jig alignment

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djm
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jig alignment

Post by djm » Wed Apr 29, 2009 10:46 am

is it important that the baseline as defined on plans be held level from station to station, when assembling the jig? Or is this even possible? when i assembled the stations and stringers i tried to hold the bottoms even, which made holding the baseline level difficult to immpossible. also you mentioned using as few screws as necessary in stitching up hull prior to gluing, but the 1/4 inch panels don't want to bend over the jig without some pretty hefty persuasion.
Thanks
Djm



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Re: jig alignment

Post by Lung Boy » Wed Apr 29, 2009 11:24 am

I believe the baseline should be level. At least it is for the FS17. I'm not sure what you mean by
hold the bottoms even
. Which boat are building? A picture is worth a thousand words.
the 1/4 inch panels don't want to bend over the jig without some pretty hefty persuasion
I stitched my FS17 like a zipper from stern to stem. It was a bit tough to bend at the bow.
Image

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Re: jig alignment

Post by djm » Wed Apr 29, 2009 11:40 am

by hold the bottoms even I mean that when i went to assemble the stringers and stations(molds) they were at different levels (heights) so i adjusted the stations to fit the bottom of the stringers, because the hull as i understand this, should sit flat on the stringers. I am building the ob 19. thanks for the advise

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Re: jig alignment

Post by tech_support » Wed Apr 29, 2009 2:01 pm

The stringer should be flush with (or very close to flush) with the stringer. Like this...

Image

Image

Panels should bend without a lot of effort. You do not want to use a lot of screws because the panels need to be free to move and take theri shape as they are bent. If you hold the panel with screws in more than one spot, then it will be much more difficult to bend, then zip up the panels. Once the panels are stitched up, I used a few screws to hold them evenly down to the molds. It much more important that the panels be fair then trying to make them fit the molds exactly.

here are where I would put screws (temporary) to hold the bottom panels before stitching. If I had put more on the forward molds, the panels would not have bent correctly went stitched up.

Image

you can also see I used a trim nail on the very center of each mold, this give you something to see the the panels are centered. It also give the nice little consistent gap you want between panels.

then it zips up to the bow

Image

Image

sides stitched up, again just a couple screws to hold the panels

Image

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Re: jig alignment

Post by jacquesmm » Thu Apr 30, 2009 9:37 am

Is this the same question than the one in another thread?
Please do not cross post, we will answer but let's not create confusion.
I will delete the other thread.

Let's take it one step at a time:
before applying any panel, are your molds (=frames) lined up?
I mean, does the rear part look fair?
When you put a straight edge (or a 2x4) lengthwise on the assembled jig, does it look fair within 1/4"?
Does it look as in the pictures posted by Joel?

If not, let's solve that problem first.
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Re: jig alignment

Post by jacquesmm » Thu Apr 30, 2009 10:02 am

In your other post, I read this:
I tried to keep the baseline level, ie exactly the same height from the top of the strongback to the baseline drawn on each station. It was impossible to keep this line level and to align the bottom of the stringers with the bottom of the stations.
Why is it impossible?
Where is there a difference and by how much?
I remember that you had a problem finding dimensions for the notch locations, I hope that is not the problem.

We must solve the jig problem before planking.
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Re: jig alignment

Post by djm » Thu Apr 30, 2009 12:51 pm

OB 19 After I moved the c station forward to where the plans said the 8'1" station would be, the stringers fit and I was able to proceed. Originally I measured from the floor up to the baseline on the transom, and set the baseline on the c station the same height from the floor. As I added the b station I noticed that to keep the bottom of the stringers aligned with the bottom of the b station (after they were notched to come together) I could no longer keep the baseline of the b station at the same height as the c station and transom. they were 3 or 4 inches off. The b station had to be shifted up in order to align the stringers and b mold. I Then when I went to set the a station i had no reference , because the baseline on the a station, when set at the same height as the transom and c station, appeared to be set about 3 inches too low. I went ahead and set the bottom and side hull planking on and stitched them together loosely. They appear to be coming together ok, except they do not meet the a station or bow mold at the right height. If I can figure out how to send pics, I will

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Re: jig alignment

Post by jacquesmm » Thu Apr 30, 2009 1:16 pm

It looks like we will need a picture.

Something is wrong with the jig assembly.
As I added the b station I noticed that to keep the bottom of the stringers aligned with the bottom of the b station (snip) I could no longer keep the baseline of the b station at the same height as the c station and transom.
Why could you not keep the baseline where it should be?
Was there a gap in the notch?


Question: if it wasn't for the notches, would things line up?
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Re: jig alignment

Post by djm » Thu Apr 30, 2009 1:28 pm

I have taken pics but can't figure how to attach them can I send them via email

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Re: jig alignment

Post by djm » Thu Apr 30, 2009 1:40 pm

The notches were not a problem. I adjusted the depth of the notches on the frames so the stringers and frames would sit even at the top of the jig. I notched the clamping boards to accept the stringers before I laminated them onto the transom. When I put the first stringer on , it fit in the clamping boards nicely, then fit in the c station nicely. Could it be that since I moved the c station forward, as you suggested,(to make the stringer notches fit), that the horizontal level of the stringer(which I assume should be level in the jig, is now in fact pushed up and out of level? Remember that the c station is forward in the jig by
5 3/8 inches MORE than where it will be after it is installed in the inside of hull. I think this may be why my stringers are so out of level as the jig is coming together

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