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Old 08-25-2015, 07:15 AM   #21
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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.
Yeah I saw that.......blast and quickly "prime" with VE resin...no acid etch, no zinc chromate primer.....I'm surprised that salt water and air that can seep through from the inside of the boat, ie through the rivets, didn't cause some oxidation and spot delamination on the bottom side...very interesting...

You mentioned the change in hull flex and weight that would make the boat act differently than designed, but you didn't mention how the boat rode afterwards...what was the consensus? Better or worse or neutral?
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Old 08-25-2015, 07:50 AM   #22
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Commuter-

I've got a 30 year-old aluminum jon boat that we use in our construction business. It's been dragged so much that it's beginning to leak through the strakes molded into the bottom.

I'd like to do a fiberglass overlay to get a few more years out of it. I would appreciate any tips you might have for fiberglassing over aluminum. Type of cloth, resin, necessary prep work, etc?
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Old 08-25-2015, 07:54 AM   #23
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Personally I would use WEST G-FLEX and a couple of layers of 10 oz fiberglass cloth (or tape). Surface prep is the key - it needs to be clean to bare metal
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Old 08-25-2015, 08:47 AM   #24
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Gerald,

Diving into theoretical space .......

I am interested in knowing if anyone has seen or knows of any boats built using either protected air beam construction ...........
They build a lot of airplanes and rockets with an aluminum honeycomb ( some of which uses a paper like product in between two pieces of aluminum) but I'm not familiar with any boats being built that way. There have been boats built with an aluminum grid and either wood or fiberglass skins.
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Yeah I saw that.......blast and quickly "prime" with VE resin...no acid etch, no zinc chromate primer.....I'm surprised that salt water and air that can seep through from the inside of the boat, ie through the rivets, didn't cause some oxidation and spot delamination on the bottom side...very interesting...

You mentioned the change in hull flex and weight that would make the boat act differently than designed, but you didn't mention how the boat rode afterwards...what was the consensus? Better or worse or neutral?
The boat pounded considerably worse, I worried about corrosion from the inside around the rivets but that has not been a problem.

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Commuter-

I've got a 30 year-old aluminum jon boat that we use in our construction business. It's been dragged so much that it's beginning to leak through the strakes molded into the bottom.

I'd like to do a fiberglass overlay to get a few more years out of it. I would appreciate any tips you might have for fiberglassing over aluminum. Type of cloth, resin, necessary prep work, etc?
Without question the prep is the key. Everybody thinks that aluminum is resistant to corrosion when in fact aluminum corrodes very quickly and its own corrosion inhibits further corrosion. You cannot bond to the corrosion, which demands a minimum time between prep and prime.
The skin that I applied was just chop ( mat / iso-polyester ) over Derakane 411-11 vinyl ester resin primer with a couple layers of 10 ounce cloth only at the abrasion points. A little higher glass content improves abrasion resistance.
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Personally I would use WEST G-FLEX and a couple of layers of 10 oz fiberglass cloth (or tape). Surface prep is the key - it needs to be clean to bare metal
WEST G-FLEX wasn't around 20 years ago and although I haven't used it myself, my understanding of its physical properties would probably allow it to be a good durable coating but too flexible to perform similar to this coating, more like a Glovit (sp) and maybe a better applied to the inside.
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Old 08-25-2015, 11:53 AM   #25
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I have used G-flex on a bunch of old grumman canoes - everything from sealing seams to rips and tears in the aluminum. Haven't lost a patch yet, but have worn a few down from scraping rock and river bottoms.
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Old 08-25-2015, 01:47 PM   #26
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They build a lot of airplanes and rockets with an aluminum honeycomb ( some of which uses a paper like product in between two pieces of aluminum) but I'm not familiar with any boats being built that way. There have been boats built with an aluminum grid and either wood or fiberglass skins.
I've seen the grid and honeycomb materials which have some weight reduction benefits. l guess the general idea on a small scale would be a Mylar balloon encapsulated with a composite skin. The inflated balloon gives the shape rigidity without any structural weight while the composite skin protects the balloon from impact and damage.

Now make the balloon an aluminum beam of .004 aluminum, roughly the wall thickness of a pop can inflated to about 14 PSI and wrap it with kevlar/carbon and a layer of glass. Tough, extremely lightweight, very little flex. Doubles as a flotation chamber
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Old 08-26-2015, 04:44 AM   #27
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Could you not weld up the holes and coat with a product like linex?


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Commuter-

I've got a 30 year-old aluminum jon boat that we use in our construction business. It's been dragged so much that it's beginning to leak through the strakes molded into the bottom.

I'd like to do a fiberglass overlay to get a few more years out of it. I would appreciate any tips you might have for fiberglassing over aluminum. Type of cloth, resin, necessary prep work, etc?
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Old 08-26-2015, 05:12 AM   #28
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Could you not weld up the holes and coat with a product like linex?
Yes, welding is a possibility. I've been welding on construction equipment for 30 years, but have very little experience with TIG or aluminum. If I have to pay a welder, I'd probably be better off buying a new boat.
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Old 08-26-2015, 06:38 AM   #29
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Could you not weld up the holes and coat with a product like linex?
2 words.

Flex Seal.

That dude in the commercial made a boat out of a screen door.
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Old 08-26-2015, 10:01 AM   #30
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That almost made me shoot coffee through my nose


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2 words.

Flex Seal.

That dude in the commercial made a boat out of a screen door.
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Old 08-26-2015, 11:01 AM   #31
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Originally Posted by buckshotgumbo View Post
2 words.

Flex Seal.

That dude in the commercial made a boat out of a screen door.
HA!
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Old 08-26-2015, 08:24 PM   #32
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Originally Posted by 1blueheron View Post
I've seen the grid and honeycomb materials which have some weight reduction benefits. l guess the general idea on a small scale would be a Mylar balloon encapsulated with a composite skin. The inflated balloon gives the shape rigidity without any structural weight while the composite skin protects the balloon from impact and damage.

Now make the balloon an aluminum beam of .004 aluminum, roughly the wall thickness of a pop can inflated to about 14 PSI and wrap it with kevlar/carbon and a layer of glass. Tough, extremely lightweight, very little flex. Doubles as a flotation chamber
The way I see it there's only three types of structure that would benefit from internal air pressure, something that resembles a sphere, something that resembles a tube, or a rectangular type structure with internal webs or stitching like the floor of an inflatable boat deck. The limitations of those structures doesn't make them very useful when a square section is so much stiffer than a round section. I understand the weight savings possibility your suggesting but it seems somewhat limited to applications we see in inflatable boats and escape slides for airplanes. It seems like tubes large enough to complement the structure of most boats would take up too much room a lesser boat looks like an inflatable.
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Old 08-27-2015, 02:04 PM   #33
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guys are there any chemical applications that will remove wax and the plug release agent from the bottom of a boat?
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Old 08-27-2015, 02:13 PM   #34
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guys are there any chemical applications that will remove wax and the plug release agent from the bottom of a boat?
Go to an auto paint store and get something like Maxx Solve or PPG DX330 wax and grease remover used for cleaning the surface before you sand or prep anything....you can also use Interlux Fiberglass Prep or Interlux 202 solvent, but the marine stuff may be more expensive per gallon...need to shop around...but they all do the same thing.
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Old 08-27-2015, 04:17 PM   #35
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Thanks maxie I knew this was the right place to ask!!
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Old 08-27-2015, 06:48 PM   #36
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This is a great option too. Citrus mold cleaner from stoner. And it smells great!

http://www.moldmoreparts.com/maintenance/a500.html

Last edited by kln; 08-27-2015 at 07:05 PM.
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Old 08-27-2015, 10:26 PM   #37
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This is a great option too. Citrus mold cleaner from stoner. And it smells great!

http://www.moldmoreparts.com/maintenance/a500.html
I'm going to try that, thanks.

Gerald
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Old 08-27-2015, 10:41 PM   #38
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You don't always need to grind all the gel-coat off...

Laminating over gel coat & Whaler repairs
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Old 09-01-2015, 01:59 PM   #39
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I have used G-flex on a bunch of old grumman canoes - everything from sealing seams to rips and tears in the aluminum. Haven't lost a patch yet, but have worn a few down from scraping rock and river bottoms.
Thank you for that, it seems as though I misunderstood the properties of G-flex. The only thing I've read of it was in an advertisement in wooden boat magazine a bunch of years ago. I thought it was more viscous and similar to Plexus Adhesive in properties, I didn't know that you could laminate with it,.
Gerald
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Old 09-02-2015, 08:50 AM   #40
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Thank you for that, it seems as though I misunderstood the properties of G-flex. The only thing I've read of it was in an advertisement in wooden boat magazine a bunch of years ago. I thought it was more viscous and similar to Plexus Adhesive in properties, I didn't know that you could laminate with it,.
Gerald
You can probably get away with using Gflex and cloth, but at 15,000 cps, its not ideal for wetting out laminate...the 655 version is even thicker. It does have similar properties to Plexus in strength/modulus but elongates less, 150% for P vs 32% GF...but the stuff is made to stick to a lot of different components including plastic, which most epoxies don't do.
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