Filling screw holes in plastic (polystyrene?) nose cone.

[rdrown]

I have a 4 inch mad cow patriot kit and it has a plastic nose cone. I had to add 100 grams of lead to nose and glued it in with gorilla glue polyurethane glue. I then inserted three screws into the glue and lead. The screws are countersink and I would like to fill this in to smooth it out. What do I use for a filler? Anything I have tried, falls out after it dries. I might add that the nose cone is very thick and looks like nylon. Very slippery. Thank you for any ideas you might have.

 

[Budro0]

What have you tried? I am looking at a similar problem (with brass rods) and was thinking Bondo putty - but if you've tried it and it didn't work...

 

[JLP1]

I just had a problem with an Aerotech nosecone that had some holes from where I cut the plastic lug off. Nothing would stick to the cone so I tried some rocketpoxy after it dried I sanded them flat. These nosecones are worse that Teflon.

 

[dr wogz]

The problem with these larger NCs is that nothing sticks to them! Glue nor paint! And Epoxy is notoriously 'plastic resistant'..

@rdrown How big are the holes you made? My only (quick) fix I have for you is to drill out the holes & plug them with a wooden dowel. Then sand the dowel ends flush with the NC.

I always drill 2 or 3 holes thru the NC, then stick chops sticks (wooden dowels) thru the holes thru the NC, then add my lead shot & epoxy. Once all cured, I then trim both ends of the sticks sticking out both sides of the NC, then sand flush to the NC surface.

@Budro0 same idea. Do your brass rods stick out? Then file them flush. If not you may try Bondo spot putty or epoxy. (The epoxy or Bondo will likely only adhere to the end of the brass rod. You may also get away with adding some 'filler' to the epoxy, like fibers or a small piece of cloth to help hold it all together) If you can replace them.. see above..

 

[rharshberger]

I just had a problem with an Aerotech nosecone that had some holes from where I cut the plastic lug off. Nothing would stick to the cone so I tried some rocketpoxy after it dried I sanded them flat. These nosecones are worse that Teflon.

They are polypropelene plastic iirc and very little sticks to them well. Usually I flush brass rods or screws to the surface, spray with a paint adhesion promoter (several available at auto parts stores), then prime with a good auto body primer (spray can is fine), fill with Bondo spot and glazing putty then prime again and finish normally. The adhesion promoter is the key and the primer is needed for the bondo spot and glazing putty to stick too.

 

[rdrown]

They are polypropelene plastic iirc and very little sticks to them well. Usually I flush brass rods or screws to the surface, spray with a paint adhesion promoter (several available at auto parts stores), then prime with a good auto body primer (spray can is fine), fill with Bondo spot and glazing putty then prime again and finish normally. The adhesion promoter is the key and the primer is needed for the bondo spot and glazing putty to stick too.

That sounds like a plan. The screws are #6, ½ inch long. Will be very easy to remove screws and redrill for a dowel. I did not know all the steps needed and am very thankful for your information.

 

[rdrown]

What have you tried? I am looking at a similar problem (with brass rods) and was thinking Bondo putty - but if you've tried it and it didn't work...

I tried 30 minute epoxy, Titebond, CWF, and JB weld for plastics. None of the bondos I looked at was recommended for plastic directly, so I posted this question. See post #4 and #5 above for some very good ideas.

 

[crossfire]

A wooden dowel works very well. Just install dowel cut it as close to flush with cone as you can. Than sand it the rest of the way flush with cone. A little filler over dowel. Prime cone and you should not even see it.

 

[teepot]

I used brass rods Sanded them flush and used Elmer's color change filler. It worked for me. The marks in the cone were very small. Then primed and painted.

 

[Sooner Boomer]

This probably sounds silly, but if Gorilla Glue sticks to the *ionside* of the nosecone, why not use it on the *outside*? Sand everything down and smear some glue on. Let it set up (foam up) over night. Sand the hardened glue to shape.

 

[rdrown]

This probably sounds silly, but if Gorilla Glue sticks to the *ionside* of the nosecone, why not use it on the *outside*? Sand everything down and smear some glue on. Let it set up (foam up) over night. Sand the hardened glue to shape.

gorilla glue does NOT stick to the inside, only used to hold the lead shot together, hence the need for dowels or brass rods to keep it in place. The gorilla glue I put on the outside just brushed off after it cured.

 

[Budro0]

I was just reading in another thread about folks using Tamiya white putty to fill seams in LPR nose cones (among other modelling uses). Has anyone tried it in this use case? Is the plastic used in Estes kits the same for these much larger NCs? Is it more or less durable than other options presented here?

 

[jqavins]

If I'm not mistaken, the Estes and Estes-like LPR nose cones are polystyrene where the big ones are polypropylene. Bonding to polystyrene is not too hard; acetone will soften it, xylene will soften it, Testers red label glue is made specifically for it.

Polypropylene, on the other hand, is virtually impervious to all adhesives and solvents.

These nosecones are worse that Teflon.

I suspect you've never tried to glue anything to Teflon^*, but it's close.

* Am I wrong?

 

[DaHabes]

I drill 1 or 2 holes in the NC tip (depending on the size of the NC and the amount of weight to add) and use 8d nails with the heads cut off. I use BB's for weight (since lead is toxic) with epoxy. Once the epoxy sets, I cut off any excess nail with my Dremel and fill the indents with Bondo. Prime and paint. I haven't had any on the Bondo break loose yet. I've done this on several builds over the past three years.