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I am building Dudley Dix’s Argie 15 from a kit. On hold now in my barn during winter in Vermont. I plan to buy a 420 mast and boom, so, the most daunting task will be laminating and then shaping the foils. 
I was wondering if I am imagining this as being harder than it really is. But
I’m also wondering whether they could be 3-D printed from the plan drawings and dimensions. My son-in-law has the ability to 3-D print, but even if it was possible, is there any appropriate material to print with that could take the stress foils are subject to?

 Thanks, John 

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Daggers need to take a guy or guys righting a boat, rudders need to take max helm at full speed - both of these things mean that there aren't any commonly available isotropic materials that aren't metals that are up to the task. So you need decent timber, or composite, or extruded alu.

If your son in law has 3D printing, check he hasn't got 3 axis CNC - if he has you can rip down some nice cores in cedar and then laminate over them, hey presto. If it were a smaller boat like an opti you could get away with half inch plywood.

 

Equally if he can 3D print hollow aluminium you could be in good shape but I'm never too sure how good the metallurgy is for 3D printed metal.

 

Cheers

 

Dan

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3 hours ago, europa said:

I am building Dudley Dix’s Argie 15 from a kit. On hold now in my barn during winter in Vermont. I plan to buy a 420 mast and boom, so, the most daunting task will be laminating and then shaping the foils. 
I was wondering if I am imagining this as being harder than it really is. But
I’m also wondering whether they could be 3-D printed from the plan drawings and dimensions. My son-in-law has the ability to 3-D print, but even if it was possible, is there any appropriate material to print with that could take the stress foils are subject to?

 Thanks, John 

Yeah... no

Centerboards and daggerboards have to be pretty strong. You could 3D print the shape minus 3mm and give it a couple of layers of fiberglass.

FB- Doug

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24 minutes ago, Steam Flyer said:

Yeah... no

Centerboards and daggerboards have to be pretty strong. You could 3D print the shape minus 3mm and give it a couple of layers of fiberglass.

FB- Doug

Core shear failure.

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1 hour ago, fastyacht said:
1 hour ago, Steam Flyer said:

Centerboards and daggerboards have to be pretty strong. You could 3D print the shape minus 3mm and give it a couple of layers of fiberglass.

 

Core shear failure.

It's small, IMHO two layers of 18oz cloth both sides would be fine if the core crumbled away completely. Make it 3 layers if you want!

FB- Doug

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Thanks for the comments. I like the  idea to make a smaller core via printing, then wrap with glass/resin. That sounds doable. I will check with my son-in-law about his capability.

Going back to part of my original question, can the information contained in the plans and drawings that came with my kit be sufficient for him to 3-D print these cores?

 Thanks, John 

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1 hour ago, Steam Flyer said:

It's small, IMHO two layers of 18oz cloth both sides would be fine if the core crumbled away completely. Make it 3 layers if you want!

FB- Doug

 

19 minutes ago, europa said:

Thanks for the comments. I like the  idea to make a smaller core via printing, then wrap with glass/resin. That sounds doable. I will check with my son-in-law about his capability.

Going back to part of my original question, can the information contained in the plans and drawings that came with my kit be sufficient for him to 3-D print these cores?

 Thanks, John 

Bad idea. Fold up like a wet piece of cardboard. Without a shear web, you ain't got anything. The shear load has to go THROUGH the thickness, not magically around the perimeter. 200 lb guy pulling up and climbing and levering in waves = 2G so 400 lb at end of board. That's foo lb of SHEAR through the core...for the entire length that is cantilevered...not just at the root...This is why when you buy a Phil's Foils 505 centerboard it has a wood core. Because it can take that vertical shear.

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I see what you're saying about the vertical shear, that makes sense if you think about an I-beam and the fiberglass skin of the board being like the two upper and lower runs of the beam. Without a strong connection between the two, it cannot take any load in shear.

32 minutes ago, europa said:

Thanks for the comments. I like the  idea to make a smaller core via printing, then wrap with glass/resin. That sounds doable. I will check with my son-in-law about his capability.

Going back to part of my original question, can the information contained in the plans and drawings that came with my kit be sufficient for him to 3-D print these cores?

 Thanks, John 

Fastyacht is more knowledgeable than I... or most here in this forum, on this topic anyway... so taking his advice is a better idea. If it were my own boat, I'd give it a try but test the skin-only board first. Many small boat centerboards and daggerboards are laid up skins from a female mold, sloppily glued on a crappy core... they generally last but it's also true they can fail spectacularly when you need them most, like pulling the boat up from a capsize. You don't want that.

Another idea for those smarter than me to check... what about 3D printing the board (so it's basically a male mold that will stay in place) in two pieces, fore & aft, so there is a web of fiberglass between the two skins? Airplane kits do something similar to this foam blanks cut to form the wings, the web down the middle forms the main spar. A 3D print would be heavier, of course

FB- Doug

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20 minutes ago, Steam Flyer said:

SNIP

Many small boat centerboards and daggerboards are laid up skins from a female mold, sloppily glued on a crappy core... they generally last but it's also true they can fail spectacularly when you need them most, like pulling the boat up from a capsize. You don't want that.

SNIP

A

Welllll, let me tell you a story or three....

One of my 15 foot OD class boats had a fiberglass board. Skins over foam. One day, after touching bottom, it folded up like said wet cardboard. The core was foam, and whole thing made in halves. The skins had a feather edge bond on leading edge (it had a crack filled repeatedly before hand). The two halves of foam were joined by a zig-zag noodle of construction polyurethane adhesive (PL259 or whatever it is acalled).
I kid you not. and that adhesive bond let go in horizontal (bending) neutral axis shear.

So that was fun. I was 4 miles offshore at the time...

I also failed not one, but TWO plywood centerboards. One on a GP14, another on a 505. Fucking rolling shear. DO not make boards out of plywood. Very bad idea. The cross plies cannot take the  shear being reversed repeatedly and fail in "rolling shear"

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The Argie is not exactly a high-performance racer, so you can compromise in the direction of strength and reliability.  Laminating strips of wood, and then shaping with a hand plane,  is not that much of an issue, but I've also had some success with an unlaminated Jelutong plank, which you shape and then sheath in a couple of layers of fibreglass.  To quote Wikipedia: "Along with balsa it is technically a hardwood with many properties similar to that wood. These properties such as the low density, straight grain and fine texture mean it is easy to work with and hence popular with model makers and within the patternmaking trade."  It warps very little, which is why you can get away without laminating it.

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5 hours ago, CapSizer said:

The Argie is not exactly a high-performance racer, so you can compromise in the direction of strength and reliability.  Laminating strips of wood, and then shaping with a hand plane,  is not that much of an issue, but I've also had some success with an unlaminated Jelutong plank, which you shape and then sheath in a couple of layers of fibreglass.  To quote Wikipedia: "Along with balsa it is technically a hardwood with many properties similar to that wood. These properties such as the low density, straight grain and fine texture mean it is easy to work with and hence popular with model makers and within the patternmaking trade."  It warps very little, which is why you can get away without laminating it.

Dyera_costulata.jpg

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I have been convinced that 3-D printing is not the way to go. Thanks to all for your comments. I will get some lumber ripped for laminating and go from there.   The plans/drawings show an outline for the foil cross section. Would a solid template be of value?

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20 minutes ago, europa said:

I have been convinced that 3-D printing is not the way to go. Thanks to all for your comments. I will get some lumber ripped for laminating and go from there.   The plans/drawings show an outline for the foil cross section. Would a solid template be of value?

Ued. Female template. Ise it to check how your planing is coming alo g

You can 3d print it :+)

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6 hours ago, europa said:

I was figuring on 3-D printing the template, but hesitated to mention that.<_<

Thanks, John

When it becomes possible to "print" at home with a suitable structural core material, everything changes. Note: in the mid 90s we already had epoxy stereolithography but it was $$$$. There is a shop in S. Florida doing laser sintering of inconel that would blow your mind.

edit: but getting joins between sections is an issue. Would have to take shear. So scarfs with epoxy or other suitable that stick to material (plexus is a possible candidate). The regular stuff I've seen in small home machines I wouldn't trust for structure but give it time...

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  • 2 months later...

Easier to cnc a core out of divinicell foam or similar with a high density foam stringer or vertically laminated cedar then glass over it.. If u want to stiffen just cut your foam core with a slot to strip out the middle and lay carbon unis then cnc again.  Or cut a section out the middle and wrap then glue the thing back together.  Or cnc a temporary mould and lay up skin then lay a stringer up the centre for each side made of something wrapped in carbon or glass and fill the rest with foam and level up to 2 half's then epoxy glue together, can rebate the leading edge or create an internal tongue on each side so there is plenty of gluing surface. Need to get the two halves aligned though.  

I built a few foils in my condo. Easiest was the wood core method with unis, came out OK if a fraction heavier.  Despite my awful faring skills. 

Maybe if u could print just the skin u could glass in the structure inside.  But would need to know that the epoxy bonds to it. That might be doable. 

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  • 3 weeks later...
On 2/16/2021 at 3:17 AM, fastyacht said:

I also failed not one, but TWO plywood centerboards. One on a GP14, another on a 505. Fucking rolling shear. DO not make boards out of plywood. Very bad idea. The cross plies cannot take the  shear being reversed repeatedly and fail in "rolling shear"

If you cut plywood into strips, stacked them on top of each other and glued, then profiled that, you would have half the wood fibres going parallel to span as before, but the other half would not be parallel to the chord, but perpendicular.  Would that turn plywood into a good shear web suitable for covering with laminate?

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