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Old 18-09-2020, 18:15   #1
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Polyethylene dinghy - Custom attachments / Eye Pads

I'm owning a cheap polyethylene dinghy which proofed to be very stable and robust. One disadvantage of this bargain buy is that all eye pads to attach lines are not very well designed and placed. I'm planning now to modify it to my needs, adding a heavy duty stainless steel padeye at the bow just above the waterline (to pull it behind my sailing boat on short journeys) and also some strong attachments to lift it up on deck using a halyard.

I'm looking for tips on how to work with polyethylene, especially waterproofing / sealing screw holes near the waterline, or maybe on methods to avoid drilling holes at all?

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Old 18-09-2020, 18:34   #2
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Re: Polyethylene dinghy - Custom attachments / Eye Pads

G-F



G-FLEX, sand it, flame treat it and gflex
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Old 18-09-2020, 19:52   #3
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Re: Polyethylene dinghy - Custom attachments / Eye Pads

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G-F



G-FLEX, sand it, flame treat it and gflex

Yes, G-Flex works pretty well on PE. Good for patching holes.



Would you trust it to tow or lift a dinghy? I kinda doubt it. I'd need to see some high-load critical applications with some sea miles first.


Tricky. I'd be looking at through bolts and backing plates, made more complicated by the double wall construction. As for sealing, Sand, flame, and try either PL S40 or PL Marine (best PE bonding).
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Old 18-09-2020, 20:46   #4
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Re: Polyethylene dinghy - Custom attachments / Eye Pads

Wow thatís cool. Iíve had no luck sticking anything to PE ever. And Iíve worked with the manufacturers reps from 3m and Bostik on this. PE is such a low surface energy plastic itís supremely hard to get anything to bond.

Iím gonna go get some gflex and give it a try. This could be really helpful!
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Old 19-09-2020, 03:48   #5
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Re: Polyethylene dinghy - Custom attachments / Eye Pads

I was definitely planning for bolts and backing plates where possible. However Its tricky due to the double walling and odd shape.
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Yes, G-Flex works pretty well on PE. Good for patching holes.

Would you trust it to tow or lift a dinghy? I kinda doubt it. I'd need to see some high-load critical applications with some sea miles first.


Tricky. I'd be looking at through bolts and backing plates, made more complicated by the double wall construction. As for sealing, Sand, flame, and try either PL S40 or PL Marine (best PE bonding).
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Old 19-09-2020, 04:22   #6
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Re: Polyethylene dinghy - Custom attachments / Eye Pads

Iíve done this once only, and it was successful

I cut outa large hole of the inside skin fill the area plus about another 100% of the size of the backing plate with an epoxy or polyester bog to create a block which is similar to what you would do between 2 fibreglass skins

This needs to be in an area that can hold the load without ripping the entire piece out, so in the photo of the dingy I would use the front bulkhead and have my attachment points about 100 mm or 4 inches below the top so you would need a backing plate both sides ,the internal area filled with bog but the bog needs to be filled all the way to the top of the bulkhead to even out the lifting load as wide as possible,the backing plates are then bolted together to form a clamp

The towing point may need a large backing plate internally which can be screwed into the bog from the inside only with a smaller one on the waterline

Basically just copy fixing points on boats with foam or balsa cores , itís not too hard and by adding the bog it makes the load distribution without compressing the skins

Others may have other suggestions but it has worked for me on a double skinned dinghy
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Old 19-09-2020, 04:36   #7
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Re: Polyethylene dinghy - Custom attachments / Eye Pads

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Iíve done this once only, and it was successful ...
Thanks, for the excellent description of an interesting idea.
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Old 19-09-2020, 04:52   #8
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Re: Polyethylene dinghy - Custom attachments / Eye Pads

Thanks Gord,

The plastic boat are indestructible but heavy little suckers,thatís why we donít see many on Davits
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Old 19-09-2020, 07:19   #9
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Re: Polyethylene dinghy - Custom attachments / Eye Pads

Google 'spin welding', this is the best, fastest and easiest way of plugging a hole in low density polyethylene, you'll need a router and adapter.
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Old 19-09-2020, 07:25   #10
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Re: Polyethylene dinghy - Custom attachments / Eye Pads

I wish I know how to edit a post, but anyway, this process is also used for installing fittings in polyethylene water and holding tanks.
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Old 19-09-2020, 07:29   #11
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Re: Polyethylene dinghy - Custom attachments / Eye Pads

Hi. Screw out plastic plates will give you access between the hulls. Your dinghy seems to have some nice flat vertical areas where you could use a door which could give you a great cubbyhole. Just get a high quality one with strength, good hinges and Ted-Gel the lock.
Backing plates...foam/glass, aluminum. Whatever, just twice the size to spread the load. Try the lifting points dry, add some water to the dink and watch for bending. You might want to add a freeing port of good size for rain or a big wave. Iím not sure if Plexus will stick...you might ask them because itís great.
Lastly...folding pad eyes. I like the cast 316 diamond eyes but the folding large sizes donít stick in your...
What make and model is your dinghy. Any lighter colors.?
Happy trails to you
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Old 19-09-2020, 07:57   #12
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Re: Polyethylene dinghy - Custom attachments / Eye Pads

Thanks for all the great ideas.

The model is locally made where I live, its called MiriPoly Poly Boat - Miripoly

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Hi.
What make and model is your dinghy. Any lighter colors.?
Happy trails to you
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Old 19-09-2020, 08:09   #13
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Polyethylene dinghy - Custom attachments / Eye Pads

Consider installing rivet nuts to screw pad eyes into...
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Old 19-09-2020, 10:01   #14
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Re: Polyethylene dinghy - Custom attachments / Eye Pads

I have a Walker Bay 10. another PE dink and it hangs on my Davits with the Yamaha 4 at the dock/anchor.

The WB seats are through bolted the hull to the gunwale. I switched the 1/4 so SS screws to 1/4 20 SS Bolts with solid rings on top. Used threadlock, permenent on the nuts which are special to the boat as they are recessed in. Simple, easy. Walker Bay designed it this way.
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Old 19-09-2020, 10:18   #15
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Re: Polyethylene dinghy - Custom attachments / Eye Pads

A technique I've used to fill a void between two walls is to drill a 1/2" hole through one side where it will ultimately be covered by a backing plate (easy to make from a chunk of 1/8" aluminum) and shoot some ordinary construction spray foam in through the hole to fill the void in the area of the fitting. Once set it's sufficiently incompressible to do the job - providing you have backing plates on BOTH sides.
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