# Foam Core and Hull lamination <15hp



## Virnut (Nov 8, 2012)

THE REEF
Designing a boat that will be somewhere in between a solo skiff and a Marsh hen.
Have been thinking about this for some time, bought and sold a couple ashcrafts. NEED easier smaller.
Really want to give a foam core original build a go.
Tried to read up on foam core "scantlings"? right word?
no luck really, not much info on something this particular.

I need you guys help

*I want to build the boat with Airex 6ib 3/8 core and Divinycell h100 1" 
Resin Research epoxy.*
Strip planked.




  








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Virnut


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Nov 30, 2018











  








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Virnut


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Nov 30, 2018







LOA 15'
BEAM 48"
(MINIMUM) Suggestions on what cloth and a lam schedule that would net something that could be powered up to 15hp.


want to stay under 250 is this possible?
I want to be able to dolly this boat.
will be used in Pamlico Sound Northeast NC
Fairly competent with epoxy


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## Guest (Nov 30, 2018)

Well you’ve come to the right place! Give me a bit to think about it and I’ll get you a lam schedule that should work pretty good for your needs. I would up the core to 1/2” though, the weight penalty is minimal and the structural gains are great!


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## Virnut (Nov 8, 2012)

Noted.
4 sheets 3/8 core is already purchased.
1 sheet of 1" already for bulkheads + Transom.

PICTURES UPDATED

** would also like this discussion to discuss further how someone would come to the conclusion of what a decent schedule is.
And the pros and cons of Less Vs More

Less and more glass in different areas of hull.


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## Guest (Nov 30, 2018)

Is this your first doings with glass work?


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## Virnut (Nov 8, 2012)

No fairly competent with composites and hand layups.

https://www.instagram.com/the_surf_shed/


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## Guest (Nov 30, 2018)

Less=lighter/ more= heavier
The key for skiff construction is finding the sweet spot for strength vs weight. Understanding the materials you are using in terms of tensile strength, impact resistance, etc... helps but there are books out there for that. I’ll get back to ya with a schedule soon.


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## Guest (Nov 30, 2018)

Ok here goes it...
Outter skin
12oz 0/90 biax 1 layer
12oz +45/-45 biax 1layer
8oz cloth 1layer

Inner
12oz 0/90 biax
8oz cloth

Overlap your seams staggering by at least 8” up to 12”.
This should be done wet on wet layup to keep weight down. Doing wet on wet uses signifigantly less resin and in my opinion produces a much stronger product. Looks like a cool concept man. Let me know if I can help more, James.


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## Virnut (Nov 8, 2012)

Wow James that was fast. Thanks for your input man why not 45 biax inside of hull?
anybody else have anything to contribute here?

-Hunter


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## Guest (Nov 30, 2018)

The 0/90 has better strength fore/aft - side/side use +45/-45 for all your tabbing though it bridges the corners with fibers in both directions where the 0/90 only bridges in a single direction. This schedule if done properly will be light!


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## Guest (Nov 30, 2018)

Virnut said:


> Wow James that was fast. Thanks for your input man why not 45 biax inside of hull?
> anybody else have anything to contribute here?
> 
> -Hunter


I lose sleep thinking of these things and have a pretty good grip on the hows and whys lol!


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## el9surf (Dec 23, 2008)

If you want to build me an extra one I will pay you. This is exactly what I have been thinking of. Bigger than a solo skiff but smaller than a Marsh hen would be a sweet solo size poling skiff.


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## Pole Position (Apr 3, 2016)

Y'all may want to take a look @ this---a Chris Morejohn design that has just come out. The plans are very close to what you are looking for and offer some unique features not found elsewhere, plus a proven laminating schedule is furnished :

https://captive-skiffs.com/index.php/the-design/


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## Virnut (Nov 8, 2012)

I Have seen that. He also has posted his "slippery dick" design which seems to be nearly the same hull captive listed.
I Follow Chris Blogs. https://www.etsy.com/ie/shop/SpankTheMermaid

Personally just want to do my own thing here but obviously my chine comes from this department of thought. There is a few paddle like craft out there that are from different builders bote,skanu,hobie. Just like anything in the world the little things will be the difference.


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## Fishtex (May 10, 2014)

If you are going with a new 4 stroke, get a 20hp, as it’s the same engine as the 15hp. The 15 is just a “detuned” 20. The cost difference is small. ( I have a Suzuki, fuel injected, doesn’t need a battery, 97 lbs. All the 20hp four strokes are pretty nice these days, ymmv.)


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## Virnut (Nov 8, 2012)

Hey Fishtex thanks. Probably will do a older 2 stroke due to weight.

Does anyone else have input into glassing this thing light?


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## trekker (Sep 19, 2015)

I'm not gonna offer up a lam schedule as I have never worked with 3/8. If you have the budget, i would really consider going a little thicker as Brains said.

As for keeping it under 250,that wont be a problem. 200 is even reasonable. I just built a 17' skiff that weighs 203 lbs.

What software was used to draw your pics. It looks great.


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## Guest (Dec 1, 2018)

trekker said:


> I'm not gonna offer up a lam schedule as I have never worked with 3/8. If you have the budget, i would really consider going a little thicker as Brains said.
> 
> As for keeping it under 250,that wont be a problem. 200 is even reasonable. I just built a 17' skiff that weighs 203 lbs.
> 
> What software was used to draw your pics. It looks great.


Yeah, she might flex a little for sure but should be good to go. I’ve used that same schedule minus the core with decent results. Yes, It had some floor flex but it was a very light build for <10hp and is still being used today. Just to give ya’ll some perspective... the ol’ Johnsens we all love are a chop skin coat equal to about 3/4oz csm another chop skin about the same thickness, 1 layer of “I believe” 18oz woven roven and all seats and such are chopped in.


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## Virnut (Nov 8, 2012)

trekker said:


> I'm not gonna offer up a lam schedule as I have never worked with 3/8. If you have the budget, i would really consider going a little thicker as Brains said.
> 
> As for keeping it under 250,that wont be a problem. 200 is even reasonable. I just built a 17' skiff that weighs 203 lbs.
> 
> What software was used to draw your pics. It looks great.


Thanks Trekker! Surfboard builder so the Boat is heavily influenced by that and will actually have a single keel to 0 the tail rocker in the last 12". Theory being that it will help the boat track straight under paddle but not too much that it will feel tracky.

*ALREADY OWN 3/8 CORE*
BoardCAD then render it in SHAPE 3D both surfboard design software.
You really have to fight this program to get a solid Hull shape. It's been a back and forth of Hand drawing the cross Sections, then Transcribing them back on here.
The pictured Hull is actually not the final design.. Thought it would be cool to surprise with the build thread the final layout.

Really stoked to hear that my weight goals will come through if I could net 250 with outboard I think this boat could really be a cool alternative to some more commonly known YAK/SKIFF hybrids. Hobie tandem mirage is 250??!

so Let's talk stringers? Necessary for ridgity?
A majority of these cross sections are just more curvy riffs of FS18 by Bateu Bought the plans to help myself understand better the Process here. In that design there is a stringer system a floor and a cap. Not sure if I want to do a cap.


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## WhiteDog70810 (May 6, 2008)

I don't have any experience with foam, but if you are using a thinner foam than recommended, stringers and gunnels will help stiffer up the hull greatly. If you want to keep the weight down, beware of full caps. I feel my cap increased my hull's end weight by about a third. Mine is 16' X 40" epoxy/ply composite and ended up weighing 312# with a full cap, so foam construction should easily be lower especially if you keep the decking minimal.

Nate


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## Guest (Dec 2, 2018)

I’m gonna agree with some stringers and floor. 
Here’s a stringer tip that works...
You can get vinyl gutters from your favorite big box store, set them upside down and glass over them with 2 layers of the 12oz biax, allow a 3” tie and a 6” tie in to the hull on both sides. You now have a light weight stringer with a nice wide top to bond your floor to. Cheap, easy, very effective!


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## PropGunOne (May 27, 2018)

Sent you a message in addition to this:

The lam schedules we have are for in-mold construction. Talked with Chris about this and he recommends 1/2-3/4” foam for a one-off, on-jig type build. Our skiff will come in at around that weight but we use areas with thicker core (3/8”), areas with thinner (1/4”) and areas with none, depending on the loads involved.

We can always use a hand with building. Parts are waiting at the Fab place and a bunch of materials making their way to Atlanta right now via UPS.


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## PropGunOne (May 27, 2018)

Virnut said:


> I Have seen that. He also has posted his "slippery dick" design which seems to be nearly the same hull captive listed.
> I Follow Chris Blogs. https://www.etsy.com/ie/shop/SpankTheMermaid
> 
> Personally just want to do my own thing here but obviously my chine comes from this department of thought. There is a few paddle like craft out there that are from different builders bote,skanu,hobie. Just like anything in the world the little things will be the difference.



Pretty similar, but far easier build. Basically S&G with foam core. Depends on what you want to use it for, as Chris will tell you. Would be an awesome utility/sneak boat I would think. Wouldn’t mind building one myself.


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## Virnut (Nov 8, 2012)

PropGun Yea your boat is for sure a more refined slippery dick wayy more suitable for a angler. SHARP purpose built fishing craft.

Looks amazing people check him out

https://captive-skiffs.com/index.php/purchase-plans/

No brainer that this boat is a better investment than some more common names.

** EDIT let's get some discussion of placement of cores and different layerings of glass to have strength where it's needed and other places not so much.
I don't understand this and would love to hear what some of the knowledge on this board thinks.


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## copperhead (May 30, 2008)

Not to rain on anyone's parade but using a generic term "foam" is a bit misleading. The quality and strength characteristics of the different types are all over the board and any discussion about a lamination schedule would have to have knowledge of the specific physicals for a given foam product. In the stuff I build, I usually use 4 different foam core products, both in thickness and foam type (ie core cell, pvc, pet and honeycomb). I like it when I see you guys working on these type of projects, I'm just kind of limited on what I can say, but have at it guys!


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## Virnut (Nov 8, 2012)

Virnut said:


> I need you guys help
> 
> I want to build the boat with Airex 6ib 3/8 core Resin Research epoxy.
> Strip planked.


Thanks for your input Copperhead I listed the materials used. Edited post to include the bulkhead and transom foam core specs. Also have access to NOMEX Honeycomb As well as vac bag/chop etc. I guess I should have elaborated more.


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## PropGunOne (May 27, 2018)

Copperhead probably knows way more about it than I do. We’re specifically using H80 Contour core Divinycell in 1/4” and 3/8” thickness. More thickness on hull bottom, decks and sole and thinner on the sides.


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## Cut Runner (Jan 25, 2017)

How bout 
(Outside going in)
One layer of 1.5ozcsm,one layer 1700, one layer .75 oz. Csm, 3/4 in miracle fiber "w" , one layer .75oz csm, 1700, 1.5oz


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## anytide (Jul 30, 2009)

this ^^^^^^


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## Virnut (Nov 8, 2012)

Cut Runner said:


> How bout
> (Outside going in)
> One layer of 1.5ozcsm,one layer 1700, one layer .75 oz. Csm, 3/4 in miracle fiber "w" , one layer .75oz csm, 1700, 1.5oz


Liking all the Help from CUT and BRAINS thank you guys for your time. Stay tuned for Updates.
https://www.instagram.com/the_surf_shed/


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## DuckNut (Apr 3, 2009)

Virnut said:


> Wow James that was fast. Thanks for your input man why not 45 biax inside of hull?
> anybody else have anything to contribute here?
> 
> -Hunter


45 is typically stitched and then you get to deal with all those threads.

If you bought the plans from Bateau, why not get the layup schedule from them for a foam build?

Honeycomb for floor would be great.

Hull stiffener on side.


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## Virnut (Nov 8, 2012)

DuckNut said:


> 45 is typically stitched and then you get to deal with all those threads.
> 
> If you bought the plans from Bateau, why not get the layup schedule from them for a foam build?
> 
> ...



I'm not sure if it's really ethical to ask him for that. But thanks.


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## Guest (Dec 4, 2018)

Virnut said:


> I'm not sure if it's really ethical to ask him for that. But thanks.


He was saying if your plans came from bateau they will have a lam schedule for the design. I don’t believe @DuckNut saw this was your baby.


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## DuckNut (Apr 3, 2009)

Virnut said:


> I'm not sure if it's really ethical to ask him for that. But thanks.


If you bought their plans there is the lam schedule somewhere on their website. Since you are only slightly altering it the lam schedule would work for yours as well.

Jacques will not give you a lam layup for your design for liability reasons.


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## CodyW (Jan 26, 2016)

Boatbrains said:


> I’m gonna agree with some stringers and floor.
> Here’s a stringer tip that works...
> You can get vinyl gutters from your favorite big box store, set them upside down and glass over them with 2 layers of the 12oz biax, allow a 3” tie and a 6” tie in to the hull on both sides. You now have a light weight stringer with a nice wide top to bond your floor to. Cheap, easy, very effective!


I'm def going to try this..... Sounds interesting and simple.


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## Guest (Feb 2, 2019)

CodyW said:


> I'm def going to try this..... Sounds interesting and simple.


Only do this if it’s a cored hull and the stringers aren’t gonna be hull stiffeners! This method is only really good as a floor support. The lay up is too thin without a core! You could glass them in and then foam fill with 4 or 8 lb foam though if you needed for strength...


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## CodyW (Jan 26, 2016)

Boatbrains said:


> Only do this if it’s a cored hull and the stringers aren’t gonna be hull stiffeners! This method is only really good as a floor support. The lay up is too thin without a core! You could glass them in and then foam fill with 4 or 8 lb foam though if you needed for strength...


It's going in a johnsen skiff, actually the blue one with the merc 25 hp that was for sale a month ago. The plan was to glass them in and fill it up with foam. I am also pouring foam underneath the rest of the floor also. I think it'll be plenty stiff.


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## Guest (Feb 3, 2019)

CodyW said:


> It's going in a johnsen skiff, actually the blue one with the merc 25 hp that was for sale a month ago. The plan was to glass them in and fill it up with foam. I am also pouring foam underneath the rest of the floor also. I think it'll be plenty stiff.


Just be carefull with the foam! For the stringers in this case here is what I’d do...
Trim the gutter to fit the hull shape, flip upside down and wax the inside of the gutter with several coats of wax. “Don’t worry about buffing back off too much”
Cap the ends of the gutter and make a simple jig fixture to support it.
Now fill with you foam “ I would use 8#”
Once foam cures, trim to match edge you made on gutter and peel gutter off the foam.
Now you have a foam stringer just like a lot of production builders use!
When you go to install, mark out where they will go and lay down two layers of 3oz csm the width of the bottom of the stringer to bed them in. Use a little weight to hold them down in the wet csm until it kicks. Now you can glass them in and viola!
Oh, clean the foam with soap and water to remove the wax and follow that with wax and grease remover, then lightly scuff the uncut surface with some 80 grit so your glass/resin will bond good.


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