Softening plastic for a DIY project 1

[AgustinF]

Hello all,

I'm trying to make a DIY skeg for an inflatable kayak after the original manufacturer hasn't been able to restock the item for replacement in months. You can read more about the project on this thread on a DIY forum. I've come to a point where the main advice and concern is regarding bonding plastic. From briefly looking on this forum it seems that before moving forward I may want to reconsider the type of plastic I'm using, to which I'm not opposed. I'm hoping to bond it to itself (fin to base) and also to these fiberglass chopsticks, which I will insert inside the biplex columns of the board, for added rigidity. I was thinking of heating up the plastic board & chopsticks in a regular kitchen oven to a softening point, about 300 Deg F, then taking it outside and working on it there to insert the chopsticks and bond the board to itself. Perhaps using an adhesive as well - idk what - recommendations are welcome. I figured hot glue or superglue. Alternatively to the oven route, or even perhaps in conjuction, I have a soldering tool I could use. I also have some metal rods (that came with the plastic board) which I thought I could use similarly to the chopsticks for rigidity. Although bonding that would probably be less successful. I'm roughly aware there are serious concerns with toxic fumes when heating plastic. Should I be concerned? How can I mitigate risk? How can I assure the most successful bonding results?

 

[TugboatEng]

Not all plastics give off toxic fumes when heated or burned. Halogenated plastics such as PVC and Teflon give off acid gasses when burned. Other plastics such as polyethylene are just hydrocarbons and have no toxic decomposition products.

 

[tygerdawg]

Seems to me that this could be easy / cheap enough:
[ul]
[li]verify the dimensions you need, or draw/trace existing design to a template[/li]
[li]find yourself a local plastics/rubber supply house and get them to sell you some good plastic sheet (offhand with no research, I'd probably go for some grade of ABS ("football helmet plastic")[/li]
[li]cut the skeg shape and the mounting boss flange out of the sheet[/li]
[li]get the right kind of glue (which is NOT superglue...cyanoacrylates are too brittle). What you want is a solvent-cement that melts/dissolves the plastic, then re-bonds into a welded joint. If done well, I think a welded joint will be as strong or stronger as a monolithic joint milled out of a single piece of plastic.[/li]
[li]File, surform, and sand to fit.[/li]
[li]develop your robust manufacturing process and start an internet business selling these things because someone's negligence created a marketing opportunity [/li]
[/ul]

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[AgustinF]

Tygerdawg,

could you link an example of a solvent-cement adhesive product, i.e. to Amazon? Any tips on this step of the glueing process? Will the chemical reaction be enough to melt the plastic or should I first heat the skeg up somehow

 

[AgustinF]

Would this work?

https://www.amazon.com/SCIGRIP-1031...cement+adhesive+product&qid=1594467279&sr=8-2

 

[tygerdawg]

I don't know, and won't pretend to be a chemical engineering expert. Contact the manufacturer's tech support team and ask.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[IRstuff]

Didn't your original website in the OP already say that glue was a bad idea?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[rickfischer51]

Do you still have the broken skeg? Where did it break? I can guess by looking at the part link, not really a very good design for a plastic part. Why do you think you need to stiffen it with fiberglass chopsticks?

Rick Fischer
Principal Engineer
Argonne National Laboratory