On Wood Strip Building Techniques
updated 11/6/11
I'm passionate, about building and passing on information that will make building easier for you. How I can let you know I have information that will make your strip building easier and fun? There is a lot of information on this page and it's growning all the time, so be patient and read through all of it because it will be well worth your while.
I've spent the last twenty years unlearning conventional
strip building techniques. I found a lot of the
techniques, passed on in books, that were vague, poorly thought out and
just didn't work. There were parts of the strip building process that were
just not fun. I've spent the last twenty years solving these problems.
My techniques for strip building are fun.
ROB'S RULE #1: If you're not having fun, you're using the wrong tool, or technique.
Yes, some parts of the building process will be more fun than others, but if you are working with dread, something is wrong. Stop! Think about it. Ask questions. Look for answers. Too many people struggle through a task using a poor technique or wrong tool, because they think that's just the way it has to be. But it doesn't. Unfortunately a lot of books on strip building are writen by people lacking woodworking and boatbuilding experience who make-up techniques which are not only poor but sometimes even counterproductive. When a novice builder buys a BOOK they assume the author knows what they are talking about and the novice just "Follows the Leader" in learning a poor technique. Sure, you can struggle through and get the job done, thinking "that's the way to do it!" And if you've "toughed it out" you'll have invested a lot of time and grief and believe you've learned all there is to know about strip building.
There is magic in every material, in every tool. And if you take the time to learn the "Tricks of the Trade" as the saying goes, you will be amazed at how easy and how much fun strip building can be.
I will reveal some of these "Tricks" here, and there is much, much, more in my instruction books.
I'm not saying the techniques I suggest are the only way to strip build. But the techniques I talk about here, used together as a system make strip building simple, quick and fun.
Novice builders will not realize that many seemingly good
techniques cause more problems than they solve.
ROB’S RULE #2: Solutions to problems are easy. The trick is, coming up with a solution that doesn't create three NEW problems!
I have a LOT of experience and I've tried just about everything.
I've spent twenty years unlearning common strip building wisdom. The methods I suggest reduce work, period and don't create problems. I have to do this as a professional builder. Believe me, after building more than 70 boats, I've eliminated techniques that cause problems or just
don't work. I do enjoy building and have fun doing it. I want you to
enjoy it too.
With the right tools and techniques, work is fun,
work is magic! Learning the techniques to make things is truly the
magic in this world. Creating a real boat IS fun magic.
Making your own little boat from some sticks and
glue, a boat that will take you, and support you, miles out to sea, is true magic!!!
Stripping Made Easy
These pages contain my latest thinking on building issues. I'm constantly adding new ideas and clarifying old concepts to update my plans and make building easier for you.
If I repeat myself in the following it is because these
are some of THE most important points to your success.
This page includes some of the ideas that set my building
techniques apart from other builders, and makes your task easier. Therefore,
I present these ideas here for you to consider before you dive into the
project, since they will guide you in a different path from other strip
builders, if you choose to use them, which I hope you will.
Strip Building Theory, The
Guiding Principles
The beauty, the genius, of the strip building method is
that IF the wood strips remain in contact with the stations & stems,
AND the edge of each new strip is aligned and glued to the previous strip,
the resulting surface IS FAIR and perfect.
THE RESULTING SURFACE IS FAIR AND PERFECT!
This is the essence and genius of strip building theory.
Everybody kinda knows this, and yet nowhere have I seen
it stated clearly. The assumption is that you will have problems aligning
strip edges and you'll just have to deal with it.
Perhaps I see the beauty of the strip building method,
brightly, because as a sculptor I had to struggle with materials like clay
and plaster trying to impose a shape on these formless materials. Where
with strip building, in a simple stroke, the strips create this perfect
surface for me.
It reminds me of the scene in "Cast Away" when
Tom Hank's character is alone in the banquet room after his rescue from
the desert island and he looks at the butane candle lighter, and lights
it a few times. You know he's thinking about how he struggled and bloodied
his hands trying to make fire. Well I've bloodied my hands struggling to
create a smooth regular surface and I appreciate how quickly and easily
strip building does this.
NOTHING YOU DO WILL BENEFIT THIS PROJECT MORE AND ELIMINATE
EXTRA WORK than taking all the time you need to insure each strip edge
is aligned with the previous strip and each strip is in contact and remains
in contact with the forms. If you do this, your hull will start off FAIR
and you will need to do very little work to finish it! I cannot emphasize
this enough.
THE ONLY sanding needed is to round the high points along
the strip joints and to smooth the surface for finishing. Each strip is
perfectly fair, just as a plywood panel on a stitch and glue boat is perfectly
fair.
The less you do to this surface the more it will remain
fair!
Of course, the above assumes you have strips of regular
thickness, if B&C, it must be correctly centered, and that your station/stem
set-up is correct.
The random orbital sander allows the builder to take advantage
of the strip building method in a way no other tool can. The random orbital
sander uses the FULL FLAT SURFACE of the sanding disk to ride on high spots
and level and round the surface TO the lowest point of VISUAL REFERENCE,
in this case, the surface down the center of each strip which is perfectly
fair.
You cannot create a fair and regular surface with unplanned
tool use.
You must carefully define the areas to focus tool use.
Imagine working on a stitch & glue boat using a aggressive
edge cutting sander or a plane on the plywood surface. You would quickly
cut through the top veneer, destroying the fair surface naturally created
by the plywood panel .
It just doesn't make sense to work a fair plywood surface
with a plane or edge cutting sander. It should make just as little sense
to work a well stripped, fair hull with a plane or edge cutting sander.
It will be counter productive.
If you take the time to align your strip edges your hull
will be perfect.
I understand that quite a few builders have difficulty
in aligning strip edges.
Traditional strip building techniques use 1/4" strips
and staples or brads to FORCE strips into place. This method creates real
problems in the most difficult areas around the keel/stems. While this
worked reasonably well for simple football shaped hulls, for more complex
modern hull shapes, kayak shapes and stapleless stripping methods, 1/4"
traditional force stripping, makes perfect alignment of strips at the hull
stems very difficult.
I've developed a number of modifications to the traditional
stripping technique to solve these problems.
The three big differences in my stripping technique
that make stripping 3X easier are:
First, use 3/16" thick strips instead of 1/4". 3/16" thick strips are more flexible
and are easier to twist, bend and align. The strength of stripper construction
is in the fiberglass sheathing not strip thickness. 3/16" strips make
as strong a hull as 1/4" strip with the same lay-up.
Second, use northern white cedar
to strip below the waterline. The area below the waterline is the most
difficult part of the hull to strip. Northern white cedar is more flexible
than other softwoods and has always been the preferred wood for canoe building
for hundreds of years because of it's bending properties.
You can buy northern white cedar strips from kit makers
or buy boards from companies listed
on my web site links page.
Third; Use a heat gun to apply
heat to bend and twist strips into place instead of relying on force.
A heat gun boils the water in the wood to bend without
having to wet the wood. This allows you to glue immediately without having
to wait for wood to dry as you would if you used a wet/steam heat method.
The heat gun applies local heat to a small area so you
don't need a large box or other apparatus. There is no waiting, no clamping,
or drying time, as in wet bending.
Northern white cedar is the best wood to utilize the heat
gun method of bending for the already stated natural bending properties.
But also, because NWC is typically air dried, the natural glue (lignin)
which holds the wood fibers together can be reactivated by heat. Kiln drying
wood alters the lignin and it will not respond as well to heat/steam bending.
3/16" Plus
Using 3/16" strips RELIES on the proper use
of a random orbital sander to level and smooth the strip surface.
A random orbital sander works like no other surfacing
tool by riding on the high spots and utilizes disk speed and disk grit
instead of high motor power and tool weight. The round pad and random stroke
will not cut deeply into a surface as long as the full pad is held FLAT
against the work surface. These features make the random orbital sander
ideal for sanding the complex curves of a stripper.
The round pad and random stroke will not cut deeply into
a surface, as long as the full pad is held FLAT against the work surface.
IF the
ROS is HELD FLAT against the surface, it will produce a fair surface.
THIS IS CRITICAL TO SUCCESS.
The ROS is moved over the surface until a uniform sanded
surface results.
You must assess the progress VISUALLY.
The original unsanded surface is your visual reference
letting you know when to move on. This will happen JUST as the lowest center
of each strip is sanded in each area. Then you must move on. This sanding
method takes off very little wood.
Learn How To Sand
Even if you were foolish enough to plane the wood surface of your boat you will still have to sand it smooth, and sand epoxy and varnish. There is no getting around the fact that building a stripper requires a lot of sanding, so learn how to do it! Learn to choose a sander and grit and how to change a rough surface into one ready for a perfect finish.
Sanding Theory
Understanding sanding theory will make your goal clear and choosing a grit straightforward. Using the right grit, the right tool, and having a clear goal, will make sanding fast and effective, and maybe even fun!
Sanding has three different steps: Leveling, Smoothing, and Polishing.
• Leveling - A coarse grit is used to cut down an irregular surface to a level uniform surface without blemishes or low spots. Coarse sandpaper grits are 24, 36, 40, 50 and 60.
• Smoothing - A medium grit sandpaper is used to remove the deep cut marks of the coarse sandpaper grits. Medium grits are 80, 100, 120 and 150.
• Polishing - A fine grit sandpaper is used to remove the cut marks of the medium grit sandpapers to prepare the surface for a finish. Fine grit sandpapers are 180, 220, 320, 400 and 600.
The hardness and the degree of irregularity of the surface will determine the starting grit and how many other grits are needed to polish the final surface. A hard surface like steel might require the use of every grit number to move to the next grit. Softer materials like wood allow many grit numbers to be skipped over. Start with the highest number coarse grit that will do the job of leveling, then choose the medium grit that will remove the coarse grit scratches, and the fine grit that will bring the surface to the desired state of polish for applying a finish.
Sanding SEEMS like a no brainer. Buy a sander, put some sandpaper on it and sand. But then, it's no fun when the sandpaper clogs up and you're moving the thing back and forth and nothing's happening. "This stupid thing doesn't work," is a common response. So people do something silly like pick up a block plane and use that, because they can see it's doing something.
You should have results as clearly when sanding, as you do when using a plane.
If you don't know which grit to use, don't understand how to use a sander, and are frustrated when you don't see anything happening, STOP!!!!! Sanding doesn't work if you don't know what you're doing and why you're doing it!
First, you must understand three common sanding problems.
ONE, people commonly use the wrong sandpaper grit for the task at hand. Most builders use 80 grit sandpaper on a power sander to rough sand their stripper.
When this does not level the surface quickly, they use an edge of the sanding disk, LIKE AN ERASER, which will aggressively remove a stubborn blemish.
This is a mistake, cutting a low spot in the hull and will leave an unfair surface. This "eraser style" of sanding is very common. Anyone using a power sander quickly learns if they roll the sander onto an edge of the disk or belt, it will cut very aggressively. So, if you use a medium grit sandpaper on a power sander, you will be frustrated at how poorly it cuts and levels an irregular surface. You will be forced to use an edge of the sander like an eraser to see any progress.
Most woodworkers would tell you to use no coarser than 80 grit, because they only remove machine marks from flat boards. The boards they use had defects and irregularities of the surface leveled by a thickness planer. A thickness planer levels a whole board surface uniformly in one pass. This is what we'd like to do to our stripper hull if we could. The strips on a stripper, have saw blade marks and strip joints that are high and must be leveled. This calls for a coarse grit sandpaper that will remove all defects and produce a uniform surface, like a thickness planer, in just a few passes of the sander. If the sandpaper you're using can't to this, or if you find you must press on a tough spot, the grit you are using is too fine. Switch to a coarser grit.
TWO, sandpaper gets clogged by glue and finishes. Glue blobs and residue must be removed before sanding, especially PVA (yellow carpenter's glue) which is reactivated by heat. Friction from sanding creates heat, and if PVA glue is present it will glue itself into the sandpaper and new sandpaper will cut nothing in seconds! Finishes and epoxy that is not totally cured will also clog sandpaper. Fine grits of sandpaper will clog faster than coarse grits. Sandpaper companies apply anticlogging chemicals to production sanding disks and belts to reduce clogging. Power tool dust removal systems are designed to remove sanding dust to reduce sandpaper clogging.
THREE, sandpaper wears out. You must tune in to seeing and feeling how new sandpaper works and when it wears out. Many people don't do this. They continue to use dull worn out sandpaper and wonder why it's not working. AND, they buy five pieces of sandpaper and don't want to use them all up. Buy a BIG box of each sandpaper grit and switch to new paper often.
The strips on your hull are perfectly fair before they are sanded, and we want to retain that fair surface by only removing the rough surface in a uniform manner. The less we do to the fair surface, the more it will remain fair. So, if you find yourself focusing your sander on a spot, you will be creating a low spot that will not be fair.
This is why I use the ROS and a courser 60 grit paper
which will level and fair the surface quickly. If you are concerned with
the aggressiveness of sanding cedar with 60 grit paper, try sanding all
the way through a strip panel while holding the sanding pad flat. It will
take a long, long time. Then sand using an edge. It will cut much faster.
Rough sand the surface with a random orbital sander and
60 grit paper. Then WET, I mean WET the surface to raise the grain. The
cut marks from the 60 grit paper will disappear. All dents and staple holes
will raise and close. After the wood dries you can sand with 120 grit because
the soft wood needs no courser grit to proceed to finishing steps.
It is important to use a firm backing pad on the ROS because this will reinforce flat, fair surfaces of a boat. Most ROS come with a medium/hard backing pad for designed for flat surfaces which will work well for the exterior of your hull. Buy an "interface" pad that goes between your backing pad and the sandpaper to sand the interior of your hull. This "interface" pad will allow you to sand in the deep concave sections of the hull bilge.
These stripping techniques and the random orbital sanding
method I describe above are the foundation of my stripper construction
technique. Each step is interlocked into the next. If you can't bend strips
you can't align the edges. If you can't align the edges, you will have
to sand more, or plane to establish a common surface and you will destroy
the natural fair surface created by using wood strips. If your strips have
not naturally created a fair surface the ROS will follow the irregularities
of that poor surface.
I urge you to focus your attention on pre-fitting each
strip.
Test fit each strip. Totally clamp the strip in place
BEFORE GLUING using spring clamps. If you cannot get the strip to fit in
a test clamp up, it will not fit with force once you apply the glue. Dry
fit, clamp, and use a heat gun to bend strips so they fit perfectly before
applying glue. This will reduce work on every future step.
If you work to align your strips the surface will be nearly
perfect and you will have less work smoothing the hull.
Any stapleless method that does not tack your strips
firmly to the stations can not keep the strips from warping out of alignment.
AFTER you have stripped your hull, if you have strips
that are mis-aligned 1/32" or more, then fix the strip alignment before
sanding.
Use a new blade in a utility knife and cut on the joint,
apply glue and realign the strip edges.
If you use 3/16" strips they will be more flexible
and easier to align.
If you use northern white cedar it will be even more
flexible.
And if you also use a heat gun to bend and twist strips
into place you will find it very easy to strip a perfect fair hull or deck.
Any one of these suggestions will make stripping easier.
If you will use all three suggestions you will find stripping
a totally painless dream.
By understanding the basic theory of strip building, by
looking at WHY we are doing something, we can focus our labors in areas
that are most productive and eliminate random and counterproductive steps.
I hope you will find this useful.
Random
Orbital Sanders
The random orbital sander allows the builder to take advantage of the strip building method in a way no other tool can. The random orbital sander uses the FULL FLAT SURFACE of the sanding disk to ride on high spots and level the surface. The ROS has a large cutting surface which works in any direction of movement easily following the surface and reinforcing a fair surface.
The beauty of the ROS is the control you have over the
aggressiveness of the cutting action. You have five levels of control which
are: disk grit, disk speed, pressure, flat or edge sanding with the disk,
and finally visual input. The last is most important. You can and must
observe the surface being sanded to tell exactly how much material is removed.
ROS use must be totally visually cued.
Variable speed is important because it allows you more
control. Fast speeds for large open flat sanding and slower speeds for
small close quarters. If you are worried about the aggressiveness of a
courser grit, you can slow down the disk speed to have more control.
The Dustless feature is important because it removes debris
from the paper, so the paper works longer and better and won't clog as
fast.
And if you hook your ROS to a good quality shop vacuum,
you'll have almost no dust in your lungs. I would not consider using
a ROS without a hook-up to a shop vac.
Light-weight is important because you must hold the sander
over internal and external curved surfaces which are often angled or vertical.
The light-weight ROS will allow you to work for a long time without getting
tired of holding the tool weight.
The heavy more powerful, 6" ROS are intended for
large mostly flat surfaces. More weight and power are important when you
are working on large flat surfaces because the weight will help in material
removal as will the power. This is the intent behind belt sanders which
are designed for flat surfacing. The combination of heavy weight and high
power remove material fast. Too fast and too hard to control for the finesse
needed to keep a stripper hull fair.
ROS come with a hard disk pad for sanding flat surfaces.
This will keep your surfaces flat only if you hold the disk flat against
the hull.
Hold a random orbital sander with the disk flat against the wood surface. Control the cutting rate by starting with a slow speed and light pressure.
Move the sander in circles, 6 to 8”, over the surface in continuous motion, progressing up or down in a small area.
Most people sand in a back and forth stroke or up and down. This can cause flat spots. Sanding in small circles will force you to more closely follow the curved surfaces on a boat with the ROS producing a fairer surface.
For the mostly curved surfaces of stripper boats, especially the interiors, a light-weight sander is much easier to handle for long periods of time and more control is available because material removal is more dependent on disk speed and grit size than weight and power.
A very important accessory for interior sanding is a soft but firm "interface" backing pad. This is attached to the regular backing pad and the sanding disk is placed on top. This soft interface pad allows the sanding disk to conform to tight interior curves without the edge of the sanding disk cutting ripples into the soft wood. Unfortunately, I've had a hard time finding one for my 8 hole Bosch sander so I made my own. I used an old worn disk backing disk from my ROS and glued 1/4" thick piece of the L200 foam I use for my kayak seats to it. Then I glued some hook material so I'd be able to use my loop sanding disks. I cut holes in the pad for the dust removal. It work's great. If you buy an interface pad or make your own make certain the foam backing is quite firm or the sanding will not be effective.
The ideal ROS for strip building is light-weight, variable
speed, and dustless, 5" disc with hook and loop paper. If I had to
choose one from the current crop I'd go for the Makita BO5020, Porter Cable
333VS or DeWalt DW423Kat about $85 at Tools on Sale - 800-328-0457 (free
shipping). If you really want cheap, Grizzly makes one for $25 - see www.grizzly.com
Update 4/08
Time to buy a new ROS as my old faithful Bosch died. I
figured after twenty years and all the sanding I do I'd get the best, so
I started looking at the highly touted highly priced Festool systems. But
after many test runs I could not see or feel a marked improvement over
my old Bosch ROS teamed with a Bosch triggered vac.
So, I replaced my twenty year old Bosch ROS with the Makita
BO5021-K 5" variable speed sander. I choose this 5" sander because
it has a D handle design like my old Bosch. I like this because it allows
me more one or two handed holding positions which helps relieve vibration
fatigue. Plus the dust outlet is a round tube that could be easily connected
to a shop vac. And when this style is connected to a vac the balance moves
to the D handle because of the weight of the vac hose. Plus, the Makita
uses the same 8 hole pattern 5" hook and loop sanding disks I had
stock piled for my Bosch ROS.
The Makita 743022A 5" contour surf backing pad is
required for interior sanding. At the same time I bought the Fein Turbo
I trigger activated shop vac to use with the Makita ROS. The Fein vac is
very quiet and very strong. Fein makes a stepped hose adapter that mates
the Fein hose to the Makita ROS dust port perfectly. I also found the Fein
hose and the Fein stepped adapter allowed me to connect to other sanders
and tools I had that I could not do so before. I upgraded the standard
cloth filter on the Fein vac to the 1 micron filter kit and paper dust
bags.
This grouping of the Makita ROS and the Fein vac is great!
This is the best I've used. If you are in the market for ROS and vac I
recommend this pair.
Tricks for Taming Rogue Strips
Heat Gun
A heat gun is a high powered industrial tool that
blows very hot air at 500 to 1000 degrees. It has many uses like removing
paint but the use we are interested in, is in bending wood.
Every place on your boat were you are twisting or bending
a strip into place with force, can be bent using a heat gun. Then the strip
will be easily placed without force. This makes stripping easier.
Many people think of steam bending when they think about
bending wood. This is because steam bending is most often used when bending
thick boards and wood sections and steam bending works well for production
bending where pieces will be bent over forms.
Steam and therefore moisture is a very good vehicle to
transfer heat. But it is the heat that is important not the water.
Heat promotes wood bending by reactivating the natural
wood glue "lignin" that holds the wood fibers together,
to move and reshape the wood fiber arrangement.
The heat gun bends the smaller sections of wood strip
we use quickly. A part of the strip can be bent or twisted, freeform, while
the strip is on the boat. The wood is not clamped to a form and the wood
remains dry so it can be glued immediately. This is a big advantage over
steam bending.
Air dried woods bend easily with the heat gun because
the natural glue that holds the wood fibers together, lignin, becomes plastic
when heated. Northern white cedar is THE BEST! air dried wood for bending
and wood strips. Kiln dried woods like western red cedar will not bend
as well, because the lignin has changed in the drying process. But kiln
dried wood will still bend if you go slow and try a few test pieces to
get the feel for working with it.
An important point to remember about wood bending is that
all the bending happens on the compression side of the wood (inside of
the curve) so to use a heat gun effectively you must apply heat to the
inside of what will be a curve.
As with any wood bending, clear straight grain wood
is important for success.
Clamp one section, near where you will bend the wood and
hold the other end with a leather gloved hand (that heat is very hot!)
or spring clamp and apply the heat from the heat gun to the flat of the
strip. Hold the end of the heat nozzle about two inches from the wood and
keep it moving back and forth in a small area. Twist or bend the wood with
your hand building tension into the wood. You will feel the tension release
as the wood reaches the right temperature.
Kiln dried woods will take more heat often toasting the
wood surface before tension is released.
If you bend too far too fast you'll hear the wood start
cracking as it starts to break on the tension surface (outside of the curve).
Don't be afraid to break a few. The best way to learn bending with the
heat gun is to play with scrap strips held in a vise.
Most of the difficult stripping on our hulls is at the
stems near the keel. Here strips from the bottom are twisted from horizontal
to vertical at the stems. Clamp and immobilize the smallest section of
the end of the strip you wish to bend. Long sections of strip will have
a lot of flex and will be hard to induce more tension for bending.
You have to over bend the piece because it will spring
back. If you end up with a tighter bend than you wish you can just re-heat
it and straighten it a bit.
At left, I'm hand bending a 1/4" X 2" mahogany
strip for a cockpit coaming.
One end is clamped in a vise while I apply bending force
to the wood. I apply heat with the heat gun to the inside of the curve
to be bent. Slowly moving the heat gun back and forth concentrating the
heat in a small area without burning the wood. I will feel the tension
in the wood release as the wood bends and I move the heat on down the strip,
applying heat, applying force and feeling the tension release as the curve
is shaped.
The force and bend made must be greater as the wood will
spring back a certain amount you must learn to judge. If you bend too tightly
you can apply heat to straighten an area again.
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