PVC Structure and Laminations

[PAR]

Having punched up some math for the problems with this idea, a few conclusions have cropped up. The biggest, as guessed is weight, by as much as 152% (depending on pipe diameters and filler needed) heavier then a solid laminate, using the lowest density foam and thinnest sheathings possible. Using typical schedules for layup, near twice as heavy as a one off single skin and even over the heavyset of chopper gun jobs done in the early 60's. This clearly isn't good.

The puncture resistance is lower then single skin, the cost is much higher, unless the PVC is free. The structure will have great longitudinal stiffness, but not much else without additional structure.

If the additional cost could be offset by strength and the lack of internal structure (like strip planking) then the costs come close to balancing, but the athwartship strengthening issues crop up and the idea goes back in the round file.

I was hoping the poly would make the thing work, but only amounted to a 30% difference over unrefined epoxies. The problem is the cost of PVC pipe and the amount of filling needed to make a fair surface from less then fair building materials, plus the skinning. A 1/4" laun plywood core would cost much less, yielding 32 sq. ft. per sheet for less then 10 bucks. 32 eight foot sections of pipe will cost considerably more and not have a reasonable fair surface to work with, let alone need welding.

The weight issue is staggering once you add everything up. Conventional, heavy wooden construction is actually lighter and anything under 30 feet rivals steel in weight (seen many steel 24' day sailers lately?)

Conclusion? Build your yacht in plywood. Use a radius chine design and strip plank the chine area using this method, but everything else with more traditional techniques.

 

[gonzo]

That's similar to what I figured. Also, the labor of fairing several times that of other methods. Laminating and fairing would require a very high level of skill. It seems very difficult to fill all the voids.

 

[JCFARER]

Hawdy all...

Well... boo hoo. It looks like we are all beginning to agree that this thread has just about come to a closing. I'm beginning to think that if PVC had a possibility someone would have possibilitizized it.

Shall we all say tada to this?

Jay

 

[gonzo]

Not really. There are possiblities for PVC. For example, sponsons on rigid inflatable lookalikes, rafts and pontoons. Also, rotomolded boats are great. Perhaps there are aplications for tubes.

 

[JCFARER]

Not really. There are possiblities for PVC. For example, sponsons on rigid inflatable lookalikes, rafts and pontoons. Also, rotomolded boats are great. Perhaps there are aplications for tubes.

Hello Gonzo...

It's good to see that you haven't laid down arms yet...but although these sound like they have a possibility in those applications...I was trying to find the possibility for its use and strength on a different level.

I will however continue to participate in brainstorming this out if it helps anybody that may have a different thought for its use. I would think that as a one piece pipe it would do great for sponsons. How would it apply to rotomolded?

Jay

 

[gonzo]

How about using heat and air pressure to modify the shape of a tube?

 

[nero]

Becarefull when suggesting a change in shape. I got scolded for it! smile

 

[PAR]

The cool idea in this method seems to be (at least to me) the ability to edge set or twist the plank material (pipe) without opening a bevel or seam as the material is bent around a set of molds. They can then be welded or glued (if a satisfactory one can be found) without regard to the cove, bevel, seam or other, edge to edge matting surfaces being misaligned. This is a big time saver.

The weight issue could be overcome with design and much less a problem in yachts over 40'. Leveling the areas between the pipe joints is another issue that could be solved with some engineering, but the weight would need be quite low as PVC isn't a light material itself, much less with foam stuffed in it.

Heat can be used to soften the pipes, but very special molds and a big press may need to be employed to make this idea work. Maybe an autoclave and vacuum bag sort of thing (Luders style) could produce the temperature and pressures needed. More tooling and special equipment means only production work would make this cost effective, one off's haven't a chance.

A chemist may have a few answers for you, JCFARER, try and find one in their junior or senior years at collage, maybe fresh out, and see how hungry they are for an interesting problem. Besides, hanging out at the local university can be quite interesting if you're single.

 

[JCFARER]

Hallooooooooo:

Been a while... how are all. Decided to do a little inshore cruising. Went down to DC and visited the grandkids...then went to Fla. to visit an old bud of mine. The ICW is one hell of a ride...those that haven't tried it should give it a shot. Have a whole other naval community in that thing. Anyway...I'm back. Wow...didn't miss much.

Par...you're the best, but perhaps we need to leave this one alone. Chemist's sound great, but the single hangout thingie ain't happening. I think that you might be right about your last one, but the changing of shape and all of that defeats the purpose of simple and quick. An old friend of mine lines the 6 inch sewer lines in New York with the PVC. Basically they put this huge roll in a "chariot" which is a covered trailer and they soften it by steaming it with a 9 horsepower boiler. Once it is soft, they pull it from the upstream manhole with a winch and after it is through the sewer, they plug one end and connect the other with the boiler again at certain pressures for specific amounts of time. The steam expands the tube and creates a mechanical bond due to the differing pressures. To complete this, although it is not relevant, they go in with robotic cutters and cut out the lateral connections to the homes. Anyway, I think that the steam idea might work pretty well for the softening of the tubes as long as you can control the shape somehow which sounds like it would be difficult.
I put this out there just to keep this alive.

Man, what do you think about not filling the grooves on one side to reduce weight? How do you think it would look if the outboard side was left with the grooves. What about the strength factor again?

Jay

 

[JCFARER]

How about using heat and air pressure to modify the shape of a tube?

Ahem...

No changee the shapee Gonzo..NO NO NO.

Jay

I think my grandfather used to scream that at me sometimes long ago when I used to try to reshape his face.

 

[Virusxyz]

PVC panels

Pvc pipes sound like an interesting idea, but I have seen a boat made from PVC panels. It was a Porta-bote, a small folding boat that some people use for tenders etc. It seems like an interesting medium that could be explored further on bigger boats.

 

[Scoots]

I was lucky to be an exchange student back in the late 80's and spent 2 months in Taiwan. In one village along the coast they were constructing boats out of PVC pipe that ranged from flat pond boats to 40' + offshore diesel inboard fishing boats. The boats were all constructed of gray PVC, similar to electrical conduit in the US. There where specialized propane torches that only "certain" guys would use to heat and bend the pipe. There were simple frames that the pipe was lashed/woven to with a black poly type cord. The pipes were capped and glued, no foam added. The transoms were made of wood and wood keels were added on the larger boats. Engines were mounted high, decks were made of fiberglass and ,no kidding, the traditional vee shaped hulls were not WATERTIGHT. The seas would flow in around the pipes, to see a 40' boat doing 10-15 knots made up of 8",6" and 4" PVC pipe was wild ( no bilge pumps needed). On the smaller side, most shrimp and fish farms had PVC rafts, some with outboard motors, used to transport feed in the ponds. They were made by heating the last 2-3' of a 4" pipe and bending it up slighly to form the bow. The frames , again lashed to the pipe, were nicely scalloped to fit the pipe, much like the battens used for corrugated roofing(it was obvious these were manufactured for this single purpose, including the holes bored for the lashing).They would nail beams and plywood to make the decks higher and haul 20-30 50lb. bags of food throughout the pond. Thes rafts were about 6-8' wide and the standard PVC length of 20'. I plan to build one that is like the above mentioned, but with a raised motor mount and a "well" for a small 7.5 hp outboard. I will try to dig out my pictures, scan, and post them for the non believers. I was very impressed with their ingenious use of eveyday materials, hey ,when the scaffolding of a 40 story building over there is made totally of bamboo, why not?

 

[capt'n ron]

hey nero, it is simply poly-styro beads that is used here in the states for light-wieght concrete. the product is called" wiegh-lite" around here. we also have the lighter walled pvc, it's restricted by national sanitary codes to be used only for drains and venting here in the states(sch80, i believe) and i have never seen it under 1-1/4 inch od. i would think the poly-styrene would have to be compacted inside the tubes to get any stiffening and or stress transfer out of it, as well as bonded to the id. compacting it would add considerably to it's wieght. i wonder if you could use two part foam poured in. ( nice mess that will make!) i also think that by the time you plank a hull with pvc (actually pretty heavy stuff) and fair it all up with epoxy, you will have a stone of a hull ( imagine the amount of epoxy it will take). on the other hand, the epoxy that is made for solid surface countertops, ie. dupont "corian", is essentially pvc epoxy, as the base material for corian is pvc. this stuff can be used to glue the tubes together with only a light scuffing of the surface, but it is costly in large amounts.
one final note,.... while not exactly in the scope of this experiment, there are companies that will extrude pvc in all sorts of shapes..... bead and cove planking of any dimension needed, made out of pvc with a thin rib at it's mid point!. in this configuration, it could be glued with regular pvc glue. now you have rigidity, fairness, light wieght and super floatation all in one..... have alook at a pvc roll up garage door!

 

[rallyview]

old thread.

I'm interested in using pvc panels we can get around here in 4'x20' lengths 1/2" 3/4" and 1". i've seen these boats:
http://rionholdt.com/HOME PAGE.html
I don't know much about his process.

on a note related to this thread I found these square pvc pipes:
http://jogjaengineer.blogspot.com/2008/05/pvc-square-profile-pipe-1-x-1.html

which may work for the original poster. They are common for irrigation here.

My questions on the sheets are:
1 will they deform and creep overtime due to the sun. how would you frame to minimize this? The panels i've seen are suposedly stable to 158 degrees F
2 Would a pvc solvent glue like used in plumbing work give a flexible enough bond for boat construction. Would i be better off using a high temp plastic welder? Polyurethane, polyester resin? G-flex?
3 I envision using these panels for stitch and glue designs. Will the large movement of these panels over the course of a heat cycle be a problem? Since the whole hull will be built of the same material i think material movement will not be a problem but maybe i'm overlooking something.

 

[jimburden]

PVC square tubes come in 1", 2", 3" 4," and 5" sizes used for fense posts, mailbox and gate posts and decking and railings. We have all seen these products in use and at lumber yards. World wide these tend to cost about $2 to $4 per pound to extrude from PVC matrial that can be about 7,500 PSI in tensile strength at 44% elongation before breaking. PVC plastic can be made flexible like rubber raft cloth coverings or hard and brittle to snap like glass in thicker sheets at 10,000 PSI at 4% elongation. The square tube walls are typically about 1/8th inch to 1/4 inch thick but walls of up to about 1/2 inch can be extruded with die modifications. 5" PVC square tubes from one supplier locally in Lincoln Nebraska are about $2.25 retail price per running foot in presently eight foot lengths. These can be solvent glued together edge wise to form many simpler hull shapes. PVC bars Thermally bent to corneer angles and ready made strutural angles can splice togeather odd angles. Tight fitting bead foam squares can be vaccume pulled and pushed inside the tubes before heating bending or fabrication giving floatation andd double hull puncture resistance.

An extruder in York Nebraska makes two foot diameter by half inch thick wall PVC thin wall irrigation pipe in 40 foot lengths. One forgein extruder I called once made 3/8th inch thick by 60 inch wide special order sheets for a customer 50 foot long that they hand loaded on a semi truck.

The thicker the walls the slower the cooling out of the die and so the slower the progress, off set by often greater materials use per minute per extrusion machine or often balancing out in cost per pound.

It is possible to make corner to corner X braces extrudded inside multi sectional square tube PVC hollow core all direction strong panels. These pannels 4 foot to five foot wide can be two inches to a foot thick by thousands of feet long. If you have the means to fabricate on site or load up to 150 foot long slabs onto a overhanging railroad trailer flat car any length boat can be fabricated from full boat length seamless. These multipile core square tube slabs can be a foot thick and foam filled right off the extrusion line at 30 PSI cooled compression strength backing up the outside hull wall while supporting the outside skins from warping untill the foam cools. this can produce structural strength, some impact strength and full weight floatation in shallow draft or large surface area boats. Additional floatation can be added at about $1 to $2 per cubic foot bead foam materials inside this double walled PVC hull at about 2% water absorpancy if the outer hull is cracked. All boats should have floatation to above the water line at full load at the time off maanufacture. Repairs can be made made with common agregate and solvent filler cement.

Many PVC plank and sheet constructed boats have been built that look like boats made of any other material. There is one US manufaturer that makes small work and fishing boats out of sheet PVC. Sheet PVC is recently being sold in our lumber yards as truck bed and impact resistant wall liners. PVC with UV additives and even without but pigmented black or softer ABS can last out of doors for maybe a century or more even without paint without cracking, if properly designed. The degredated thickness is often less than and eight of an inch. Why do you think people worry about plastic bags and objects lasting forever buried in the environment or under water.

These giant PVC hollow core or foam core planks can be edge glued together and a 100 foot long boat built from a pile of materials in an hour or so if proper clamping and handling systems are used such as using multiple ratchet straps to pull the full length pieces together. A special set of two extrusions might make Vee hulled or round chined power or sail boat hulls out of two to four of these pieces. Round chine filler pieces might finish off boats with thicker corner skins. Try breaking in the middle of a 6 inch diameter sch-80 PVC pipe with a sledge hammer. These giant double walled planks can be curved over greater lengths to form pointed stems and sterns. A special extrusion might be used to form diagonally cut planks together as a glue I beam tapered splice. This is no different than gluing pipe together only very fast applicators are nesassary to roll the solvent glue and primer the length of a long seam as fast as a person can walk it. you have about 20 seconds to put the pieces together to stop air evaporation.

The problem in all of this is most extruders need about one to two million dollars for such large dies and then often do not have the shop length to pull off such soft and hot pieces in one length to cool dead flat. Different kinds of wall and vacume supports are used during this cooling process. The extruders are use to cutting eight feet to twenty feet long pieces off of continous extrusions and palletizing inside existing plants. I am not aware of a machine that is aimed at a garage door opening with nothing in the way. Most extruders in possibly a hundred countries now making plastic pipe, gutter, fense posts, wall panels or sheets used for truck bed liners and would be happy to supply a capital friendly mass production boat builder that wants to make ocean going bargain, unsinkable houseboats or yachts.