Question for Jacques - FS17 Lamination mistake

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cape man
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Re: Question for Jacques - FS17 Lamination mistake

Post by cape man » Wed Aug 07, 2019 8:00 am

I posted on your other thread. The OD 18 called for just gluing down the stringers but I taped them with 12 oz on each side. You're fine..


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Re: Question for Jacques - FS17 Lamination mistake

Post by jacquesmm » Wed Aug 07, 2019 11:16 am

On the OD16, glued down is for the stringers made from 2x6's but plywood stringers should be tabbed. You made the right decision.
Back to Narfi now.

It is a problem. I am scratching my head since I saw your post, trying to find an easy solution but had not success.
My notes say 2 layers of 12 oz. each side. One layer is not sufficient.
The outside skin reinforcements will help a little bit but one layer 6 oz. is 4 times weaker than the required total of 24 oz. biaxial each side.
years ago, some builders who wanted a super light FS17 low sheer used 12 oz. total each side and I did not hear of any problems. I still prefer 2 layers 12 oz. each side, there is almost no extra weight to worry about.
In your case, the boat looks heavier than what I designed. Nice features but we must plan for that heavier displacement.
6 oz. is not enough but what do we do now?

I see only one solution: go through the soles with large inspection plates or cuts and add tape to the stringers. It's not deep, you can get in there and after cutting the sole, you put the lids back and it will be hidden by the non-skid.
Let me know if that is possible at this stage.

I thought of filling with heavy foam but that is not enough. Extra tabbing is needed here.
Look at the good side: you caught it before launching the boat.
Jacques Mertens - Designer
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Re: Question for Jacques - FS17 Lamination mistake

Post by piperdown » Wed Aug 07, 2019 11:50 am

jacquesmm wrote:
Wed Aug 07, 2019 11:16 am
On the OD16, glued down is for the stringers made from 2x6's but plywood stringers should be tabbed. You made the right decision.
Back to Narfi now.

It is a problem. I am scratching my head since I saw your post, trying to find an easy solution but had not success.
My notes say 2 layers of 12 oz. each side. One layer is not sufficient.
The outside skin reinforcements will help a little bit but one layer 6 oz. is 4 times weaker than the required total of 24 oz. biaxial each side.
years ago, some builders who wanted a super light FS17 low sheer used 12 oz. total each side and I did not hear of any problems. I still prefer 2 layers 12 oz. each side, there is almost no extra weight to worry about.
In your case, the boat looks heavier than what I designed. Nice features but we must plan for that heavier displacement.
6 oz. is not enough but what do we do now?

I see only one solution: go through the soles with large inspection plates or cuts and add tape to the stringers. It's not deep, you can get in there and after cutting the sole, you put the lids back and it will be hidden by the non-skid.
Let me know if that is possible at this stage.

I thought of filling with heavy foam but that is not enough. Extra tabbing is needed here.
Look at the good side: you caught it before launching the boat.

JM, he did use 12 ounce biax to tab, just 1 layer per side. Does that change your thoughts?
Eric (aka, piperdown)

"Give an Irishman lager for a month and he's a dead man. An Irishman's stomach is lined with copper, and the beer corrodes it. But whiskey polishes the copper and is the saving of him." --> Mark Twain

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Re: Question for Jacques - FS17 Lamination mistake

Post by silentneko » Wed Aug 07, 2019 12:24 pm

I think you missed the fact that he also poured it full of foam too.
Built: 15ft Skiff, 16ft Skiff, Modified Cheap Canoe.....FS17 coming soon!

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Re: Question for Jacques - FS17 Lamination mistake

Post by narfi » Wed Aug 07, 2019 12:40 pm

jacquesmm wrote:
Wed Aug 07, 2019 11:16 am

The outside skin reinforcements will help a little bit but one layer 6 oz. is 4 times weaker than the required total of 24 oz. biaxial each side.
I used 12oz tapes, so 2 times weaker.... how much does the skin reinforcements contribute? negligible or some % ? It is filled with 3 kits of foam, inside and outside each stringer, also negligible or some % ?

jacquesmm wrote:
Wed Aug 07, 2019 11:16 am
years ago, some builders who wanted a super light FS17 low sheer used 12 oz. total each side and I did not hear of any problems. I still prefer 2 layers 12 oz. each side, there is almost no extra weight to worry about.
It is not the weight I am worried about now, it is the labor.

jacquesmm wrote:
Wed Aug 07, 2019 11:16 am
In your case, the boat looks heavier than what I designed. Nice features but we must plan for that heavier displacement.
6 oz. is not enough but what do we do now?

I see only one solution: go through the soles with large inspection plates or cuts and add tape to the stringers. It's not deep, you can get in there and after cutting the sole, you put the lids back and it will be hidden by the non-skid.
Let me know if that is possible at this stage.

I thought of filling with heavy foam but that is not enough. Extra tabbing is needed here.
Look at the good side: you caught it before launching the boat.

So your suggestion is to cut 15 large panels out of the sole between each bulkhead and stringer, Then cut out the foam, grind the foam down to the fiberglass, lay in another layer of 12oz each side, pour foam back in, use 4-6"? reinforcements around each of the 15 holes and glue them back down, seal and glass or tape the seams?

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This is my fault, and I will try to do what you think best, but this is a huge psychological setback, probably even more than the labor right now.

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Re: Question for Jacques - FS17 Lamination mistake

Post by narfi » Wed Aug 07, 2019 1:15 pm

Also, the above sole bulkhead/box sides are spaced differently than the below the sole, so might be difficult cutting large enough holes to work through without cutting them out as well.

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Re: Question for Jacques - FS17 Lamination mistake

Post by cape man » Wed Aug 07, 2019 1:29 pm

Dont cut it up! With the extra tape on the bottom, the super wide cleats on top, the foam, and 12 oz on both sides you will be fine. Just take it easy especially when running into a tight chop, and she'll be okay. If it does come loose, which it won't, then consider cutting it.

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Re: Question for Jacques - FS17 Lamination mistake

Post by Jeff » Wed Aug 07, 2019 1:38 pm

Narfi, so sorry for this horrible hit!!! Let us know what your final decision will be regarding your options!!! Jeff

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Re: Question for Jacques - FS17 Lamination mistake

Post by narfi » Wed Aug 07, 2019 2:04 pm

Jeff wrote:
Wed Aug 07, 2019 1:38 pm
Narfi, so sorry for this horrible hit!!! Let us know what your final decision will be regarding your options!!! Jeff
I will wait to see what Jacques says from my updated information.

This is difficult both for me and for him, he has to be conservative, I have to be able to interpret what he says.
I do not have the experience to know best, many of the guys posting here have a lot of experience and knowledge, but ultimately it is Jacques design so I need his input.

The 3 external 'stringers' are 1 1/2" x 1 1/2" triangles, so approximately 1.125 inches tall covered/tabbed to the hull with 24oz of biax (2x 12oz).
The foam would help prevent the stringers from folding over (I dont think they would being glued so well top and bottom) but doubt it would do anything to keep the stringer attached to the hull should the tabbing fail.

You state that a lightly built fs17 LS was built with a single layer of 12oz tabbing in its stringers.

I am what? roughly 50% heavier than them? How do the 3 external 'stringers' compare to their 2 12oz tabbed internal stringers? 1/4 the strength? 1/2?

This boat will never see the ocean. It is on a large lake and used for fun, not for work, so while the water can get rough, its not something we will frequent or seek out.

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Re: Question for Jacques - FS17 Lamination mistake

Post by jacquesmm » Wed Aug 07, 2019 7:21 pm

I will reply in detail tomorrow but at first, I read that it was 6 oz., not 12. If it is 12 oz. one layer plus the foam, it may be OK.
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