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PostPosted: Tue Jul 15, 2014 10:57 am 
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Plastic welding does work. I've repaired a crack in my Maui and this guy converted a round hatch to the new rectangular one with MAJOR amounts of welding: http://www.hobiecat.com/forums/viewtopic.php?f=78&t=46585&hilit=weld+hatch

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PostPosted: Tue Jul 15, 2014 12:56 pm 
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RockHillHobieNewbie wrote:
I don't ever plan on using the sail option, so could I not just shorten the mast insert and put it back in.....the floor of the mast insert is still there? Or does the mast insert need to make contact with the bottom inside of the hull for some reason?
You could. However, it wouldn't be difficult to repair it. Benefits are:
1. it also acts as a stiffener or structural support (deck to hull)
2. if you cut it short it will dangle and leave a hole that needs to be filled (is only sealed near the bottom)
3. if you remove it, you still have a second hole to fill with something
4. You may never use it, but someone one down the line may -- it would be harder to replace later than fix it now.

Good news. Rummaging around the garage I found a couple of Hobie blue sample discs (see pic below). They measure 2 3/4 " diameter. I'll be happy to send them to you if you decide to go that route. You can PM me with an address. Hobie also makes welding rod in various hull colors and I don't believe they charge for it (maybe shipping?). Some is shown in the picture that is some "dune" colored rod I use occasionally. If you decide to weld, practice first -- if both sides aren't heated before you use the rod, it might lack bonding strength -- could pop off.

Image

Finally, I have some Goop and am running a sample bond with it on Hobie's PE (also in pic). I, a firm believer in trying something first-hand before assassinating it. To that end, I'm a little disappointed in some here that would make blanket statements about products without at least some investigation. The epoxies I have recommended to you I have used on several occasions in high stress areas on Hobies. If you care to open the first link I posted earlier you would also find a test sample that I had to chisel apart. I'll report the actual results of the Goop test tomorrow after it cures. If you have doubts, I recommend you call 3M and Loctite and discuss these products with them before deciding how to proceed (as I did). I wonder if any "doubting Tomasas" have actually tried these specific products before pronouncing them ineffective.

If you decide to go with the preheated cutting board, I would think you would want to have the boat standing by close enough to the heat source to install it before the patch cools. Have a burner plate in the garage or bring the boat in the kitchen when the wife is away?? 8)


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PostPosted: Tue Jul 15, 2014 1:24 pm 
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I didn't say they were ineffective, just that they aren't the ideal product for bonding this material. Ideally you want something that will flex with the plastic hull as it moves, bends, elongates and shrinks due to both temperature and use. The adhesive needs to share many of the same characteristics of the material it's being asked to bond. But this isn't my opinion - it's the opinion of the man who you trust your life with when you fly on any commercial jetliner.

What you'll find when you use GOOP, is that you can get the pieces apart if you try hard enough. But if you properly prepare the mating surfaces (water-break-free process/condition) it's going to be very tough to do.

I would still go with plastic welding, in any event. I made a "below the waterline repair" to my AI after my trip out in it. Since then it has yet to take on more than a few drops of water inside the hull, and that likely came from opening the hatches while on the water.


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PostPosted: Wed Jul 16, 2014 10:42 am 
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I'd buy a new hull.


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PostPosted: Wed Jul 16, 2014 10:47 am 
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Easy enough said Tom King.......disposable income must not be an issue for you like it is for most of us. Think I'll try the repair first.


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PostPosted: Wed Jul 16, 2014 11:17 am 
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Since I mentioned GOOP earlier, I should add that if you use it to adhere large expanses of material, you need to allow it set and dry for a couple or three days. It contains a solvent that must evaporate completely. And... do not mar the surface with deep scratches and gouges from coarse sandpaper or files. Clean it, scour with fine Scotchbrite (or 400 grit sandpaper) and adhere. Do not wipe the surface with a solvent once a water-break-free condition has been achieved.


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PostPosted: Wed Jul 16, 2014 3:57 pm 
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Even though I ran a small test sample, I'll wait an extra day to let it reach its full potential and have put it in the warm sun to accelerate the cure. Will report back tomorrow. 8)


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PostPosted: Thu Jul 17, 2014 8:39 pm 
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Roadrunner wrote:
Even though I ran a small test sample, I'll wait an extra day to let it reach its full potential and have put it in the warm sun to accelerate the cure. Will report back tomorrow. 8)
I tested the sample today after about 50 hours of cure (the instructions ask for 24). Unfortunately, this is not a product that I would use or recommend for PE under any circumstances. It took virtually no effort to separate the discs. None of the glued patch adhered to either disc -- they're clean as a whistle. The glue itself had very little tensile strength -- would stretch and rip easily. Looking at the package, it specifically cautions: "GOOP is NOT recommenced for... polyethylene...." As most here know, Hobie kayaks are made from polyethylene (more specifically known as HDPE) Here are some pics:
Image
Image

On the other hand, Tom Kirkman's advice is highly regarded. It's quite possible that I used the wrong variety of GOOP, or that it wasn't fresh enough. I also didn't make any special surface preparations. I'll just say that I just couldn't confirm his results.

If gluing below the waterline, especially in critical high stress areas where flexing may be an issue, I want something that won't get knocked off, bumped off or popped off. The example below shows some 3030 bonded to the PE. It won't peal off as you can see. Below that is a test sequence I performed on this piece a few years ago to see how good it was. You can judge for yourself:

Roadrunner wrote:
Here are a couple of HDPE sample disks that I smeared some (fresh) 3030 on. They were unprepared (no solvent, cleaning, sanding, pressure, etc). Here I tried to separate them with pliers and only succeeded in breaking one of the disks:
Image

The only way they could be separated was with a hammer and chisel:
Image

If you will examine the separated disks, you will see that none of the glue detached from the PE bond on either piece, but ripped within the glue itself:
Image


Finally, I'm including links to the spec sheets for these products. They are specifically formulated for this type of application. For reference, read the sheer strength for HDPE.
http://solutions.3m.com.au/3MContentRet ... =ImageFile
https://tds.us.henkel.com/NA/UT/HNAUTTD ... 030-EN.pdf

I hope this has provided enough specific information on products to to see that certain epoxies can be used without reservation where appropriate. 8)


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PostPosted: Thu Jul 17, 2014 9:58 pm 
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RockHill, if/when using PE patches, an easy way to shape them to the hull is with hot water. You should be able to get an almost perfect fit this way without risking burning the PE. Here are some tips:

Working inside the hull is usually a one armed job and you usually can't see what you're doing while doing it. If possible, rest the Outfitter on its side on saw horses or ground. If you put a small screw in the center of the patch you'll be able to see it centered in your hole and using pliers, hold the soft patch up against the hull by grabbing the screw while reaching around from the other side with a oven mitt for positioning and pressing.

Slowly heat by dipping it in the scalding water -- take your time -- once it softens it goes fast. Press it in place and hold it at least a minute or two until it regains its rigidity. Have a Sharpie ready to make a couple of witness marks showing orientation and location -- before moving the now hardened patch. A good fit will make for a good bond later.

The products I use are available from an industrial supplier like R.S. Hughes, Granger, etc. Shop around. The nearest R.S. Hughes to you is in NC or Fl. -- they charge about $40 for the 8010 plus shipping. Phone 877-774-8443.
__________________________________
Another way to approach this project is to position and tack the inner piece with whatever you have (G-Flex could be an option here), heat shape the outer piece, slather G-flex or GOOP (?) in the space the screw the outer plate to the inner plate with pan head stainless screws. Once set up, you could screw fore and aft, trim the sides, screw the sides, trim the centerline, then reinstall about 4 screws. For extra durability you could through-bolt. The glue acts as a sealer/gasket and the strength comes from the screws. Just an idea.


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PostPosted: Fri Jul 18, 2014 5:05 am 
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Roadrunner:
That last idea is the best I have heard, and likely what I would do in this situation especially if the area inside is difficult to reach. Where my hot plate idea if the area is hard to reach might be iffy on the inside. Actually the hot plate welding technique is commonly used in industry. I'm one of the the guys who initially developed the pressurized cooling systems in cars back in the 80's first for Mercedes in Europe then for Chrysler in the us. If you look under the hood of any car you will see a big white reservoir with a pressure cap on it. Our nickname for the thing was the living lung because it has to withstand 15 psi of pressure at 220 degrees. It's made from Un-filled polyethylene plastic in two halves. To weld it together during development we placed the two halves on what looks like a pancake griddle. Once the surface was molten we pressed the two halves together and everything bonded on a molecular level to become one piece. Basically the molecules become very excited. In development we also found you can heat up just one surface and it will still bond, but in production we heated up both just to insure a pressure seal. Today virtually every pressure vessel is made the same way, we used the same exact method to develop disposable medical filters used in hospitals.
If I were doing this repair I would use your method on the inside with screws, I would then sand the outside fairly flat, lay a clothes iron on the hull for a minute or so, then remove and press the molten patch from the fry pan over the repair spot and press in place until cool. I would then file/sand the patch to match the hull shape. Just to be safe I would have a water hose spraying on the inside of the hull while doing all this.
You could probably do the same with the Hobie welder, building up the area slowly but you would have to stop and rest often in order not to overheat the hull. A hose spraying the inside the hull while working with the Hobie welder would be recommended, (tip: only the outermost surface needs to be blue, underneath it can be any color rod you have handy). You may need as much as 5 or 6 ft of repair rod if it as deep as it looks in the pic.
Actually I'm not sure how well goop can handle heat, you may want to use GE clear silicone as your gasket material as it is good to about 600 degrees, and bonds similar to goop on PE, also silicone is hydrophobic (water won't wic). Roadrunners epoxy may also work ( I'm going to order some and try it out just to mess around, interesting stuff though most epoxies are terrible in any water environments).
Hope this helps you
Bob

Edit: After reading the specs on that 3M DP8010, I would can the hot plate and welder crap altogether (unless your into that stuff), I would make a 3 inch contour patch like roadrunner describes for the inside, then just gob that 3M 8010 on the surface of the contour patch, then screw it down with flatheads from the outside, I would then just gob the same stuff on the outside and contour it with wax paper to the shape of the outer hull and call it good, who cares about the color (it's a patch, you can't hide it LOL), you can probably do the whole job in an hour. This has actually been very interesting. If the boat is ever struck by lightning and burns, the only piece left would be the patch (reference to another thread with a blue boat).


Last edited by fusioneng on Fri Jul 18, 2014 5:33 am, edited 1 time in total.

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PostPosted: Fri Jul 18, 2014 5:30 am 
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Thanks again Roadrunner and Fusioneng for all your advice......almost seems like a work project here at work with everyone in R&D participating LOL. I've got some great ideas now combining both of your advice. Good news is I'm 6'2" and have long arms.......and need them to reach the mast insert area. There is room to work but in trying to get the mast tube out the other night .....whew it was tough. They must me installed with some type of long T-handle screwdriver as there is a slot towards the bottom of the tube. I actually cut the bottom of the tube off as it would not unscrew using a large pair of channel lock pliers. I'm pretty sure I can get it out though. I'll add an endcap of the right length as Roadrunner suggested to replace it and cut to the right length. So anyway, there is room to reach the hole and I already sanded all the drag marks out on the outside of the hull after removing the protruding piece of the mast insert. Will keep you guys informed as this project will take place this weekend. How do I post pictures here?


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PostPosted: Fri Jul 18, 2014 6:39 am 
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Funny, when I apply it (GOOP) to Hobie hulls, and I've used it for a large number of items, it's all I can do to get the stuff off. It takes hours to pull, peel and pry the stuff off.

I don't want to second guess your surface prep, but your experience with GOOP on PE is not even remotely what mine has been. I would trust my life to any repair I make to a Hobie hull with GOOP.

Ultimately, you'll need to use whatever you have the most confidence in.


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PostPosted: Fri Jul 18, 2014 7:35 am 
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Tom:
To be honest I have never tried goop except to repair tennis shoes. This has been an interesting topic, I'm definitely going to try all the different ideas including the goop. I went to their web site and they appear to have several recipes. Surface prep is probably important, do you rough up the surfaces first so it can get a foothold.
Bob


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PostPosted: Fri Jul 18, 2014 7:42 am 
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Surface prep is in fact, the most important thing you can do for any adhesive or paint. Heavily scratching and gouging the surface with coarse abrasives to provide "tooth" actually weakens the bond of nearly any type adhesive. On some substrates, it almost guarantees failure. But it continues to pervade all sorts of documents and advice.

You want to obtain a "water-break-free" surface condition for the best adhesive bond.

1. clean
2. degloss
3. adhere

You can read more here, if you're interested:

http://www.rodbuilding.org/library/waterfree.html


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PostPosted: Fri Jul 18, 2014 9:06 am 
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RockHillHobieNewbie wrote:
THow do I post pictures here?


Image FAQ: http://www.hobiecat.com/forums/viewtopic.php?f=18&t=8574

Images must be hosted at a location on the internet. We do not host images or files on our Hobie servers for security and liability reasons.

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