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Old 08-04-2015, 12:20 AM   #1
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Default A composite thread

Canarianfish is doing some really neat stuff in his build thread. Bill in his thread as well as outhers have some really cool projects going on and when a question comes up in one of those threads the discussion is often muted so as to not derail the thread.

How about a thread for follow-up discussion on some of the many great ideas/questions that surface in some of these other threads. Maybe throw in some unusual composite projects or some unusual solutions for old problems.

Canarianfish just built an amazing jig to hold his longitudinal hull stiffeners parallel and in plain, and provided some excellent thoughts about Plexus Adhesives;

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Originally Posted by clt_capt View Post
Have you considered Plexus Adhesive for bonding the grid in prior to lamination?
Quote:
Originally Posted by CANARIANFISHER View Post
Hi Capt, IMO, Plexus or any other methacrilate familiy member adhesive could be worth for glueing a composite piece but for bonding foam, being a relatively soft material would be a waste of an expensive adhesive because the surface of the foam would not even come close to the strenght of the adhesive itself ... another thing would be if glueing an already cured composite piece where the goal, still I believe methacrilate adhesives to be unnecessary considering that the amount of contact surfaces can be designed to be quite large making then unnecessary to use an adhesive that while very good if you are in the neeed to bond parts that have small surfaces in common, has many disadvantages like needing special application gear, having a short shelf life .... not to mention their outrageous price ....., as you probably know bond strenght is proportional to the surface of the bond or contact surface so any builder can choose to enlarge the surface and get an equally strong bond as someone using a mega expensive system and little contact surface, in addition to all this, main pieces in a boat are quite interlocked so chances of a bond to fail are slim, in some places like the shear line where the cap is joined to the hull the surface is not too much but then there the fasteners that retain the protective perimetral belt act as retainers of the cap to hull joint as well, IMHO, only in a fast high volume production environment can the use of that glue be justified ....... off course others opinion can differ ... as is usually the case when talking about boats
I share these views but would suggest they having a place when bonding dissimilar materials and I have been troubled when I run into them in production boats in need of repair, I haven't had much luck bonding to Plexus adhesives and have had a few jobs get quite a lot larger because of the stuff. I have not yet tried sticking Plexus to Plexus. Others' experiences?

Here's a few photos of a different composite project, kept me busy a big part of May and June and included Plexus Adhesive and a jig to maintain near zero tolerances :-)
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Old 08-06-2015, 11:13 PM   #2
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That looks very nice and well done Gerald, a motion controller gyro you have some wealthy friends ...
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Old 08-07-2015, 01:00 AM   #3
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That looks very nice and well done Gerald, a motion controller gyro you have some wealthy friends ...
Thank you. Yes, the gyros are little expensive and considering the loads involved the installation is a little challenging.
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Old 08-21-2015, 11:56 AM   #4
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It's been suggested that I bumped this thread to give it another chance at life, composit projects particularly those that are supported with photographs are welcomed here.

A little follow-up on the Gyro project to illustrate the loads involved, please note that the loads listed are per mount, over 16,000 pounds down on one side and 16,000 pounds up on the other reversed mid-wave and then repeated on the next wave. There's other forces as well but the up and down are the big ones.
Gerald
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Old 08-21-2015, 12:21 PM   #5
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I'm going to pull some stuff from some other threads to try to jumpstart this.
This is from the fight club and a discussion about Kevlar.
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Originally Posted by commuter boats View Post
After you grind it, you can shave the fuzz off and gain a good surface to laminate to.
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Originally Posted by 1blueheron View Post
What do you use to shave it off or grind it with? Does it tend to cause abrasives to load up"
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Originally Posted by commuter boats View Post
I don't get a lot of Kevlar repairs, occasionally a kayak or rowing scull. I typically use a razor blade or a scraper that I make from used power hacksaw blades. I don't have a photo of it cutting Kevlar that here's a couple of it cutting gelcoat, handles similarly.
Gerald
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Old 08-21-2015, 12:33 PM   #6
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A link to a hull extension I did on my nephew's Parker..
http://www.thehulltruth.com/boating-...-4-stroke.html
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Old 08-21-2015, 02:13 PM   #7
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A balsa repair job...
22 year-old, mid tier, balsa core boat with damage and repair
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Old 08-21-2015, 02:24 PM   #8
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Extending lift strakes...
For the small whaler crowd
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Old 08-21-2015, 05:25 PM   #9
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I unfortunately do not have anything to add, but am interested.

I will be starting some work on a small Ray Hunt designed boat. O'Day Hunt 14.
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Old 08-22-2015, 09:04 AM   #10
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Originally Posted by ian_upton View Post
I unfortunately do not have anything to add, but am interested.

I will be starting some work on a small Ray Hunt designed boat. O'Day Hunt 14.
Thank you for the bump I hope you participate when you get started on your project.


These quotes are from the fight club...
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Originally Posted by maxie View Post
Saw your thread on glass. Wish more builders got onto that discussion Would be very interesting
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Originally Posted by 1blueheron View Post
Really enjoying the good discussion and learning a lot guys. A few of the Tolman builders have batted about pros and cons of glassing panels pre-assembled and flat vs. assembled in the jig. Discussion reached about he same conclusion. Some guys feel it quicker and easier glassing flat, but the secondary bond issue and time for stringer/bulkhead installation was a concern for some. Others feel it is just as quick and easy to glass after assembled assembled. Pre-glassing can cause additional stiffness which with any tight bending radii might make it impossible on the second fit/assembly if not allowed for. I guess it boils down to personal preference and habit?

The tabbing discussion is very interesting. I am assuming the terms tabbing and seaming are being used synonymously here. In my build the tabs are temporary place holders and then replaced or glassed over with permanent seams containing a healthy amount of biax. I am mentally debating the benefits of temporary tabs vs. temporary angle blocks and screws which seem quicker, and cleaner with less waste.
I have checked out the Composite thread several times and I find it interesting Perhaps a bump now and then would help.
Since much of it does not apply directly to my build, and I don't have anything to add with my limited experience I have just been a lurker. It certainly isn't an issue of "bad internet breath". I think it is just a very small niche of builders. Maybe put Contender or Yellowfin killer in the title and it will go viral...
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Originally Posted by twitch View Post
I thought the composites thread was a good call and was hoping it would get some traction. I agree that is only appealing to .05% of the THT populous and will probably take some time to draw a crowd,
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Why not add a link here?
Thanks for the encouragement.

Last edited by commuter boats; 08-22-2015 at 09:35 AM.
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Old 08-22-2015, 09:22 AM   #11
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A discussion brought over from the fight club...

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Originally Posted by Lenm555 View Post
Fine looking boat Adam - will have to track down your build thread.

Regarding the Kevlar talk, what is its proposed purpose in the boat build?
Sheathing?

My experimenting with it is that it always needed to be vacuum bagged down.
When compared to an equal weight of glass cloth, it always seemed to swell when impregnated with epoxy and making faring troublesome (at laps) if not vac bagged down.

I recall a catostrophic failure of a windsurfer board I built once.
It sheared in half after flat landing off a large wave. Despite total failure of all composites (H80 PVC + epoxy + carbon + SGlass), a Kevlar layer in the deck layup keep the board together enough to get back to the beach safely (albeit a bit floppy).
A similar failure with an all carbon/SGlass was a complete shear in two pieces and a swim home.

Took me a bit to twig that increasing sandwich thickness was the most efficient way of increasing Resistance to shear failures.
Not putting down more layers of glass or carbon.

A 5mm PVC with 1x 6oz either side was better than 3mm with 2x 6oz either side.
Composite selection and fibre orientation is critical when aiming for minimum weight and maximum strength. More use of unidirectional fibres (carbon) in the high compression areas and Kevlar in tension. The staggering of weaves, 1st layer 0,90 direction, 2nd layer 45 degrees, 3rd layer 0,90 always seemed better in impact resistance and radial stiffness.
balancing of inner and outer Layers to the sandwich is important and the blending in of various layers to distribute loads gradually as to not create 'hard spots' which could initiate a path for shear.
Double sandwich skins have merit, esp in compression and impact.
A layer of 0.5mm rotary cut pine veneer, sandwiched between layers of carbon/Kevlar cloth has an unrivalled Resistance to impacts.
Anyway, not strictly boat related however some of the concepts may transfer...
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Originally Posted by Lenm555 View Post
I have no experience in palowina either.
I've always thought about the pros and cons of a single layer vs multiple layers on a boat.
Ie. A single 24oz vs 3x8oz in your case.
On my small scale stuff, I've always preferred the latter for waterproofing and have seen pinprick size voids between the weave which were not 100% sealed by the lightweight fairing and paint finishes. Needless to say these wick in water without you knowing. Probably not a issue on an epoxy treated plywood core, however not good if there is foam sandwich behind the laminate.
Peel ply can resolve the weave fill however far from perfect.
As mentioned previously, staggering the weave rotation is also possible with multiple layers . Conducted a test once where we lay up a rectangular flat panel of 6 layers of 6oz carbon all at 0/90 orientation.
We then lay up another panel of 6x6oz but alternating the weave orientations to 0/90 45/45
I could not believe how horrendous the first panel was in a twist type load
.
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Originally Posted by commuter boats View Post
Thank you, I wish we could get more discussion of such things.
Adding to the discussion; For the type of boat that I build, I like 0/90 on the bottom and 45/45 on the topsides, some unidirectional ( longitudinally) in the deck and on top of the stringers. Stringer laminate's and cockpit decks should be 0/90 in my opinion.
Gerald
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Originally Posted by Lenm555 View Post
Hi Gerald,
excuse me for not having the time yet to go back over the hundreds of pages in this thread. May I ask what type of boats that you build and your reasoning for the 45 in top sides.
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Originally Posted by commuter boats View Post
Hello, now my delay sorry. I'm very low volume but have a few running around, most of my boats are slender plaining boats and designed to be very stiff. Most of my panels are cored and I use more substantial transverse members then you'll typically see in small boats. I just posted a couple photos In the Raptor thread (http://www.thehulltruth.com/boating-...r-project.html ) and won't clutter this thread additionally.

I've got a boat going for my lady and myself in which I'm using five different foams, balsa and core mat for cores with three-quarter inch balsa in the highest loaded parts of the bottom.

Longitudinally I see my boats as a beam with the topsides being the web, deck/ house and hull bottom opposing each other.

A good discussion on the merits of 45 x 45 versus 0 x 90 for tabbing structural members would be interesting, I'll start by going against the trend and advocate for mat - roving for its ability to spread loads out and reduce the effects of peel.
Gerald
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Originally Posted by Lenm555 View Post
Good debate Gerald re tabbing.

Nice boat btw. - looks very functional and well layout.

If 0/90 is used for tabbing, i can't understand what purpose the 0 direction fibres are providing? They are essentially parallel to the joint. To me these seem redundant?
The 90's are Perpendicular to the joint, and therefore mechanically link the two panels.
Only 50% of the fibres in the cloth are being mechanically utilised.

A 45/45 tabbing has all of the fibres running more or less perpendicular to the joint and hence mechanically link the two panels utilising 100% of the fibres.

Now peel surely must have something to do with surface tension? The mat provides a good bedding to the panels and cloth. I.e a good medium for mechanical bonding as well as dampening loads (any direction) due to its multidirectional fibres.

I propose that a thin layer of mat followed by a 45/45 would be the optimum.

Feel free to burn me down as do not profess to be a naval architect or composite engineer..

I am about to conduct a test to see if peel is improved by putting down a fine layer of mat prior to the cloth (Angel hair).
I.e. Layer of angel hair followed by a 6oz Kevlar or Eglass.
The angel hair looks to be around 1oz weight.
Attachment 560909
Quote:
Originally Posted by 1blueheron View Post
This should be interesting. I am curious about the functionality of mat in plywood/epoxy cold molded builds. The first boat I looked at building was supposed to use a single layer of 1208 biax inside and out. 1 layer of 3/8" plywood and one layer of 1/4" for a total of 5/8" plywood core. I assume the 1208 used the mat to create a resin rich layer between the fabric and the wood and help prevent epoxy starvation while the biax was to provide the strength.

I have read in numerous places that matte serves no purpose in epoxy building. It has no strength and only is used to provide bulk. Much different than in Polyester or Vinylester layups where it has more function.

The boat I am building now rejects the notion of matte and uses a min. of 12oz biax on all seams and a total buildup of 30oz. combined biax and woven. Seems like two different schools of thought or methodologies.

Does skinning a plywood layup with glass fibers running at diagonals to the wood grain or parallell to the wood grain provide the greatest stiffness and strength? Since the cold molded boat was diagonally planked and the S&G boat uses panel construction, it seems both have the bulk of wood and glass fibers all running the same with no diagonals. Wouldn't placing the glass fibers at diagonals to the wood create a triangulation effect and provide more stiffness to the structure?
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Originally Posted by commuter boats View Post
It's not getting much interest here and really isn't in the theme of the "cold molded construction fight club" , I tried to start a thread on composites but there doesn't seem to be much interest or I have the Internet equivalent of bad breath

Thank You

No burning for me, I'm neither naval architect or composite engineer either but I have spent a considerable amount of time attempting to educate myself but because I'm self educated the probability of being misguided is high...

I'm going to post a diagram from an engineering manual showing the flexural strength of three different laminates which will illustrate that roving ( woven 0/90) has only a 2000 pound advantage over mat ( 27,000 verses 25,000 psi ) on a diagonal ( the same orientation as a double bias ) while providing 43,000 pounds in the orientation of the wrap ( 0°). Please note that flexural strength is not the same as tensile strength which would be considerably lower. Many of the woven roving's that are available are not balanced, 40% of their fibers are in the fill and 60% of their fibers are in the wrap ( length of the roll ) which is why the graph is showing different values for the roving.

It was my intent to ramble on about fiber orientation but really except in relatively highly engineered structures the thickness of the tabbing is far more significant than what it's made up of, most of the failures are a result of inadequate stiffness.

Probably the most common tabbing failure to see in the repair industry as a single layer of Stich mat ( a balanced 24 oz woven roving ( typically with fewer and larger bundles ) bonded to a 1.5 ounce mat ) torn loose from the tension side of the structure.

The side of the tabbing that goes onto the grid is being loaded in sheer, the tabbing that runs out on the hull is applying tension to its glue line, what's referred to as "peel". Because fiberglass reinforced plastic (FRP) flexes quite a lot as it takes a load it's hard to apply that tension to much of that glue line. Better glues can only provide better adhesion to the small amount of area that the tabbing can distribute the load to.

Running a single layer of 1708 10 inches out onto your hull is pointless as the laminate is not stiff enough to carry the load more than an inch from your vertical member, some manuals call for tabbing to be 10 times as long as it is thick, they are suggesting that it requires 1 inch of thickness in the tabbing to carry the load out 10 inches. ( Oversimplified..but.. )

To improve peel, the tabbing needs to be stiffer, you can go exotic ( carbon fiber, etc.) or you can go thicker and making the tabbing thicker ( stiffer ) regardless of which glue will allow more square inches of the tabbing to work for you.

Fiberglass is heavier and more expensive than resin, if my goal is to spread my loads over 6 inches of tabbing I'm going to need .6 inches of laminate at the root of my tabbing. If I build that with 60% glass content it will be heavier and more expensive than if I built it with a 40% glass content. The 60% glass content would be stronger not stiffer, is it justified?

These thoughts are generalizations, there will be exceptions for differing constructions techniques but in the crafts that I see a lack of stiffness is the most prominent failure in fiberglass structures and amounts to probably near 70% of the tabbing failures with a lack of tensile strength and poor bonding techniques being about equal.

Lots of boats have the grid installed entirely with a chopper gun and they often get away with it, it's heavy but if it's thick enough ( stiff enough ) it works.

Gerald
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Last edited by commuter boats; 08-22-2015 at 09:43 AM.
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Old 08-22-2015, 09:45 AM   #12
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Fiberglass over aluminum..
Extending the useful life of a riveted boat
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Old 08-22-2015, 12:26 PM   #13
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Commuter, tell us a little bit about figuring the fiberglass layup schedule for the gyro mounting base. That's a hell of a dynamic load even if the vessel is engineered for it during initial construction, Was it a metal hull or fiberglass?
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Old 08-22-2015, 03:15 PM   #14
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Here is my Bertram 20 Bahia Mar (one on the left). Hoping that the Hunt will be as nice.
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Old 08-22-2015, 07:12 PM   #15
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Commuter this thread is a great idea and will take some time to get going. That said, I have question on your lift strake extension. What did you build the strakes out of?
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Old 08-23-2015, 09:37 AM   #16
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Commuter this thread is a great idea and will take some time to get going. That said, I have question on your lift strake extension. What did you build the strakes out of?
Thank you, brought over from that thread...
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Originally Posted by commuter boats View Post
The bottom got black bottom paint and gelcoat was sprayed ( very modestly) above the waterline. The gelcoat should of had just a touch more blue pigment but even as it is it will match much better in a few months, the gelcoat was also shop made and primarily a vinylester laminating resin which will darken with light exposure.
The only fill on this project that wasn't laid glass was the microballoon / airosil filler for the strake extensions and two rolled coats of high-build primer, there was no putty applied with a putty knife, all low spots were filled with small torn pieces of mat, the only difference from the original construction is a better quality of resin and a higher glass content.

The owner rigged the boat ( I had input on engine height) and is definitely happy with what he got for $1400.
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Old 08-23-2015, 09:54 AM   #17
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Commuter, tell us a little bit about figuring the fiberglass layup schedule for the gyro mounting base. That's a hell of a dynamic load even if the vessel is engineered for it during initial construction, Was it a metal hull or fiberglass?
The vessel was a 30-year-old fiberglass hull with fiberglass covered plywood decks and bulkheads. The framing under the deck was laminated construction grade 2 x 4s.
After my client and I identified a workable location for the installation we commissioned a Naval architect to handle the back-and-forth with the Gyro manufacture and he recommended the layup. For me it was good insurance to build a structure that was stiffer than what the N/A recommended, he recommended a 3 1/2 inch core for the longitudinal stringers with a finished width of 4.8 inches. I worked with a 3 inch core and yielded 4.9 inches. I utilized 14 3/8 inch carriage bolts through the deck beams and into stiff parts of my structure and there are over 50 1/4- 20 galvanized bolts going through my tabbing and into the bulkheads fore an aft.
I've added a photo, you can see two of the bolts to the right of the Gyro mount and near a dozen of the quarter 20s into the bulkhead. All the fasteners are glassed over and also run down underneath those transverse bulkhead stiffeners.
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Old 08-24-2015, 06:25 AM   #18
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How well does glass hold up over the long term in salt water when applied onto aluminum? Are you using similar type etching/priming work that's used when painting aluminum?
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Old 08-24-2015, 08:17 AM   #19
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How well does glass hold up over the long term in salt water when applied onto aluminum? Are you using similar type etching/priming work that's used when painting aluminum?
That boat is still in use today 20 years after glassing it. If you click on the link with the photo there's a little bit of a description but the preparation was soap and water followed by sandblasting with silica. With the hull completely sandblasted, tools and vinyl ester resin were readied and the surface was again brush blasted and then coated with a minimum time in between.
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Old 08-25-2015, 06:41 AM   #20
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That boat is still in use today 20 years after glassing it. If you click on the link with the photo there's a little bit of a description but the preparation was soap and water followed by sandblasting with silica. With the hull completely sandblasted, tools and vinyl ester resin were readied and the surface was again brush blasted and then coated with a minimum time in between.
Gerald,

Diving into theoretical space here and hoping I won't get flamed. Aluminum being an extremely strong material by weight if you can prevent deflection without adding a lot of material thickness. It is a great boat building material if you can prevent oxidation in salt environ.

I am interested in knowing if anyone has seen or knows of any boats built using either protected air beam construction ( a thin skin of aluminum inflated with enough pressure to make it rigid and hold a shape) similar to a RIB but aluminum, or wood reinforced with a thin layer of aluminum in a laminated layup with lumber or plywood on either side and then epoxy/glass encapsulated.
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