Strip planking vs wide planking

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

 

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?

 

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.

 

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.

 

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?

 

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.

 

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

 

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.

 

Yes 1600 gr / m2

 

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.

 

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.

 

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...............

 

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

 

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....