Strip planking vs wide planking

[jfblouin]

I'm building a 6,80m (22.3 feet) sportboat with cedar, epoxy and fiberglass.

For the most part of the boat, I'm using cedar strip planking but for some straight section can I use wide plank (100 mm to 200 mm)?

Thanks for help

[Raggi_Thor]

Why not use plywood in the straight areas, it's a stable material. You can use wide cedar planks also, I guess. Do you use enough glass on both sides to stabilize the wood?

[marshmat]

I don't see any reason why you couldn't use wide planks if the hull curves are suitable. Plywood's great for this type of construction; stable and strong and gets along well with the epoxy. The cedar would keep the look better though if that's what you're after.

[jfblouin]

3/4 inch marine plywood cost $3 by square feet.
cedar plank cost me $0.75 by square feet.

Also plywood plank will be between strip planking section and my interior and exterior skin are 45-45 biaxe. For plywood, 0-90 will be better.

[PAR]

One of the important considerations for strip dimensions, in this construction method, is to insure a stable substrate. Increasing the width of the strips will introduce potential internal stresses in the lumber, decrease the planking stability, without framing to control the inner face of these larger strips warping and cupping will begin to creep into the structure also (on those larger strips) A lot depends on the designer's intensions with the structure. If it's a wood cored laminate, then you'll likely be okay, if it's a wood hull with 'glass sheathing for abrasion, then you'll have issues.

Though plywood, at first glance seems like a good option, I'd not use it on a hull that is strip built with cedar. There's a big difference in the weight of the two materials and considerable properties variables that should be looked into. What are your normal strip dimensions and the inner and outer biax weights? How much bigger do you want to make these larger flat area strips? Fastenings and other related structure (bulkheads, furniture, etc.) in the affected area(s)? Percentage (a good guess) of the total hull surface area affected by these enlarged strips?

[jfblouin]

The boat is my own design. The boat is 22 feet (6.80m) long. It is a kind of RIB with Rigid Tube (Rigid Boyancy Boat). I use Gerr Scantling number to draw up thickness. I add a extra safety for rough water. I want to reach Zodiac Hurricane stiffness. The boat will be plane at about 35 knots.

I use 3/4 inch (19mm) by 1 1/2 inch (38 mm) strip with about 50 onces biaxe inside and outside. I add a 20 onces kevlar 16 inches wide strip on the keel.

I think to use 6 inches (150mm) wide plank. Thoses planks will cover about 40% of the wet surface and 15% of the hull. I will put 5 bulkheads and 5 half-height bulkhead. I have also 5 stringers all lenght of the hull.

I make a dry lay-up of the strip. Each strip have a 4 degres bevel on one side and I will cover all the hull with Mayo epoxy in one time. With larger plank, I have less groove to fill.

[Raggi_Thor]

Is 50 ounces approx 1500g? Per m2 (square meter)?

[nero]

Just from the photo you posted, it looks like you would be better off using plywood sheets. Maybe use 2 or 3 layers of 5 mm and laminate them on the forms. Just a guess.

[jfblouin]

Yes 1600 gr / m2

[Raggi_Thor]

[QUOTE=jfblouin]3/4 inch marine plywood cost $3 by square feet.
cedar plank cost me $0.75 by square feet.
QUOTE]

Do you include the extra glue (epoxy) and glass you need with cedar?
Plywood can do with maybe 450g glass (+450g epoxy) while cedar need 1600g glass (+1600g epoxy). One kg of epoxy costs maybe 20$.
These numbers are per m2 so divide by 10 (11?) to get per feet2.

Okume plywood has a density of 420kg/m3, what is cedar? 320? But then again, glass+epoxy is very heavy...

[PAR]

Jfblouin, those enlarged strips (150 MM) seem to rival carvel construction in width. That width of cedar is much too wide for 'glass to keep in place. Your bulkhead count is fine for strip, but not for a hull that's near half carvel. At three inches (75 MM) wide I'd still worry a bit, but would be a much better size to expect the glue line and sheathing to hold in place. Basically you be cutting the stripping effort in half at this dimension, but the fitting accuracy would need be high on these larger strips, to insure good bond and load transfer.

Judging by the photo, you may very well save a lot of planking time with a plywood laminate (2 layers of 3/8" or 3 layers of 1/4") The hull weight will climb a good bunch, but it depends on your interests. Now you are interested in getting it built so speeding up the build is on the front burner, but you're building a "sport boat" and the requirement typically needed there is "keep it light" so you have to decide what you want, a quicker build resulting in a heavier product or a slower build producing a lighter craft.

Personally, the bottom line on any boat is the performance envelope (this is why we follow plans in the first place) any deviation from the plans can and likely will effect the performance, so only performance enhancements (making her lighter for example, rather then heavier) are a good choice. In other words, don't forget the goal is a sport boat.

[masrapido]

Hi all,

I wish those who still use their fingers and legs to measure length start using mm, cm, etc. It cuts out from reasonable discussion and ideas exchange us who have only heard about these old and outdated types of measures...Can't believe there are still people using them.

[jfblouin]

Some kind of change need many many years. In Canada we change for metric in 80's.
In 2005, I always buy 2 x 4 lumbers, 4 x 8 plywood sheet. I buy fuel in liters and for my food it is some time in pound, some time in Kilo.

My children study metric only...............

[nero]

2 x 4 lumber is no longer 2" by 4". 1/2 inch plywood is less than 1/2 inch. like many things in america they are not what they use to be. But get an american to admit it is time for an intelligent change?

This would "screw up the economy". (probably a good thing) So many things here are based on something that is not quite what it is. Or maybe it is based on something we want it to be. But it is not based on reality.

So if we quantify things here in the u.s. with a simply clear measuring system the whole of america would be lost, confused, and pissed off for people medaling in american affairs and "hurting the economy"

So back to strip planking.

Finally, I finished laying the planks on 1/4 of my cat. Working solo, it takes a long time. I tried the dry method on some of it. Big mistake! While it feels good to lay down a big section of planks and not have epoxy covered gloves on, it takes forever to sand off all the epoxy mess.

When I wet planked eveything, I can keep the mess confined.

a 3 to 6 degree bevel (depending on strip placement) was helpful at hold the thickened epoxy in place.

Now I am filling all the screw holes, and getting the nerve up for glassing.

The results of strip planking are beautiful and strong, but, it ain't easy ... in english or metric. smile

[marshmat]

On the planking: Like nero says, strip planking is pretty and strong. If done well (ie. with lots of patience and care) it will last forever. But it is by no means easy.

Now, the Metric vs. US Customary (as the old English system is now officially known) debate: What chaos! A 4x8 foot sheet of 1/2" plywood is actually a 6mm thick sheet. We have at least 4 different things called 'gallons': 3.78 L, 4.0 L, 4.4 L, or 4.55 L, depending who you ask and where. And let's not get into fathoms, chains, rods, stones, poundals or any of that. Any sort of math or computation is generally easier in Metric (thanks to Base-10). Even the US was beginning to make the change until Reagan decided otherwise. But today it's simply too big an effort and too large a shift for too many stubborn people to adapt, so we live with our 205mm x 16" car tires and such for now....

[PAR]

The metric/standard debate isn't as easy an issue to resolve as it would appear.

Not only do you need to convince folks it's a better system, they need to be retrained in every aspect of their lives. It's much more a mater of economics then tradition or stubbornness or unwillingness. It boils down to dollars and cents.

Every road sign with a mileage on it will need replacement, every map, every fastener sold or used in production and manufacturing (most large companies already have made the change) Entire industries will have to remove and replace equipment to be compliant with the "new" standards and frankly it's not really going to help much. Well be dealing with fractions of a metric measurement, because everything was designed in a US standard. These individually may seem trivial, but even with a 20 year phase in period, the cost would be outrageous and this is the basic reason our government hasn't worked very hard to make the transition. The studies done show it would take a couple of generations to just get thinking in metric and only then could a long term phase in of metric replacements be implemented.

This education process is coming to the end of the first generation of "metric kids" and the children of these will have to vote for a process of bringing in metric. This will still be a difficult thing, because we Americans are a historically proud and rebellious bunch. We do not take to being put into an "everybody else is doing it" mold. In fact, we typically cast this off and come up with an even newer, usually rather clever, method of doing things. Then the world will have to be convinced (once again) how it's important to be like us (not that this has always been a good idea or in everyone's best interest)

This particular trait has been a hallmark of American's for a couple of centuries now. This country's tossing off a colonial rule showed the rest of the world they don't have to be subservient to an uninterested overload. The next hundred years following saw other countries resist their political bondage and many a constitution was written, interestingly enough, patterned much like ours. The very premises our country is founded on, causes this to happen. Freedom isn't the ability to do as you wish without hurting others, but it is standing up for a person, who has spent their whole life in opposition to your own views, to defend his right to have a voice, live and within this opinion. It makes for strange bed fellows from time to time, but this is why it works.

It basically boils down to organized chaos. When anything is this country becomes a big enough issue that each region has had to enact laws to work around a dysfunctional element of our system it becomes a national issue. Very quickly a national riot is on the hands of the government and a national referendum is presented to the people for their opinion. If the issue isn't popular, but is found the right thing to do, by the folks educated sufficiently about the crisis and it's elements, our congress acts, because after all we are not a democracy, but a republic. Case in point would be the civil rights amendment to the constitution in the early 1960's. 70% of the country was not in favor of this law, according to the polling done then. The people we elected to be informed about the issues, felt we didn't understand the issue very well and passed it anyway.A large campaign was launched to educate us, so we'd make the right call when ratification came up in our region. It worked and it was ratified. Many times in our short history as a country this has happened and it's a good thing. Good for us and good for the world, because if you don't think the world doesn't look over here for examples, then you're kidding yourself.

With the burden of being the ones most tend to follow, we've found we like to lead. This can sometimes makes us seem arrogant and full of ourselves, but this is a common thing among leaders. Folks follow the "alpha" not the omega and this breeds contempt in some. All one has to do is look at what we've done in the short time we've been a free, self governing body. We have our flaws, but so does everyone. We provide more for the rest of the world then the top ten other countries combined.

We don't have health care provided by poorly trained and government allotted doctors, we work our ass off for it. When the heads of state in these other countries get deathly ill, they come to our un-government sponsored medical abilities. In fact we work harder then most everybody and still have time to splash a boat on the weekend and have fun. We don't have a government that subsidizes mass transit, or major industries, hell we're lucky to get the mail on time. We bust our butts and look what we've done. We have the largest and more numerous cities in the world, that have an infrastructure that is rivaled by none. We can travel for thousands of miles on a ribbon of highway, without having to "show our papers" at the border of each state. We are free nation of individuals, who's only calling to fame is the ability to have individuality. Conformists we are not and frankly any measure system can be used, some admittedly easier then others, but hell we're the alpha, we like it hard, we're used to it being hard, it makes us stronger and you can peal my US standard tape measure out of my cold dead fingers, because I'm intelligent enough to understand and use both, I just prefer US standard. Besides, what would we call football, 2.36 liter ball? Don't evn ask me to get used to meter marks on the field . . .

[yokebutt]

The US not using the metric system as a standard is a problem, since it's more dependent on international trade than any other country in the world.

Today we have Americans grumbling over having to deal with foreign products that are close but not exactly the same as the domestic stuff, and vice-versa, the rest of the world grumbles when they have to use American things that almost, but not quite, fit.

So what system should we choose to standardise? Well, since the metric system is only used by measly 97% of the world population, I vote Imperial.

[PAR]

The USA has made dramatic efforts in standardizing with metric sizing. It has done so for over 30 years now.

Every fastener on every American car except it's lug nuts are metric. All electronics are metric standard except the screws that open the case. Most every container is metric. By 2020 the country will be, without really being aware of it, on a metric standard.

The problems arise when things need to be redone to a metric sizing. An example would be all the 10' wide driveways in front of everyone's house. The cost of changing the plot plan, for this measurement alone, for every damn driveway, would stagger the best of us. Most don't realize just how big this country truly is. I'm not talking about the number of people, or the amount of cheese we eat in a year, but the big picture. Our richer states have an annual budget that is more then most other countries GNP. The amount of food that goes down our collective garbage disposals could cure the hunger problem in the third world nations. We use more bathroom tissue then nearly the whole world combined.

We are big, really huge and a major impact on the world sociality, economically, politically, materiality and productively. We routinely out perform even our own projections, hold up the world with our economic might, bail out countries that have no brained themselves into another hole and will release them from their dept to us in 20 years when it becomes obvious they can't possibly pay it off. As individuals we come to the aid of the world in times of crisis and need, with more help and money then they know what to do with. Of course they bitch about the Imperialist American dogs that tried to take over their country when a McDonalds attempted to open in their capital.

We put our dirty laundry on the front page of our free press for everyone to see. We don't quietly remove powerful people and not talk about them any more like a lot of other countries ashamedly do. Hell no, we screw them good, then drag their ass into criminal court, then into civil court and let big Bubby have them when they do get to prison. We're not trying to kid anyone (except the CIA)

We use more then any one, buy more then anyone, fix, invent, innovate, recycle, produce and generally do more then any other nation on this planet. If anyone deserves some grease, it would be us. We represent about a 16th of the world's population, yet we easily out do any other nation on just about everything in all the columns we measure these things. Were would the world be without the effect of America, under the rule of the Third Reich in Europe maybe? The USSR would have surly taken over the world after WW II, we all would have really enjoyed that. If any nation deserves it's own standard it would be us, damn it. Though frankly I'll still vote for an imperial measurement standard, because the pints of beer work out better for the buzz . . .

[jfblouin]

Nero

I'm just beginning planking with dry method

Can you explain more about your project with dry method?

Thanks

[nero]

jf

I'll take a photo this afternoon and post it tonight. The cat renderings are posted in the multihull sailboat gallery. There are some photos of the forms some where else in the projects gallery.

The strip planking is on female forms (I like women. smile) The strips are 40 to 50 mm wide. The 40 mm strips were used below the waterline inorder to more closely follow the tighter radius.

I started cutting bevels on one side of each strip to get a tighter fit on the bottom side of the joint and allow a larger space to work the epoxy into. I am using two epoxies on this boat. Both are EPON one is a thick 828 and the other is thin. The thick epoxy will flow into the joint and set up "bridging" up to 3 mm of gap. Then I can poor more of this into the joint before the other has lost it's tack.

I also tried thickening the 828 with coloidal silica. This seemed to reduce the flexibility of the resin.

After breaking several test pieces, I found that even thickened resin is stronger than the cypress strips it bonds.

My problem comes in with the female forms. As I understand a true dry technique is to shape the planks then lay glass over it. The joints suck and hold the resin down into them by capilary action.

Since all my screws holding the strips to the forms would be encapsulated, the hull would come out looking like a blow fish. The forms would be destoyed. The screws have to be removed after the joints are bonded and everything sanded fair enough for the uni glass to layover.

So, here I am sanding all the excess epoxy (it sets up too fast to get all scraped off). I was also in too much of a hurry. On the next half, I am going to be rententive about cleaning up as much of the resine as I plank each one.

Since your project is one male molds, you will not have as much fun time in sanding as me.

Did this explain your question?

[nero]

PAR

As usual you're excellent posts have provide great insight. Now if we can just convert the americans from beer drinkers to appreciateurs of wine. We could all get along easier with less trips to the toillet. smile

[nero]

Yesterday there was too much powder in the barn to take a photo. Today I am done with sanding. Prep to try glassing tomorrow. I am going to try wetting out 2 layers of 10 oz uni at the same time.

I held the strips in place with drywall screws thru fender washers. Before moving the last of the screw I used PU construction adhesive to bond blocks to the hull. The blocks are screwed to the forms. This seemed to keep the stripping from rising off the forms.

Fingers crossed for tomorrow.

[LP]

Nero,

"I tried the dry method on some of it. Big mistake! While it feels good to lay down a big section of planks and not have epoxy covered gloves on, it takes forever to sand off all the epoxy mess."

Curious about the "dry method." Sounds like you are beveling your strips to intentionally leave a gap that will later be filled with epoxy?

I am experimenting with a similar method along the same lines, but I'm trying a thinnned epoxy to aid the capillary action of the epoxy into the joint. Is this your own method or is there other documentation available?

learpilot

[nero]

learpilot

It is not "my method". I read about it here on BoatDesign forums. The post was "dry method" ... I think. It was for dry stripping over a male mold. They left a mm gap. Nailed the planks. Faired the planks and then glassed it. The planks got glued by the resin used in glassing. (Seems too easy)

I started to bevel the planks for three reasons. The planks laying below the waterline were had to have extra bog worked in from the outside inorder to fill the joint. The planks on "light bulb bulge" were opening up to the outside. This made them in accessible for filling once in place. It would have been difficult to hold bog/resin in them by either method.

Thirdly, it seemed easier to get the resin started into the joint.

If there were two people doing it, perhaps the excess resin could be scraped up before it set too much??? I am shorthanded so on the next hull half I am plan to lay it up one strip at a time .... with strips with a bevel on one side.

Note on sheathing. The 2 layers of uni glass wetout at the same time with no problem. I use a small squeege to pull the excess resin up the the sides. On uni glass pull with the fiber direction only. The vertical side cloth gets held in place with plastic pinch clamps.

[capt'n ron]

there are allot of us in the us that deal with the metric and the customary system every day at the same time as a matter of normal course. anyone who does any kind of precision work, machine work or works on machinery of any type, etc., operates in base ten, in most all production millwork shops the machinery set-up is metric based, our money is base ten as well. i think we all have the basic understanding, it's just that we aren't all used to visualizing in base ten, that's the hard part. i know that i've been looking at plans from over seas that are all metric and i always find my self at the calculator converting to inch/feet because it's hard to visualize "610mm" vrs. "2 ft.". one day ,i thought to myself," i've gotto stop converting this stuff and start seeing in metric". if i do build off of metric prints, i will lay out metricly to avoid the possible calculation errors that i am sure will bite me at some time during the build if i don't.

[chandler]

I build homes, mostly with fairly complex roof lines. When calculating rafters valleys, etc. we use a scientific calculator, change the feet inches, and fractions,into decimals. What's the big deal? Same thing isn't it?

[marshmat]

Decimal inch is quite common, ya. Engine builders do it all the time, as do carpenters, etc.
Essentially, as long as you're consistent on any given job, either way works. It's when you mix them that you get problems. Most construction-type work can be done either way. For stuff like chemistry, orbital mechanics, electromagnetics, etc. the calculations are much nicer in metric, though (wanna try computing burn times for mars orbit injection in imperial? it just doesn't work!)