Basic Pros and Cons of Various Hull Materials . . .

[djambalawa]

Hiya folks just wondering what the basic pros and cons are of each material for someone who isn't experienced in maintaining vessels and would be buying 2nd hand - hopefully about 10 years old but perhaps much older.

I'm thinking I'd buy fibreglass but would like to hear the considerations about each like steel, wood, fibreglass (I understand you also get fibre over wood?) and aluminium.

For instance is aluminium more expensive but stronger/lighter and has a longer life?

This is for a trawler type craft - single or multihull. Any advice appreciated thanks.

[delmarrey]

I've been working on boats since 1970 and I've come to a few conclusions. These are my own personal opinions so I'm sure there will be those that will disagree, or maybe add to this.

I consider the best builds up to 60' to be out of a epoxy/fiberglass with a foam cored hull and a balsa cored deck, if done properly!!!!.

Most boats done these days are a polyester/fiberglass, some cored, some not. And second runner up would be fiberglass over ply with epoxy resin composite. Composite boats can be a blessing or HELL, depending on their construction, as well.

I do not like plywood cored decks or hulls (sandwiched between two layers of FG) due to their tendency to get soft (rot) over time from water intrusion. Any thruhull or fastener is a leak path. It could be sealed like what's done with foam or balsa cores but takes greater effort and is usually skipped.

Steel boats, for me would have to be over 45'. Small corners in steel tend to gather moisture (condensation) and rust requiring continuous maintenance that will not give one a break unless on the hard and under cover, or in Arizona. I do like steel over 60' if I could afford to pay someone else for up keep. If properly painted inside and out a lot of problems can be avoided! For larger boats, it's still the least expensive to build.

Aluminum boats, again over 45'. Aluminum has a tendency to crack next to welded seams. So it takes a fairly think plate to get a boat that doesn't flex enough in relation to it's size to avoid stresses that will not fatigue. Also if it's going to be painted, it has to be prep'd properly. One unseen scratch can turn into a blister. And once erosion sets in, it can not be welded until one grinds down to clean metal, unlike steel.

Wood boats (mahogany, teak, oak, kauri, douglas fir & etc.) require the proper skills to build and is unforgiving if a problem arises let go too long. I do like the feel of a wooden boat under sail and how quiet they are. They are warm in the winters and cool in the summers. They don't sweat and some have a pleasant odor but some woods can give off a toxin. The problem today is that the materials are getting so expensive. It would cost $5000+ just for the screws in the hull planks for the old Pacemaker that I owned 30 years ago.

And then there is farrell cement construction, which I know little about except how it's basically set up and formed. I've never worked on one. They scare me off.

There is a lot more I could add to this but I'll let others pipe in.

[GordMay]

See ➥ Boatbuilding Materials

[u4ea32]

MHO:

Foam cored fiberglass made with Vinylester.

No plywood. No structural wood anywhere. Very little wood even for decoration.

While epoxy is in some ways superior to vinylester, the advantages are small, the disadvantages are more clear: its easier to repair and make secondary bonds with Vinylester, and epoxy is more expensive on every level (material cost, process cost, labor).

Polyester is a very poor resin, and should be avoided: its brittle, its heavy, its weak, its not waterproof (leading to boat pox). Barrier coats only deal with the waterproof issues, it does nothing for the fact that since polyester breaks before the glass, polyester boats actually look perfect as they structurally decompose at a microscopic level (the bonds between glass fibers and resin breaks deep inside the laminate). You can be perfectly OK with a polyester boat IF you barrier coat the bottom to fix/avoid the pox, AND if the boat is never ever "driven hard" so the stresses on the structure stay very far below the designed strength of the vessel.

While Balsa seems like a good material, its actually too stiff for structures (prevents load from being distributed, leading to local failures), its heavier than foam (not just the core weight, but the glue needed to bond the core to the laminate and the amount of resin that gets uselessly absorbed by the balsa) and it does rot.

All other materials are inferior: more expensive to build, more expensive to maintain, less comfortable, and in nearly all cases, far less attractive visually except for those first moments where its just been finished. There is a reason almost every boat that looks good in a marina or at anchor is simple fiberglass.

If you ever own or work on a boat built of aluminum, or you just pay attention to what happens to your aluminum spars or T-tops etc., you will know that the unpainted aluminum is both ugly and dirty, and painted aluminum is high maintenance and bad for the aluminum. Its also much more expensive and heavier than foam cored vinylester fiberglass.

Carbon is simply inappropriate for hulls and decks: its expensive, very little weight savings is every actually realized, is very brittle and therefore much weaker than fiberglass, and its NOISY AS HELL underway. Its great for little things like masts and spars and rudders. Its bad for big stuff. Just like you can throw a shot glass through a plate glass window, small things can be made out of brittle materials, while big things... not so much.

Steel has some advantages in that you can always tell where its starting to rust: you can't miss the orange streaks. So at least you know exactly what you are going to be chipping, grinding, filling, and repainting today, and most every day. Unless you want your boat to look like a garbage scow of course.

Wood is simply idiotic, unless done purely for the aesthetics. There is no possible rationalization for wood construction: its substantially more expensive, wildly more labor, much weaker, far more failure modes, outrageously more maintenance, heavier, weaker, more flexible, less room inside, leaks all over the place that move with weather and sea conditions, ... But wood boats sure can look beautiful!!!!! Of course, wood boats usually look like hell, as a stroll through any marina will clearly demonstrate. And, of course, wood smells very bad: moldy, damp, like a mushroom farm.

[delmarrey]

Wood?

Then there is cold molded, basically a wood core sealed in epoxy. http://www.cruisersforum.com/forums/...tml#post693083

[seafish]

I agree with delmarrey on 60' plus being steel. I have gutted the fish hold on an 85' shrimper that is 12 years old. The steel was covered with sprayed poly foam and looks new underneath...considering this area has been submerged in salt water and shrimp repeatedly it is amazing. With that in mind I've sprayed the whole interior of the boat [minus engine room] with foam. Insulation and no more sweating is a plus...

[Butterman]

Can anyone tell me about composite hulls? Particularly those from the 1980's. I've found a boat I like but am unsure how to assess composite hulls.

[Jim Cate]

Originally Posted by Butterman

Can anyone tell me about composite hulls? Particularly those from the 1980's. I've found a boat I like but am unsure how to assess composite hulls.

We would need a lot more info about the specific vessel that interests you if we are to give any advice.

I would make one generic statement about timber epoxy composite construction: the success depends greatly upon the skills of the builder. Most such vessels are one-offs. Some are built by talented shipwrights (like ours!), some are built by dedicated but inexperienced amateurs, and some are built by folks who shouldn't have started. The usefulness of the product reflects these differences.

Jim