do this measuring)...see your local boating place
6.)   ½" long SS  # 8 screws  with SS washers to secure carpet on the underside of the bunks (at least every 8 in.) ...see Lowes
Tasks:
     0.)  CRITICAL! get boat and trailer on a flat surface (garage floor, shading tarmac, etc)
1.)   measure the existing bunks
2.)   cut POLYWOOD (there are many suppliers, be sure it's solid) to #1's length
3.)   measure the distance between the vertical post edges (inside edge to inside edge)...this will determine the distance for the placement of the 2 "L" brackets (keeping them inside the post makes sure that they do not ever damage the boat)
4.)   measure the length of the aft end of a bunk to the inside of its vertical post
5.)   lay out the #3 and #4 distances on your new POLYWOOD bucks (be sure to remember PORT vs STARBOARD bunk and each aft's end
6.)   cut the boat carpet and attach to the new bunk (use screws, see #6 above, on the underside of the bunks...yeah, we know you know that, but jest saying)
7.)   mount new "L" brackets CORRECTLY on new POLYWOOD bunks with screws #4 above (these will need pre-drill for those screws, check distances from  #3 and 4 above (we actually laid each new bunk up near the post to check the final mount)
8.)   get two jacks, two short (6 in) of 2"x4" blocks, and two plywood sacrifice pieces to place between the top of the jacks and the fiberglass keel
9.)   place one jack just forward of the front roller
10.)   place the other jack just aft of the back jack
11.)   be sure the boat does not have its trailer strap on AND the boat to trailer belt is loosened a bit (watch this as when you elevate the boat off the trailer equally the trailer belt must allow this
12.)   slowly (here is time for a helper) operate both jacks slowing elevating the boat on the keel until the 2"x4" pieces can fit under the keep at each roller...ease the jacks a bit so the boat sits on the 2"x4" on each roller
13.)   now the boat will be up and can be GENTLY  'tilted' port to starboard. Tie down the opposite side you wish to start with (apologies to WC)

14.)   This will be done on the port and starboard existing bunks...in your sequence.
a.)   if the OLD bolts holding the 'L" brackets to the vertical posts cannot be loosen'd...hacksaw them...after all you are replacing with SS bolts
b.)   remove old ?rusted? bolts (recycle metal) and remove old bulk (you can decide to re-use the carpet, but our advice is "it ain't worth it")
c.)   mount the newly carpeted POLYWOOD bunks with its new "L" brackets and SS bolts to the vertical posts. Tighten these bolts and position the bunks as if it were to 'hug' the boat hull. Do not worry about the center 'bend' for the bunks, the boat will do this.
15.)   Repeat #14 for other side
16.)   Slowly jack the boat back up again, remove the 2"x4" block from the rollers and ease the jacks back down
17.)   Tighten trailer belt and replace the Port/Starboard strap.

That's it...go sailing if all is ready.

[buckaroo]

Great info, Ameysails, thanks!

[Garyandjoanlee]

I just installed keel guides for my 16 with carpeted bunk boards You may want to check out my post under modifications. Here are a few relevant photos: