Metalizing a boat hull

[Kurt Sallaz]

Originally Posted by Mercury

Hello Kurt,

Thanks for your post. I am sorry but I am not sure what UHMW is?

Terry

It stands for Ultra High Molecular Weight polyethylene. It has extreme wear resitance. Alaska Air Boats, Thunder Jet Boats and Christensen Yachts are just a few companies that use UHMW for protecting their boat bottoms. It slides over rock bars with ease. It is used in the food industry to process sticky, sugary foods because they can't stick to it. That's why it makes such a good bottom coating- bio films can't stick to it either and being in contact with food, it's also eco-friendly. In water, it has 98 percent bouyancy factor. Once applied, it has the impact resistance of steel.

If more specific information is needed I will be happy to supply it via email or private message.

[MikeJohns]

Originally Posted by Kurt Sallaz

It stands for Ultra High Molecular Weight polyethylene.

An added benefit is increased hull strength

It has extreme wear resitance.

it has 98 percent bouyancy factor.

Once applied, it has the impact resistance of steel.

Whilst it may make a good self cleaning coating I suspect it only applies to high speed boats. For the rest it will still need regular scrubbing as do the teflon coatings.

It cannot make your boat stronger since a more elastic coating than the base material will not contribute structurally until long after the base structure has yielded. And then there's the coating to base bond strength.

Once applied it may in some conditions exceed the abrasion resistance of steel to flat sliding surface abrasion but it is not going to improve collision resistance, it will only protect from some contact abrasion. Elastic coatings can be prone to rucking and peeling from the base in collisions.

Impact resistance is a very confusing term when considering highly elastic materials. An inflatable boat for example is virtually indestructable from a collision viewpoint. Much better than if the same boat were made of metal

[Kurt Sallaz]

Originally Posted by MikeJohns

Whilst it may make a good self cleaning coating I suspect it only applies to high speed boats. For the rest it will still need regular scrubbing as do the teflon coatings.

It cannot make your boat stronger since a more elastic coating than the base material will not contribute structurally until long after the base structure has yielded. And then there's the coating to base bond strength.

Once applied it may in some conditions exceed the abrasion resistance of steel to flat sliding surface abrasion but it is not going to improve collision resistance, it will only protect from some contact abrasion. Elastic coatings can be prone to rucking and peeling from the base in collisions.

Impact resistance is a very confusing term when considering highly elastic materials. An inflatable boat for example is virtually indestructable from a collision viewpoint. Much better than if the same boat were made of metal

While UHMW is "elastic" (subjective term) bonded to a rigid surface, it's impact resistance IS increased by the fact that it is now a thicker hull,
is now a laminated hull, now has an "elastic" componant to absorb enregy from an impact that might otherwise dent or crack a hull without UHMW just like an inflatable.

We have taken a piece of 1/4 inch steel with 1/4 inch UHMW bonded to it with epoxy and bent it in a 20 ton press to 90 degrees then flatened it out, turned it a quarter turn and bent it to a 90 degree angle again with no cracking or delamination. We have had a university do it's own independant testing on similar samples including shear tests and impact tests.

I'll attaching a comparison chart for anyone intrested.

As far as "scrubbing" (subjective) UHMW is easily cleaned by wiping. Bio-films cannot adhere to it.

[MikeJohns]

Thanks for your reply, bear with me but you probably need to put some numbers to your claims otherwise they are all subjective.

Arguments such as " it ends up a thicker hull so it must be stronger " are misleading of course they are correct but not structurally significant Remember that the elastic material is the extreme fibre....not where you would want it

Given that UHMW is significantly more elastic than other boat building mterials (more than 300 times that of steel ) it will never contribute significantly to strength any more than the foam in a foam core composite does.
It's a bit like glueing 1mm of polythene sheet to your 1mm car panels to make them stronger in collisions..... it will but not significantly.

Also consier that softer surfaces can be a two edged sword. If a colliding object (eg sharp rock) can dig into the surface then you could end up with a much higher load and considerably more damage than that which would have occurred if it had just glanced off a harder surface.

However considering anti-fouling all that would be required would be thin sheets I could see an advantage in having the material shear strength weaker than the epoxy bond strength which would prevent large sheets self peeling once/if they started particulalrly from an edge (eg after a collision).

What about gradual UV degredation of the waterline material ? Once this roughens it will foul.

I'd also like to see the long term immersion performance in sea-water.

[Bahama]

I've been reading with great interest about the different metalizing methods and metals available. I was really suprised to find that any metal that is available in wire form can be used to metalize a steel hull--Monel, Copper/Nickel, bronze, and Zinc are all possible.

I was also very interested in seeing how the newer Arc Spray methods appears to be better than the older Flame Spray method.

Obviously Monel on the hull would be great if it could be done affordably, so I didn't know what that would cost or how long it would last on there; but certainly having the option to many nice materials using metalizing is a great thing that seems to be getting better and better as time moves along.

This product call LuminOre was also very interesting but I'm not sure if they are in the marine industry yet. http://www.luminore.com

[jonr]

People have arc sprayed zinc/aluminum combinations onto metal and fiberglass hulls and it was reported to work well. As I recall, they had to use a coat of epoxy containing hollow microspheres and then sand it some to get a good surface for bonding to fiberglass.

Would be interesting to know if such a technique (using hot air, not an arc) could be used to spray on UHMW plastic beads. A slippery hull with sustain less damage (slide over those rocks, don't grab hold of them) and is easier to clean.

[Mercury]

Originally Posted by Kurt Sallaz

It stands for Ultra High Molecular Weight polyethylene. It has extreme wear resitance. Alaska Air Boats, Thunder Jet Boats and Christensen Yachts are just a few companies that use UHMW for protecting their boat bottoms. It slides over rock bars with ease. It is used in the food industry to process sticky, sugary foods because they can't stick to it. That's why it makes such a good bottom coating- bio films can't stick to it either and being in contact with food, it's also eco-friendly. In water, it has 98 percent bouyancy factor. Once applied, it has the impact resistance of steel.

If more specific information is needed I will be happy to supply it via email or private message.

Hello Kurt,


Yes please I would like to learn more of this coating.

Thanks,


Terry

[jonr]

Here is a video of flame spraying plastic onto a boat. Don't know if it is UHMW but I suspect that it is easy to clean.

http://www.youtube.com/watch?v=0viw_hOsD0Q&feature=fvw

[Bahama]

Originally Posted by Bahama

I've been reading with great interest about the different metalizing methods and metals available. I was really suprised to find that any metal that is available in wire form can be used to metalize a steel hull--Monel, Copper/Nickel, bronze, and Zinc are all possible.

I was also very interested in seeing how the newer Arc Spray methods appears to be better than the older Flame Spray method.

Obviously Monel on the hull would be great if it could be done affordably, so I didn't know what that would cost or how long it would last on there; but certainly having the option to many nice materials using metalizing is a great thing that seems to be getting better and better as time moves along.

This product call LuminOre was also very interesting but I'm not sure if they are in the marine industry yet. http://www.luminore.com

I've been researching more and found this to be interesting so I'm adding it to my original comments. On page 148 in the 2006 Third Edition book (or page 119 in the 2001 Second Edition), "The Complete Guide to Metal Boats: Building Maintenance and Repair" by Bruce Roberts-Goodson 2006; he clearly does NOT like metalizing boats and devotes half of the page enclosed in a special box to say why. Here is the quote:

"This method of applying a protective coating is included here because we're still occasionally asked about its merits for a steel hull. Metal spraying was at one time popular with some steel builders. During the 1970s, when it was most popular. There were many who decried its use on the grounds that if it chipped or otherwise failed, water would creep underneath and cause considerable invisible corrosion problems. Time has proven these critics correct, in fact, and the method is infrequently used today. Another drawback was that the materials used for these coatings were notoriously averse to holding paints as intended. The development of modern epoxy and urethane protective coatings has allowed flame spraying” (or “metalizing” as it was popularly known), to fade from the scene. In the interests of thoroughness, however, here are the details.

Hot-metal spraying is accomplished by melting either zinc or aluminum metal wire in a special gun that drives it at high speed onto the bare steel in the form of molten droplets. Like a surface prepared for painting, the steel surface must be prep pared by grit blasting down to white metal. Without this etched surface, the hot metal spray will either roll off or flake off after cooling.

Many advocates of this method claim a chemical bond forms between the aluminum or zinc and the steel; they claim that the metals are “fused” together. Actually, the hot-metal spray forms a mechanic cal bond only. It depends on the correct spraying techniques, as well as a grit- blasted surface, to maintain its grip on the steel. If you plan to metal-spray your hull, don't use sand as the blasting agent. Commercially manufactured grit is necessary to give the correct key for the metallization process.

If you use a hot spray involving aluminum or zinc, then you should apply a special wash to the aluminum coating before applying any paints. An example of such a wash is Interlux Viny-Lux Prime-wash, which is specially formulated to adhere to bare aluminum and is a good primer for the other coats that will follow. If you are considering one of the hot-metal spays for your boat, you should seek out the latest information on the subject. My advice is stick to the well-proven regular painting procedures for metal hulls."

I'm curious what people think of what he said; I didn't like the news because I was hoping that this was an economical way to coat the bottom of the hull with Monel or some Copper-Nickel alloy that would provide great corrosion protection and antifouling at a nice price. This was sad news to me.

[jonr]

Arc spraying is somewhat better than flame spraying for zinc and aluminum. Overall, the results can be compared to hot dipped galvanizing - which has some uses. My understanding was that the price of metalizing was the major downside.

http://flamesprayauction.homestead.c...plications.doc
http://www.corrdefense.org/Academia%...028%202003.pdf
http://www.armedforces-int.com/artic...rotection.html
http://www.dtic.mil/cgi-bin/GetTRDoc...f&AD=ADA458160

Originally Posted by jonr

Arc spraying is somewhat better than flame spraying for zinc and aluminum. Overall, the results can be compared to hot dipped galvanizing - which has some uses. My understanding was that the price of metalizing was the major downside.

Both have no place in boat or shipbuilding. And the results can NOT be compared with hot dipping!

Although really not a fan of Bruce Roberts, I have to agree with his paper on this topic.

Btw. we are far off topic here! This thread was opened to promote a (non functional) antifouling, not a corrosion protecting system. If you need the latter, do it as all the professionals do, apply a proven system of epoxy primers and coatings on the bare steel structure.

Regards
Richard