vinyl/plastic siding

[Valiviirre]

Is it possible to use plastic exterior siding sheets that are 4'x8' instead of wood plywood for a stitch and glue boat building project? I am building HH Paysons Diablo.
http://www.instantboats.com/diablo.htm

the reason is I would like to not use fiberglass cloth over plywood.

I have previously built a 16' lapstrake double ender/Plywood.

[rasorinc]

Things to consider. What adhesive is compatable with rigid plastic?
What strength factors does the plastic offer?
What type of fasteners would you use?
If it is flexible plastic I don't see how it would work. Can you bend it over on itself? If yes then the answer is NO.

[robherc]

Why don't you want to use fiberglass over plywood?
That's what you gave as your reason, but I'm not understanding the reasoning behind it. (sorry, I'm starting to confuse myself too)

[PAR]

No, the plastic panels you speak of are not self supporting, weight a bunch more then plywood, have little inherent strength, don't hold fasteners well, can't be easily bonded (without welding) and generally are unsuitable in your application.

It's easy to understand your desire to not use goo and fabric over plywood.

Plywood and solid wood are fairly unique materials. Darn near all man made materials try to emulate wood in some fashion, because of it's unique and wonderful physical qualities. For example, good grade plywood is pound for pound stronger then steel, can easily out flex it, is considerably lighter, cheaper and a fair piece easier to work with. Most man made materials would love to have similar physical properties to wood, particularly weight, cost, ease of machining and flexural tolerance.

Back to the plastic planking. Nope, it doesn't work for several reasons, nor does the "handy plank" stuff or concrete board and other land based building sheathing materials.

In defense of goo and fabrics over plywood. If you work neat, using good technique, it's not as messy, nor as difficult as your first attempts. Experience makes you better at using the stuff, though becoming sensitive to the goo is always an issue, new formulations are much better for those that have developed a reaction to it.

[marshmat]

Hi Valiviirre,

Diablo is an excellent design. (I built one in '01 and it is still in great shape.)

This boat's entire structure is plywood, and she's engineered accordingly. Glass is used in this design to join the hull seams, to secure bulkheads to the hull, and to put a protective sheathing on the outside; the actual strength comes from the wood. You can't substitute something else for the plywood. The plastic panels you mention are not suitable for any structural purpose. Although I know of at least one Diablo built in heavy welded aluminum plate; the design does adapt well to aluminum with suitable re-engineering.

My Diablo is built of polyester resin, 10 oz cloth, and AC exterior fir ply. She's logged 175 voyages (and at least 10,000 km of Ontario highways on a bad trailer) in 7 years and, apart from having to beef up the seats (as drawn, they're not adequately braced) there is no structural damage at all, no rot, no cracking, anywhere.

I will not use polyester again, though. It does work, but it's finicky, the catalyst is a pain to mix, sometimes it doesn't cure properly and you have to scrape it all off.... epoxy is much easier to use, stronger by far, more waterproof, and adheres better to the plywood.

On a related note- it isn't entirely correct to call the Bolger/Payson glass-ply boats "stitch and glue". Bolger has a way of matching curvature between panels that causes them, if cut accurately, to lie perfectly edge-to-edge at the joints without the stitching that is required for most other glass-ply designs. Hence, they're known as "tack and tape".

[Valiviirre]

thank you everyone, the truth is I am just terrible at laying fiberglass, more bubbles than I care to mention. I thought that maybe vinyl siding would work. Homedepot has an exterior vinyl siding that is 4'X8' sheets at 1/4 inch thick.

[robherc]

hmmm, maybe you should try with some lower viscosity epoxy...won't work for crap (unfilled) if you have to make a fillet, but it's a LOT easier to get rid of the bubbles by using a very low viscosity epoxy, then adding the fiberglass to the already wet epoxy-on-wood. Then you can use a roller (avail. from a few diff. boat-building websites) to mash the fiberglass down into the epoxy...haven't tried the method myself yet, but it seems promising...I usually have pretty good luck with simply pouring a nice, LOW vis. epoxy over the f.g. cloth & smearing it around with a plastic putty knife.

Hope that helps.

[marshmat]

Rob, I've tried the method you suggest, and it does work very well.
Stretching dry cloth over wet epoxy makes it very easy to keep the bubbles out. The air has plenty of room to escape through the still-dry cloth, instead of getting trapped. I've never had much luck with the ridged rollers (people don't clean them, so they clog up) and now generally just use a plastic spreader blade. If you do want a roller, don't spend $40 for one, just stack alternating large and small washers on a piece of steel rod or a paint roller handle.

Valiviirre, everyone has a hard time laying glass at first. It's not a high-skill job, but it does take some practice to do a good job of it quickly. Diablo is a good project to practise on; the cloth drapes nicely over her lines and everything is easy to reach.

[tom28571]

A couple of things. Plastic squeegees have a terrible habit of quickly developing a rough edge that catches on FG cloth and doesn't leave a smooth surface on anything. I highly recommend rubber squeegee from Thalco. Seems expensive but it can be used for a long time and cleaned by vinegar, acetone, lacquer thinner or sanding if you forget and let the epoxy set up. I have two that have lasted for 20 years and will go to my heirs.

The second hint is to get a large wide mouth glass jar that is used by restaurants for pickles and other stuff and pour in a couple inches of acetone. When doing a job that will last more than a short time, I use brushes and FG rollers and just toss them into the jar, and close it of course. When needed just take them out and shake or blow out the acetone a bit and start using. Works until the goo starts to build up in the jar and needs changing. You can also toss the plastic spreaders in the acetone but not the rubber ones which will swell and deform. Not fatal but takes a day or so to get back to normal.

I nearly always put any sheathing cloth on dry, but that is just my choice. If it was cold weather when sheathing, I would probably go with a first epoxy coat to insure better penetration. In my experience, it's messier though. A hot air gun will help with bubbles and penetration if those are problems.

[Boston]

ok this one is my cup of tea
answer is
hell no
having been a custom home builder for about 30 years I can assure you
that plastic siding/paneling you're talking about is nothing to stake your life on
stick with the recommended materials and dont try to cut corners
best thing to be asking yourself whenever you think of something like this is
"how far can I swim"?

[marshmat]

Valiviirre,

Just bumping the thread here,.... are you still interested in building the Diablo? Feel free to email / pm me via my profile here, or just ask in the forum, if you'd like more on the boat and how she behaves.

[tgerhart]

I made a boat out of PVC extruded foam panels. It's a modified Diablo/Nymph hybrid. Not a drop of expoxy or a scrap of wood in it. The attachment shows a picture.

[robherc]

good job, what'd you hold it together with?

[tgerhart]

I first used a commercial 2-part methacrylate adhesive called Bond & Fill. This kind of product is apparently what builders use to join pieces of trim panel around window frames. Unfortunately it didnt hold up well with prolonged salt water immersion. The bilge seams started to leak. So I redid them with ordinary PVC cement, thickened with filler powder when needed to fill gaps. This has worked quite well. And is much cheaper. I reinforced all the seams with fiberglass tape, again using ordinary PVC cement. Then, I painted the PVC sealed fiberglass with ordinary vinyl latex house paint for protection against UV damage. I painted the boat inside to cut down on glare [making it easier to see the fishfinder image] and hide fishblood stains in the longitudinal thwart underseat compartment.

[Boston]

well you sure did a nice job of it
Ild have said it would never work but you proved me way wrong in the end
nice touch with the ABS/PVC glue
way to think outside the box
Im guessing those panels are not basic house siding cause Ive installed those and they are paper thin
oh
and that B/F glue is more aptly named BS glue as we never used it past the first few complaints
basically it comes in the right color
as apposed to the plumbing stuff which is purple or black
we just used touch up paint on the plumbing stuff
best
and great job
B