Glue/Weld Plastic? - Page 2 - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 
  #11  
Old 08-08-2008
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 9 Times in 9 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
The problem with tapping a new hole is that you generally shouldn't use metal fittings in plastic openings... since the metal will generally expand more than the plastic and lead to stress cracks in the plastic.

GBurton-

You really should start a new thread instead of hijacking this one.
__________________
Sailingdog

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.

Still—DON'T READ THAT POST AGAIN.
Reply With Quote Share with Facebook
  #12  
Old 08-08-2008
Francophobe
 
Join Date: Oct 2007
Location: Atlanta, GA
Posts: 168
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
TheFrog is on a distinguished road
Quote:
Originally Posted by sailingdog View Post
The problem with tapping a new hole is that you generally shouldn't use metal fittings in plastic openings... since the metal will generally expand more than the plastic and lead to stress cracks in the plastic.
I would actually say that while the metal expansion is part of the problem even if a plastic nipple were used there is a high chance of stress cracks due to the plastic fitting not being designed with sufficient wall thickness to deal with the tensile (hoop) stress it will encounter when a NPT thread (tapered) is screwed in. The reason when the NPT threads are effective at sealing well is due to the taper applying a force radially outward on the female thread. For this to work well in plastic there needs to be a fairly robust wall thickness to not crack. I doubt that the existing plastic has the required thickness.
__________________
_________________
"Ventarrón"
Flying Scot # 4964

Quote:
Golf is an exercise in Scottish pointlessness for people who are no longer able to throw telephone poles at each other.
-Florence King

To get the most from Sailnet, follow the link in
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
's signature.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Reply With Quote Share with Facebook
  #13  
Old 08-08-2008
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 9 Times in 9 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
True, but it would be worse with a metal fitting. If you used an NPS fitting, the hoop stress would be lower, since it isn't tapered. No need to use a threaded nipple if you're epoxying it in place though.
__________________
Sailingdog

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.

Still—DON'T READ THAT POST AGAIN.
Reply With Quote Share with Facebook
  #14  
Old 08-08-2008
Francophobe
 
Join Date: Oct 2007
Location: Atlanta, GA
Posts: 168
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
TheFrog is on a distinguished road
Spin welding

Quote:
Originally Posted by sailingdog View Post
True, but it would be worse with a metal fitting. If you used an NPS fitting, the hoop stress would be lower, since it isn't tapered. No need to use a threaded nipple if you're epoxying it in place though.
SD, I agree with you but I am concerned that it would be very difficult to get epoxy to adhere well enough to the Polypro to glue a nipple in place. PP is just too slippery to glue easily.

Another idea. Find a polypropylene nipple, threaded on one end only. Cut off the old nipple, clean the stub of the old nipple and the unthreaded end of the nipple well. Chuck the nipple up in a drill (preferably a drill press, or make sure you have very steady hands and great alignment). Put the drill on high speed and spin weld the new nipple onto the fixture. Forward Technology | Plastic Assembly - Spin Welders
This is really done best with a drill press and the fixture well supported, you spin the nipple while apply light pressure of it against the fixture. When the plastic starts to melt you stop the spinning and maintain pressure until the plastic hardens. It does result in pretty solid bonds.
McMaster (McMaster-Carr) has a decent selection of polypropylene pipe nipples.

Good luck.
__________________
_________________
"Ventarrón"
Flying Scot # 4964

Quote:
Golf is an exercise in Scottish pointlessness for people who are no longer able to throw telephone poles at each other.
-Florence King

To get the most from Sailnet, follow the link in
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
's signature.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Reply With Quote Share with Facebook
  #15  
Old 08-08-2008
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 9 Times in 9 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
But you'd have to get the facing part of the body to be fairly flat to get a good spinweld IIRC. I've done a bit of work with spinwelding, mostly HDPE.
Quote:
Originally Posted by TheFrog View Post
SD, I agree with you but I am concerned that it would be very difficult to get epoxy to adhere well enough to the Polypro to glue a nipple in place. PP is just too slippery to glue easily.

Another idea. Find a polypropylene nipple, threaded on one end only. Cut off the old nipple, clean the stub of the old nipple and the unthreaded end of the nipple well. Chuck the nipple up in a drill (preferably a drill press, or make sure you have very steady hands and great alignment). Put the drill on high speed and spin weld the new nipple onto the fixture. Forward Technology | Plastic Assembly - Spin Welders
This is really done best with a drill press and the fixture well supported, you spin the nipple while apply light pressure of it against the fixture. When the plastic starts to melt you stop the spinning and maintain pressure until the plastic hardens. It does result in pretty solid bonds.
McMaster (McMaster-Carr) has a decent selection of polypropylene pipe nipples.

Good luck.
__________________
Sailingdog

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.

Still—DON'T READ THAT POST AGAIN.
Reply With Quote Share with Facebook
  #16  
Old 08-08-2008
poopdeckpappy's Avatar
Senior Member
 
Join Date: Jul 2006
Location: San Diego
Posts: 5,538
Thanks: 23
Thanked 38 Times in 32 Posts
Rep Power: 10
poopdeckpappy has a spectacular aura about poopdeckpappy has a spectacular aura about
Almost any plastic can be welded, one of the many tools I had while racing offroad was a plastic welder, I used for many things but mostly cracked fuel tanks or body parts ( not mine, the bikes )

PP can be welded, ( DIY ) the question is it worth investing a little money into the welder ( which isn't that much )

to help you figure out what plastic you have and what's needed to repair

Identify Plastic

and here's the supply house

Urethane Supply Company - Plastic Repair and Plastic Welders
__________________
1978 Tayana 37

Freedom comes when you’re ready to sail away. True freedom comes when you don’t have to return


Cut off from the land that bore us, betrayed by the land we find, where the brightest have gone before us and the dullest remain behind, .......but stand to your glasses, steady,.......tis all we have left to prize, raise a cup to the dead already, hurrah for the next that dies

Last edited by poopdeckpappy; 08-08-2008 at 04:11 PM. Reason: add links
Reply With Quote Share with Facebook
  #17  
Old 08-09-2008
Member
 
Join Date: Feb 2007
Location: Virginia
Posts: 73
Thanks: 1
Thanked 1 Time in 1 Post
Rep Power: 8
bhcva is on a distinguished road
Thanks Pappy...I'm off the the boat to dismantle the fixture and get a photo...back in a few days.
__________________
"Solitude" Caliber 40
Ches Bay
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Plastic Lumber Cabin Sole jmcpeak Gear & Maintenance 20 03-18-2007 03:21 PM
Plastic Fuel Tank... marinesniper Gear & Maintenance 4 02-14-2007 11:05 AM
Plastic paint for tired looking plastic parts Goodnewsboy Gear & Maintenance 3 01-01-2007 06:15 AM
Plastic Through-Hull Valves and Valve Flanges John Kretschmer Gear and Maintenance Articles 0 05-27-2001 08:00 PM


All times are GMT -4. The time now is 02:16 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.