Bow notching on malahini

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Bow notching on malahini

Postby footer » Sun Mar 25, 2018 8:21 am

So I am to the point of putting the side plywood on. The book says to put a notch in the transition of the bow.
Well, I did, but I screwed it up a bit (I cut it a bit too shy). What is the actual purpose of this transition? The pictures in my directions show both, stepping down and stepping up, but say to step up at the bow. If it steps up at the bow, it creates a very difficult joint at the Chine because of the steep angle of the junction forward.
I'm not finding any good shots of the proper way to do this and need some direction. If I cant fix it, is this transition necessary enough to throw this board away and cut another one? Or can I just run my bottom ply straight the bow?

Second question; the ply at the bow laid right down, but the ply at the stern bunches up a lot. I'm assuming because of the different angles I'm trying to bend the plywood is why?! Am I right? Do I just force it down with a lot of screws?
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hoodman
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Re: Bow notching on malahini

Postby hoodman » Sun Mar 25, 2018 10:22 am

Your transition joint looks like you are on the right track to me. At some point it goes from a lap joint aft to a butt joint right about where you have it. It's a little but fussy fitting the bottom and sides in that butt joint area but you just keep trimming little by little until it fits.

You may need to use towels and boiling water to loosen us the side panel in the back. The Malahini's tumble home has caused many sheets of plywood to crack. And is looks like you have alittle bit of a kink on that sheet too but it's hard to tell.

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vupilot
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Re: Bow notching on malahini

Postby vupilot » Sun Mar 25, 2018 3:18 pm

The transition of your side planking looks ok to me. I never did exactly get a perfect "joint" it just kinda transitioned like yours does then I just made the bottom planking fit in the space not taken up buy the side planking. As for the bunching up, I like to clamp starting in the center of the sheet and work fore and aft from there, sometimes helps, maybe you already did that.

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DrBryanJ
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Re: Bow notching on malahini

Postby DrBryanJ » Sun Mar 25, 2018 4:54 pm

The bow transition is fine. I had the same issue at the stern and found I had to do a little more fairing.
Bryan

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Re: Bow notching on malahini

Postby Hercdrvr » Mon Mar 26, 2018 12:39 pm

Kind of hard to tell from pictures but is that chine fair at the last frame? I’m seeing a little more time with a 36 grit paper belt sander. Not trying to step on any toes, just what I see.
Matt B

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Re: Bow notching on malahini

Postby footer » Mon Mar 26, 2018 2:11 pm

Thanks guys for your input. Sometimes, its hard to tell from pictures, exactly how things are supposed to go. I would like to know the whole story why the notches are there and on the transition between the keel to the stem.
The Chines are faired. The ply is just roughed in and may look off. There s Sodom smell glue in spots that Nike it look funny. I figure once I get it fitted better, I'll be able to see any other discrepancies.

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Re: Bow notching on malahini

Postby footer » Mon Mar 26, 2018 2:14 pm

Oh jeez, guess I should have checked my script better before send. I meant, there are some small spots of glue.

PeterG
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Re: Bow notching on malahini

Postby PeterG » Mon Mar 26, 2018 2:20 pm

What I see looks great for fairing, location of the transition notches and fitting of the plywood. You want to keep the butt joint between the bottom ply and the side ply on the faired line along the chine, from frame 4 to the center of the chine at the stem. See the Glen-L link: http://www.glen-l.com/methods/plywood/mthdpw07.html Your fairing looks like you've done that, you've left extra material on the side planking to trim to that line.
The buckling or bunching of your ply is due to the forced compound curvature in the plywood. The 1/4" ply is fairly flexible but will bunch like that if you don't force it into place with lots and lots of clamps. For fitting purposes, you could try a batten along each edge, say about 1/2" x 1", between the clamps and the plywood, to spread the clamping force. You've got an excellent start, don't get discouraged and most of all, have fun! And keep posting photos!
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hoodman
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Re: Bow notching on malahini

Postby hoodman » Mon Mar 26, 2018 4:43 pm

Maybe you've done this, but on the chine between the forward-most frame and the stem you'll want to draw a line down the middle of the chine dividing it in half. Then you'll have a better idea of where to trim your side planking. I pulled a string line around the chine to make that mark on my chines.

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Roberta
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Re: Bow notching on malahini

Postby Roberta » Tue Mar 27, 2018 6:50 am

I think you are talking about the place where the bottom planks and side planks meet and transition from a lap joint in the aft portion of the boat and a butt joint in the forward portion of the boat. Generally this is done about the point along the joint line where the angle of the lap joint becomes to great to make a proper joint and the butt joint becomes a better choice. Here are some pics of that transition.

You can see where the chine and plank is shaped to accept the lap joint and where the plank is notched to become the butt joint. Then the bottom plank is step notched accordingly to make the transition to the butt joint. As the planking progresses towards the stem, the butt joint angle becomes less until it is flat at the stem.

Roberta
Attachments
bottom final 015.JPG
bottom final 019.JPG
transition joint 003.JPG
transition joint 001.JPG
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Re: Bow notching on malahini

Postby froberts » Tue Mar 27, 2018 1:29 pm

Hey Footer,

I had similar issues with my build at the stern. Because the ply can take the slight compound curve it buckled inwards a tad. You can see in the picture where these low spots were and how I "fixed" it with some fairing compound. Image
Fraser

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Re: Bow notching on malahini

Postby footer » Wed Mar 28, 2018 3:35 am

Thanks for all the input. I really appreciate it. Pictures are always a great help. I think I'm OK with the notching now. Moving on to the stern and the center piece.
Thanks again.

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hoodman
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Re: Bow notching on malahini

Postby hoodman » Wed Mar 28, 2018 8:33 am

You'll figure it out. We've all been there!


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