great design . in rc scratch building with foam board we use regular hot glue guns on the foam . it bonds like CA glue without the brittleness . the pieces are darn near welded together
I believe so, hoping to start building an overland expedition mobile in 1 years time, doing my studeies now and it seems fiberglass insusion is the way for my box/cabin. My main worry is humidity to destroy things and especially inside. I think good fiberglass and aluminum primer will do the job!!!!!!!
With an exception. Well not really an exception so much as a difference. The squareness of a camper needs to be attended to strengthwise. All the curves in a boat get naturally ’strong’ whereas with campers you need to assure torsional load transfers with out ‘point loads’ at intersections of the sides.
Looks like Airex C70 or similar. No divinycell, which works as well. Plenty of closed cell foams out there that work. Polyumac had some interesting ones, so does CarbonCore. Check the specs. As for “how big can I build” questions... that depends on a lot of things. Design, lamination schedule, lots of things factor in. Done right, there isn’t much the average home builder can come up with that foam core won’t work for.
Almost anybody can build a boat large enough to liveaboard. The method demonstrated is very good. You can also build a strongback and lay strips of cedar along its' length and then apply fibre glass. Use good quality epoxy resin. Avoid plywood, even if it's 1066 grade, use closed cell foam for the bulkheads.
It seems really easy to work with, fast and straight forward. I wonder why so many amateur boat builders, especially catamaran boat builders, go the plywood/fiberglass route.
Availability and shipping are a factor. I can buy marine ply in ATL pretty easily... foam core not so much. That said, after two small ply boats, my next will be foam core. Too many better possibilities with foam vs ply.
Down Under a lot of cat boat builders use this method, or balsa cores instead of foam, to build extremely light and strong boats (which then are very fast under sail with better payloads). Hardly anyone here builds with plywood / glass any more, that's 1960's construction technique. It's all balsa / glass / epoxy construction now, with many vacuum bagging as well to further reduce weight.
@@ApprenticeGM Not experienced at all with this way of constructing, but assume a lot of planning and forethought goes into designing strength in higher stress areas that typically a plywood builder would just glass over as part of the whole boat.
What’s a square foot of plywood compared to a square foot of foam? Cost wise? That’s a start. The second thing is that plywood has a structural element that foam cannot match: all the strength of building over foam has to do with the fiberglass and (to a small degree) the adhesion to the foam. Wood/plywood on the other hand has an intrinsic strength it donates along with it acting as a form.
Thank you for making this video because books don't really show you how easy this can be for the average person. I might try this on a small scale to gain experience then move up to novice? Thanks again.
If I wanted to do a 1 off build, 55' long...and you had 3 yrs to do the job.. would you ever consider using this same method to do a larger sized boat? Saves money on the mold being that you can cut the mold costs in half, is what I am thinking. Or am I crazy?
@@firemanjim324 - Home Depot Foams are not Boat Building "Structural Foam", as they are Insulation Foams, but might suffice, if Water Absorbing Property is not a matter of interest, as well as UV Tolerance challenges are not a concern.
@@scotthummel4248 - West Epoxy Suppliers, likely have Choices if Cores, including this type. Boat Building Suppliers. "Aircraft Spruce" catalog or website, are also Options.
Thanks for this video. I know it's an older one, but in case you're still reading this: Do you (or anybody else reading this) have an idea what a typical foamcore thickness in larger production boats (/catamarans) is? Let's say for a typical boat with 12 m length. And what's a typical fiberglass thickness (g/m2) of the inner and outer skin around this foamcore? Google doesn't give me any good answers. ~ Also: is there any reason not to use XPS foam (the stuff that's used for house insulation, e.g. Styrodur, i.e. the closed-cell stuff and _not_ EPS)? I know it comes with some (solvable) challenges with some of the very rounded parts like e.g. the bow shape because it doesn't bend easily (almost not at all), but it can easily be cut into shape with an electrical saw (and correcting surface details with a pad sander also works very well). The reason: I think beyond being incredibly low cost (and much more affordable than PVC foam or honeycomb materials), it actually has great properties, especially being very resistent to compression (entire houses are standing on this stuff, despite of it's low density of only ~35 kg/m3), which is the one thing the fiberglass (tensile and torsion forces) can't do. It's also waterresistent and works with epoxy (but not polyester resin). And good ol' low cost wood glue also sticks to it quite well and can conveniently be used to keep parts together before the glassing stage.
The short answer is there is no typical laminate schedule using foam core. Every boat is engineered differently. For example, some might use a thinner core with a thicker fiberglass laminate while others use a thicker core with lighter laminate. A lot of work and consideration goes into designing a proper laminate schedule on any boat, especially a catamaran.
XPS has very low shear strength compared to PVC cores. It's good in compression though (hence it's under slab usage). It can be used for some things, but you need to be careful.
Excellent explanation! How many layers of fiberglass do you use on each side? If, the answer is yes, do you have to consider a specific orientation-angle between each one of the layers? Thanks! Thumbs up!
So you fiberglassed in the inside, and then you stripped it from the wood form, and then fiberglass the backside. Correct? So a both that is 1 layer foam thickness? You say 5.5 lb/CF foam. What is this when buying foam as H60, H80 ?
HDPE foam is whats used in Building those offshore boats but to sandwhich core you could use the two part 4lb density available at any Boat Building supplyers but is polyester better then OMG brain fog but also use two layers of chop strand may @ 1.5 longitude and then opposite way with 1708 and 24oz or 32oz wovenroven
Rune Martin Guildberg - No. Just a good Surface Coat on the Foam, a few Thousandths of an inch thick. The Resin is a Primer, and a Binder, but the S-Glass, Kevlar, or Carbon Fibre is the Strength. The Cores add Separation, causing Skins to Load up more in Tension & Compression, than in Bending - making the Total Stronger.
HI MY CRABBER FRIEND TOLD ME A BOAT BILDERS SECRET. PAINT THE STYROFOAM WITH 2 COATS OF LATEX PAINT LET IT DRY AND THEN USE POLYESTER AND FIBERGLASS CLOTH . I HAVE NOT TRIED IT SO DONT GET MAD AT ME IF IT DOESN'T WORK. DO A SMALL TEST FIRST.
Great method! I'm very much considering building a Glen-L slide-in camper. I want to try and keep the weight to a greatest minimum as possible. In this case, what is the hull strength and integrity for your foam core hull? Specifically, overall strength
It depends on how thick you lay the glass. For a slide out on a camper, I'd probably frame it out of 1x2's , with gussets , 5mm plywood (underlayment) , and some XPS foam sandwiched in between. 3 -4 layers of 7oz tight weave cloth on the outside, and 2 on the inside. Use epoxy resin as it's stronger than polyester resin and it's completely waterproof, whereas the polyester isn't ...
I thought this was a great video. Well narrated and demonstrated, but I don't see how this is superior to plywood in strength and rigidity? I get that it is more weather resistant but you can get that from plywood if you cover it with FG and epoxy and vacuum infuse it properly.
+gus bisbal. Plywood is stronger as a core material, but since closed cell foam is significantly lighter, a foam sandwich can have a thicker core with more layers of glass for the same weight as a wood sandwich. The extra glass and core material can mean the foam core is actually stronger and much more rigid. Structural rigidity of a part in bending is proportional to the thickness *cubed*. Every time the thickness doubles, the resistance to bending octuples. The maximum stress in bending is at the outer surfaces of a part, so thicker glass at the edges also helps resist bending as well as increasing the tensile strength of the sandwich. Regardless of strength, the foam is easier to work with and, as you said, resistant to weather/delamination without any additional steps. That said, wood still wins in terms of sheer strength. It's like aluminum vs steel. While the foam sandwich boat can be lighter and/or more rigid, it will still always be easier to put a hole in the side of one than a comparable boat with a wood core. But it's not like either boat would come out unscathed in a point impact, so you have to ask which would be easier to repair. My money is on the foam core, since it's easier to work and especially since you don't have to worry about areas around the repair rotting after the fact.
until you have made a foam core sandwich you just can't believe how strong and stiff it can be. (wood is still stronger but foam is very very very strong too)
High Modulus built the hull of the 124' superyacht Ermis2, the 2nd or 3rd fastest yacht in the world(60 knots WOT)with a 10" sandwich of Airex foam overlaid with carbon fiber/kevlar to withstand 2.2 gravity entry in heavy seas. So they agree with your assessment of the strength of foam. It's amazing to see Ermis2 come to a complete stop from 60kn almost within its own length with triple KaMeWa waterjets.
Plywood is SOOO much heavier than the foam board, and Marine Plywood is also more expensive. Plywood is around 2 lb/SF + the fiberglass coating. Foam is 65% lighter. Both need the fiberglass overlay. The strength of the plywood is not enough to make plywood preferable. Stick to the foam. Nobody wants to deal with a plywood boat in 30 yrs. I'd always choose an aluminum or fiberglass/foam boat over a plywood boat.
Chaddyjp Campbell fiberglass with foam core construction is very strong. Numerous boats built with foam core construction sail the high seas with decades of service. The trick to a strong build is the right glass to resin ratio. Too much and it's brittle, too little and it's very weak in the spots that don't asorb resin.
Interesting method using a female mold with strips of foam. I have been trying to come up with a way to build a vintage jet boat. Length around 17- 18 ft. Big block engine with a Berkely jet pump. With enough for thought the mold could be made so there would be no hull to deck seam.
"COMPATIBLE WITH EPOXY" One of the most important things you said - but barely! I just watched video about having to paint foam with 4 to 5 coats of interior latex so the foam wouldn't melt from the thermal action of the epoxy! Does Home Depot and the likes carry the foam needed?
No, you will not find structural foam core at a big box store. Divinycell, Airex, Klegecell, CarbonCore, Corecell, and others can be purchased through local or online marine supply stores.
The epoxy won't melt the foam. What you were probably seeing is someone trying to use polyester resin on polystyrene foam. They are incomparable since the styrene in the polyester resin will melt polystyrene, hence the barrier of latex. Not a good idea for anything structural.
Realistically, how large of a boat can you build with foam core??? I am seriously considering the Glen L boat the Herculese. I think it is 24 or 25FT long and can be extended by 10%. This boat would have a forward berth, head and shower room/area, small stove and sink and a cock pit for fishing. It is shrimp boat and or trawler design. The original plans are for plywood and fiberglass.
There is no limit to how large a foam core constructed vessel can be. However, the hull laminate schedule and structure has to be designed for this type of construction.
Thank you for the video. This video didn't explain the structural integrity very well. It seems there would be weak points where the two halves meet. Also weak points where the bulk head meets the planks. Can you explain this more if only in a reply here?
There's no weak points - the fibreglass is what gives it strength. After the 2 halves are joined another layer of fibreglass is applied, usually on both sides (inside and out) and that's where you get the strength, not relying on whatever join you had. This is the basis for sandwich construction, where the 2 outer layers are held apart by the core (think of it like webbing in an I beam) and the whole thing is very strong and very light. As for where bulkheads meet planks, again you are fibreglassing over the shape created not relying on the join. It helps to build up a small radius at the joins eg in Q-cell or thickened resin so the glass isn't doing a hard 90 degree bend.
Hi. I want tu build trimaran with foam sandwich metod. The size is 6 meter length and 1 meter width. How I started? I want to have strong and light boat.
For this demonstration we used 5.5 lbs/ cu. ft Airex foam but any brand of closed-cell structural foam compatible with epoxy will work. The foam can be found at most online and local boatbuilding supply companies.
When you "wet out" the foam, do you wait until its dry before you place your glass on? In the video it looked like your glass didn't stick to the resin when you flopped it on the bulkhead.
+Pig Farmer Ben With epoxy it is critical when you apply the next coat. You wait until it is "late stage gel" And then on to the next step. It you wait for a hard cure you then have 2 major problems with bonding. 1 being it becomes a secondary bond and the surface must be scuffed. 80 grit is usually recommended. 2 being the big big big one. Amine blush. If you use retail grade epoxy or almost any pro grade you get blush. That is the reaction between humidity in the air and the hardener. It leaves an oily film on the surface preventing adhesion. It must be cleaned of with clean hot water only. Solvent does not cut it. Neither does soap. Rinsed and wiped off and then sanded. If it is sanded before it will grind the blush into the surface. By using a non/low blushing epoxy like West 105/207 or system3 clear coat you get better secondary bonding. When I start the inside of a craft the epoxy never cures hard till it is done. Same at the outside. I even apply light amounts of faring compound in places I know I will need it so it cures as one solid mass.
@@tireballastserviceofflorid7771 How are you preventing the epoxy from curing hard before you're completely done? I'd have thought it would be very difficult to complete a project that fast.
Would it be a good or bad idea to build the entire boat from foam then fiberglass all the foam in one go, rather than the traditional fabrication method. Of course fitting in solid material for were fixtures will be before the glass is applied. If it is a bad idea, can you explain why.
The foam that is used is specifically made to be used in lightweight sandwich construction using epoxy, vinylester or polyester resins. This is not the polystyrene insulating foam that you find at your local hardware store.
For this demonstration we used 5.5 lbs/ cu. ft Airex foam but any brand of closed-cell structural foam compatible with epoxy will work. The foam can be found at most online and local boatbuilding supply companies.
The foam needs to have a high shear strength, hardware shop foam does not work well at all. The cost of the hardware shop foam compared to the boat building foam will be a tiny percentage of the cost of the boat.
Dalt Wisney the foam has nothing to do with the flotation. Compare two boats, one built of foam one of metal, assuming they have the same weight and same hull shape they will have the same buoyancy. Check out Archimedes principle
No, the foam is closed cell which means you cannot suck the air out, open cell foam allows air and water to pass through it. Closed cell boat foams specifications always say whether you can use infusion, ie will not deform with 1atm of pressure.
Yes, structural PVC foam. For this demonstration we used 5.5 lbs/ cu. ft Airex foam but any brand of closed-cell structural foam compatible with epoxy will work.
Looks like a great way to build except for the epoxy. Epichlorohydrin, one of the constituents of the epoxy resin monomer is a skin sensitizer. In addition, epichlorohydrin is classified as carcinogenic in the category, ‘presumed human carcinogen’, according to the EU classification.
For this demonstration we used 5.5 lbs/ cu. ft Airex foam but any brand of closed-cell structural foam compatible with epoxy will work. The foam can be found at most online and local boatbuilding supply companies.
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One of the better "how to" vids in boat building I have come across. Thanks very much.
Thank you so much for the video. You have confirmed that scarf joints are unnecessary with foam core construction 😊
You have the voice of a senior pilot, Captain I would say. Nice technique with the foam.
great design . in rc scratch building with foam board we use regular hot glue guns on the foam . it bonds like CA glue without the brittleness . the pieces are darn near welded together
That was just fun to watch and very helpful on a hard-dodger idea I'm working on. Thanks so much!
I would have liked to know what epoxy you're using. Knowing what works well on foam and what doesn't is extremely valuable info.
amazing technique, exactly what I was searching for my project
Awesome, I'm not building a boat yet but the technique you use is helpful. Thank you for sharing this👍
I'm getting ready to build a 17 ft. Garvey Jon this way. This is a great video!
Pretty slick way to build...Well done Sir...!
That's really well explained and the video demonstrates it all well . Thank you for sharing 😊
Thanks for taking the time, I appreciate your effort.
One of the most useful vids ever. Thanks.
I did enjoy the video and learn a bit more about boat building. Cheers
Excellent informative video ..I was thinking seriously about using ply but this seems so much easy and has to be lighter ..
The video was very nice and boat looks great. Nice of your guys to do this. :)
What kind of foam?
Seems to me you can use the same method to form the shell of a travel trailer. Like one of those Shorty-style trailers.
I believe so, hoping to start building an overland expedition mobile in 1 years time, doing my studeies now and it seems fiberglass insusion is the way for my box/cabin. My main worry is humidity to destroy things and especially inside. I think good fiberglass and aluminum primer will do the job!!!!!!!
They call those trailers foamies
With an exception. Well not really an exception so much as a difference. The squareness of a camper needs to be attended to strengthwise. All the curves in a boat get naturally ’strong’ whereas with campers you need to assure torsional load transfers with out ‘point loads’ at intersections of the sides.
Looks like Airex C70 or similar. No divinycell, which works as well. Plenty of closed cell foams out there that work. Polyumac had some interesting ones, so does CarbonCore. Check the specs. As for “how big can I build” questions... that depends on a lot of things. Design, lamination schedule, lots of things factor in. Done right, there isn’t much the average home builder can come up with that foam core won’t work for.
Almost anybody can build a boat large enough to liveaboard. The method demonstrated is very good. You can also build a strongback and lay strips of cedar along its' length and then apply fibre glass. Use good quality epoxy resin. Avoid plywood, even if it's 1066 grade, use closed cell foam for the bulkheads.
It seems really easy to work with, fast and straight forward. I wonder why so many amateur boat builders, especially catamaran boat builders, go the plywood/fiberglass route.
panther105 simply it's stronger & it's not nice feeling when your boat break into two half's two thousand miles from land 😂✌️
Availability and shipping are a factor. I can buy marine ply in ATL pretty easily... foam core not so much. That said, after two small ply boats, my next will be foam core. Too many better possibilities with foam vs ply.
Down Under a lot of cat boat builders use this method, or balsa cores instead of foam, to build extremely light and strong boats (which then are very fast under sail with better payloads). Hardly anyone here builds with plywood / glass any more, that's 1960's construction technique. It's all balsa / glass / epoxy construction now, with many vacuum bagging as well to further reduce weight.
@@ApprenticeGM Not experienced at all with this way of constructing, but assume a lot of planning and forethought goes into designing strength in higher stress areas that typically a plywood builder would just glass over as part of the whole boat.
How far can you scale this technique up, and when scaled up how do the costs compared to plywood construction ?
What’s a square foot of plywood compared to a square foot of foam? Cost wise? That’s a start.
The second thing is that plywood has a structural element that foam cannot match: all the strength of building over foam has to do with the fiberglass and (to a small degree) the adhesion to the foam. Wood/plywood on the other hand has an intrinsic strength it donates along with it acting as a form.
Awesome video.im guessing you could build a cataraman like this
Thank you for making this video because books don't really show you how easy this can be for the average person. I might try this on a small scale to gain experience then move up to novice? Thanks again.
If I wanted to do a 1 off build, 55' long...and you had 3 yrs to do the job.. would you ever consider using this same method to do a larger sized boat? Saves money on the mold being that you can cut the mold costs in half, is what I am thinking. Or am I crazy?
Yes, that's the reason for this build method - no moulds.
@Randy Warner- for this demonstration we used 5.5 lbs/ cu. ft Airex foam but any brand of closed-cell structural foam compatible with epoxy will work.
Cerny Yacht Design
Where do you get the foam?
@@scotthummel4248 closed cell foam insulation from HomeDepot would work.
@@firemanjim324 - Home Depot Foams are not Boat Building "Structural Foam", as they are Insulation Foams, but might suffice, if Water Absorbing Property is not a matter of interest, as well as UV Tolerance challenges are not a concern.
@@scotthummel4248 - West Epoxy Suppliers, likely have Choices if Cores, including this type. Boat Building Suppliers. "Aircraft Spruce" catalog or website, are also Options.
So the transform is divinycell and glassed as well or did you use an alternate material for the section
Very interesting! Can poly be used??
yes that's all I use building my foam core boats
What kind of foam ?
I want to build a small boat and was wondering what particular type of foam was used on your project and if all closed cell foams work.
thanks
So its basically coosa board thats not already manufactured??
What are the green planks made from ?
Are there any workshops one can attend to gain some experience? Nice Video.
Thanks for this video. I know it's an older one, but in case you're still reading this: Do you (or anybody else reading this) have an idea what a typical foamcore thickness in larger production boats (/catamarans) is? Let's say for a typical boat with 12 m length.
And what's a typical fiberglass thickness (g/m2) of the inner and outer skin around this foamcore? Google doesn't give me any good answers.
~
Also: is there any reason not to use XPS foam (the stuff that's used for house insulation, e.g. Styrodur, i.e. the closed-cell stuff and _not_ EPS)? I know it comes with some (solvable) challenges with some of the very rounded parts like e.g. the bow shape because it doesn't bend easily (almost not at all), but it can easily be cut into shape with an electrical saw (and correcting surface details with a pad sander also works very well). The reason: I think beyond being incredibly low cost (and much more affordable than PVC foam or honeycomb materials), it actually has great properties, especially being very resistent to compression (entire houses are standing on this stuff, despite of it's low density of only ~35 kg/m3), which is the one thing the fiberglass (tensile and torsion forces) can't do. It's also waterresistent and works with epoxy (but not polyester resin). And good ol' low cost wood glue also sticks to it quite well and can conveniently be used to keep parts together before the glassing stage.
The short answer is there is no typical laminate schedule using foam core. Every boat is engineered differently. For example, some might use a thinner core with a thicker fiberglass laminate while others use a thicker core with lighter laminate. A lot of work and consideration goes into designing a proper laminate schedule on any boat, especially a catamaran.
XPS has very low shear strength compared to PVC cores. It's good in compression though (hence it's under slab usage). It can be used for some things, but you need to be careful.
Hi How did you put two half together . Do you Have more video on this topic. Thanks Nick.
Fiberglass tape over the center seam. Then fiberglass entire outer hull.
so you dont need stringers when in foam cored like you do with ply cored?
The need for stringers is completely dependent on the design; type of boat, size, intended use, etc.
Excellent explanation! How many layers of fiberglass do you use on each side? If, the answer is yes, do you have to consider a specific orientation-angle between each one of the layers? Thanks! Thumbs up!
So you fiberglassed in the inside, and then you stripped it from the wood form, and then fiberglass the backside. Correct? So a both that is 1 layer foam thickness? You say 5.5 lb/CF foam. What is this when buying foam as H60, H80 ?
Correct. 1 layer of foam in the hull. Yes, H80 is 5.5 lbs/cu. ft.
The interior of the boat is fiberglassed, the boat is removed from the jig, and then the exterior is glassed.
HDPE foam is whats used in Building those offshore boats but to sandwhich core you could use the two part 4lb density available at any Boat Building supplyers but is polyester better then OMG brain fog but also use two layers of chop strand may @ 1.5 longitude and then opposite way with 1708 and 24oz or 32oz wovenroven
What type of foam is this? What density?
Nice work... Congratulations...
what kind of foam did you use that it can stand the chemicals of the resin? and what resin too, thanks.
How does this methodology go making a sharp chine? Assuming it needs a fillet on the inside to avoid creating a stress riser?
Thanks! Now I see what is the boat foam
A very interesting and informative video.
Nicholasf94- we prefer using thickened epoxy but any adhesive compatible with the foam will work just fine for gluing the foam to itself.
Like Gorilla Glue?
How big can u build with foam?
is the foam 1/4 in thick or 1/2 in thick>
for d boat under 7 foot long could I us 1/8 in thich or 1/4 in thick foam?
Thank you for making this video to share :)
Hello!
What was the foam thickness in that project ?
I want to build small fishing boat (3m length) using the foam-core sandwich techology...
3m can likely get away with 1/2” or possibly smaller if laminated correctly. 3/4” very common starting at about the 16th range
what kind of foam is that? where would you buy it?
Do you think that if i make a Stick n Glue kayiak using foam(instead of wood or plywood) and them dress it with fiberglass and epoxy resin will work?
Hi. Did you do it? I‘m about to build a kayak s&g with airex 8mm and carbon fiber
Brilliant.
Thanks for sharing 😌
Have u got any plans for 12ft fishing boat to be constructed in this way?
When you Fiber Glassed the outside (bottom) of the boat, are there problems with the vertical sections? How do you stop the resin from running?
what type of epoxy did you use?
Are foam sheets wet all through with epoxy.
Rune Martin Guildberg - No. Just a good Surface Coat on the Foam, a few Thousandths of an inch thick. The Resin is a Primer, and a Binder, but the S-Glass, Kevlar, or Carbon Fibre is the Strength. The Cores add Separation, causing Skins to Load up more in Tension & Compression, than in Bending - making the Total Stronger.
what resin was used so it didn't melt the foam?
Epoxy that is suitable for boatbuilding was used in the construction.
HI MY CRABBER FRIEND TOLD ME A BOAT BILDERS SECRET. PAINT THE STYROFOAM WITH 2 COATS OF LATEX PAINT LET IT DRY AND THEN USE POLYESTER AND FIBERGLASS CLOTH . I HAVE NOT TRIED IT SO DONT GET MAD AT ME IF IT DOESN'T WORK. DO A SMALL TEST FIRST.
Don't use styrofoam. this is structural foam
Mike G i
JoeSmith.....dumbest idea ever, if your outer skin is not glued properly to the foam then it loses most of its strength.
Great method! I'm very much considering building a Glen-L slide-in camper. I want to try and keep the weight to a greatest minimum as possible. In this case, what is the hull strength and integrity for your foam core hull? Specifically, overall strength
It depends on how thick you lay the glass. For a slide out on a camper, I'd probably frame it out of 1x2's , with gussets , 5mm plywood (underlayment) , and some XPS foam sandwiched in between. 3 -4 layers of 7oz tight weave cloth on the outside, and 2 on the inside. Use epoxy resin as it's stronger than polyester resin and it's completely waterproof, whereas the polyester isn't ...
There is something new from the field of construction that revolutionizes the weight-to-strength challenge.
Do you cut the foam into planks or do they come that way?
what is the weight of the boat at the final stage? Thanks!
Yes, I’d love to know the weight too
what kind of foam do i need ?
I thought this was a great video. Well narrated and demonstrated, but I don't see how this is superior to plywood in strength and rigidity? I get that it is more weather resistant but you can get that from plywood if you cover it with FG and epoxy and vacuum infuse it properly.
+gus bisbal.
Plywood is stronger as a core material, but since closed cell foam is significantly lighter, a foam sandwich can have a thicker core with more layers of glass for the same weight as a wood sandwich. The extra glass and core material can mean the foam core is actually stronger and much more rigid. Structural rigidity of a part in bending is proportional to the thickness *cubed*. Every time the thickness doubles, the resistance to bending octuples. The maximum stress in bending is at the outer surfaces of a part, so thicker glass at the edges also helps resist bending as well as increasing the tensile strength of the sandwich. Regardless of strength, the foam is easier to work with and, as you said, resistant to weather/delamination without any additional steps.
That said, wood still wins in terms of sheer strength. It's like aluminum vs steel. While the foam sandwich boat can be lighter and/or more rigid, it will still always be easier to put a hole in the side of one than a comparable boat with a wood core.
But it's not like either boat would come out unscathed in a point impact, so you have to ask which would be easier to repair. My money is on the foam core, since it's easier to work and especially since you don't have to worry about areas around the repair rotting after the fact.
Great answer, thank you.
until you have made a foam core sandwich you just can't believe how strong and stiff it can be. (wood is still stronger but foam is very very very strong too)
High Modulus built the hull of the 124' superyacht Ermis2, the 2nd or 3rd fastest yacht in the world(60 knots WOT)with a 10" sandwich of Airex foam overlaid with carbon fiber/kevlar to withstand 2.2 gravity entry in heavy seas. So they agree with your assessment of the strength of foam.
It's amazing to see Ermis2 come to a complete stop from 60kn almost within its own length with triple KaMeWa waterjets.
Plywood is SOOO much heavier than the foam board, and Marine Plywood is also more expensive. Plywood is around 2 lb/SF + the fiberglass coating. Foam is 65% lighter. Both need the fiberglass overlay. The strength of the plywood is not enough to make plywood preferable. Stick to the foam. Nobody wants to deal with a plywood boat in 30 yrs. I'd always choose an aluminum or fiberglass/foam boat over a plywood boat.
I'm thinking about building one like this.. how strong is it Against the waves with a 30hp Engine? Will it survive against the rough seas?
Chaddyjp Campbell fiberglass with foam core construction is very strong. Numerous boats built with foam core construction sail the high seas with decades of service. The trick to a strong build is the right glass to resin ratio. Too much and it's brittle, too little and it's very weak in the spots that don't asorb resin.
Interesting method using a female mold with strips of foam. I have been trying to come up with a way to build a vintage jet boat. Length around 17- 18 ft. Big block engine with a Berkely jet pump. With enough for thought the mold could be made so there would be no hull to deck seam.
My 2 cents on that is no foam. the hp and torque would be to much for foam. Solid glass.
David- hows the build going?
What about a camper trailed or a truck camper.
"COMPATIBLE WITH EPOXY"
One of the most important things you said - but barely!
I just watched video about having to paint foam with 4 to 5 coats of interior latex so the foam wouldn't melt from the thermal action of the epoxy! Does Home Depot and the likes carry the foam needed?
No, you will not find structural foam core at a big box store. Divinycell, Airex, Klegecell, CarbonCore, Corecell, and others can be purchased through local or online marine supply stores.
The epoxy won't melt the foam. What you were probably seeing is someone trying to use polyester resin on polystyrene foam. They are incomparable since the styrene in the polyester resin will melt polystyrene, hence the barrier of latex. Not a good idea for anything structural.
learned several cool tricks thanks
Realistically, how large of a boat can you build with foam core??? I am seriously considering the Glen L boat the Herculese. I think it is 24 or 25FT long and can be extended by 10%. This boat would have a forward berth, head and shower room/area, small stove and sink and a cock pit for fishing. It is shrimp boat and or trawler design. The original plans are for plywood and fiberglass.
There is no limit to how large a foam core constructed vessel can be. However, the hull laminate schedule and structure has to be designed for this type of construction.
What does the hull weigh ?
Thank you for the video. This video didn't explain the structural integrity very well. It seems there would be weak points where the two halves meet. Also weak points where the bulk head meets the planks. Can you explain this more if only in a reply here?
There is a new product that solves this potential problem.
There's no weak points - the fibreglass is what gives it strength. After the 2 halves are joined another layer of fibreglass is applied, usually on both sides (inside and out) and that's where you get the strength, not relying on whatever join you had. This is the basis for sandwich construction, where the 2 outer layers are held apart by the core (think of it like webbing in an I beam) and the whole thing is very strong and very light.
As for where bulkheads meet planks, again you are fibreglassing over the shape created not relying on the join. It helps to build up a small radius at the joins eg in Q-cell or thickened resin so the glass isn't doing a hard 90 degree bend.
How big can you go using this technique ?
Hi.
I want tu build trimaran with foam sandwich metod.
The size is 6 meter length and 1 meter width.
How I started?
I want to have strong and light boat.
How did you glue the foam pieces together in the part around 1.33?
Please reference 6:38 of the video
What type foam?
For this demonstration we used 5.5 lbs/ cu. ft Airex foam but any brand of closed-cell structural foam compatible with epoxy will work. The foam can be found at most online and local boatbuilding supply companies.
Is there a spray-on closed cell structural foam that can be used for boat building?
Sorry, not that I am aware of.
When you "wet out" the foam, do you wait until its dry before you place your glass on? In the video it looked like your glass didn't stick to the resin when you flopped it on the bulkhead.
+Pig Farmer Ben With epoxy it is critical when you apply the next coat. You wait until it is "late stage gel" And then on to the next step. It you wait for a hard cure you then have 2 major problems with bonding. 1 being it becomes a secondary bond and the surface must be scuffed. 80 grit is usually recommended. 2 being the big big big one. Amine blush. If you use retail grade epoxy or almost any pro grade you get blush. That is the reaction between humidity in the air and the hardener. It leaves an oily film on the surface preventing adhesion. It must be cleaned of with clean hot water only. Solvent does not cut it. Neither does soap. Rinsed and wiped off and then sanded. If it is sanded before it will grind the blush into the surface. By using a non/low blushing epoxy like West 105/207 or system3 clear coat you get better secondary bonding. When I start the inside of a craft the epoxy never cures hard till it is done. Same at the outside. I even apply light amounts of faring compound in places I know I will need it so it cures as one solid mass.
Naked Acres peel ply will also negate blushing if applied to the skim coat while its curing
@@tireballastserviceofflorid7771 How are you preventing the epoxy from curing hard before you're completely done? I'd have thought it would be very difficult to complete a project that fast.
Would it be a good or bad idea to build the entire boat from foam then fiberglass all the foam in one go, rather than the traditional fabrication method.
Of course fitting in solid material for were fixtures will be before the glass is applied.
If it is a bad idea, can you explain why.
Delll
Delll
Where do you get the foam?
were did u get the foam from
really good video.... I thought that the foam were formed the shape with a heat gun ...
What kind of epoxy do you use
Any epoxy brand that is formulated to be used in laminating glass cloth can be used - West System, System Three, MAS, Totalboat, etc.
How do you keep the foam from breaking down when applying resin?
The foam that is used is specifically made to be used in lightweight sandwich construction using epoxy, vinylester or polyester resins. This is not the polystyrene insulating foam that you find at your local hardware store.
@@CernyYachtDesign Which material is it?
What kind of foam do you use and where can it be found?
For this demonstration we used 5.5 lbs/ cu. ft Airex foam but any brand of closed-cell structural foam compatible with epoxy will work. The foam can be found at most online and local boatbuilding supply companies.
The foam needs to have a high shear strength, hardware shop foam does not work well at all. The cost of the hardware shop foam compared to the boat building foam will be a tiny percentage of the cost of the boat.
Does infusion bagging foam core remove any buoyancy benefits?
Dalt Wisney the foam has nothing to do with the flotation. Compare two boats, one built of foam one of metal, assuming they have the same weight and same hull shape they will have the same buoyancy. Check out Archimedes principle
No, the foam is closed cell which means you cannot suck the air out, open cell foam allows air and water to pass through it. Closed cell boat foams specifications always say whether you can use infusion, ie will not deform with 1atm of pressure.
Boat weight please?
Are there any books covering this technique?
Did you find any?
how strong is it ?
this is PVC foam?
Yes, structural PVC foam. For this demonstration we used 5.5 lbs/ cu. ft Airex foam but any brand of closed-cell structural foam compatible with epoxy will work.
@@CernyYachtDesign Thank you :)
thats preety cool. how much does it way?
*weigh
so you correct my misspelling but cant answer the question? Thanks.
JOEGGGJOE
I'm going to build one. I'll let you know when it's done, but I would guess 100-200 kilos.
ok, thanks.
So you answer the question but with made up units, thanks.
18'8"x 6'8" and 16.6 X 6'6" stringers full tank compartment live well and wash down tank
how you can fix core delamination in this kind of build
Use quality core that doesn’t delam and pre-coat everything with resin and let cure prior to glass layers.
Awesome video loved it are youbstill around
Looks like a great way to build except for the epoxy. Epichlorohydrin, one of the constituents of the epoxy resin monomer is a skin sensitizer. In addition, epichlorohydrin is classified as carcinogenic in the category, ‘presumed human carcinogen’, according to the EU classification.
Would the sealing (paint) prevent those effects?
@@CorvetteCarCraft It's only dangerous while working with it.
Tthat looks workable to the point any plonker can do it
whats a bulkhead ? that isnt a spacula . epoxy is resin?
Nice info, thx for sharing
what kind of foam.. my foam melts
For this demonstration we used 5.5 lbs/ cu. ft Airex foam but any brand of closed-cell structural foam compatible with epoxy will work. The foam can be found at most online and local boatbuilding supply companies.
Farriers method ... Works well
Very cool and clever
Good video !!!