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Discussion Starter #1 (Edited)
I,m building a strip built kayak soon and the plans have forms ( that you make from 1/2 mdf) that slide over the frame and are positioned at intervals .
The forms have a 2" x 4" slot and the "strongback" as they call it is a temporary 2'x4" frame as well as the forms.


Strip built meaning that typically 1/4" x 3/4" wood strips are glued together over a series of spaced out forms with the hull and deck done separately.
Then they are joined together (deck and hull) , the whole thing is glassed inside and out making for a very strong lightweight and stiff boat.
The company uses a plywood box half lapped idea for the frame.


I am wondering if I could use a LVL beam and rip it to the 4" ( or joint it rip and plane it to size).
The LVL would be 1.75" thick , I could rout out my slots in the forms to this smaller thickness or glue on some additional thickness to the LVL.
The important thing is to have a frame that is straight and stiff will stay straight while you build your boat.
After your hull and deck are built the frame and forms go in the burn pile ( they are temporary).
Oh yeah the frame is needs to be around 15' long.
Is LVL straight and stiff enough for the task or is there better ways? ( 2" x4" x 15')
 

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It seems simple enough to ....

Make the slots in your forms using a router and template to the 1.75" dimension. Locate them according to the plans along the LVL by tacking on 4" wide strips of 1/2" material on both sides that are the dimension minus the MDF thickness. These will keep the form vertical like making a dado. Now the forms are stlll removable, but will remain in place. If you go to all the trouble to make the frame and forms I would sell it or keep it disassembled rather than burn it. :smile3:
 

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Discussion Starter #7 (Edited)
Yeah good idea Wood on the supports for the forms , but my question is if LVL is stiff and straight enough to use for my application ( especially after sizing it down to 4").
With the laminations only in one plane it could be noodly as heck in the other plane....maybe not...


Ok just saw your new post . The strongback in my design is inside the forms..so a 2x4 rectangle cut inside the forms.
The strongback is then supported by however you desire.
 

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I think an LVL would indeed be noodly along its narrow length, but not top to bottom. That said, I think it would ultimately be straighter and stronger than a 15' 2X4. I'm not sure why you'd be sizing it down to 4". The taller it is, the stronger and straighter it would be, right? If you had two LVLs, you could make them into something like a half section of an I beam which I think would be super straight and strong.
 

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Discussion Starter #10
Previous post pic shows the full size prints glued to 1/2" osb.
They will go to the bandsaw next and then edged sanded to size.
It's hard to see but there is a 2" x 4" rectangle through the forms for the frame that these will slide onto.
I'll use a jig to router out the rectangle.
I may experiment with some plywood glued up in to different planes and staggered joints for my frame .
The truer the frame the truer the boat.
 

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Discussion Starter #12
Are you sure you're only going to make one? I've heard these things can be habit forming...
Don't think so but I may just rout out copies of my forms...just in case.
My neighbor ...and it's all his fault (talked me into it)..heh heh ,is on boat two ( first was a rowing skiff and finishing up a kayak).
He had enough western red cedar trucked in to do several more ...for what reason I don't know but he will build another kayak this winter as boat two is close to being finished.
I better stick to one as my wife jaw dropped and she was speechless when I told her how much 7 boards of 1"x6"x19'
clear cedar cost me.
 

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Discussion Starter #13
Ha ! Here's an old project that has come to life.
I needed a internal strongback(temp frame) to attach my kayak forms to.
I made one out of plywood and was not happy with the lack of stiffness.
Ended up going to Metals Express and getting a rectangular aluminum tube....nice and stiff.
Boat forms slide over it and I made U shaped plywood spacers to hold distance between forms.
Forms were hot glued to the plywood spacers and spacers were sheet metal screwed to the aluminum strongback
This is a Cedar stripped kayak and I'm using 1/4x3/4 strips, hand planed/fitted to one another.
How do you like my boat carriage with 2 sawhorses locked together and on wheels.
kayak 2018-2.jpg
Next I worked on making the top half. Here's the cockpit just roughed in.
kayak11.jpg
kayak8.jpg
6 oz fiberglass cloth and 3 coat of epoxy later here you are. You have to apply the 2nd and 3rd coat while the previously applied epoxy is still tacky. (1.5/2 hr later) or it wont stick. Otherwise you would have to sand it for additional coats. After the boat is done you sand the epoxy smooth and apply 5 coats of marine varnish. ( I'm a long ways from being done).
Next pic the deck has been gently pried loose from the forms and you will see it suspended from the overhead joists.
Here my friend that has built a few strip boats already is helping me glass the hull.

kayak12.jpg kayak14.jpg
Next I will flip the hull and take out the strongback , smooth the insides and glass it.( I will start that today)
More to come as I progress.
 

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Beautiful. that had to be a lot of fun to build. I made a model one about 4 foot long a few years back just for the fun of it. It was a lot of fun to me. Your build turned out fantastic.
 

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LVL story - when building my house i installed a 4" x 12" x 50' down the middle of my 48' foundation. we ended up trying to roll it into place. HA! when vertical, i don't think that thing sagged 1/4", but when horizontal, laying flat, it bowed so much it almost fell down into the 48' opening. pretty sure its all about the direction of the laminations, super strong in one direction, not so much in the other...
 

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Discussion Starter #16
Beautiful. that had to be a lot of fun to build. I made a model one about 4 foot long a few years back just for the fun of it. It was a lot of fun to me. Your build turned out fantastic.
It's fun and somewhat intimidatingly at the same time. But the farther I get the more confidence I have.
Helps to have a friend to keep you steered in the right direction also.
I have enough strips left over to build a model ...hmmmm.
 

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It's fun and somewhat intimidatingly at the same time. But the farther I get the more confidence I have.
Helps to have a friend to keep you steered in the right direction also.
I have enough strips left over to build a model ...hmmmm.
I may make another one, one day, it was a fun project.
 

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Discussion Starter #19
Ok last Sunday we glassed the inside hull with 6oz glass (and Mas epoxy with slow hardener).
You will see a lot of blue tape in use here.
Under the tape are sticks to a precise length , they are in line with were the boat form were. Measurements were taken before we removed the forms and strongback and marked on the hull.
The boat will spring one way or another once free. All points pulled in around 3/8-1/2" .
Before you glass the inside(outside already glassed) you need to hold the shape to exactly what it needs to be.
Once the second side is glassed the boat is very stiff and would be difficult to force it into position.
The top has to fit.
The tape is over the sticks so they don't move out of position .
Two coats were enough to completely fill the glass.


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