hull repairs

 A friend asked me to take a shot at repairing a hole worn through his family kayak. The area worn away is at the stern on the keel tip.  The hole had been "repaired" with some sort of goop.
After cleaning the boat and scrubbing off the goop residue, I got a good look at the challenge ahead.

Looking for NWKA advice and suggestions before I dive into this project.

If it is the typical HDPE plastic found in most roto molded kayaks today, find yourself a similarly colored HDPE plastic bucket as a source of new material.

-Sand or grind down the area to be repaired to remove any embedded rocks or sand and to get the area rough gouges smoothed out to a more uniformed state.
-Clean off the new bucket with some acetone to remove any oils or other contaminants.
-Cut out 1/8" - 3/16" strips of this bucket with whatever method you have available.
Note: it will cut pretty easy with big scissors once heated and lightly softened.
DO NOT USE A TORCH!!!!  Completely uncontrollable for the heat input. 
-You can soften the plastic by placing rough cut chunks out on parchment paper and carefully heat these up in the oven or with a heat gun (ex Harbor Freight) until they are lightly softened and have relaxed, but do not let them get burnt or get bubbly.
-Go ahead and cut the strips and place back on the parchment paper to be resoftened for the next step.
-Once the strips are resoftened and pretty flexable, apply heat from a heat gun to the affected area on the kayak until it starts to gloss.
-Quickly taking one strip at a time, and lay the soft hot piece down on the heated kayak and press down with the back of a heated metal spoon and massage it into the kayak plastic. This is like welding so you are trying to get the two materials to mesh together.
-You will need to keep applying heat to the kayak, the new piece and spoon as you go to keep all of it working.
-Continue adding strips of new plastic side by side to the old plastic until you have new single layer covering the old worn area of the kayak.

-Prepare more pieces of bucket material as you did before.
-Preheat the kayak repair area and spoon again.
-Continue welding on a new layer only now 90 degrees offset from the last layer.
-You'll want to build up this area thicker than what it was prior to the damage.
-Also, by building up the layers you will have material you can sand back to get the shape correct that the keel needs to perform correctly and look good too.
-Once you have the shape dialed into how you want it, carefully heat the surface again with the heat gun just until it begins to gloss.  STOP and let it cool down without touching it.

Or you could use this to do the same thing.

https://nextadventure.net/hobie-kc-welder-pro-w-rod-stock.html

If you have a heat gun, I found a silicone hand-press roller to be more handy than a spoon to get patch material pressed together smoothly.

https://www.amazon.com/WildPlatt-Silicone-Roller-Premium-Bearings/dp/B01M6U1PEF/ref=sr_1_2?ie=UTF8&qid=1493937810&sr=8-2&keywords=silicone+roller

The spoon definitely works.

If you have a heat gun, I found a silicone hand-press roller to be more handy than a spoon to get patch material pressed together smoothly.

https://www.amazon.com/WildPlatt-Silicone-Roller-Premium-Bearings/dp/B01M6U1PEF/ref=sr_1_2?ie=UTF8&qid=1493937810&sr=8-2&keywords=silicone+roller

The spoon definitely works.

This is an interesting idea Tinker. 
I might have suspected that the roller might stick to molten plastic. Apparently not.
Do you have any pictures of your work?
Thanks

Or you could use this to do the same thing.

https://nextadventure.net/hobie-kc-welder-pro-w-rod-stock.html

 Thanks for sharing this! Im curious and may order one for future projects.

For now Im using..

If it is the typical HDPE plastic found in most roto molded kayaks today, find yourself a similarly colored HDPE plastic bucket as a source of new material.

-Sand or grind down the area to be repaired to remove any embedded rocks or sand and to get the area rough gouges smoothed out to a more uniformed state.
-Clean off the new bucket with some acetone to remove any oils or other contaminants.
-Cut out 1/8" - 3/16" strips of this bucket with whatever method you have available.
Note: it will cut pretty easy with big scissors once heated and lightly softened.
DO NOT USE A TORCH!!!!  Completely uncontrollable for the heat input. 
-You can soften the plastic by placing rough cut chunks out on parchment paper and carefully heat these up in the oven or with a heat gun (ex Harbor Freight) until they are lightly softened and have relaxed, but do not let them get burnt or get bubbly.
-Go ahead and cut the strips and place back on the parchment paper to be resoftened for the next step.
-Once the strips are resoftened and pretty flexable, apply heat from a heat gun to the affected area on the kayak until it starts to gloss.
-Quickly taking one strip at a time, and lay the soft hot piece down on the heated kayak and press down with the back of a heated metal spoon and massage it into the kayak plastic. This is like welding so you are trying to get the two materials to mesh together.
-You will need to keep applying heat to the kayak, the new piece and spoon as you go to keep all of it working.
-Continue adding strips of new plastic side by side to the old plastic until you have new single layer covering the old worn area of the kayak.

-Prepare more pieces of bucket material as you did before.
-Preheat the kayak repair area and spoon again.
-Continue welding on a new layer only now 90 degrees offset from the last layer.
-You'll want to build up this area thicker than what it was prior to the damage.
-Also, by building up the layers you will have material you can sand back to get the shape correct that the keel needs to perform correctly and look good too.
-Once you have the shape dialed into how you want it, carefully heat the surface again with the heat gun just until it begins to gloss.  STOP and let it cool down without touching it.

 Thanks INSAYNE!  I appreciated the helpful reminders and solid info. It helped make this project a success.
There were a few critical moments that could have gotten ugly, but Im happy with the finished work.
Projects like this have me looking forward to when 3D printing makes roto-molding obsolete.

I chose to switch from my old hot air gun to a hobby torch.
I enjoyed using it due to its speed and size but there are obvious risks, especially around plastic this thin.

I had some blue material from a WS boat and was hoping that it would be compatible with the Perception plastic. Some seem to have a lower melting threshold. Malibu plastic can be very challenging to mix with others. Anyway, the WS plastic was a fit.

Right on!   Looks awesome, too!

I usually don't recommend the use of a torch unless I know the person has good hand control because as you said, it could have gone bad on you. 

Some day I may go ahead and pick up one of the KC Welders as this would probably be the easiest method overall.  But, I've been successful with just using a good heat gun, my soldering iron and a hot spoon.

I fixed a cracked seat peg hole on my Hobie Revo at camp during ORC one year with just a spoon I got at Dollar Tree and my camp stove.  Still water tight today. 

Sorry, I didn't take pictures of the repair.  It was the same spot, but not as big a repair as your project required.  I used the roller to put as much weight on the patches as I could while welding them together.

The silicone doesn't soften at the temperatures at which we're working, and it helps to "pre-heat" the roller and to keep heating the work area as you press the pieces together.

Great job on that repair.  That was nasty looking before you got started.

(I still use the roller it to smooth the edges of gravel rash)

I usually don't recommend the use of a torch unless I know the person has good hand control because as you said, it could have gone bad on you. 

Some day I may go ahead and pick up one of the KC Welders as this would probably be the easiest method overall.  But, I've been successful with just using a good heat gun, my soldering iron and a hot spoon.

 The bernzomatic torch was nice to work with. It has a dampening attachment that protects the plastic from the flame and the heat source is adjustable. Its ultra light and there is NO CORD.
It's not for every job though. Working around scuppers with any heat source requires my full attention but this KC welder has a potential to be super helpful when welding scupper holes.

Here is a photo of a previous stern repair. (Malibu 4.4) Used the hot air gun and a kayak plastic salad.
Just like the above project, it took a lot more material than I had expected.

If anyone stumbles on this later and thinks, "Man, I wish I had some Hobie yellow PE plastic to match..." please message me. I've been keeping chunks of yellow Hobie material I found in a dumpster and I'd be more than happy to mail you some.

Thanks Redbeard. Your offer is very generous and possibly critical to a Hobie welders success.
I do hope that this thread can eventually be a resource for someone when needed.
I know that as long as I am using roto-molded boats, I'll need to be a plastic welder.

Here's some of my scupper work on the raspberry Scupper Classic. This hole was created by stress secondary to oil canning. There was no additional material used on this air gun and hot steel combo fix. This gen of PE was sensitive and I had concerns trying to reinforce the area with superior plastic.

If anyone stumbles on this later and thinks, "Man, I wish I had some Hobie yellow PE plastic to match..." please message me. I've been keeping chunks of yellow Hobie material I found in a dumpster and I'd be more than happy to mail you some.

Captain Redbeard I'll happily take you up on your offer if we can work out shipping to AK. Got a nasty gouge on the bottom of my Oasis from tire wear towing it behind my bike for about a half mile in Whittier on a homemade trailer last summer. Still plenty of hull thickness for now, but I should really look after properly repairing it soon.




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If anyone stumbles on this later and thinks, "Man, I wish I had some Hobie yellow PE plastic to match..." please message me. I've been keeping chunks of yellow Hobie material I found in a dumpster and I'd be more than happy to mail you some.

Captain Redbeard I'll happily take you up on your offer if we can work out shipping to AK. Got a nasty gouge on the bottom of my Oasis from tire wear towing it behind my bike for about a half mile in Whittier on a homemade trailer last summer. Still plenty of hull thickness for now, but I should really look after properly repairing it soon.




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How the hell did you manage that?!?!? You had good clearance when you pre towed it here!!

If anyone stumbles on this later and thinks, "Man, I wish I had some Hobie yellow PE plastic to match..." please message me. I've been keeping chunks of yellow Hobie material I found in a dumpster and I'd be more than happy to mail you some.

Captain Redbeard I'll happily take you up on your offer if we can work out shipping to AK. Got a nasty gouge on the bottom of my Oasis from tire wear towing it behind my bike for about a half mile in Whittier on a homemade trailer last summer. Still plenty of hull thickness for now, but I should really look after properly repairing it soon.




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How the hell did you manage that?!?!? You had good clearance when you pre towed it here!!

I think we offset the hull channels from the bars on the trailer at your place. Did the same thing here then strapped it down tight. I'm thinking either too tight or the load shifted when I rode over railroad tracks. Still significantly tough, but I'll need to fix it before beach abrasion takes its toll.


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Guess you'll be stopping and spot checking on longer bike rides from now on won't ya?