split coamings - some ideas
Nearly everybody's coamings have split because they are attacht to the sidedeck with a hard
right angle cutout at the end of the cockpit that is designed to split by pushing and pulling
on the unsupported part of the plank. It's a 'natural'. Shows coamings are made with real wood!
Don't know what or why I said 'fiberglass or teak biscuits', if I did, have to amend it.
Will go with Ben and Bill and glue the split together.... FIRST. The split FITS together and the
irregularities will Probably make a good bond. There are some problems, especially if the coamings
at one time were varnished with the crack open and splinters, or any other crud is in there.
Carefull cleaning by hand is called for. Dental picks are good. Try not to gouge the face. Do some
careful dry runs clamping together to see if it wants to close up OK. Choice of glue is worthy of
discussion. I'd use epoxy - because it's clear, easy to use. Thickens with cabosil. Mix up a
loose gel so that it doesn't run out the crack while gluing - stays in there while cranking on the
clamps at the same time. You want squeeze-out. Old surfaces aren't great for gluing...
Want to prime inside the crack surface wilh liquid first. Let it run out. Dry wipe it off the TAPE(~~)
Do the priming just before you do the thickened epoxy. I like to dab with a two-inch bristle brush.
But imco, it's really important to add some kind of reinforcement where the crack is, because
the same random forces will crack it open in the same place...... again.
[As for fiberglass dowel inserts: There are nice precise dowel-rods available in small diameters
like 1/4" & 3/8" You want to improvise a jig* so that you can drill 1/4" (my choice) holes up
into the plank from the bottom. Maybe 3 or 4 inches deep, crossing the split. A jig is needed
to make sure deep holes do not wander. Holes are straight, and must stay centered all the way.
These solid white fiberglass rods (Tap Plastic) are made with oriented strands of glass. They will
work well, but I think better dowels are made with mahogany wood - which has definite grain.
Precise (1/4" diameter is exactly 1/4") HONDURAS MAHOGANY DOWELS are available from
Constatines. Wouldn't do larger than 1/4" dowel in 3/4" coaming. 3/8" OK in thicker coamings.]
After you have the crack closing good in trial clampings, then wedge it open just a little more
at the end where the crack begins. A little helps a lot. Might clamp the coaming
at midway where it isn't separated yet so you don't split it any more. Then....mask the split...
~~TAPE the crack on both sides , on both faces, with wide blue (3M 60 day painter's) tape.
Just the empty crack shows. Try to use single long strips that you trim with an Xacto knife to fit.
This allows slathering room for lightly gelled epoxy applied with two inch bristle and acid brushes,
flexible puttyknife or plastic spatula. Remove wedge. Carefully draw split closed. with bar clamps.
Lift off squeeze-out from tape with puttyknife, wipe with dry folded dry paper towels. Remove final
squeeze-out after final check to see that coaming has not cupped during clamping. Clamp firmly
- but not too tight. (If needed, improvise CROSS PLANK CLEATS and spring clamps to keep plank
flat while curing.) After partial set, ie no longer wet-sticky, but gummy, slice off the remaining
ridges of squeeze-out with a sharp flat chisel. Pull the tape before epoxy sets - so it doesn't bond.
Cured epoxy is harder than wood coaming - make sure there is no pronounced ridge - which can
cause uneven sanding on the old surface.
DOWELS. Set up a movable JIG* for deep HOLE DRILLING. Space them where ever wanted.
Think you need no more then one every ten inches along the bottom - could have more
- with maybe a couple dowels three or four inches apart at the beginning of the crack.
Textbook is to shallow GROOVE THE SIDES (2, 3) of the dowels with a western hand saw
(makes a wider channel than a pull saw). This will allow dowels when coated with epoxy
to be tapped home by letting captured air in the hole to escape. Chamfering the tips helps, too.
Your coamings look quite weathered. Imco, the two-stage gluing & doweling should be
compleated before any sanding prep. Would NOT run the boards through a planer or drum
sander. The sander would be the better choice, but once the sanding progresses the temptation
for a perfect surface will probably end with coamings too thin to be usable.
Glue the coaming together first. Then do the doweling, separately. Mahogany dowels at least
an inch deep beyond the crack - into good old healthy wood - drilled thru the bottom edge
- is the best way to go. Imco same wood cross grain dowelling makes a closer bond than
glass or threaded metal. Sand, leaving the coaming blocks attacht, if in good condition.
Would pre-dowel new coamings same way, anticipating they will want to split otherwise.
Just long winded opinion. Just ideas. Ebb's really not a frikkin know-it-all.:o
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*JIG: Drill a 90degree dowel- sized hole thru a square piece of 1 1/2"-2" wide hardwood stock
that matches the width of the coaming. Glue or screw two extension legs to the sides of the jig,
making a 'U' to clamp onto the edge of the plank. Drill a test piece in scrap before drilling
a coaming. And tap in a long dowel to check if it's actually parallel with the sides.
Drilling deep holes with the coaming flat, will make it easier to clear the holes while drilling.
Need to acquire an 'extended reach' drill bit (8" - McMasterCarr). Not a short-flute 'aircraft' bit..
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After sanding, seal with two coats slightly thinned epoxy. All over. Add 10 coats good UV varnish.
If you have converted to LeTonkinois, coat the bare wood and mount the coamings between
coats. Imco, warm butyl tape or Dolfinite are better bedding compounds than tube rubber.
