Thought you could learn from my mistakes so, with a red face, here it is.
First, definition of Scarfing: It's a joint, usually to make a piece of plywood longer done by tapering the ends to be jointed then gluing them so that the resulting longer wood does not, as much as possible, show the seam. This joint is also intended to preserve the properties of plywood.
The boat I'm building is 22.5ft long so I needed to scarf three pieces of plywood for the longitudinal bulkheads. Here's how I did it:
After cutting the three pieces of plywood into the three sections of bulkhead to be scarfed, I planed the ends to be joined and sanded to come up with this:
First mistake: Scarf first, then cut the whole piece to the required shape. With what I did, I needed to be very accurate in joining the pieces; no room for error (and I usually make lots of them).
Then I wet the scarfs with epoxy, then put thickened epoxy, put the overlapping scarfs together, wrapped in plastic (to prevent clamps from sticking to them), and clamped them this way:
Big mistake. Those pieces of wood are too flimsy to press down the middle part. It came out like this when the glue dried:
Aargh! After a lot of chiseling, sanding, sungkit-sungkit, epoxy-puttying, then resanding, managed to solve the problem. I'll be a smarter man next time.
Oh, one thing right I did was I put dowels (last photo) on the scarfed ends to prevent the sections from slipping. Epoxy is a great lubricant when wet so one has to watch out for movement while waiting to dry.
Re: How Not To Scarf
Thanks for sharing. Goof ups are the best way to gain experience eh. I also do just the same. My Dad was a boat builder, and I want to get into it now that I'm getting close to retirement. Maybe I can remember how to do some of the things we used to do, building.
I do have a question for you. I have enjoyed so much reading this forum, we live on Samal Island and I'm not familiar with wood here. I have used the so called marine plywood from the hardware, and that is not marine plywood by any words! It just falls apart in the rain. I haven't seen any good plywood. Can you recommend what to use or where to get it? also what is best for frames and keels? I was used to white oak for frame work and marine fir ply.
Thank you for any help
Gary
Re: How Not To Scarf
Hi Gary, welcome to PHM. You can try looking for Tuff ply (available locally) in your area. it is a little hard to find and cost twice as much as regular plywood but quality is spot on. I believe this is the plywood of choice by boat builders (I'm not one though). from the manufacturers, I was told that the tuff ply is much better than even the baltic birch which I haven't come across locally.
goodluck and enjoy the site. Please keep it clean.
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Re: How Not To Scarf
Thank you, I'll search this week.
Re: How Not To Scarf
Ding, Have you come across Bowclamps? if not, the net has lots of info about it, even how to make one. I reckon, it should help you lots...
click my signature and it will take you there........
Re: How Not To Scarf
How about if some thick angle bars were used instead of the wood? Maybe it can press the middle portion of the jointed plywoods better.
Millermatic 180 Autoset Mig Welder
Miller Spoolmate 100 Spool Gun
Victor Firepower 350 Oxy Ace Outfit
3M Speedglas 9002X AD Helmet
Makita LC1230 Dry Cut Saw
Ingersoll Rand Air Tools
Snap On Tools
Metabo Power Tools
Norseman Drill Cutting Tools
Bosch Power Tools
3M PPS
Re: How Not To Scarf
Thanks, Timber and JayL.
Yes, on bowclamps. That scarfing was done sometime last year when I only knew F-clamps and C/G clamps. Been collecting clamps ever since. Seems like clamps are a boatbuilder's staple.
Joe833a, as Timber mentioned, Tuff Ply is the best around. That's what I use. Fellow boatbuilders have put it to the boiling test (not sure what that is) and it passed with flying colors. We also sheathe the plywood with fiberglass and epoxy to make it waterproof and abrasion resistant. But I'm sure your father has taught you that already.
On wood, I am using ordinary lauan which, I am sure, is abundant in Samal/Davao. Another boatbuilder, Lorenzo, is also from Samal and he is building a strip-planked boat like mine using Gmelina. Gmelina is softer than lauan but looks nice and blond if you prefer that and, with proper epoxy-fiberglass treatment, should be ok. Heck, I know a professional boatbuilder who even uses foam as the core and builds it into a hull using epoxy-fiberglass.
For frames and keels, go for the hardest but still absorbent wood you can find. Hard for strength against knocks, absorbent so epoxy can seep in. Offhand, I'd say yakal should be perfect. I have some and still debating in me if I'd use it for the mast or keel.
Re: How Not To Scarf
Oh, and forgot to elaborate on the bowclamps.
They sure are nifty but also pricey. I keep thinking I could make some myself but I'd probably need the bending properties of the wood I'd use to make the caul, then translate that into the curve/bow.
Maybe someone here can make it as a project!
Re: How Not To Scarf
Oh, and forgot to elaborate on the bowclamps.
They sure are nifty but also pricey. I keep thinking I could make some myself but I'd probably need the bending properties of the wood I'd use to make the caul, then translate that into the curve/bow.
Maybe someone here can make it as a project!
dali lang yun brader, you don't even need to rout the space for the clamp head eh. all you need is a straight piece of wood and a handplane :p
click my signature and it will take you there........
Re: How Not To Scarf
Ahhh, yes...the hand plane.
Tried those handplanes I got from Hong Kong (mujifang) first tme today, untuned, straigt out of the brown paper wrapper. Those planes are to-die-for. Of course, I have to mallet the iron into place every now and then, but shaving long thin strips are easy and...I was going to use some provocative adjective but don't know how unwholesome this site is.
Re: How Not To Scarf
Any pics of bowclamps please?
Millermatic 180 Autoset Mig Welder
Miller Spoolmate 100 Spool Gun
Victor Firepower 350 Oxy Ace Outfit
3M Speedglas 9002X AD Helmet
Makita LC1230 Dry Cut Saw
Ingersoll Rand Air Tools
Snap On Tools
Metabo Power Tools
Norseman Drill Cutting Tools
Bosch Power Tools
3M PPS
