Laminated Hull Construction

[imported_Glenn]

I am looking at laminating a 1/2" cedar hull using four 1/8" veneer strips with each layer running diagonal to the other. I will not be doing this with a vacuum bag but instead I will rely on the staples and epoxy to do the job. I am using monel staples and my question is this...

Should I dry fit the entire boat with a layer of laminate by stapling each piece in place and then number and remove each piece to finally roll on my epoxy over the entire hull to then place each piece back in place and then once again staple each piece and wait for the epoxy to dry...

...or, should I mix enough epoxy (slow drying) to cover 6 or 7 pieces of veneer and skip the dry fit step above allowing me to staple down the veneer as quick as I can get a good edge to edge fit from one piece of veneer to its neighbor?

Thanks for your feedback

[Bill Berrisford]

Glenn-
You really don't have to dry fit the strips. Apply enough resin for about six strips (depending on the width and length). Tack the first one where you want it then tack the second one parallel to it and within 3 inches from it. (assuming 3" wide strips.) Use a cutting jig set to 3" to cut away the edge of the second strip leaving a uniform 3" gap between the first and second strips. Lay the third strip in the gap and staple at the edges...repeat. (Get a few hundred little squares of plastic film from your local carpet cleaner to staple through.)

Good luck...

[Venchka]

The top (outer) layer of veneer ought to run fore-aft.

Barging in to ask a related question:

Originally posted by Bill Berrisford:


...tack the second one parallel to it and within 3 inches from it. (assuming 3" wide strips.) Use a cutting jig set to 3" to cut away the edge of the second strip leaving a uniform 3" gap between the first and second strips.

Good luck...

What tool, hand or power, would be appropriate to cut the 3" gap?

Wayne
In the Swamp.

[ 09-01-2004, 03:00 PM: Message edited by: Venchka ]

[JimConlin]

In my (old) copy of the Gougeon book, there is described a truly scary circular saw tool for this purpose.
I recollect seeing somewhere someone using a router to apply the same concept. The widest gap between the un-shaped veneers was maybe 1-1/4".

I haven't taken a survey, but i think that all-veneer cold-molding is less commonly done these days than strip composite methods. Strip methods take less labor and the materials are easier and cheaper to acquire. I don't now know of a source of 1/8" WRC veneer that was the 'standard' material for cold-molding.

[Venchka]

Originally posted by JimConlin:


...I don't now know of a source of 1/8" WRC veneer that was the 'standard' material for cold-molding.

Ain't it the truth! Looks like roll your own is the current solution.

Glenn from NH: How did you come by your veneer?

Wayne
In the Swamp.

[George Roberts]

I don't use veneers much but ...

There is a internet business that will resaw your boards to 1/8" or 1/10". They have a little gang saw that will handle stock 8" high. The 1/10" has a much better yield and should lay flatter.

There is also a veneer businees that custom cuts veneer upto 1/8" thick.

Wish I could be more help.

[Dale R. Hamilton]

Bill- just curious, Say you lay in one 3" strip, then another beside it and 3" away- a gap. Then you cut a third strip, and lay it in the gap between #1 and #2? Why not just lay them alongside each other, 1,2,3,? And Glen, consider using the nylon nails made by Talon. You dont remove these- just sand them off.

[Buddy]

The biggie here is to slather"staright" resin on all surfaces of th strips, but when you start overlaying the next layer, also add enough thickened "catsup" epoxy to fill and even squeeze out the edges to prevent air pocket voids between layers. It takes lots of staples working from the center of each strip out to its edges to accomplish this, and lots of thickened epoxy. Many fewer staples will hold everything in places and the hull will look great, but you will have voids and less strength. Precoating all surfaces with straight resin will virtually prevent the possibility of any water reaching hidden pockets from starting rot, but it still won't be as strong. String enough probably. That's why the move to vaccum bagging. It does a better job much faster. Staples enough to hold everything in place, but lots of pressure everywhere to mash it all together.

[imported_Glenn]

Thanks for everyone's interest on this topic. It is the first laminated hull I am looking at doing so hence my initial questions.

I get my veneer by taking 4/4 rough sawn cedar and ripping the board on my table-saw into 3" wide strips. Next I resaw each 3" wide board into 1/4" pieces on my bandsaw. I finally plane the 1/4" pieces down to 1/8". Doesn't seem like a big deal to me.

I am using T50 monel staples from Arrow. I have heard about the plastic staples but I think you need a special staple gun for that.

Also, I should say that I am building a sort of hybrid hull by steam bending oak frames around the mold ribbonds and then lining off the hull where I then place my first layer of veneer fore and aft similar to a plank on frame job. I staple each each of the veneer to the oak frame below using 5/16" monel staples. I then brush on a light coat of thickened epoxy on the joint between each first layer of veneer to prevent epoxy from oozing through when I lay on subsequent layers of veneer. Next I lay on my second layer of veneer but this time at a 45 degree angle stapling this layer using 3/8" staples through the cedar into the oak frame below. I stagger the direction of each layer and put my epoxy on both the back of the veneer and the hull of the previous layer to then lay it on the boat and staple it down. I use 1/2" staples on my 3rd veneer layer to sink into the oak frames below and 3/8" staples to hold down the veneers between the piece being laid down and its neigbor. On the final layer, I do the same but this time I remove the staples when the epoxy kicks. Before turning the boat over, I screw the hull into the stem, keel and transom and I also apply rivets and roves through the hull and oak frame just above the sheer line to hold the frames secure. I finally fair the hull with a long board, get the hull a coat of 2 part epoxy primer, brace the hull above the sheer line and then turn her over.

I have just finished building a trial hull panel where I set up two molds, bent my oak frames around on and applied my veneer. Seems to be a very strong hull with the look of a traditionally built plank on frame boat with the ease of maintenance of a cold molded hull.

So off I go...

Any questions?

[helmuth]

Hello Jim,
you wrote, strip planking is more commonly used than cold moulding, using veneers.
I'm thinking about building a golant gaffer, and therefor I have to decide whether I should build her as described by the designer (that means strip planking) or using veneers; that means cold moulding, using a block that already exists in switzerland, although I haven't contacted the ownwer of the block yet. The cold moulded GG looks really great, and it seams to be very stiff.
What do you - or other members - think about the stiffness of strip planked hulls, compared with cold moulded? Some boatbuilders said, that the cold moulded hull is lighter an will last longer, but it will take more time to build. What is your opinion about a combination: strip planking and one or two layers of veneer afterwards on the outside instead of glass cloth?
Helmuth

[bainbridgeisland]

My experience is that cold molding is faster than strip planking. However, the relative speed of construction depends strongly on the experience and skill of the craftsman as well as the particular boat design.

In my case I have built more than a dozen cold molded boats to 42' but only 4 strip planked boats to 26'. So it is very possible I am biased on this subject.

To be quick with cold molding, the craftsman needs a little more skill than to be quick with strip planking. Beginners can build perfectly good cold molded boats too, but it is hard for them to be fast.

Most important of all, to build in the minimum amount of time, the design details must support the construction method. If you tried to build a carvel planked boat exactly the same as a lapstrake boat, you would find the method inefficient. The same can be said for cold molding verses strip planking. Maximum speed is obtained when the design details suit the planking method.

How fast is planking when cold molding? For a professional Shipwright allow about 12 square feet per man-hour per layer of planking. This does not include finish work, just cleaning off glue drips as you go and removing the last layer of staples.

How fast does the fixture to shape a cold molded hull take to build? It depends on the framing method defined by the designer. An example for a frameless hull: 48 man-hours for a 34' sailboat hull fixture including laminating up the sheer clamps, keelson and stem. Again this time was for a professional Shipwright.

Adding it up for the 34' example, 20-hours lofting, 48-hours fixture and 128- hours planking produces a complete hull without bulkheads, floors frames or finish in 196 hours. Again this is for a professional crew.

Why is cold molding faster? The time needed to clean up glue squeeze out from strip planking is excessive. If you do not mind a rough finish, let the glue drip and grind or plane it off later. You could then compete with cold molding on speed. But, the quality of finish would suffer, so we can't compare it to cold molding directly.

Another reason that strip planking is slower is because the narrowness of the planks means lots of glue joints are needed. Turns out that if you are skilled enough to easily fit cold molded planks, then cold molding is faster than making up all those joints.

We have only touched the surface of this subject. So many tricks of the trade speed up construction of both strip planking as well as cold molding that we are really comparing apples and oranges here. To make a true comparison, one must build equivalent boats with equivalent crews equally skilled with the two methods. I have built 2 boats of the same design using the two methods. However, even this was not the best method of comparison.

Originally posted by helmuth:
Hello Jim,
you wrote, strip planking is more commonly used than cold moulding, using veneers.
I'm thinking about building a golant gaffer, and therefor I have to decide whether I should build her as described by the designer (that means strip planking) or using veneers; that means cold moulding, using a block that already exists in switzerland, although I haven't contacted the ownwer of the block yet. The cold moulded GG looks really great, and it seams to be very stiff.
What do you - or other members - think about the stiffness of strip planked hulls, compared with cold moulded? Some boatbuilders said, that the cold moulded hull is lighter an will last longer, but it will take more time to build. What is your opinion about a combination: strip planking and one or two layers of veneer afterwards on the outside instead of glass cloth?
Helmuth

[JimConlin]

I'm simply suggesting that the builder should do a little arithmetic. Here's mine:

Getting 1/8" veneers out of 4/4 stock will involve, at least, 50% waste. If you pay $3/BF for good clear stock, your veneer cost for 4 layers will be, at minimum, $4/ft^2 for 4 layers before cutoffs, losses at edges, imperfections and spiling.

In strip composite construction, assuming, say 1/2" x 1-3/4" planks, the cost is close to $1.00.
Add the savings in epoxy and staples.
Add back the labor and materials cost (figure $1.50/ft^2 for materals) for the structural skins and add some value for the fact that the skins impart some impact resistance.

In labor, Consider that it takes a more elaborate mold (more materials and labor) to support 1/8" veneer than 1/2" strip planking, that you're applying not 4 layers, but one, and that they're not spiled at all.

To me, it's understandable why, particularly for small craft, cold-molding of veneer died out. It explains why the key supplier (The Dean Company) is no longer in business. For bigger boats, where the losses of milling 1/4"+ 'veneer' are less extreme (The Hodgdon Bros yachts) the concept is viable. 'Miracle fiber W' lives!

If there were a supplier still slicing (the efficient way) 1/8" WRC veneer, I'd use it for special projects, but the labor and materials losses of sawing it just sinks it.

Jim

[ 09-03-2004, 02:36 AM: Message edited by: JimConlin ]

[ErikH]

Please excuse my dumb questions (I don't know much about coldmolding or strip yet, though I"m learning)

I was reading this and wondered (re strip) why the cleanup is so bad. Seems you could just blue-tape a lot of it (figure $500 of tape, not much if you consider the man hour saved). My wife and I are big taping fans, and once you're fast at it it'll be a joy.

Or why not paint? I mean, you're going to paint the outside--and the inside--anyway. And though I know it's almost impossible to wipe epoxy off bare wood because it soaks in, all it requires is a coat of sealer to make it easy to remove. Seems a light coasting of paint would go on fast to the uninstalled strips, and allow you to easily wipe off drips (that rhymes!). You're going to have to paint it anyway.

Or maybe just apply the primer you plan to use. Then you wouldn't even have to sand it off. the biggest issue of course would be not painting the glue joints, but (depending on grain direction) maybe you could paint the larger boards before resawing to avoid that?

I know its a dumb questino but I couldn't keep from posting it

[bainbridgeisland]

1/8" thick veneers are actually too thin for best efficiency of construction for many boats. One reason so many boats were built with 1/8" material is because the Dean Company could provide quality material at a good price. Larger boats especially benefit from thicker planking. Even 3/8" thick material works on large boats. Relatively thin, sliced veneer, 1/16" or less is available and not too hard to find. It is perfectly suitable for small boat construction.

Today through the internet, small custom milling services are expanding markets for specialty work. With effort I think you can find a custom sawmill to mill almost anything you need. The price is higher than your local Home Despot without doubt. However, without the middleman prices are actually reasonable in comparison to the finished value of a boat.

Having said this, it is true that strip planking material is more readily available. Material quality is not as important to strip planking because unsuitable portions of timber are easily culled. There are important reasons why one should consider strip planking. I just do not think speed of construction is one of them.

[bainbridgeisland]

To answer Glenn's original question: My preference is to only spile one more plank than the number I plan to glue down in one operation.

Assume for a moment you spiled all the planks and then started gluing them down. If you make even the slightest error when positioning the planks as you glue them, the error can be compounded by the hull shape as you work down the hull creating a gap between planks. To bring the plank edges closer together and make up for the problem, you must re-spile a plank (preferable) or edge-set a plank. Edge setting makes an unfair hull and may introduce voids between staples.

The reason you spile one extra plank is to keep your tools clean as you continue to work. Glue all the planks except for the last one. Squeegee off the excess glue. Then lightly staple the last plank in place. Spile the next plank. Then remove the 'last plank', wipe off any glue left on it and set it aside. Continue this process.

[JimConlin]

Different people have different skills, and consequently different opinions about what methods are productive.
If there are sources for 1/8" veneers at tolerable cost, i hope someone will post them.

[Ex-Oceangoddess]

This is a very interesting exchange, since I am about to start building a 22' hull, and have been vacillating between cold molding and strip planking. I will paint the hull, so epoxy smears on the outside from strip planking don't really worry me.

However, when considering cold molding, absent a vacuum bag, it dawns on me (thanks to one of the previous posts) that if you don't spile the veneers accurately and have to force the veneers into unnatural configurations (i.e. doing the bigger hammer thing) I might end up with a problem fairing the hull when its all done. However, we do have a fully equipped woodworking shop so getting the veneers out wouldn't really cost too much. I would just have to consider the waste factor.

If anyone can offer advice on the relative worth of the two methods of building a hull, their 2 cents worth would be most appreciated. Being somewhat of a purist I was leaning towards cold molding, but I might rethink this in light of the above comments.

On a totally crass and cheapo aside, I have built four ocean kayaks with 1/8" mahogany doorskins from the lumber yard, totally encapsulated with epoxy and 6oz FG, cost less than $200 apiece, and in one of which my son continues to cruise around the Gulf Islands 8 years later. I wonder if the epoxy saturation thing will really work long term with cheap wood....

[bainbridgeisland]

Originally posted by ErikH:
I was reading this and wondered (re strip) why the cleanup is so bad.

Or why not paint? [/QB]

Assuming you strip plank a 30' boat over the outside of transverse molds, there will be about 4,000 linear feet of glue joint, each one interrupted by the transverse frames. Clean-up is not a simple job like running a squeegee down the length of the boat. You have to clean between each transverse frame. For a top quality bright finish, you want to get as much glue off as possible, otherwise you will need to spend literally man-weeks bringing the inside surface up to par. (Part of the problem is that power planes and flat sanders are not terribly efficient on the inside curvature of the hull.) For a hull built over 2-foot frame spacing, cleanup can double the time needed to install a plank.

If you choose to paint the inside of the boat, only clean the glue off next to permanent structure like the stem, keelson, floor timbers, sheer clamp and frames. You can later use a foam-pad disk sander to quickly clean up the rest of the inside of the boat. A couple coats of sanding primer and reasonable elbow grease will then bring the interior up to snuff for finish paint.

Using transverse temporary frames outside of planking and a hull painted on the outside is faster for strip planking than internal mold frames. You can then easily clean off excess glue on the inside of the boat. If the outside of the boat is to be painted then only minimum cleanup of the outside will be needed. Power planers and production sanders work well on the outside of the boat too. The difficulty of this method is that you need to manhandle large surfaces into position on a pre-made keelson and stem. All the internal structure like bulkheads and floor timbers will then need to be fit to the inside of planking. These are quite difficult assembly steps, beyond the ability of many.

Most strip planked hulls take more time to fair the outside of planking too. Using our 30' example, the extra fairing would only add a day or two to the job. Cold molded boats tend to take only a few hours to fair the outside.

[bainbridgeisland]

Originally posted by Ex-Oceangoddess:
However, when considering cold molding, absent a vacuum bag, it dawns on me (thanks to one of the previous posts) that if you don't spile the veneers accurately and have to force the veneers into unnatural configurations (i.e. doing the bigger hammer thing) I might end up with a problem fairing the hull when its all done.

Even beginning Boatbuilders can plank a cold molded boat and keep it fair. It is easier to keep a cold molded boat fair than any other construction method. You just have to remember two things:

1. Don't ever edge set planks when you spile them.

2. When gluing up and finding a plank must be edge set due to misalignment of previous planks, stop work; clean off the excess glue on the plank and the hull and discard the glue, refit the plank; re-glue it in place.

Now professionals do edge set planks a little to speed up production. But poor judgment will result in an amazing mess. After you have routed out a badly fitted plank the first time, you will be careful to minimize edge set.

There are methods, as mentioned by others, to mechanize plank spiling. There are a few variations that work but they are all slow compared to simply fitting each plank as you go.

I suppose each Boatbuilder has his or her favorite method to spile planks. This is what is fastest for me: Temporarily staple the plank at centerline. Lay the plank along its neighbor, the plank it will be spiled too. It will overlap the neighboring plank. Use a pencil in your index and first finger and run your little finger along the edge of the neighboring plank, drawing a line on the plank to be spiled. Use a razor knife, blade up, pulled towards you and trim within an 1/8" of the line. Starting back at centerline, use a block plane set extremely course to fit the plank as you lay it down. You will need a few temporary staples to keep the plank flat as you go. A second block plane set fine can be used on layers that show to obtain a near perfect fit. For interior joints 1/32" gaps will be filled with glue and will not be a problem.

The above method takes a little bit of practice and skill but is very fast. I know this is fast because planking crews often compete to see who can get the most done in a shift. I was usually able to fit a plank with this method in the time it took for another Shipwright to just set up the router method mentioned by others.

There is a place for the mechanized spiling method. Though I don't like "wood machining" much for boatbuilding, some folks never will have the time to develop the skill to make good joints by hand. Though the mechanized method takes longer, it does produce good joints with less skill.

[Big Red]

Q1. What is edge setting and why shouldn't it be done ?

Q2. Couldn't some of the problems with cost be solved using plywood for planking material?

Cheers, Red.

[bainbridgeisland]

Originally posted by Big Red:
Q1. What is edge setting and why shouldn't it be done ?

Q2. Couldn't some of the problems with cost be solved using plywood for planking material?
Cheers, Red.

Try this: Lay a sheet of paper flat on a table. Press the top of the paper against the table with one hand so it can't move. Grasp the opposite side of the paper and slide it sideways a little. This is edge setting. You will immediately see why it causes unfair planking. Timber can accommodate a little edge setting because it is thicker but if you misjudge, you will never be able to fasten the plank flat enough for a good glue joint. Since cold molded planks are usually only lightly stapled in place during the spiling process, it is not easy to see if the plank has been edge set or not.

Plywood has been used for cold molding (or double planking) since at least when I started my apprenticeship in 1972. It has mixed results. The main problem in my opinion is that you are limited to species of wood that are not highly resistant to rot. The edge grain of plywood is especially vulnerable. However, I have seen some extremely well made boats built this way that are still sound.

Check out Reuel Parkers work to see one version of cold molded plywood.

Using cedar and epoxy together is like belt and suspenders as far as rot is concerned. The cedar is extremely rot resistant. The epoxy tremendously reduces the air and fresh water needed to get rot going.

An aside: I am a firm believer in using the right timber species if you want the boat to last. One of my favorite boats in Puget Sound is a 50-year old troller converted to a yacht. It was built in Grays Harbor of Pot Orford Cedar planking, stem, keel, clamp and deck over White Oak frames. Though worked hard and receiving only 'fishermans' maintenance, only the covering board and sheer plank have been replaced to date. The boat was reasonably well built and maintained but the longevity is due to the quality of the materials.

[Tonyr]

Bainbridge, I am really encouraged by your remarks about materials choice. Thank you! I am in the process of building a 24' lobster type boat using atlantic white cedar nearly exclusively. In particular, I am aiming for a minimum weight boat (for efficiency at displacement speed), so our local cedar seems right, even if it is a pretty weak wood. I am slathering the planked hull with epoxy/fibreglass right now (thoroughly unpleasant job compared to woodworking) with the idea that if I do this correctly, and keep the cedar dry, I should finish up with a stiff, light boat.

The main design tradeoff is the requirement for a seriously big skeg, so the boat does not skid all over the place. I hope to end up with a minimum rot hull, with nice dry bilges.

Tony.

[ 09-05-2004, 05:25 PM: Message edited by: Tonyr ]

[Cecil Borel]

I have been following this thread with interest, since I have recently completed the hull for a 32' strip-planked, cold molded sailboat. Pictures of the process available here (janetess albumn) . Bainbridgeisland's comments mirror my experiences very well. Since I used both strip planking and cold molded veneering, I think both have their advantages. For Jim Conlin, I would recommend Global Veneers (www.globalveneer.com) for 1/8'th inch spanish cedar veneers: they supplied me with 17' long veneers ranging from 4-10" wide that were ideal for the outer two cold molded layers.
Incidentally, I was very pleased with the additional strength that the veneer layer added to the strip planked hull.

[paladin]

Forgive me if I have misunderstood something...it's 10 p.m. and the percocets have addled my somewhat limited reasoning a bit....and lullaby time would seem to be near.....but (Gawd, izz the lights dimming?)......You are using steam bent frames with a cold molded hull.....(I told you I'm fading fast)....but wouldn't the frames have a tendency to contract and expand somewhat with the humidity, no matter how built...and cause a wee bit of unwanted stress on a potentially very rigid hull. I installed frames in ways of bulkheads and chainplates etc...but all were laminated from as thin as possible pieces to insure dimensional stability....