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PostPosted: September 22nd, 2007, 8:30 am 
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Bryan and Battenkiller

Thanks... I just wondered where the difficulty pertained to Boatbuilding?

I've done Bead & Cove in Millwork applications on full circles, and
attained integrity... all a matter of clamping methods... in that application.

Is there something specific with respect to Boatbuilding that limits it....?

Purely educational for me...

Thanks

Sundown


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PostPosted: September 22nd, 2007, 10:08 am 
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Sundown wrote:
Bryan and Battenkiller

Thanks... I just wondered where the difficulty pertained to Boatbuilding?

I've done Bead & Cove in Millwork applications on full circles, and
attained integrity... all a matter of clamping methods... in that application.

Is there something specific with respect to Boatbuilding that limits it....?


Sundown

I'm really just in the armchair stage of my building, so don't take what I say as gospel. I've done almost all the operations of building a lapstrake cedar canoe during a class, but I haven't built a stripper yet.

But I have been over thinking it. :lol:

The only problem that I know about is that 1/8" bead and cove sets aren't commercially available, or at least I've never seen them. If you go with a larger radius bit than the plank thickness, the gaps on the outside of the compound curves become more visible.

Anyway, you won't get a better looking fit than you can achieve with a sharp block plane. If you do a nice job, there will be solid wood to wood contact across the strip thickness. No gaps. Plus, you get to learn and practice a traditional boat building skill (lots of practice with 60+ strips) and have the pleasure of hearing the plane slice through the wood rather than the scream of the router as it pulverizes it.

As far as the closer station mold spacing goes, 1/8" strips are considerably less stiff than 1/4" ones and won't "self fair" as well and you will get dips in the hull between the stations if they are set at 12" (so I was told by Nick Schade), a major problem come fairing time, particularly with an 1/8" hull. You might actually sand through in spots! :o

One solution I thought might work would be to use long Plexiglas fairing battens on the outside of the strip seams and use a bunch of mini springs clamps to hold the strips to the Plexi while the glue dries, during which time you cut the bevel on the next strip. Might slow up the hull stripping process a bit, but for someone who hasn't learned how to loft yet (or use the spiffy computer lofting programs) I don't know how you'd get the extra section shapes for the closer spacing required for the 1/8" strips.

Anyway, this is how I understand it at 11 AM on Sept. 22, 2007. Someone with a lot of experience may chime in here and tell me I'm full of it. :oops:

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PostPosted: September 22nd, 2007, 10:24 am 
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Battenkiller

No: "Not Full of It at ALL" Gracious, I'd say....

It comes clear to me now... you're using a Router Station instead of a
Shaper Station.

With a Shaper you just use a larger compound moulding bit, and "Nose"
the fence in "just right" ... at height and at depth... and you can achieve
1/8" or FAR LESS, if you wish... to achieve a tight bead and cove. I have
been known to whirl 6" Shaper heads with "minimal contact" at 12000 rpm
to get the desired joint. (As Siren1 might state... it's a Capricorn Thing! :lol: )

The problem then, isnt the theory, just the access to larger equipment
and Shaper Heads, some of which run to $8000 a piece, to achieve the
bead and cove. (And, you need a good 4 Roller Power Feed too)

You're right... the bevel-to-bevel would compensate for Router usage, but
clearly with less surface-to-surface lay-up joint-length... and, I suggest,
substantially less-longevity/rigidity.

I could actually Tongue and Groove it with the right "Heads" to even largen the bond... or vee-groove... etc...

Thanks for answering the puzzle... I was just sincerely puzzled as I thought it was a "Boat-Building" limitation I'd not been exposed to.

Cheers
and
Happy Day

Sundown

PS Graybeard... take note... if you "Contract Out" your strips for bead/cove,
you might get to 3/32 with better adhesion, and be able to add that extra
length, while still achieving your weight criteria??? (Now, I'm curious again!!)


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PostPosted: September 22nd, 2007, 3:01 pm 
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Sundown wrote:
With a Shaper you just use a larger compound moulding bit, and "Nose" the fence in "just right" ... at height and at depth... and you can achieve 1/8" or FAR LESS, if you wish... to achieve a tight bead and cove.

The problem then, isnt the theory, just the access to larger equipment
and Shaper Heads, some of which run to $8000 a piece, to achieve the
bead and cove. (And, you need a good 4 Roller Power Feed too)

You're right... the bevel-to-bevel would compensate for Router usage, but
clearly with less surface-to-surface lay-up joint-length... and, I suggest,
substantially less-longevity/rigidity.

I could actually Tongue and Groove it with the right "Heads" to even largen the bond... or vee-groove... etc...

Thanks for answering the puzzle... I was just sincerely puzzled as I thought it was a "Boat-Building" limitation I'd not been exposed to.

PS Graybeard... take note... if you "Contract Out" your strips for bead/cove,
you might get to 3/32 with better adhesion, and be able to add that extra
length, while still achieving your weight criteria???


Great ideas, but for strip built canoes it is way overkill.

For starters, there is no real need for increased rigidity along the glue lines. The entire hull will be encapsulated in fiberglass, which makes small differences in joint strength a moot point, particularly with cedar which will split upon impact way before a glue line gives out.

Guys use bead and cove strips primarily for cosmetic reasons and for ease in aligning consecutive strips, just like tongue and groove flooring helps to keep adjacent floor boards at the same relative height. Tongue and groove or vee cut canoe strips would only achieve a tight fit if they lay flat like in a floor or a table top. A domed table top (who'd want one) would exhibit large spaces between the boards on the convex side (see diagram below) if vee or tongue and groove joints were used. The bead and cove with the tight radius fits best, almost like a ball and socket.

Please excuse the fancy artwork. :oops:

The extremely thin strips on the left show what would happen when you faired 3/4" wide strips smooth. You would need to make them about 3/8" wide if you went with 3/32" thick strips which would double the work, while making a very unfair and weak hull and saving doodley squat in total weight.

Enough folks out there have made these things for long enough now that everything possible has been thought of and tried. 1/8" seems to be the practical limit in a wood strip canoe.

Image

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PostPosted: September 22nd, 2007, 9:35 pm 
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Battenkiller

Sorry Bud...

My joints just dont look like those.... So, I see your point of those ones.

Sundown


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PostPosted: September 23rd, 2007, 2:20 pm 
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Sundown wrote:
Battenkiller

Sorry Bud...

My joints just dont look like those.... So, I see your point of those ones.

Sundown


No, no...I wasn't implying that they did. My little drawing was just to show the problems involved with the geometry of trying to fit any kind of machined joint but a bead and cove around a curve. And since the curve is constantly changing throughout its length, a very complex joint would have to be created for absolutely no noticeable gain in strength.

The diagram on the left shows another geometric problem that will occur in 3/4" strips if they are made too thin. It has nothing at all to do with the shape or quality of the joints.

BTW, only one bevel has to be cut when fitting with a plane. It has to fit the shape of the edge of the preceding strip as it changes throughout due to the twist that is put into it as it bends around the compound curves of the hull. The other edge can be left square.

If these rolling bevels are done well, they should be stronger and look better than the bead and cove, which itself is never a perfect fit due to the constantly changing angles and curves.

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PostPosted: September 27th, 2007, 7:27 pm 
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Heres a few photos of Nick Schade's "Nymph" prototype that my wife took at the Wooden Boat Show this summer.


Image




I think the carbon-Kevlar cloth looks real nice....and makes a very tough hull.

Image




Check out the tight seams you can get with a block plane in this blow up of the bow.

Image

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PostPosted: September 27th, 2007, 9:25 pm 
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Sundown & Battenkiller,

This business of joints and joint shapes has more aspects than have come to surface so far. Some things to keep in mind:

1. the primary purpose of cove and bead is to aid in maintaining proper edge-alignment of strips while keeping "perfect" joint tightness.
2. beveling the edge or edges makes tight joints but doesn't aid alignment
3. from a strictly geometric perspective, 1/4" beads and 1/4" coves on 1/4" strips doesn't work; once the two strips join at an angle, joint tightness is compromised (insignificantly). Draw them in CAD, blow them up, and try.
4. 1/4" beads and 1/4" coves on 3/16" strips work much better. Some alignment perfection is lost if both shapes are centered on the strip thickness but the alignment loss is both insignificant and sanded away anyway on outside curves since it occurs on the "peaks".
5. The more practical problem for the vast majority of stripper builders is finding a router bit for, say, 3/16" diameter coves and beads to use on 1/8" strips. When I built my first stripper, 1/4" cove and bead cutters were extremely difficult to find and I wound up using a molding head on a tablesaw. Now I use a shaper and set it up with stacked cutters and a sub table for the higher one, then cut a bead going one way and immediately a cove going the other way. But DIY stripper-builders with shapers are about as common as flamingos in Algonquin.
6. Even with a shaper, I wouldn't even spend time seeing if 3/16" cove and bead cutters are readily available because the cost of cutters is so high that for a single experiment in 1/8" strips it wouldn't be worth it.

The more interesting question for me is whether 1/8" strips are over the tipping point. I'd like to see some empirical data comparing, say, 1/8" strips sheathed with 4 oz glass versus 3/16" strips sheathed with 2.5 oz. glass. There are so many potential failure points in composite construction that it's hard to predict what's going to fail in an untried schedule. Will it be tensile or compression strength of epoxy/glass? compression strength of cedar? shear strength of cedar? bond between glass and cedar? I suppose that from an engineering point of view everything should be so well balanced that everything fails at once--the flip side of which is that everything is fully used--one minute you're canoe paddling and the next minute you're dog paddling.

I think we need to keep in mind that it took Nessmuk to enlighten Rushton about how good wood actually is.

b

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PostPosted: September 28th, 2007, 6:35 am 
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Graybeard

Since you have the Shaper, and Doublestack Bed, why not ignore 3/16 bits,
altogether, and use the 1/4" ?

Once stock is doublerun Cove & Bead, slip stock into your Planer
(or thickness sander) and reduce stock to 3/16, with alternate side passes...
or 1/8 if you think structural integrity wont be compromised?

Personally, I feel the 1/4" profile... even thinned-down... would be stronger?

You obviously know your way around a Shaper... so, I think you could
achieve the accuracy to achieve that "perfect joint".

Just a thought.

Sundown


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PostPosted: September 28th, 2007, 6:56 am 
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1/8" strips are not unknown or untested, same with lighter glass layups, its just finding the people who know about them and getting them to share...

My recollection is 2 oz glass inside and 4 oz outside... or two layers of 2 oz....

John Winters has quite a bit of experience building boats and has done all of the above for racing hulls. Maybe he can chime in with some suggestions on lightweight layups.

I do know that the trim (gunwales) etc can add a lot of weight. (and I think we touched on this earlier.) But the lightweight boat guys are saving quite a bit using full composite gunwales. Something to think about, or using cedar and hard wood/CF facings.

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PostPosted: September 28th, 2007, 7:31 am 
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Sundown wrote:
Graybeard

Since you have the Shaper, and Doublestack Bed, why not ignore 3/16 bits, altogether, and use the 1/4" ?


Sundown,

That's just what I do....on 3/16" stock. 1/4" coves and beads centered on 3/16" stock provide good help in maintaining alignment while allowing the strips to conform to the curvature of the canoe section. If the strips were then thinned down to, say, 1/8" the coves and beads would become shallower, providing less help in maintaining alignment.

But in the real world, this is nit-picking. I'll use 1/4" cove and bead cutters. If I want to use full 1/4" thick strips then I'll make sure I use a good gap-filling glue, which I do anyway. If I really want thinner strips then I'll linger longer with the sander after the hull is stripped. That, by the way, would also allow tailoring final strip thickness to anticipated stresses in various parts of the hull, but again that would be nit-picking.

I repeat; we're exploring new territory. We don't have a map. If the goal is to minimize weight without sacrificing strength we don't have enough data to make an informed choice between less wood or less glass and epoxy. For that matter, we don't have enough data to know whether we've reached the limit in weight saving without becoming dangerously weak. Most of us wear a PFD even though we've never had to rely on it for it's intended purpose.

b

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PostPosted: September 28th, 2007, 10:47 pm 
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Rapt wrote:
1/8" strips are not unknown or untested, same with lighter glass layups, its just finding the people who know about them and getting them to share...


Okay, I'll share... Back in the day, someone on the kayakforum got into a big argument about 1/8" strips and threatened to sue unless all his posts were removed. After much, they were.

I used to have them all saved and perhaps I do, but the skinny comes down to this: use 1/8" strips and cover them with multiple layers of 3.5 ounce tight weave glass. You want to maximize the glass/resin ratio to arrive at a very light hull. I used three layers of 3.5 on the outside, and two layers laid in perpendicular to the keel line overlapping three inches to form ribs now and then. So, this must have been similar to what was written about. The hull was very light. Unreal light and then I added ash gunwales, thwarts, decks, and seat. My Lassie which I grew to 11'11" and added height must weigh under 25 pounds and I bet I could get it less than that now with a better use of wood for the finish. The hull is also very stiff and seems to be durable.


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PostPosted: December 4th, 2007, 11:48 pm 
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Update time.

Hull is stripped, sanded outside, and glassing is underway.

Strips used were a mix of NWC and butternut bandsawed to 3/16" thick and not thickness planed or sanded. Coving and beading done with 1/4" dia. flute and bead cutters on a shaper, centered on the strip thickness.

Glue used was Titebond II. Clamping of the strips was an experimental method that worked well. Briefly, I put a 1/4" dowel into the edge of each mould tangent to the sheerline and stapled the first strip to the moulds resting on the dowels. I then ran a screw into each mould more or less in the center of the face and tied a length of 1/8" braided nylon cord to it. From then on, as each strip was placed I put a short piece of 1/4" dowel in the cove to protect the sharp edges, ran the cord over the dowel, then around the dowel supporting the sheer strake, then tied off with a trucker's hitch. Where the cord went over the dowel in the cove, two force vectors were produced; one more or less perpendicular to a tangent to the mould at that point, the other in the direction of the tangent. The choice of nylon for the cord allowed enough stretch that active force remained even if knotting allowed a small bit of slip. Once progress produced convex curvature, the cord held the entire side tight against the mould. In areas where there was little or no curvature, I ran in a 16 ga. 1" nail through a scrap, then through a strip and into the mould about every four inches just for insurance (or reassurance?) The process was somewhat fiddley at first but became very quick and effective in hardly any time at all. I'll do it this way again. It not only eliminates staple holes, it also provides dynamic pressure on the joint, something that stapling can't do.

Smoothing the stripped hull with block plane and ROS was entirely conventional.

I'm glassing with 2.3 oz. satin-weave E-glass. This is my first time with satin-weave. Smoothing the fabric over the hull preparatory to 'glassing was more difficult than with open weave but with patient attention was not impossible. The time spent futzing with smoothing the satin weave was well paid back with an amazingly smooth surface with just the wet-out epoxy. I suspect that with practice one could eliminate ALL weave-filling coats and see no fabric texture. If (when?) I do another I'll be prepared with a greater assortment of squeegees to find what works best to get a filled weave with the wet-out epoxy. Penetration of the weave to full clarity was not a problem, even with WEST 105 resin at 65* F. Heavier satin weaves may be a different story.

Less satisfactory was another experiment. Wanting to minimize gunwale weight but retain stiffness I tried to incorporate a 1" wide tow of carbon fiber at the sheer. This was a product that Gougeon Bros. sold many years ago as 701, since replaced with a similar product with cross-stitching but not in the 1" width. The tow without cross-stitching is simply unmanageable in my hands on a curved and twisted surface. In short, I botched it. Back to the drawing board on that one.

b

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PostPosted: December 5th, 2007, 7:06 am 
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Graybeard wrote:
Clamping of the strips was an experimental method that worked well. I'll do it this way again. It not only eliminates staple holes, it also provides dynamic pressure on the joint, something that stapling can't do.


A very interesting technique, Graybeard... Thank You.

Any pîcs at this stage?

Regards

Sundown


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PostPosted: December 5th, 2007, 10:00 am 
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Sundown wrote:
Any pîcs at this stage?
Sundown


Well, I took some, but the only ones showing the strip tie-down procedure were a preliminary method that didn't work out well. Then I didn't remember to take new ones after working out the problems. One that might be of interest, however is here: http://www.vermontel.net/~bobmoran/rotate-strongback.jpg It shows the hull shape in a general sort of way that is not particularly informative but also shows my rotating strongback which has been quite handy but needs some structural redesign. (One of the pivot shafts broke during 'glassing :oops: ) Fortunately, no other damage was done and I was able to continue in the conventional down-on-your-knees posture.

b

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