Frameless Construction

[Scylla]

Hi everyone

I am looking to purchase my first yacht and have found this site to be most useful. I am managed to work out that I am after a steel boat that is insulated to prevent the condendation (and therefore reduce rust) and of course keep out the cold.

I am in Queensland, Australia and most of the steel boats I see around here have not been insulated, I guess because Queenslanders don't like the cold. I have some idea though, that I will be cruising to Tasmania and NZ where it does get cold so will need the insulation.

I have been looking at a 1991 steel van de stadt 34 and have been told (by the vendor) that it is a frameless boat and therefore it would be a "simple" job to insulate it myself with spray on foam.

With all your experience, what would you advise, is it a simple job to spray the foam?

And...

Are frameless 34' van der stadt yachts strong enough to do blue water passages?

Thanks for your thoughts

[Tim B]

Van De Stadt are a good yard, and they produce good boats. I'm afraid condensation is a problem you'll just have to live with with a steel boat. There's no easy way (that I know of) to insulate them without the insulation absorbing water and slowly deteriorating. If you want a warm boat, go for GRP. you should be able to find a similar size yacht for a similar amount that is also blue-water capable.

Alternatively, take a good sleeping bag or a cabin-heater.

Tim B.

[Bergalia]

For a southern 'pom' - Tim B talks vague sense...but honestly...GRP...Pah - Timber, sir. It's what nature intended. And there are still some well founded timber craft around the Australian coastline... even in Queensland. Try one of the many 'boatie' magazines at your newsagent "Just Boats' for instance. And if you spot one - put your money in a 'Folkboat'. Scandanavian design - and they of all people know about insulation...

[Tim B]

Thankyou, Bergalia, I'll take that as a complement.

Actually, I was going to include wood, but then I changed my mind... Wood is a fantastic insulator, and produces some very comfortable boats, but if you want a wooden boat for blue water cruising with decent performance, my suspicion is that there are very few on the market (I could be wrong), so you're looking at a custom design and custom build in an unusual material. That could be quite expensive. If you do manage to find one, really look around it carefully, jot down your own notes, then get it surveyed.

GRP boats on the other hand tend to be 10-a-penny in comparison to a custom job, and there are usually plenty for sale.

Tim B.

[D'ARTOIS]

First of all, to correct Tim B, Van de Stadt is not a yard but a Design-Bureau - e.g. Naval Architects.
Their designs are good and they have done a lot to develop yachts that can be build by amateur-builders. One of the methods they have invented is the building of steel boats WITHIN a framwork. This concerns in all cases a multi-chine steel construction. That does not mean that there are no bulkheads and/or frames in the boats, it simply means that initially they are build in a kind of cradle and later on the required frames can be added. It is that simple.
Question: "Are the VdS boats strong enough for a sea-voyage?"
Answer: If they are constructed to the VdS requirements, specifications, yes they are definately!

Using foam, to insulate the boat is an unwise step. Why? Because you have the foam in between the hull and the wainscots etc.
Now if you want to weld something on deck or hull, you have to tear the woodwork away in order to remove the foam insulation and do the welding. Otherwise you will burn your insulation or boat.
Use therefore Rockwool or the like and start about 5 inch above the waterline. For obvious reasons.

Check if there are any knees placed in those spots that carry loads. The previous owner/builder might have overlooked the fact that they might be required.
If you let me know which design it actually is, I may ask VdS to give an advise in this respect.

[MikeJohns]

Tim
You said " If you want a warm boat, go for GRP "

Thats a pretty prejudiced comment. GRP is only warmer if you ignite it :-).
If you are talking composite GRP-foam-core then they do have some insualtion but I would recommend a solid layup in the hull if you use this material for a cruising boat.

Really it comes down to the insulation, there is no reason that any hull material would not support a snug and well insulated interior.

I am not keen on sprayed on foam, it complicates maintenance as DArtois says.

Do not simply spray it into the lining/hull void on than existing boat. The application of foam is only to the bare hull interior.

There are other effective methods using sheets of easily removed closed cell foam, but with an existing interior you will have to remove the ceilings(linings) whatever you do.

You will find that the insualtion is particularly of the deck important in keeping the heat out.

Frameless designs have the frame effectively in the structure , for boats of the size you are talking they are perfectly adequate but you may want a heavier displacement boat for the Tasman sea depending on your malaise threshold.

you can email me for advice.

[Scylla]

Thanks for that everyone. It seems that steel's only advantage for someone buying a second hand boat, is that it's stong. I have been reading that Ferro boats are strong but have low impact resistance.

How can it be strong but not resist impact? Also are there the same problems with insualting a Ferro boat?

I know the USA doesn't like ferro boats but you have to admit there are some quite old, and good looking ferro yachts still cruising the oceans.

[Bergalia]

The impact resistance qualities of a 'concrete' boat depends on the quality of its original construction. A well made ferro-cement craft will knock the crap out of hidden rocks and reefs. GRP fractures and falls to pieces; Steel boats tend to dent - at worst tear (viz Titanic vs. Iceberg). Timber boats on the other hand have a pleasant tendency to 'bounce' off most obstructions.
But if in doubt - avoid hiden rocks and reefs.
Insulating ferro-cement - as MikeJohns suggests is best done by applying cell-foam sheets. This is usually done during original fitting out. Though timber panelling is preferable (but more expensive) but does allow you to hammer in nails for hanging pictures...

[Chickadee]

Foam must be sprayed carefully on metal, without any air "pockets", because differentiated ventilation brings corrosion. Maintenance will be a problem, as noted before, and for security you should always have the possibility to keep an eye on any square feet of your hull. So you'd better fix/glue the foam to removable plywood panels and leave some millimeters free so that the foam is not in contact with the steel at all, and condensation can "flow" down the hull surface. For better isolation, the joints between the panels must be tight, but at the same time their fixations should not be 100% rigid (use synthetic bolts, also better to avoid corrosion), as slight hull deformations occur in rough conditions.
If you want to keep your boat for some years, spend some time and money to work this insulation thing out.

Or choose a wooden boat ! Old classic constructions are surprisingly comfortable (noise and temp.), but I believe solid ply or moulded wood is still better than plastic. Since I spent months in a metal boat (no insulation), freezing at night and sweating under the sun at 10 in the morning, I swore that my next boat (if any ) would be a wooden one. To be honest I have nothing against well insulated steel boats, it's only that I have never seen one.

[MikeJohns]

Originally Posted by Scylla

Thanks for that everyone. It seems that steel's only advantage for someone buying a second hand boat, is that it's stong.

It is also very easy and cheap to repair. Since we can weld steel to 100% original strength. It means you can chop out and weld in the exact replacement of any member or plate or part thereof without any loss of strength.

Originally Posted by Scylla

I have been reading that Ferro boats are strong but have low impact resistance. How can it be strong but not resist impact? Also are there the same problems with insualting a Ferro boat?

It depends what the material does once the yield point has been reached.

Metals yield then stretch giving a huge margin for safety before the surface ruptures . Ferro , GRP and wood too involve brittle failure at yield, ie it ruptures . So for any given hull ( we design to the materials yield strength ) the metal boat turns out to be so much stronger . The UTS of steel is several times higher than the design yield strength.

A simple example is a pulverised hole in ferro or glass or kindling in a wooden boat compared with a dent in steel.

Ferro boats tend to have massively strong stems/keel forefoot but the shell is not so good at resisting impact so if you hit that reef head on with the keel leading edge you'll often be fine , but if she washes side on to the reef then its a different story.

[FAST FRED]

Most spray on foams are extremly flamable, and very hard to extinguish once lit.

The electrics and exhaust will need to be very carefully done .

FAST FRED

[masrapido]

Good old cork is the best insulating material. Low ignition, high insulation coefficient for noise and temperature, high durability. Might also come out as a bit expensive, but so durable, it's worth considering.

[yokebutt]

Condensation has a lot to do with how the ventilation system is arranged. As far as I know, the best set-up is to funnel the incoming air into the bilge. Since the under-water portion of the hull is cooled by the surrounding water, any air funneled into contact with it will cool off and excess moisture will precipitate out. As the air rises up from below the floor-boards it will assume ambient temperature again, but since some of its moisture was precipitated out, it's relative humidity will be lower than ambient, and thus make the cabin a lot drier.

Another fine Swedish invention, patented even, if you can believe that.

Yoke.

[yokebutt]

What the hell, I'll chip in a couple of sentences on hull materials too. I have no quarrel with metal boats, although they corrode sometimes, or wooden boats, although they rot sometimes, or even ferro, although I fail to see any good reason for using it, because none of these materials fall within my area of expertise.

Composites on the other hand, and let's limit ourselves to fiberglass here, I don't think either carbon or mud-and-straw are of any pertinence to the present discussion.

What usually fails first in fiberglass laminates is not the glass, but the resin. Glass in itself is acually remarkably stretchy, on the order of five percent or so, but polyester resins are very brittle, 1/2-1% elongation before failure is the typical range, approximately an order of magnitude less than glass. Couple that with the fact that the bond-strength of polyester is only in the range of 200 psi or so, wich makes it vulnerable to peel-failure, and is full order of magnitude less than a good epoxy. Consequently, what we have is a chain where one link is much stronger than the other, and this is why I'm such a strong advocate of epoxy resins, because they match the properties of the glass so much better by having a higher bond-strength and stretchiness.

So what I'm saying is- don't write off glass too easily, properly used it's an incredibly tough material.

Yoke.

[Bergalia]

Gold star to Masrapido. That's good lateral thinking. Cork, of course. With extra bouyancy as a plus factor.