Centerboard Trunk -HELP Needed from Those who've gone before

[Maria CS20 104]

Hey ALL, trunk is together no warp issues, shaped to conform to hull curves and angles, space in place and I am ready to install but I have to cut out the opening in the hull.  Any advice?  Do I need to brace the sides of the hole to be cut?  Ideas begged for and welcome.  Heart is pounding from FEAR and excitement at our progress.  Once installed we'll put the forward beams in place and seat hatch beams, add some braces and go for the turn and hull work.  Once turned how high is recommended for ease of reach while fairing and sanding?  Thanks for the input and guidance.

Jim A

[John Burritt]

Install the trunk, then cut the opening.  Make a couple of pilot holes (one close to each end of the opening)with a diameter just smaller than the projected opening before installing the trunk.  Makes it easier to line up the cut after the trunk is installed.  Cut w/a jig saw.  DON'T hold it flush to the bottom.  Hold it vertically.

[brigait1]

I've seen the results of how Charlie does it and I have to say I think it's the best method. First, install the case including the fillet and tape around the outside perimeter where it meets the sole. Then drill out a pilot hole from the bottom and use a router with a flush-cut bit to cut the opening. This will leave an opening that is perfectly matched to the dimensions of the case. The only place that will need a little work is in the corners where the round shape of the router bit will leave a bit of material. A sharp chisel will take care of the in a few minutes. Then epoxy coat the newly cut hole and add some fiberglass tape from the bottom, folded up into the inside of the case.

PeteB

[Scott Dunsworth]

A router is my best friend, drill a hole and rout it out with a flush trim bit as Pete said. Just remember that you need to take into account the angle of the hull bottom as your routing.

Scott

[Tom Lathrop]

I use the pilothole and router method and cut a narrow slot as above.  There is no compelling reason to square up the ends.

One more thing that is sometimes a life saver.  Insert a piece of plastic wrapped wood of the width of the trunk a few inches from the bottom of the trunk.  Do this before assembling the trunk sides.  This will hold the trunk sides straight and to the proper dimension.  After routing the full slot in the hull bottom, knock the wood plug out.

[wkisting]

Pilot hole and flush-cut bit on the router is definitely the way to go. Afterward, I went around the edges with 1/4" roundover bit also. Worked great.

As Scott said, be mindful of the angle so that the flush cut bit is riding parallel to the trunk. After I drilled the initial pilot hole, I carefully expanded the hole to a nice large slot (an inch or two wide) that would permit me to see into the trunk clearly. Then I set the router in place with the flush cut hanging down through the hole. Then I securely taped a small block of wood to one edge of the router base, sized so that the router would ride on the hull bottom at the correct angle to keep the flush-cut bit parallel to the trunk. Then I started routing (taking care not to rotate the router base, which would change the angle of the bit). Very easy, great results.

[Peter HK]

Just to let you know there are other ways...I cut the hole in the hull large enough to fit the case through. The case had been left a little long so that it protruded through the hole. I marked the protruding case with a pencil when dry fitting it then removed and cut off the extra. I then glassed it in (with the spacer to prevent the sides of the case from bowing). When I turned it over I routed with a round over piece and glassed it.

Cheers

Peter HK

[Bikermouse]

Peter, I only have a daggerboard trunk, not a centerboard, but that's basically what I did.  Seems good so far, and the overlap of the trunk down into the keel just feels stronger than a fillet joint.  Not tested or mathematically proven, but it feels intuitively good.

[Peter HK]

I'm not sure it's any better structurally but two things I like about this method is:

1 No time wasted fitting/spiling the case to the hull- poke it through and a simple pencil line determines the angles and curves.

2 The case to hull join is much easier to see and make sure it is sound when filling any bubbles/gaps in the glue line and glassing over.

It's just another way.

Cheers

Peter HK

[Rod Thompson]

Having no router skills/confidence I traced around the CB case, removed it, adjusted the lines to the inside dimensions of the CB case, then cut the hole with a jigsaw.  Trimmed it to exact dimensions with a file and sandpaper, sealed the edges, then taped on the case.  When the hull was flipped over for painting I put fibreglass over the joint. As Tom did, I kept spacers in the trunk to ensure it kept the desired shape while marking lines and taping.