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russkaiser
07-02-2014, 02:08 PM
I am going to build a small row/sail boat soon that will use a sailfish lateen rig that I have on hand. I am seriously considering adapting the Bolger Junebug concept with just a bit of side flair to get the oarlocks a wee bit further apart. I am rowing quite a bit these days for exercise and want something that moves through the water a bit faster than my 14 foot Lowe aluminum boat. My main question is would it be structurally acceptable to cut strips of 3/4 inch cabinet grade plywood to use for the chine logs? The Junebug specs 1 x 3/4 strips. I have some partial sheets (8 ft. x 2 ft.) of the plywood and ripping this for chine logs seems like a great way to get rid of it.

slug
07-02-2014, 02:26 PM
Sounds like a bad idea. Poor strength and unless your boat shaped like a refrigerator how will you edge set the chine logs in place.

Epoxy fillets and tape works well.

willmarsh3
07-02-2014, 02:30 PM
Hi and welcome to the forum. I'm glad to see you are building a boat.

I found a June Bug build here that shows chine logs: http://mgalvin.com/boatbuilding/JuneBugPage.html

To answer your question I would avoid the use of plywood for the chine logs. The cross grain nature of the plywood allows only half the wood to contribute to the stiffness and strength. The other half doesn't do anything because the grain runs perpendicular. Also the cabinet grade plywood might not be water resistant. Because this is the hull of the boat you really want to do it right. Also your proposal would be a builder mod. Having built my own boat I found it easy to allow myself to make builder mods that were not as good an idea as they seemed at first.

Good luck with your build and be sure to post pictures and updates.

Thorne
07-02-2014, 02:40 PM
I strongly recommend against modifying anything until you know a lot more about materials and design -- the result can be a very expensive and frustrating experience for all concerned. there are a gazillion designs to meet nearly any need, pick the best one and built it as planned. Once you've learned the basics (and not screwing into the edge of plywood is very basic knowledge), you can try experimenting

I have several friends that insist on experimenting and self-designing small wooden boats. I carry tools and glue to help with the inevitable field repairs, and try to ignore their anger and frustration when they can't keep up with other similar boats either rowing or sailing, or when gear breaks -- but it ain't easy.

James McMullen
07-02-2014, 02:40 PM
. . .unless your boat shaped like a refrigerator. . .

Not familiar with the Bolger Junebug, eh slug? Granted, most refrigerators aren't pointed at the one end, but other than that. . . .

I think you'll not be happy with plywood chine logs for the reasons given by willmarsh. Half the plies are running the wrong direction for strength, and there's a whole lot of exposed end grain down in the bilge where that's a problem waiting to happen. But inexpensive construction lumber will do fine and his wholly appropriate for this sort of build.

russkaiser
07-02-2014, 03:14 PM
This was my first post here but this isn't the first wooden boat I've built. I thought plywood was probably a bad idea but I wanted to make sure, that's why I asked. From the number and speed of your responses it seems unanimous that solid lumber should be used in that location. Finding good utility material is a challenge around here. It seems that 90% of the lumber at the box stores is treated and the non-treated lumber is white pine with tons of knots. Any piece as small as a 1 x 3/4 would likely have it's entire breadth bridged but a knot every few feet. My last project didn't have chine logs and for what little framing it had I was able to use clear yellow pine. That lumber was given to me and it's all gone. Yellow pine is also very heavy. About the only other cost effective option for this boat is to buy a western cedar board and rip it.

slug
07-02-2014, 03:56 PM
Visit your local lumberyard . Just about any straight grain wood will work.

red cedar is weak and not well suited for chine logs.

local woods like cypress

Bregalad
07-02-2014, 04:00 PM
Southern Yellow Pine has properties very similar to Douglas Fir. There is no reason why a good piece of SYP, not pressure treated, couldn't be used for chine logs. There isn't enough of it in the boat for the weight to be an issue, It holds fastenings much better than Western Red Cedar. Here in N GA most 2x dimension lumber 8" wide and wider (think floor joists or rafters) is SYP. For a long time I've been hoarding nice pieces I've seen while picking lumber for other jobs. You wouldn't need much for the chines on such a small boat. The good news is that SYP is among the most inexpensive woods in this area. I'd be surprised if you couldn't find a suitable piece for ~$10.

If that won't work, there's no reason that boat couldn't be built Stitch and Glue fashion. Replace the lumber chine logs with a fillet material and fiberglass cloth set in epoxy.

Cuyahoga Chuck
07-02-2014, 04:08 PM
You had to ask? Just take a look at a piece of plywood. There are laminates with the grain of each at right angles to each other. That means that no matter how you try only half the wood in the sandwich has grain going in the direction you need. It also means the any screws you might use will only have half the grip they need for a secure attachment. Chine logs went out with high-button shoes. Build Stitich and Glue and your creation will outlive you.

Dannybb55
07-02-2014, 05:08 PM
Cornelius need to be tough, that's why they are not called branches. My junebug rowed like a charm. The oars need to be right for you. A Gloucester Gull rows sweet to and floats like a leaf. Sam Rabl drew a sweet 16 foot skiff that can carry a crowd of 10 year olds and a beefy rower. I wish I Had photos of her. Build to the plans as drawn and you will get something worth having.

DavidC
07-02-2014, 09:21 PM
Buy a couple of 8, 10 or 12 foot 1 x 6 or 1 x 8 pine boards. Rip the chine logs out of these. You should be able to get enough knot-free lengths to do the job with a scarf or two.

David G
07-02-2014, 09:56 PM
Visit your local lumberyard . Just about any straight grain wood will work.

red cedar is weak and not well suited for chine logs.

local woods like cypress

This does not fit my experience. Western Red Cedar is not as strong as white oak, douglas fir, or even mahogany. That much is true. Unsuitable for chine logs? Not true. It's rot-resistant. It glues well. It holds fasteners ok. It's light. It's a pleasure to work with. All one has to do is beef up the scantlings slightly.

One good example. My buddy, the Aussie small boat designer Michael Storer calls out wrc for all the framing (yes, including chine logs) for his Goat Island Skiff design. There have been quite a few built, and nary an issue with the chine logs. I've sailed ours (sometimes quite hard) for almost a decade now. No issues. We dropped her off the top of a van. No chine log failure (just a split in the Ipe outwale).

I've seen several boats over the years built with wrc chine logs. No problems.

David G
07-02-2014, 09:56 PM
Visit your local lumberyard . Just about any straight grain wood will work.

red cedar is weak and not well suited for chine logs.

local woods like cypress

This does not fit my experience. Western Red Cedar is not as strong as white oak, douglas fir, or even mahogany. That much is true. Unsuitable for chine logs? Not true. It's rot-resistant. It glues well. It holds fasteners ok. It's light. It's a pleasure to work with. All one has to do is beef up the scantlings slightly.

One good example. My buddy, the Aussie small boat designer Michael Storer calls out wrc for all the framing (yes, including chine logs) for his Goat Island Skiff design. There have been quite a few built, and nary an issue with the chine logs. I've sailed ours (sometimes quite hard) for almost a decade now. No issues. We dropped her off the top of a van. No chine log failure (just a split in the Ipe outwale).

I've seen several boats over the years built with wrc chine logs. No problems.

Plywood chine logs? Very bad idea.

Doug Schultz
07-02-2014, 10:44 PM
I have found that the best place to find knot free lumber in the big box stores is to buy the largest dimensional lumber.
2x12 has to be cut from pretty large trees. You should be able to mill out what you need for chine logs from that. A little more expensive than buying the right size from the box store but far better lumber can be had.

ShagRock
07-03-2014, 01:46 AM
This does not fit my experience. Western Red Cedar is not as strong as white oak, douglas fir, or even mahogany. That much is true. Unsuitable for chine logs? Not true. It's rot-resistant. It glues well. It holds fasteners ok. It's light. It's a pleasure to work with. All one has to do is beef up the scantlings slightly. Slightly? Is that a scientific term or a genuine boatbuilders term? Say 3/4 mahog for a transom in a small outboard skiff. What size red cedar would replace it? Big 2 x 8" pieces? Why don't we see this more often among boat builders up north in the land of red cedar? Is this a common practice in your neck of the woods? Any hard-core boat fishermen (not pond dwellers) frame their boats in wrc? Do you have the the 'in' on this or are you just taking a poke at Slug? Curious minds await your wisdom?

willmarsh3
07-03-2014, 06:27 AM
Here's how I did my shear clamp.

http://www.willmarsh3.net/el/elver073103.html

I got this wood out of doug fir or more likely SYP 2x10s cut into 1/2" strips and scarfed to make pieces long enough to go from stem to stern.

I think you could build your chine logs similarly.

David G
07-03-2014, 09:36 AM
Slightly? Is that a scientific term or a genuine boatbuilders term? Say 3/4 mahog for a transom in a small outboard skiff. What size red cedar would replace it? Big 2 x 8" pieces? Why don't we see this more often among boat builders up north in the land of red cedar? Is this a common practice in your neck of the woods? Any hard-core boat fishermen (not pond dwellers) frame their boats in wrc? Do you have the the 'in' on this or are you just taking a poke at Slug? Curious minds await your wisdom?

Slightly is neither a scientific term, nor boatbuiders jargon. Do I detect a note of skepticism tucked in there somewhere?

OK... here's an illustration of what it would mean to substitute wrc for another wood as a chine log --

Say the designer had specified a chine log of 0.75" X 1.125" in White Oak. You can't get it, but have lots of wrc you could substitute.

First thing to do is look up how the strength of w.o. compares to wrc. You can find values a lot of places - but my usual source is the Forest Products Lab's "Wood Handbook". Chapter 5 has mechanical properties. And my usual first approximate of strength (there are a lot of types of 'strength') is Modulus of Elasticity. So - here we discover that w.o. has a MoE @ 12% moisture content of 12,300, while wrc is at 7,700.

So... w.o. is almost 60% 'stronger' than wrc. That would put the scantlings of your new chine logs at 1.2" X 1.8"

Voila!!! There you have it!

But wait! When you happen to mention to the designer your intention to substitute the wrc... he tells you that the actual strength requirement for a white oak chine log worked out to be 0.625" X 0.9375". He increased the size in his specifications for three reasons: provide adequate faying surface; make it easier to hit with fasteners; 'insurance'. Thus illustrating the importance of discussing proposed changes with the designer wherever possible, while happily making your substitution scantlings more accurate.

So increasing THOSE dimensions would put you at something like 1" X 1.5". At that dimension you have adequate strength, as well as adequate gluing surfaces. If YOU are interested in building in some insurance... maybe you increase that to 1.125" X 1.625".

Now... it's true that such a substitution is only practical on smaller boats. If you start building a trawler - the increased scantlings would quickly become cartoonishly intrusive. But folks in the NW, and Canada do use a lot of wrc in boatbuilding - including in the framing of small boats that they want to be as light as possible. I intended no poke at Slug, and I hope he didn't see one.

Now... if you have a better idea of what I was hinting at when I said 'slightly'... I've got to attend to my SnarkDetector... for some reason, it's smoking and making funny noises.

willin woodworks
07-03-2014, 02:42 PM
Sounds like a perfectly reasonable explanation to me David, except that I typically refer to "The Engineers Companion" by Mott Souders.

Bob Cleek
07-03-2014, 03:34 PM
Pretty amazing that the OP's question could generate 18 posts so far when there could be now dispute that the correct answer has only two letters in it. :D

kc8pql
07-03-2014, 04:52 PM
^ Well, it is the WB Forum after all...

willmarsh3
07-03-2014, 07:19 PM
Its much more interesting this way :)

L.W. Baxter
07-03-2014, 09:19 PM
I wouldn't have any problem using plywood for chine logs in a plywood planked boat. In fact, laminating with rips of plywood is an effective way to make bent parts, such as a blank for a stem.

If your chines are especially curvacious, and you dont have any green, bendable wood on hand, laminating may be your only option. And as long as you are laminating, what's the dif?

Bluegill
07-03-2014, 09:32 PM
Screws and nails will not hold well in plywood. Don't use plywood.

Watergoat
07-03-2014, 10:10 PM
Lowe's usually has a pretty good stock of fir, and at times some decent yellow pine. I am about to build a Harkers Island well skiff, and was going to rip some 16 ft 5/4 x 6 decking to make the chine logs. What is the reason not to use pressure treat?

L.W. Baxter
07-03-2014, 10:29 PM
Screws and nails will not hold well in plywood. Don't use plywood.

They will hold just fine, especially in conjunction with adhesive, which you should definitely use in plywood construction.

I have done frames, stems, and chines from plywood. Sealed and painted, they are indistinguishable from "real wood". As is the plywood planking, for that matter.

Let's face it, most plywood boats, even big ones like Devlin's larger powerboats, don't need chine logs at all, just glass tape. Building "plank on frame" is fun though. Use what you want and enjoy yourself.

pipefitter
07-03-2014, 10:30 PM
I wouldn't have any problem using plywood for chine logs in a plywood planked boat. In fact, laminating with rips of plywood is an effective way to make bent parts, such as a blank for a stem.

If your chines are especially curvacious, and you dont have any green, bendable wood on hand, laminating may be your only option. And as long as you are laminating, what's the dif?

Agreed. I used ply lams for chine logs in my own. It's perfectly fine in a glue build. No splits around screws near the ends over time, dimensionally stable etc.

russkaiser
07-07-2014, 12:19 PM
Wow, you go away for a couple of days and you have all sorts of good things to read. Thanks for all your input guys. I just found a local source for 16 ft. long fir strips at a true lumber yard so if I decide to go with chine logs I will source them there. As for using glass tape and epoxy, I've done that with a smaller boat and I was planning on using tape and epoxy on the outside of the chine seam. If I have any questions about modifying the June Bug plans I will start another thread.