# Conchfish floor flex



## Joekurimai (Jan 9, 2015)

Well I finally wet tested my conchfish 17.5 recently and all was well but i have more flex in my floor than I care to live with. So option 1 is what Morejohn advised which is 3-4 layers of carbon uni, which would be easier but I’m unsure if it will be enough to make it feel like I would like. Option 2, which I’ve pretty much talked myself into, is double core. I feel like the double core will be a much more solid feel but cutting drainage will be much more work. Anyways looking for a second or third opinion. Thanks


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## 7665 (Jun 9, 2014)

I have a floor in mine and there is no flex, I know that is not helpful. I think you would have to add a lot of cloth to stop flex without something like a stringer to create a "T" or "H" like the false floor does. 
It must go like a bat out of hell with that 60!!!


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## TroutNreds12 (Jan 4, 2016)

Bryson should chime in he did the same thing to his go read his threat in bragging section.. skiff looks great!!!


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## BadKnotGuy (Jul 8, 2012)

Harry Spear has a series of youtube videos on his boats builds - one of them is about the floor. Double core is pretty much what he does.


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## bryson (Jun 22, 2015)

Skiff looks really nice!

I'm sure the cooler step helps some (since it makes the unsupported panel smaller), but if you want it to feel solid like a skiff with stringers, then you'll probably want to double the core. I think a carbon "stringer" like Chris mentioned would help, and if done nice and thick it will help prevent "functional" issues like cracking or core failure, but it will still feel like a "no-floor" skiff.

I actually thought that I wouldn't mind the feel, but eventually changed my mind. If you want a really solid feel then doubling the core is the way to go. It's a pain, but not terrible. What core did you use? I increased the lamination schedule on mine as well, but I used H60 instead of H80 and was worried about core failure. I think I probably also have a larger unsupported panel than you do.


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## C Brueckner (Mar 22, 2016)

Dang man, beautiful build. Do you have a thread or a social media account with more photos???


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## ZaneD (Feb 28, 2017)

I am no builder but I can tell you that my no-floor HB Waterman has no flex at all. I believe those hulls have the double-cored floor. It also looks like you are decently setup to put the second layer in since you have the "step" along the cockpit parallel with the gunnels. Looks like an awesome build, nice work.


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## Sublime (Oct 9, 2015)

Man, your build looks awesome. What color is the cap? I can't wait to finish my Conchfish.


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## m32825 (Jun 29, 2018)

I am not a mechanical engineer, but from what I remember about moments of inertia, when you double the thickness of a section you get eight times the stiffness.


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## bryson (Jun 22, 2015)

m32825 said:


> I am not a mechanical engineer, but from what I remember about moments of inertia, when you double the thickness of a section you get eight times the stiffness.


I am a mechanical engineer and that is more or less correct -- for a simple beam the stiffness increases with the cube of the thickness increase. So, increasing thickness X2 will increase stiffness times 2^3, which is X8.

It gets a little different when you have sandwich construction (different materials for core and skin), but the relationship is similar. Increasing core thickness is the best way to increase stiffness with a minimal weight penalty.

@Joekurimai If I had closed bulkheads like you do, I would really consider just doing a center stringer (which would serve as a drain) with maybe one transverse frame, and a false floor that goes to the level of the cooler step you already have. I didn't do that on mine for two reasons -- one, I like the feeling of extra freeboard with a deeper floor. And two, I would have had to completely rework both my fwd and aft bulkheads. However, if I had, I wouldn't have done all the extra fiberglass on the hull exterior and cockpit floor. I'm not sure which would have ended up lighter, but my skiff came in heavier than I expected at around 430#.

If you want to talk deeper about those options and how they might relate to lamination schedule, shoot me a PM. I can at least share what I've found with my skiff, even though it will be slightly different than yours.


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## Joekurimai (Jan 9, 2015)

Thanks everyone for the kind words. The boat came together pretty well, still have to fill a few thousand pinholes on the topside but I left it in primer gray for the test run. Final color will be ethereal blue i think. I did not chronicle the build anywhere but I have some pictures on my phone and maybe make a 100 fish review.

Right now the boat feels a bit hollow, like a gheenoe, when running which is steering me away from the carbon stringer idea. Maybe if I was lower Hp it would appeal more. I built the hull in H60 but i would use some H80 I have left over from my hatch lids for the double core. Ive pretty much decided to copy Bryson on his floor and burying the bow hatch drain between the layers. It was my original plan but deviated when the drainage became an issue and hoped the step would be enough. I am also going to flip and put a layer or two of basalt on the bottom which is going to suck grinding my paint but it will make me feel better.


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## bryson (Jun 22, 2015)

Probably no need to go with the H80 for the core -- I'd keep the core material the same all the way through. Same thing with the skin -- I wouldn't add basalt over e-glass for example, I'd just thicken up the existing material if you want to add some to the hull bottom.

Look forward to seeing some more pictures! Where are you located?


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## hillcharl (Feb 7, 2011)

Not to derail your thread, but I was looking at your transom. Is that engine a 15" or 20"?


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## C Brueckner (Mar 22, 2016)

Joekurimai said:


> Thanks everyone for the kind words. The boat came together pretty well, still have to fill a few thousand pinholes on the topside but I left it in primer gray for the test run. Final color will be ethereal blue i think. I did not chronicle the build anywhere but I have some pictures on my phone and maybe make a 100 fish review.
> 
> Right now the boat feels a bit hollow, like a gheenoe, when running which is steering me away from the carbon stringer idea. Maybe if I was lower Hp it would appeal more. I built the hull in H60 but i would use some H80 I have left over from my hatch lids for the double core. Ive pretty much decided to copy Bryson on his floor and burying the bow hatch drain between the layers. It was my original plan but deviated when the drainage became an issue and hoped the step would be enough. I am also going to flip and put a layer or two of basalt on the bottom which is going to suck grinding my paint but it will make me feel better.
> 
> View attachment 179369


My goodness the way you ended the upper chine similar to a certain skiff manufacture looks awesome man. That little touch really sets yours apart. 🙌🙌🙌


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## VANMflyfishing (Nov 11, 2019)

One thing you for drainage you could do is lay the core flat for a double core and cut a 2-3" gap down the middle, glass that. Then add a 6" of solid glass to be glassed in. Same thing Chris did inside the hatch and what I'm doing inside my hatch.


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