Replaceing rotted wood.

J

jmas

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1987 340 Express fishing Boat.
I have found lots of rotten wood in storage areas on outer cockpit area.Damage caused by years of rain and some Termite damage. I am removeing all wood and remaking the storage areas using plastic only.
I have a question about what would be the best material to use.
Starboard=Cant use adhesives or paint.
PVC=can be sanded and will accept adhesives, also can be painted.
Both materials are redally available.
Any negatives to either material?
 
Not necessarily a negative, but certainly a consideration: Starboard ( actually, all HDPE ) has a rather high rate of thermal expansion. Or "in English" you must build in such a way that as the plastic expands and contracts with temperature it does not cause other problems. Much of this issue can be controlled with careful design. But it must be dealt with. The rate is much different from wood or fiberglass, so it will need to have "moveable joins". Also note that this makes sealing it a real challenge, since sealants and adhesives won't stick...

This makes PVC more attractive since it's rate of expansion is lower than HDPE, and adhesives and sealants will stick.

For both, the better the design ( PVC does "breathe" with temp changes... ), the better the result. Failure to include allowances for this expansion will cause warping and/or cracking.

I'd vote for the PVC. Not everyone will agree with my choice.
 
Plywood is the only way to go unless you can afford that exotic cored material I forgot the name of.

I've done a couple such projects and used plywood on 90% of the construction. Just seal every surface with epoxy...and DON'T use FOAM.

You don't need marine plywood either. Marine grade plywood is only necessary for surfaces in constant contact with water (hull).

Just about everything can be made with 3/4" plywood. If you need thicker pieces, epoxy them together to get thicker pieces.

And for epoxy I've been using Tap Plastics epoxies for over 20 years. It's cheaper and you get full gallons instead of gallon 'KITS' which are ripoffs.

The last big project I replaced every sliver of wood from the transom to the helm...about 13'. I added 4 layers of roving to the inner hull. I also used 25 gallons of epoxy, though I waster at least 3 gallons.
 
I tend to agree with what Charlie said - wood is my material of choice. It is strong, light, holds fasteners real well and will readily accept virtually any adhesive, sealant or epoxy.

I have used a lot of Starboard in various thicknesses for different projects in the past and to me the biggest drawbacks are the excessive cost for the material and the weight - that stuff is HEAVY! It does tend to held screws better than I thought it would over time, but not being able to use adhesives or epoxy is a real drawback to me.

I did remove all the cockpit trim panels from my 36 Trojan and replaced all of them with 1/8 inch PVC sheets and they looked good for years, right up to when I sold the boat. PVC is a lot cheaper than Starboard and I found that regular old contact adhesive (like you use with formica counter tops) worked great to stick it to plywood backing when necessary.

For me, the best material I have found is regular old exterior grade plywood. Exterior grade means they used waterproof glue to bind the layers. I believe the primary characteristics of "marine grade" plywood is that it too uses waterproof glue and every single void in each ply has been filled with solid wood. Since I am not overly concerned with minor voids in the plywood, the doubled price of marine plywood over exterior grade plywood is not worth it.

Also like Charlie said, if you are mindful of longevity of your work in a marine environment, be sure to seal all sides of the plywood with a good quality epoxy. I myself use a two-to-one non-blushing mix from RAKA - I especially like the lengthier pot life of this brand.

If you do use plywood and epoxy, be sure to pay careful attention to sealing up the edges of the plywood. I usually put at least three coats of silica thickened epoxy on all edges, which seals out water intrusion.
 
I ve done a lot of stuff with starboard and never had expansion problem, may be an issue up north though but in your case I wouldn't worry

I like that you don't have to paint it and that screws hold VERY well. Properly supported it can be structural

Never used PVC...

Marine ply soaked in epoxy on all sides and edges is the easiest way to go fir this project and should last forever. At least for the structure, for the doors if any starboard would be good. Check out buckswood craft website in marathon, they do very nice starboard storage doors with frames
 
My onetime experience with starboard says that it gets brittle with time. I had some left over from a project. Several years later (after I had sold the boat) I noticed that the starboard had become brittle and cracked easily.

George
 
quote:
Originally posted by gcolton

My onetime experience with starboard says that it gets brittle with time. I had some left over from a project. Several years later (after I had sold the boat) I noticed that the starboard had become brittle and cracked easily.

George

Click to expand...


You sure it was starboard?? I have had a few pieces of different thickness in external places for over 5 years now and it hasn't changed a bit.
 
HDPE degrades in UV. It'll form cracks as well as get brittle. Besides, any of HDPE/Starboard type plastics are not structual...and NEVER use screws in a structual application.
 
My first response was to answer the "which is better: HDPE or PVC?" question.

I agree with the choice of plywood/epoxy however. Very versatile and works fine.
 
I have starboard pieces in use outside in so FL sun for 10 years.. Like new

The only two materials i use screws in are starboard and jatoba (a hardwood that's 30% stronger than mahogany). In either case I know they won't rip out!
 
HDPE without the uv inhibitors that Starboard contains will crack. The cockpit cover boards I replaced with Starboard were doing great the last time I saw them and that was 14 years after I did that job. This was on a commercial boat and they were also used to cut/clean the fish on (mfr stated USDA approved at the time). On the negative side, the surface is slick (even though it has what looks like a non skid texture) so watch your step.

I also replaced lots of rotted plywood cockpit panels with starboard. If the customer wanted a finished on the panel I would use PVC foam/sign board with choice of mica vacuum bagged using epoxy.
 
Thanks for all the comments. I will use PVC wherever there is direct contact with rain.
I will use exterior grade plywood for any Panels that are out of the sun and rain and will be sure to Epoxy all edges and surfaces.
So far I have removed all old wood.

Will post Pix as I go.
25 years of water and critter damage.
P1010001_zpsd0ff7668.jpg


P1010002_zpsef04ffb1.jpg

All old wood removed.
P1010004_zps220fc919.jpg


P1010003_zpsb6447e5c.jpg

PVC and treated Ply installed
P1010006_zps2e0943fd.jpg

Slider Frame is Iron Wood(jatoba) with teak oil finish, Slide doors are Black Plexi.
P1010005_zps4429af03.jpg
 
Nothing there looks particularly structural. Kinda like cabinet work. Screws should be fine. The only problem is possible screw holes that go into wood framing behind the fiberglass. They would allow water to migrate to unseen areas.

My boat is a '78 so it's coming on 35 years old. I did the wood replacing around the 25 year mark. The water damage was extreme. The more I inspected as I went, the more damage I found.
 
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