To scarf or not to scarf

[PAR]

I don't understand why someone can take this, an impersonal environment of opinions, voiced on an internet discussion forum to heart or as a personal attack. I don't believe this was what could be derived from my comments, nor to I think I stated more then reality for a project of this scope and build type.

I've built this type of project, single-handed and more then once. The last was a 48' ketch (which displaced just under 15 tons) which consumed 7 years and is currently afloat in Daytona Shores on the east coast of Florida. Previous to that was a "Spray" replica" (yep, a 41' replica). I do understand the issues associated with projects of this size and complexity.

I hope I don't have a "gift", though I'm sure I have pissed off more then one over the several years I've participated here.

Unlike many posters here, I rarely frequent the open discussion, nor entertain myself or other members with idle banter about what constitutes a proper head on a beer. This stuff just leads to misunderstandings and artificially inflated (or deflated) "reputation" points. My average since the turn of the century is about 1.5 replies per day. My attempt to pass along some of this stuff, 'cause I ain't getting any younger and there are few to fill the void. Some here post a dozen of more times a day (clearly needing something better to do in their lives) and have higher reputation values then me.

I also don't think I veer very far off topic, trying to stay on point and in focus for the most part. If folks find offence with this then I'm disappointed, though not particularly sorry (there I go pissing people off again) as it's a discussion forum, not your local pastor telling you to change your life or expect to go to hell. Thin skinned sailors should just watch videos.

[Boston]

well said

[erik818]

I've tried to avoid scarfing but found that plywood panels won't bend uniformly unless they are scarfed. Still I'd like an easier way to scarf than to plane and sand a stack of plywood sheet to get the 8:1 or 10:1 edges. (Last time 6:1 had to suffice.)

I've not seen any scarfing tools in the local shops in Stockholm. What are they, and can they be found on the internet? When buying floor boards, they always come with profiles at all four edges for scarfing. Would such profiles do for boat building as well?

Erik

[PAR]

I've found the fastest way to scarf is to quickly rough in with a power plane then come back with a hand plane. I can scarf a plank in the time it usually takes to setup a router jig.

Most scarffing is on a single plank or plywood edge. If multiple scarfs are necessary for the day, then it pays to set up a jig.



This is a jig I use for making long scarfs, though it works on short ones too. It's very simple, has no moving parts and clamping isn't obstructed by the jig. It's not much more then a couple of 2x6's attached to the frame of a work bench. With a 7 1/4" circular saw, you get 10:1 on 1/4" plywood, 6.6:1 on 3/8" and 5:1 on 1/2".

There are several types of router jigs, but most I don't like because of setup time, clamping issues and actual bit in the work time as you plow through lots of waste material.

Maybe one day I'll find a way to swing a 10" blade in a similar rig as above. This would make 13.6:1 scarfs on 1/4", 9:1 on 3/8" and 6.8:1 on 1/2".

Honestly, unless you have a bunch to do at once, with just a little practice, you'll find a power plane, belt sander, sharp chisel and hand plane, the best tools to make up a scarf.

The joint can be intimidating, but after just a few, you'll be making good scarfs. If using epoxy to join the pieces then you don't have to be especially precise, in fact it's better if you're not. On brightly finished work, you should have some practice under your belt, before you sacrifice good lumber to the attempt.

[philSweet]

If I understand the build method correctly, you're going to use planks to get a fair hull shape, then apply two layers of ply over this. I would not scarf the plywood. The most important part of getting the skins on is to avoid voids, and smaller peices will be easier to install than larger ones. One option is to install all the sheets (one layer), then putty all the joints, then plane out a 3 inch by 2 mm dado and lay in one layer of 10 oz glass tape. the main advantage of this is it can all be done at one time rather than fiddling with each peice as you go. The putty and tape do a good job of preventing water from migrating along the joints.

At the risk of beating a dead horse, I don't think $500/mo. is going to get this boat built. $500/mo. isn't even enough to maintain the boat; so at some point it will be falling apart faster than you're building it. I recently planned out a build of a 38 foot plywood double-ender with an 18,000 pound displacement. I figured $400/ day out of pocket for 18 months; then figured it would have no resale value when completed. This didn't make much sense when I can trick out a Pacific Seacraft 37 for $110,000 and have a boat I can sell for $110,000. So in the end, I rebuilt an older boat which I bought six months ago (not a Seacraft), and I'm going cruising in about 10 days.

[erik818]

Thank you Par,
I'll arrange a jig similar to yours. It seems like a stright-forward solution.
Erik

[ancient kayaker]

Par, I could not open the picture of your jig, but I am interested in it as I have not been able to make decent scarfs with a regular hand-held power saw.

I have had a lot of success for repetitive scarfing of stringers using this jig for a miter saw. The jig is just a ply plate with a fixed guide and a 2nd moveable guide held by a wingnut that is set to the thickness of the wood. The blade is rotated to the desired angle. I used 7 deg, about 8:1. Once a cut is made the same angle must be used with the jig. I use a spring clamp to prevent the blade sucking the wood in as it cuts, that ensures an accurate cut. The scarfs do not need any further work before gluing.

Because it takes care of alignment and clamping it is very fast as well as accurate. However, it only does one at a time.

As shown it is only good up to about 1/2 x 1 inch because my saw is only 7-1/4 but if you are blessed with a 12 incher or a radial you can go bigger.

[erik818]

I'll help with Par's picture. I couldn't open i directly either but it was possible to follow the link in steps to reach it.
Erik

[ancient kayaker]

Thanks Erik! I remember that idea of Par's from another thread.

I tried it a couple of years back. It worked, but I was trying to scarf cheap 1/8 ply at the time. I had problems with the feather edge tearing and it was difficult to get a straight cut because the thin ply kept springing up in the middle of the cut, so I changed to a router/jig method. I have learned a lot since then; now I use proper marine ply. I also realized my saw bearings were worn beyond redemption. Mea Culpa.

As I now have a lovely thin-kerf blade and a new saw with ball-bearings I must try it again. Thanks for the idea Par, and the reminder!

[Boston]

looks dangerous
my old man had a jig for about a hundred pound Rockwell ancient router he swore by
was a simple flat plate of steal ( about another hundred pounds )
with two adjustable legs on it
the legs went on the high side of the cut and you adjusted em based on the thickness of the wood
once set
you just place the wood in the thing
bolt it in
and flip the router to airplane mode
would plow out a perfect joint
it even allows for a slight hook based on the angle of attack at the leading edge if you wanted one
my grand Dad hated the thing
and argued endlessly it was a piss pore excuse for craftsmanship
it was like alstar wrestling whenever they were in the boat house together
I could draw it for you if you want to see it

[ancient kayaker]

You confused me, Boston. Which jig looks dangerous? Par's is just a circular saw doing what a circular saw does best, and mine is just a miter saw ditto ...

Your Da's jig sounds neat; there are several around that use tubes as guides and work well by all accounts if you have the space and money. They have to be metal though; wood is not stiff enough to keep straight over a long distance. What I'd really like though is a video of your Dad and Granddad ...

[Boston]

you mean a video of em strangling each other

you should have tried being the kid in the middle
when Robby was in the shop you had best do it his way
when pops was working it was tow the line or tan your hide
take your pick it wasnt pretty

shoulda been there when my brother sliced the cord off Pops ww11 skill saw

[PAR]

Clamping is always an issue with a scarffing jig. With my jig, the blade turns and helps hold the lumber down. A sacrificial piece of plywood over the cut will make the edges clean and hold an unruly piece. I also use a vacuum table on full sheets.

Boston, your grand dad is right, craftsmanship is faster and more rewarding too.

[Boston]

well Par you're gonna have me beet on joining ply any day
I never really worked in the stuff much
would love to see the vacuum table

the kinda scarf joint we used was more like a hook scarf with out the hook
at least in the planking
we never brought it to a point but always kinda reverse cut the ends
if you leave a little meat there it keeps it from splitting
course we were dealing with 4/4 and up material pretty much all the time
ceder
so it was easy to chisel and clean up the birds mouth with a hand saw
least thats what Robby would do

Pops would take the planking and clamp it to the bench with a dog and wedge
then bolt the template down over the end of the plank and go to town
pissed off Robby no end when it got everything covered in dust
there would be a sacrifisial piece on the end were the template clamped to the table
Ill have to make you a drawing Mr Kayaker

[ancient kayaker]

Boston: please; sounds interesting.

Par: the vacuum table sounds like a good idea, I thought about it but so far haven't gone any further.