Strips thicker than 1/4"

[Bill Baillie]

I have been reading the strings about cutting and shaping your own 1/4" strips using table saws
and bead and cove router bits. If you want to produce strips that are, say 1/2" thick, can
you use a round over bit with two passes for the bead and a box cove bit for the cove? I have
read that a spindle shaper would be preferred but these are not cheap to rent or buy.
Any opinions?

[JimConlin]

For any reasonable thickness, there are 'bullnose' router bits which form the bead.
For strips thicker than 1/4", I've needed to take a different approach to the cove, using 'core box' or round-nose bits. This requires a different router table setup than the bead side.

See http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/routerbit.html

[Bill Baillie]

Thanks for the info on the bull nose and core box bits. Have you had any problem with the edges of the cove getting torn out when you use the core box bit?

[Todd Bradshaw]

Unless I was trying to build a bright finished hull with 1/2" strips, I don't think I'd even bother to attempt to bead and cove them. Strip thickness and the size of the gaps between strip edges on the outside of curved areas tends to scale-out with the size of the boat and the sharpness of the hull's curves. There are plenty of curvy boats being stripped with 1/2" or bigger, square-sided strips and during the fairing process, just about any epoxy/filler mix will easily exceed the grain strength of the woods commonly used for stripping. In most cases, beading and coving the strips doesn't seem to me to be worth the trouble for strips that thick.

Keep in mind that the whole bead and cove thing was developed for stripping canoes, primarily to keep light from showing through the tiny cracks between strips. For that type of construction, it was primarily a cosmetic improvement and as far as I've seen, doesn't make the boat any stronger.

[ 10-17-2002, 01:50 PM: Message edited by: Todd Bradshaw ]

[JimConlin]

Cove & bead edging of planking strips serves another function, too. It helps keep the strips aligned with one another, especally if the station spacing is large relative to the waywardness of the strips and you're butt joining the strips between station molds.

[Bayboat]

Bead & cove for strip planking is a little stronger than glued plain edges, and assembly is easier. Jim Conlin has supplied a good source for cutters. MLCS sells shaper/router cutters for bead & cove, 1/4, 3/8, 1/2 & 3/4. With a 1/2" shaper cutter to router adapter, also available from MLCS, you can use them on a large router, either with variable speed or with a speed controller, set at about 10,000 rpm, no faster. Catalog: 800-533-9298 or www.mlcswoodworking.com. (http://www.mlcswoodworking.com.)

[ 10-18-2002, 01:17 PM: Message edited by: Bayboat ]

[Todd Bradshaw]

Stronger in what way? We don't know what the boat is, or the rest of it's lay-up, but if you hit a strip boat hard enough to damage the strip core to the point of breaking the strip-to-strip bonds, do you really think bead and cove edges are going to do much to prevent the damage? I certainly don't. Some of the cruising trimarans like the Farrier F-25A have been built using square edge cedar strips (1/2"-5/8" thick as I remember) and they stand up to very high rig loads at downwind speeds approaching 20 knots. The same is true of those built with Duracore strips (veneer-covered balsa core) and foam stripping. By the time you get to the point that your boat is big enough to need that kind of strip thickness, the layup is providing most of the strength, not the strip-to-strip bonds.

[Ross Faneuf]

I wonder how many times we've argued this?

My experience with thick strips (3/4") is that the bead & cove thing is a waste of time. The geometry turns out to make the way the radii match actually hurt alignment in some parts of the hull (note that larger boats often have a more complex shape than, say, a kayak, which is part of the reason). The contribution to strength is close to nil, particularly if you don't starve the joints (epoxy assumed). In my case, there were no butt joints; I scarfed every plank before installation (max length 38').

[Lowell Bernhardt]

I have always wondered about this: why bead and cove? Couldn't one just set the table saw just a bit off of 90 degrees and use this edge on the inside? Yeah the angle would be difficult to surmise but you would be no further off of the mark than if you just used square stripps.

This is just a thought. I don't know much about hull strength or design (but I'm learning). Please any comments to this affect would be very heplful.

[john welsford]

Try a router with a big chuck, preferably 1/2 in, get a "non structural" fingerjoint bit set. Mount the router in a plywood table with a full length fence and good solid reinforcement underneath so it stays straight, make it at least 6ft long, you'll need to have feather guides above and alongside the strip as it goes through as movement away from the fence or up and down in ralation to the cutter will give you an unuseable product. You'll find the tongue and groove profile very easy to use when planking, makes the bead and cove look positivley diffficult by comparison.

JohnW ( who sells installs and teaches the operators of machines for doing this sort of work)
[

QUOTE]Originally posted by Bill Baillie:
I have been reading the strings about cutting and shaping your own 1/4" strips using table saws
and bead and cove router bits. If you want to produce strips that are, say 1/2" thick, can
you use a round over bit with two passes for the bead and a box cove bit for the cove? I have
read that a spindle shaper would be preferred but these are not cheap to rent or buy.
Any opinions?[/QUOTE]

[Cecil Borel]

I have been strip planking a 33' sailboat with 1"x1" strips. I toyed with the idea of cove and bead, and tongue and groove, but, following advice of the forum, decided to glue the strips up square, After a couple of runs, I found the strips would lay flatter if I tapered one of the edges by about 3 degrees off of 90. So now if have 3 ninety degree edges and one about 87 degrees so that the inner edge is thinner than the outer edge. It seems to make the gaps narrower between the planks.

[Bill Baillie]

It seems that I have asked a question to which there are no answers, but plenty of points of view. The two main reasons, as I see it, for cove and bead are strip alignment
and the fact that the trough of the cove holds the epoxy in place while the next strip is aligned and secured. Assuming that there are other ways to align the strips, could you use a long pieces of masking tape on the outer edge of the strip to hold the glue in place while the next strip is attached? This would take a LOT of tape but what the heck, it's cheaper than epoxy.
One further question: If I were to build a hull with strips, fair it off, then cover it with fairly thick mahogany veneer laid on for and aft would this provide the appearance of carvel planking with the advantages of a composite cold molded hull? Or am I creating a lot of unnecessary work for myself? I read about this in the Nicholson book where he said there are "theoretical advantages" to this without going into any great detail about it. All other references to the combined strip/veneer construction have the veneer applied at an angle to the strips. Any comments?

[Bill Baillie]

Sorry, I should have said that if I were to use the for and aft mahogany veneer on the outside of the strip built hull, I would forgo the addition of a layer of fibreglas. (fiberglass?)