Here is a great report from Frank Smoot about his new 24-foot trimaran LocoMotion. What he is able to do with so little money in so little time is, IMO, sort of amazing.
This is especially the case for us guys who seem to always take longer to do projects we thought would just take 1/4 of the time — and sometimes easily go over-budget too. (I certainly don’t have myself in mind here, nosireeeee, no way, it’s other guys I’m thinking of ;-)
Frank wrote this article with us in mind here at smalltrimarans, by they way … and we’re sooooooo glad he did. Many thanks my friend!
………………….
Our New 24 Footer – “LocoMotion”
By Frank B. Smoot, Jan 2013
www.DIY-Tris.com
Why would a guy with two 16’ trimarans need to build a third boat? Because this 24 footer does things the smaller boats just can’t do.
See, as much as I like my two 16-footers (one belongs to my wife, Laura), they have their limitations. I can’t seem to make them exceed 13 mph, and the ride is bumpy and wet in waves bigger than a foot or so. Plus, both of the 16-footers are just single seaters. They’re great estuary cruisers/explorers, but not really designed for “big water.” So we can’t take them out on Tampa Bay or the Gulf of Mexico to visit some of the local barrier islands that are so appealing.
My goal was to build something faster, smoother-riding, and capable of dealing with waves up to at least 2’. That meant a long, narrow hull with lots of freeboard and enough rocker to be nimble. I also had a couple of 85 sq ft unbattened “plain Jane” sails I wanted to use, so I wouldn’t have to pop for (yet another) rig.
Since these sails have booms of 11’6”, the masts had to be a minimum of 12’ apart. The only practical way I could see to get both of those sails and both my wife and I in a tandem seating arrangement was to design a 24’ boat. Luckily, that length could be built diagonally in my garage if I moved some stuff around.
While all of the dozen or so hulls I’ve built up to now have been 100% stitch and glue, I wanted to try something different this time. I wanted a truly sexy curved bottom, with none of the limitations that plywood imposes. My solution (inspired by a 40-year-old photo of an early home brew California catamaran hull) was to make the bottom 8” of the hull out of 4 layers of 2” Styrofoam – that blue stuff you can (sometimes) find in the big home improvement box stores).
So to get started, I just built a hull 24’ long with slightly flared sides (3mm ply) and a flat bottom of 6 mm ply. Then I turned the hull upside down and started gluing on the foam. I have to say, sculpting that much foam into the shape I wanted wasn’t something I’m eager to try again. The plus is that was able to get exactly the shape I wanted, but geez, is it a messy, fussy process!
Another plus is that I ended up with about 1300 lbs of unsinkable flotation – so much that that flat inner bottom rides 2” above the waterline! But of course, foam is about the most fragile hull material there is, and I always beach launch. Slamming into the shell-strewn beach (and occasional oyster bed) can really take a toll, so I had to make it tough enough for that. My solution was to cover the foam part with 4 oz glass, lapped on to the wood about 2”, and then to cover the entire hull in 6 oz glass. So far, it seems to be holding up.
Also, I am a huge fan of leeboards here in our sometimes-very-shallow local waters. Centerboards get stuck in their trunks when shells and other crud gets jammed in there from beaching, and daggerboards always seem to be in the way of something. Plus, both of the aforementioned require trunks that not only poke through the hull, but are invariably in your way, especially in very narrow boats.
Leeboards, on the other hand, work beautifully. My “friction-fit” pivot system keeps them in whatever position you put them with no need for a chunk of lead to hold them down. They simply pivot up and out of the way when they hit anything underwater, and they can be used to fine-tune your helm balance on all points of sail.
On my smaller boats I just have a single leeboard, directly operated with its handle. But on this bigger boat, I wanted twin leeboards to create enough lateral resistance to offset 180 or so sq ft of sail. And since they needed to be amidships, where I couldn’t reach them directly, they needed to be both synchronized and “remote controlled” – which ended up requiring about all the engineering creativity I could muster.
Finally, I wanted to be able to control both sails from my aft seat, so I set up dual controls for the main sail. Depending on which direction you ran the mainsheet, the main sail could be controlled either from my wife’s seat or from mine. After a few outings where I tried to get my wife to control the main while I controlled the mizzen, we both concluded that it would be “much better” if I just did it all myself ? And the truth is, the mizzen is pretty much a “set it and forget it” sail anyway, especially going upwind.
The resulting hull was so long and lean it lookd like a big gray fish. But how did it sail? To be honest, the first outing was not very encouraging. Although I had made a brand new set of 4’ leeboards just for this boat, I had been too lazy to make a new rudder, and simply “borrowed” one from an earlier boat. Also borrowed were a pair of “planning” 12’ long amas that had proved a bit too big (and hard-riding) for one of my earlier 16’ boats.
On top of that, my “remote control” setup for simultaneously raising and lowering the leeboards didn’t work as intended. Just couldn’t get the dang things to stay down! And I also didn’t have vangs on either boom. How I (and the sails) survived for a few years without them still amazes me…
Yet another problem we encountered showed up immediately as we launched into a headwind. The smoothly rounded hull bottom and the barely-in-the-water leeboards just didn’t provide enough lateral resistance, so we very nearly ended up in the mangroves before we’d gone 100 feet!
The “final” major shortcoming of our maiden voyage was that I had opted for us to sit in smallish folding beach chairs. I mean, hey, the floor was flat and sturdy (covered in 6 oz glass) and the chairs were just one more thing I didn’t have to make myself! Well, we soon found out that this, too, was a bad idea…
Once we finally got out into open water, we found that the boat was plenty quick — but not at all nimble. In fact, it was all I could do to get it to come about. Bottom line: This was NOT a fun boat to sail. Verdict: Time for some changes!
What to change? Over the next week or so, here’s what I spent my time doing:
• making a big new rudder
• adding fins (skegs) to the amas
• making a line to hold the leeboards down,
• replacing the beach chairs with fixed seats
• putting vangs on both sails
Result? The 24-footer is now an excellent boat! It goes really fast and comes about easily and almost instantly. I took out my tracking GPS (Garmin Colorado) and discovered the following:
• Top speed (with smaller sails) of 13 mph on a beam reach in 11 mph of wind.
• Points a bit less than 45 degrees off the wind – and makes an astonishing (to me) 9 mph while doing it!
• Comes about almost as quickly as our 16-footers, and never gets stuck in irons.
Now I think it’s a truly amazing boat – smooth as glass and quick on all points of sail. Here are a couple of videos:
Video 1: First sail with “teething” problems fixed:
Video 2: Bunces Pass, FL (near Ft. DeSoto State Park):
I’ve tried this boat now with a variety of sails and the best combination for performance is the 102-sq ft main coupled with the 85-sq ft mizzen. This is the setup we used at a recent meetup of the local trailer sailor’s group, where the wind was 11 mph or better all day.
The “going home” leg was directly upwind for the 2 miles back to the launch point. We (Laura and I) were one of the last to head back, yet we got there so far ahead of everyone else we could barely see them still tacking in. Here’s what our group president said about the 12 boats in attendance when he listed them in an email blast later that day: (We’re #5 on the list – I’ve delete the other names):
1 – O’Day Daysailor – Ft Myers Beach (visiting guests)
2 – Norseboat – had best looking boat
3 – Goat Island Skiff – excellent swimmer and boat rescuer
4 – SP Tri – (dinghy racers from Englewood)
5 – 24 ft Tri – Frank & Laura Smoot – fastest damn thing I’ve ever seen
6 – Escape Rumba – [ ]& daughter – a great sailor
7 – Tri Kayak – back from Georgia!
8 – Potter 15 – solo today
9 – Paradox – Got the cabin top on!
10 – Hunter 26 WB – with lovely lady (forgot name) from Michigan
11 – Sail Canoe – sailed to the ramps
12 – [ ] – visiting – no boat but owns an O’Day DS
“Fastest damn thing I’ve ever seen?” Hey, I can live with that description! And in a subsequent “name the boat” contest, someone suggested “Locomotion.” I thought it was perfect for this boat, and am going to spell it “LocoMotion.” Just seems to fit…
I gotta tell ya, this 24’ tri is just amazing. Points higher and goes faster upwind than any boat I’ve ever seen — and it cost under a grand to build it. And that’s consistent with my ongoing goal as an amateur designer/builder/sailor to make boats that will deliver 90% of the performance of “commercial” boats at 10% of the cost. So far, so good!
Cheers – Frank
Click here to visit Frank’s website at DIY-Tris.com for more on his boats and projects.
Nice boat! The foam bottom makes a very seaworthy option — I am considering it for my next boat but worried about the foam hitting the beach, so I am wondering if a wooden keel going down the center of the bottom, cut to the planned rocker curve with the foam faired flush with it, will provide some protection with only a moderate addition of weight?
Does it have good leeway with that tiny leeboard? I had a 4 foot leeboard on my 16 foot outrigger with only 90 square feet of sail on it and needed to move to a 5 foot board (3 feet of board clear under the bottom of the center hull) to get to windward (footing vs. just pointing) decently. Carry on!
Again, thumbs up for Frankie !! Great job. I’m going to steal some hints from this one, in particular adding some floatation BELOW the waterline thus rasing the whole hull which in return raises also the amas and reduces drag ( while rasing the amas in the attempt of getting them out of the water may just sink deeper the main hull, as it happened to me )
As for Wade’s question which I also asked myself,of supporting the lay up and foam with a wooden profile, I’d perhaps gor for one more layer of 6 oz fibre set in epoxy. This will add up to more most boats would have anyway, and without an inner core to support the external skin.
Another option is to choose a more costly outer layer. Live with blue foam inside, but then add a 1/4 or 1/2 inch termanto on the outer side. This is structural foam and bonds very well with epoxy but density is almost triple than styrofoam (it’s the red stuff that fishing corks are made of basically: expanded PVC). Not to mention the cost…
Let us know what you did :-)
I like Wade’s idea, which isn’t much different from how surfboard stringers are set up- you could even draw out the rocker on the ply and then glue it up with the foam in a big block, and then use a power planer to take it all back to the rocker line.
Another way to do it would be to cut the final curve on the ply stringer, laminate it all together, and then use the stringer as a guide for a hot wire. Also you don’t have to limit it to one stringer and can use multiples both for strength and as guides for further machining/shaping.
Once the hull is shaped and covered, for something subjected to serious repeated beachings I would probably go one step further by adding some type of sacrificial strip of plastic or metal that would act as the direct point of contact.
I really like the boat and the new amas really make it all come together….one question I have is what was the issue with the seating? I’m still not clear why they didn’t work as planned or what the fix was…
Hi Guys – I never put keels on my boats because the water here is so shallow, and it also makes coming about much slower on tris. The foam bottom has two layers of glass, so I think it will be strudy enough – especially since I only beach it on sandy places. Sorry if I didn’t explain in the article just how sturdy I have tried to make the hull bottom. And yes, the foam provides so much flotation that the flat floow is about 2″ above the waterline!
As for the lateral resistance, there are two very big leeboards on the hull as well as two fins on the amas. It points higher and goes faster doing it than any of my other boats, or for tha matter, and of the boats I’ve sialied with – keeled monohulls included.
The original seats were beach chairs. I was looking for a quick and cheap solution – but that wasn’t it. Not only were they uncomfortable, but they also moved aroun too much. Now I have some cheapo moulded plastic seats mounted on pedastals I made. They work great – stable, comfortable, and totally weatherproof. In fact, I’m using the same seat on my new 19′ tri.
Cheers – Frank
What is the area of the leeboards that extend under the hull? You have about 160 square feet of sail, so going by the rule of thumb of “leeboard area should be 4% of sail area” (daggerboards with the hull bottom serving as an end-plate can have less area) that suggests a need for 6.5 square of leeboard (not counting topsides bearing surface) — I am a rank amateur, so I’m just repeating what other pros have told me, and I’m very interested in others’ experience since for the foreseeable future, all of my outrigger craft will use leeboards. I suppose the faster the boat sails, the more the dynamic pressures on the board will replace board area? And the situation changes if you use assymetric boards. No critique of your design, just curious.
I read all the same stuff you read, Wade. How much of it is true, I can’t say. But I have sailed one or another of my boats for several hours at a time, about three times a week for the past 3 years, so I can at least tell you what my personal experience has shown.
The twin synchronized leeboards on the 24 footer (AKA “LocoMotion”) extend about 32″ below the waterline, and are 14″ wide at the bottom. So conservatively, they give me about 5 square feet together. And the ama fins are 8″ x 30″, so whichever one is in the water is giving me another 1.6 sq ft or so. What I can tell you for sure is that this boat goes upwind like gangbusters. We can make a steady 9 mph at 45 degrees off the wind if the wind speed exceeds 10 mph.
This blows the doors off of any other boats we’ve sailed against. At a recent meetup (West Coast Trailer Sailors) the group had about a 2.5 minle run dead upwind to get from where we were gathered on the beach to our launch point. We were about the last to leave, but by a wide margin the first to arrive. We not only outpointed all the other 11 or so boats, but went a lot faster doing it.
To quote the group leader, “Fastest damn thing I’ve ever seen.” I’m not 100% sure why this boat is such a screamer upwind (and on all other points of sail) but that was definitely my goal when I built it. Waterline length is almost 24′ and the waterline beam is about 23″. Coupled with the 187 sq ft of sail we were carrying that day, you’re gonna have a pretty quick boat. Plus, it weighs only about 350 lbs fully rigged. So I have to say, although there was a definite learning curve to sail it well, it has exceeded my best expectations.
– Frank
Frank,
Great job! The photos and your write up here do a very nice job of showing off your design and the detail that went into this truly successful project. You have reason to be proud. And at nearly twice the weight, similar sail area and a shorter (17.5′) waterline, it’s clear Dalliance will be easily out paced by LocoMotion, come Cedar Key this May. I look forward to meeting you and swapping stories and design ideas. My boat has been a progression with parts being repurposed from one incarnation to the next. I still have parts on Dalliance left-over from the 16′ CLC Millcreek Kayak that grew into my first small trimaran, Oceanid. The first set of akas I designed for my boat were also blue builders’ foam. The foam was built up to an 8″ BOA with a plywood keel/stem/profile (ala Gary Dierking) and short fins like your’s for lateral resistance and protection from oyster bars.
There appear to be some significant similarities between LocoMotion and Tribal Menace
designed by Chris Ostlind. But I don’t think he has had the pleasure you have here, in that I am not aware of completed build of his 22.5′ Everglades Challenge intended trimaran just yet. Have you had the chance to share any thought with Chris? He is pretty prolific with his designs, and seems to favor fast day sailors too.
Joe, I am a first time poster here, but a frequent visitor. Thank you for the fabulous work you do in bringing us interesting stories and news, and in promoting small trimarans.
I am sure I do not comprehend the magnitude of maintaining a continually interesting quality blog like this, but please do keep up the great work!
Hi Ron, and welcome to Joe’s first-rate blog! Great to see you here. I’m sure that Joe would love to have you write an article or two about Dalliance. I have always admired her from afar – mostly because my small tris couldn’t catch her :) She’s a work of art, and I definitely look forward to swapping stories at Cedar Key. I talked Laura into coming with me this year, so I’ll be able to bring LocoMotion. (Unless / until I turn it into a folder, it requires two to launch.)
I haven’t communicated with Chris Ostlind, but I have seen many of his great designs. He does seem to share an interest in quick day sailers, so one of these days I hope to meet him as well.
I also want to build a camp-cruiser. One of the reasons I don’t spend more than Saturday at Cedar Key is because I can’t sleep on any of my boats. Perhaps when I see Dalliance up close, I’ll be inspired to remedy that.
Looking forward to meeting you at Cedar Key, and possibly at the EC “fleet assembly” on March 1 as well.
Cheers – Frank
Thanks for previous answers. I want to ask one more before I start on my own foam-bottomed outrigger. I have assumed that the foam need merely be scored with a 50 grit sandpaper before epoxying the blocks together. Did you use any other trick to ensure the foam lamination stays together, aside from glassing over it all onto the topsides?
Hi Wade – I didn’t score or rough up the foam sheets at all before gluing them together. I don’t think it’s necessary. I uses PL Premium, which sticks fine regardless. But next time I think I’d look for a contact cement of some kind, because anyplace you cut into the PL Premium it tends to tear out chunks of the foam. Any contact cement should be plenty strong for the job, and would also eliminate the tearout problem.
The strength of the overall structure comes partially from the two layers of glass over the foam, and partially from the 6 mm ply flat floor that the foam is glued to. (I would uest the PL Premium here again, but not between the foam layers).
Hope this helps – Frank
Hi Ron,
Thanks for your kind words (I changed the wording in your post to reflect the reply you sent a little while ago). It’s guys like you that make smalltrimarans.com a fun, informative and inspiring resource for lots of us “little tri folks” all over the world.
And YES … I’d love for you to share some info and pics about “Dalliance” (assuming she is in trimaran configuration). Great stuff!
Joe
In regard to Wade’s question, one trick that can help when assembling and shaping a laminated foam block like this is to use strategically placed wooden dowels and epoxy as tie rods to “pin” the sheets together before shaping…kind of like a long wooden rivet running at right angles to the plane of the stacked sheets.
If you run them long you can use the extra bits sticking out like cleats to lash it all together with twine and hold the sheets tight. When the laminating glue cures the block will stay together rigidly while it is in the un-glassed state with almost no chance of it coming apart even under very aggressive machining.
One safety warning: If you use epoxy or anything that cures hard as your laminating adhesive, be *extremely* careful when shaping laminated foam sheets, as the exposed edges of the cured adhesive can cut you like raw sheet metal if you slip while shaping, or more likely when you unwittingly rub your hand across the surface to feel your work or get the dust off.
Wade, if you use contact cement (as I definitely will next time), there’s no need to pin the sheets together at all. They will stick on their own – with so much adhesion you won’t be able to separate them. Ergo, you’ll need to make sure the alignment is spot on before you allow them to touch.
PL Premium, on the other hand, gives you the option of moving things around after they touch. But you’ll have to use weights of some kind to hold the sheets together until the PL Premium sets — and hope you don’t encounter any of that very sturdy glue during the sanding process!
Cheers – Frank
To Frank: for tue gluteing process i would use rope and spanish windlasd . Please tell us more of how ti SHAPE the foam
Thanks for ideas.
Frank is right that you don’t need the extra mechanical strength of the glued in wooden pin idea, but one other advantage to using that type of thing is that allows you to register the sheets for perfect alignment when gluing- just get the block of sheets where you want it, ram a couple of un-glued dowels through and then you can dis- and re-assemble it as much as you need to with everything matching back up perfectly.
another thing that comes to mind is that while large foam shapes like this are very feasible structurally, building a big block of foam that will have much of its volume removed in shaping can add a lot of expense for little real benefit to the final product. Even “cheap” foam is incredibly expensive these days, and sure, it’s easy to cut and shape but the resulting dust and scrap is a huge mess of previously valuable material.
For that reason if I were doing a shape of this size I’d do the rough shaping of the lines by cutting the various curves and profiles on the individual sheets prior to gluing them, using the pin registration thing to keep all the puzzle pieces oriented as they go together…then once it’s all glued up all that is left is to take the ridges off.
It might seem overkill for a one off experimental deal but especially if you are using expensive marine grade materials it could be a substantial savings both in materials and labor…and if you wanted to do the work, you could also selectively remove interior material for even greater weight savings over a monolithic block of foam.
I’d suggest that anyone interested in this type of construction look to surfboard shaping and manufacture, not just foam/wooden stringer type modern boards but also earlier balsa and redwood boards that were not just planks but very sophisticated assemblies of separate elements that use integral voids that help with overall weight, weight distribution, tuning of rigidity, etc.
This is an extreme example, but illustrates what I’m talking about-
http://www.tpsurf.com/tp230/large/L-113_1310.jpg
note that you can orient the plane of the sheets vertically or horizontally…and you can mix the two as well. You can also bury all manner of reinforcement inside the foam plug- even a single layer of FG cloth/resin between two sheets will stiffen the entire structure a lot, and by cutting in channels that allow the glass to deform when it is being wetted out, a lamination like that can form internal stringers and ribs that are much like the stamped shapes in car floors and pickup truck beds that add rigidity.
Hi Stefano – It’s not nearly as much of a “fight” to get the foam stuck to the flat wood bottom or to itself. The bottom of my boat had only about 1.5″ of rocker over the 24′, so the foam in 8′ long piece took the curves very easliy. I’d use PL Premium to glue the first layer of foam to the ply “false” bottom of the boat. Then Id’ put weight on it until it was set (6-8 hours) , and then the contach cement will hold the suibsequent layers together simply by contact, with no weight needed.
Shaping the foam is much trickier than installing it. Did you look at the pages on my web site? Thsy give a prettly good overall explanation of the process and sequence. I would not be in a hurry to do it again, as it is VERY exacting and I’m a bit too lazy to do much more of that. It’s more art than science, but keeping it both fair and symmetrical is a bit of a challenge.
Details at http://www.diy-tris.com/2012/10-24-footer.htm
Cheers – Frank
The foam really isn’t all that expensive, and yes, the pieces were cut roughly to size before installation. Positioning dowells are simply not necessary, would constantly be in the way, and would have to have theholes filled later on.
Have you been to the site to see how I actually did it? I can’t imagine a simpler or less wasteful approach. The whole idea of pins and registration is not only unnecessary, but would add time and labor that need not be spent with the much simpler method I used.
– Frank
Didn’t mean to step on anyone’s toes- and I certainly didn’t at all mean to imply that there was anything wrong with doing it simply…just saying that there are a number of ways to build a foam cored structure, that can address things like structural rigidity and the need for extra framing, or can save shaping time, weight, money if you are using very expensive materials, add some desired functionality or extra safety margins, etc.
There are a lot of overlapping industrial applications with well developed technologies for doing this type of structure that as I said may or may not be overkill for any particular project or budget…but even something like a hot wire used to cut high tech composite aircraft wing cores is dirt simple to DIY as technology goes, so taking advantage of the technology *if you need/want to* is not as involved as it might seem and there are all manner of very simple foam shaping and covering tricks and tools used by surfboard shapers and aircraft builders and sculptors and sign makers and auto body people that are out there, should anyone care to look them up…and my saying so is only intended to add to the reference base here, not take anything away from anyone’s personal experience or cast aspersions on their creations.
My main point was that with sheet foam you can do the shaping work on a big block after assembly *or* sheet by sheet, and I never intended to give the impression that one was better or worse, and of course there are pros and cons to both. Same goes with refining the plug assembly process to add layers of reinforcement fabric or a stringer or backing plate in a glue up **that you are doing anyway**- that kind of addition can do amazing things for the strength and stability of the structure both during machining and in use, with hardly any addition in time or complexity or cost considering the final benefits- remember, the assembly labor happens whether or not you insert the extra goodies or not.
Simply stacking some sheets at right angles and laying some glass cloth or plywood in the glue up can create longitudinally oriented internal box and I-beams in a foam plug, out of nothing but a few extra cuts through some foam and a few bucks in reinforcement materials, were someone to be concerned about overall rigidity or wanted to fine tune it. If someone wants to do selective removal of internal areas of the plug sheet-by-sheet or add stringers or cockpit drain plumbing or something where they needed to disassemble and re-stack and finally glue things with great accuracy, the time and labor to set up the pin registration is that needed to get a dowel, and ram it through a stack of foam sheets where it won’t get in your way, or take it out when it does…this is garage tech, not NASA.
Whether or not it is worth the effort or “needed” is totally a matter of subjective assessment by the builder and I’m not questioning anyone’s particular choices, just pointing out that the real beauty of working with sheet foam is that there are so many options on putting it together and covering it that have so many benefits to exploit should one decide he needs or simply wants to do so.
Not that anyone *has* to use them or *should*, but they are out there and while I’m all for simplicity, sometimes other factors take precedence and the simplest or quickest method isn’t necessarily the best for everyone or every application.
It’s all good Ian :-)
to Ian… I am curious about hot wire links for shaping without too much dust…any hints for the database records ? Thanks in advance, Stefano
Hi Stefano-
There’s a number of sites that go into the technical aspects of setting up a cutter, which is essentially a high resistance wire that heats up without burning up when a current is applied…it’s an easy DIY but it is *extremely* important to understand that done improperly such a rig can kill you by electrocution, so be careful and only try it if you know what you are doing with electricity.
Anyway, here’s a basic “bandsaw” style setup –
http://www.spacemodeling.org/new/how_to/foam_cutter.htm
and one with a hand held frame that would be better suited to free form cutting of large shapes-
http://www.public.iastate.edu/~orman/air/cutter/hotwire.html
here’s some commercially available tools-
http://hotwirefoamfactory.com/home.php
I can’t attest to the suitability or ultimate safety of the electrical portions of those DIY designs or to the quality of the commercial stuff, but I can say that even with a commercially built unit it will take some practice and fine adjustments to get everything running really smoothly at any particular feed rate…when everything runs right you can get incredibly accurate cuts even over long spans, but too little heat or too fast a feed can cause the wire to distort or even break due to drag and/or getting glued in place by melted material cooling in the kerf before the (too slow) wire gets past it.
The opposite situation of too much heat or too slow a feed rate can cause more ragged cuts and re-adhesion of the cut parts due to globbing/pooling of extra melted material, and larger kerfs that decrease accuracy.
The trick is to keep the kerf thin enough for smoothness and accuracy, but not let any of the waste material get re-bonded to the shape you are cutting either because the kerf is too narrow (wire too small or cold) or because you melted out too much material and it bridges the gap (wire too hot or slow).
Also, keep in mind that the longer the span you are cutting, the more you will have issues with keeping uniform heat across the cut using smaller wires, as well as issues with tension and keeping the wire from bowing and running off track…at some point you need to almost build or modify the system for the particular cuts you need to make, rather than developing a one size fits all carving tool.
The cut and operation is probably most like a band saw, if the blade were to be a laser beam instead of metal- you can move it in any direction perpendicular to the wire and cut things like letters and 90 º angles without having to reorient the workpiece as you cut, the way to have to with toothed saws.
One neat trick is to use heat resistant templates that define the edges/ends of the profile you are cutting, that are lightly attached to the plug and act as guides for the hot wire-this is how multiples of things like lettering and tapered airfoil cores are cut, and strategically placed hard layers in a sheet foam plug lamination could be pre-shaped in a similar manner, so that they acted as templates to guide a cutting wire. It would be a lot of setup work up front in exchange for minimal carving at the end, but could give you far greater accuracy than less technical machining, plus surfaces that require little or no extra sanding or fairing.
This is more or a strip planked on frame core, but shows the kind of technical detail and integrated sub-structure that can be shaped in a sheet foam core with very simple hand tools-
http://hotwirefoamfactory.com/customer/gallery/industrial_davel_b.htm
even though that shape is formed by bending strips over a frame, you can see that it could also be built up in flat layers oriented horizontally, vertically or in combination and the curves could be pre-cut rather than bent…the sections can even run athwartships-
http://hotwirefoamfactory.com/customer/gallery/industrial_karap.htm
Doing an entire hull that way would be a lot of work if you don’t have a CNC wire cutter, but one place where the technique might be very useful is in creating concave hull sections that might be difficult or impossible to cut in an accurate single pass with a wire…think something like a very flared powerboat bow shape or bilge turn.
To do something like that wouldn’t even require orienting the cuts for the entire plug that way, and various tricky curves or areas that need great accuracy can be shaped as sub assemblies and combined with less technical shaping methods where those make more sense or where there would be little benefit to using the wire. Very detailed molds and plugs for lost foam and concrete casting are often made this way.
Speaking of lost foam, while it is traditionally used with hot metal casting, you can also use a foam plug as a basis for a laminated shape and then use solvent to eat away the foam leaving a shell…not an everyday need and exceedingly toxic, but it just goes to show you how many ways you can manipulate this stuff with simple tools and tricks-
http://www.rcgroups.com/forums/showthread.php?t=188980
Amazing info with links Ian!
One other benefit of the wire technique is that it allows very precise shaping of a variety of foams that can be very difficult to machine accurately, like expanded polystyrene bead based foams that are super cheap but make a mess and don’t hold much detail when cut and sanded. A hot wire makes EPS a very attractive material when it is probably the worst foam to work with using traditional tools and methods, except for the price.
Wire cutting can also create very detailed profiles the slick, soft/flexible polyethylene and polypropylene foams used in packaging, pool noodles and flotation devices, which in turn can be used in molding operations where you need a curved line or a press fit… they’re stiff enough to take the pressures of molding without ever snapping, and even intricate undercuts can still be easily removed due to the material’s bend-y, compressible and if you need it, easily tear out-able nature.
For something like damming off a hull and creating bulkheads, the compression allows for very tight seals with minimally accurate cut shapes…you can just put the slightly oversized sheet foam backer station form in with maybe some hot glue to keep it in place, lay up against it with no mold release needed, and then pull the foam out after it cures…and because the foam bends easily, that bulkhead form could be curved as well to add foot room or form an integrated back rest or tank wall.
Using that kind of foam and a hot wire after you are done molding hulls you could also do things like make custom fitted flotation elements or chafe guards, or integrated bumpers or seat padding out of the softer foams, all with high accuracy and little to no extra work needed to finish the parts.
I briefly considered hot wire forming for this foam hull, but very quickly realized that it was impractical for a such complex / compound shape and would ultimately have required much more effort than the approach I used, which was quick, simple, and accurate.
– Frank
Hi Frank,
I totally get where you are coming from and agree that the wire cutting wouldn’t have been much of a benefit in creating a single unit, unless you already had the tool at your disposal and were going to use it to rough in the shape.
And even then, one other potential issue is that the cut from the wire forms a skin of sorts of melted material, that is harder and denser than the surrounding foam and can make integrating the wire cut portions of the shape with the virgin parts more difficult to do.
The end effect is like dealing with wood that has very hard and soft grain combined, where the pressure and time needed to sand through and shape the hard stuff can easily take away too much of the softer parts.
So you are absolutely right to be concerned about potential pitfalls and added effort that won’t improve the boat; it’s very possible to go there. The method you used is tried and true and the results speak for themselves.
One thing that I didn’t see in your article was any description of the foam that you used as far as the actual material type and structure- compatibility with glues and resins is another piece of the puzzle when doing this kind of build, and some things work together well and some foams will self destruct the moment they come in contact with things like polyester resin…that’s one advantage to the pricier marine/aircraft grade foams that are engineered for this kind of procedure, over things like insulation foam that isn’t designed to do anything but sit there.
There’s nearly always a work around (epoxy is pretty benign in this regard), but anyone considering this type of build needs to be aware that just slapping any old resin over any old foam can cause all of your hard shaping work to literally melt before your eyes.
Same goes for solvent based adhesives that can cause the mating surfaces to melt and actually draw away from each other…in your pics it appears that the foam you used is clad with a thin layer of plastic film and I’m wondering how that might have affected things like the adhesive selection/glue up and subsequent shaping- PL premium will definitely melt a lot of foams but something like the plastic or foil found on typical foam insulation panels might allow for more adhesive options by keeping the glue isolated from the foam itself.
PL Premium was created to be a construction adhesive. As such, it is quite compatible with all common foam types used in home construction – the blue stuff and the white stuff and the pink stuff. I have never seen it “melt” any kind of foam. Any plastic sheeting on the outside of the foam needs to be removed before using it in a sculpted hull, as it will interfere with both sanding and epoxy adhesion.
The downside of PL Premium is that it sets up harder than the foam, which leads to tearouts when shaping. If I had it all to do over again, I’d opt for some kind of contact cement.
Hi Frank,
There are different formulations of PL and similar construction adhesives that are designed specifically for foam, that are water rather than solvent based or eliminate most of the solvents so as to not cause the foam to melt.
But the term “construction adhesive” on the tube does not in any way mean that one can safely assume that a product is compatible with foam, or any plastic for that matter. Trust me on this one.
http://www.halloweenforum.com/halloween-props/78945-liquid-nails-ate-my-homework.html
PL has a product specifically designed for foam insulation board with one of the listed features being “Foamboard compatible -Will not attack or burn through foamboard (if used as directed).”
http://www.loctiteproducts.com/p/pl_ca_300_voc/features/Loctite-PL-300-VOC-Foamboard-Adhesive.htm
The regular PL premium may work fine for certain applications, but they specifically don’t recommend it for use on certain plastic-
Not Recommended For
Water submersion applications
Polystyrene, polyethylene or polypropylene
Plastic Tub Surrounds
Certain materials such as rubbers and plastics may have bonding difficulties; test before use
http://www.loctiteproducts.com/p/pl_ca_prem/overview/Loctite-PL-Premium-Polyurethane-Construction-Adhesive.htm
again, not knocking any particular product or method and I’m all about using the wrong tool for the right job…I’m just pointing out that there are a few pitfalls to be aware of when working with foam and covering it…as more and more products go low VOC it will become less of an issue, but the fact that PL and others still make foam specific adhesives tells me that non-compatibility is still something to consider when choosing materials…
one other thing to consider is that an adhesive may have very different results with foam depending on how easily any trapped solvents can escape- if the joint is relatively small and open you are less likely to have issues, but in something like a sheet lamination where those solvents can get trapped, the added exposure time can present issues.
Even some low VOC glues still have enough solvents in them to do this, so testing is the key, as is ventilation when using the stuff not just for health and fire safety but to keep the VOC concentrations low.
So- just be careful…or don’t :)
http://www.youtube.com/watch?v=aqomKnvF2Uk
For what it’s worth-
Most open cell foams and some closed cell varieties can be glued with water based wood glues like Elmer’s, Titebond, etc. and the bond will be *very* aggressive.
You can also get a contact cement like bonding action with these glues by applying them in a similar manner; coat both surfaces, allow to dry slightly (not as long as contact cement though) and then press them together.
It might need extra clamping until cured if you are bending the sheets to pre-shape your plug, but the final bond is super strong due to the fact that these glues excel on porous surfaces.
The other big benefit is that you don’t have to worry about your covering resin getting into the seams and loosening the exposed glue joints in the lamination before the covering hardens. You may never have had this type of plug begin to come apart when the resin is applied and softens up the glue joints, but it *can* happen…again, trust me on this one.
hi Frank, sorry to bother you here, when I clicked on your email at your website it wouldn’t go thru (my end, not computer effective)…anyway would like to try and build one of these, do you really think a novice can build one? seems like many tools needed (although basic)…probably take me ten years! Robert – pestpro77 AT yahoo DOT com