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Scurvy Dog
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Discussion Starter · #1 ·
I have an old Sandpiper 8 dinghy and I just can't bring myself to junk any type of boat. It is still perfectly fine for me to use for mooring maintenance or puttering around in the wetlands. Problem is the bottom is wearing out. I am looking for advice on repairing the bottom of a plastic dinghy.

A few (twelve?) years ago I tried using epoxy and fiberglass cloth, but that didn't hold up well (see pictures). Any other ideas to save this old "classic"? Thanks!
 

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You might try googling some motorcycle forums. They, especially off road bikes, use plastic fenders and gas tanks, etc. There are various repair materials available for fixing those. The types of plastic used vary, and so do the repair materials. As I understand it, you do a form of what is called welding to fix cracks, holes, etc. I once saw a book for sale which showed how to fix each type of plastic.
Don't know how this would work if you wanted to redo an entire bottom.
 

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Tartan 27' owner
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Looks to me like your dinghy is FRP (fiberglass) after all and not plastic (hdpe).
It also looks to me as though you did not fair (sand) around the holes/cracks before putting epoxy and cloth back on.
It also looks to me as though you did not put nearly enough layers of epoxy and cloth over the keel, which is the wear point on that hull.
You should probably use a thickening powder like West Systems 403 or 404 for this job too.
Try again.
 

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snake charmer, cat herder
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if it is waxy plastic, heat gun and empty and clean milk bottles and a metal backing piece that you move as you actually weld the plastic to the boat with heat. my plastic kayak that had a hole in it has been fixed perfectly with that process. if it truly i splastic, g flex will not work. btdt.
 

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Maine Dub
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215 Posts
I tried marine silicone goop and it did not keep the water out for a week. I think when the plastic gets too brittle it is time to junk the dink. It seems when you fiberglass one bad spot another pops up. If you glassed the entire bottom of the hull it might give you a few more years but at what cost?:confused:
 

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snake charmer, cat herder
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the plastic kayak i bought in 2001 is again water tight after my repair with welding plastic to the original plastic--is not as hard as it seems but you need to use a metal block back to do it right---and my plastic dinghy, wb8, and my plastic kayaks have not become brittle in sun of tropics--red kayak is 2001, walker bay is 2002 or older, and yellow kayak is 2011. mebbe it is different if one actually uses the plastic boat---i saw 2 on land in mazatlan with cracked and brittle plastic--was a cheapo coleman row boat left there by someone some unknown number of years ago, and an unidentified plastic generic boat left for storage in bright desert like sunlight

i had tried EVERYTHG to patch that hole--i used that kayak as my main dinghy in sd---nothing worked.nothing....when this plastic was heat gunned to the boat---hooyaaahhh--i again had my provisioning kayak intact. is still good and not damaged after one years service so far. is a win!!!!!!
 

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Jnoiur Mebemr
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182 Posts
if it is waxy plastic, heat gun and empty and clean milk bottles and a metal backing piece that you move as you actually weld the plastic to the boat with heat. my plastic kayak that had a hole in it has been fixed perfectly with that process. if it truly i splastic, g flex will not work. btdt.
G-Flex is specifically for plastic... Straight from West's site "Repairs plastic canoes, kayaks and inflatables made from HDPE, LDPE, ABS, PVC or polycarbonate plastic" Heres a video G-Flex Torture Demo
 

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snake charmer, cat herder
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G-Flex is specifically for plastic... Straight from West's site "Repairs plastic canoes, kayaks and inflatables made from HDPE, LDPE, ABS, PVC or polycarbonate plastic" Heres a video G-Flex Torture Demo
maybe that info works for those of you who have yet to fix a waxy plastic boat--but where in my saying been there done that does it say i have yet to try it---is one of the first things i tried and has a huge FAIL on it it just does not work. not at all. g flex ifs a badly inferior alleged fix when compared to returning the plastic to the boat in welding it with a heat gun and the things the boat was originally made of , if it is waxy plastic-- old used but clean milk jugs and water jugs of the non transparent kind. .please stop insulting my intelligence an d experience. it took me 5 years to finally get the fix on my waxy plastic kayak done correctly-- gflex is NOT the answer, sorry BTDT. now, if you like your dinghies to have incoming water problems, please by all means use g flex-- but NOTHING, not even gflex, bonds with waxy plastic except more of itself. with heat.

yes i followed directions rodlmao
 

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Scurvy Dog
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62 Posts
Discussion Starter · #10 ·
Wow, great response, thanks everyone. I can assure you that the dink is some type of plastic and not fiberglass. And it was well prepped when I put on that fiberglass cloth and epoxy many years ago.

That G-flex video is hilarious, and it looks awesome. I'm on more of a milk-carton and heat gun budget because it is such a large area to cover, but might cough up the $$ for the G-flex if that doesn't work. I had used the West System epoxy on the old repair, but never tried G-flex. I suppose dragging it on the beach all those years didn't help matters any :rolleyes:.

It is double hulled and the inner hull is still water-tight, so I can use it for now. But I would like to stop the water from filling up the outer hull, it makes it a bugger to drag when full of water.....
 

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if the outer hull fills with water and make it heavy then either repair it again and keep the water out or dill bigger holes in the outer hull and let the water out faster.
 

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You might try googling some motorcycle forums. They, especially off road bikes, use plastic fenders and gas tanks, etc. There are various repair materials available for fixing those. .
Exacting, repaired many tanks especially vintage ones. Everything you need from determining what kind of plastic your dealing with to material/tools to repair it can be found here
 
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Scurvy Dog
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62 Posts
Discussion Starter · #15 ·
Great site, Pappy! That "KC Welder Pro" for kayaks and canoes looks like the one. The price is reasonable, and I might have other uses for a plastic welder. Welder $63.00, 16 oz. of G/Flex $63.00. Hmmmm? Welder can be re-used, G/Flex when it's gone, it's gone.

I don't think they make the Sandpiper 8's any more, but from browsing some old online ads it looks like they are ABS plastic. Now I wonder if the welder will work over top of the previous fiberglass/epoxy repair attempt?
 

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Pappy -
You play with the AHRMA guys (and girls)?
A lot of my desert racing buddies did Vintage MX , I stay with open desert, enduros, supermoto and sometime trials, mostly desert. I did have a 501, TM400, yz465 and a IT465 never raced any of them, they were more show off bikes, I raced KTM's from 200mxc to a 520mxc

This was my last show off bike



This was a basket case, a buddy who rode for Yamaha used up two 426's, he ended up getting two new 450's and said here,do your thing, so I did. This is my vision of a retro 1991 YZ ( based on a 2001 426YZF and inspired by the Hanna edition YZ ) All the control and suspension is Pro Circuit thanks to a bud who rode for them, frame is powder coated red, swingarm silver, wheels anodized gold, rubs black, I drew up the graphics and my graphics guy made them up. All fasteners including axles and pinon pin are Titanium motor is 440+CC.

I was offered 10k for it but, I gave it to my son and it's now in my storage
 
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