This *MIGHT* Be Crazy... But Then Again... Methods For Filling Grooves In Nosecones.

[K'Tesh]

I've spent a little time with the sandpaper today cleaning up some nosecones. Some of them have some nasty grooves where either the mold halves came together, or swirls from a poor injection/cooling process. This got me thinking... How to fill the grooves before sanding them out? I don't have any filler putty (such as Squadron Green or White Putty). Previous experiments with CA were unimpressive (to say the least). So how to do this?

What about stretched sprue? The idea would be to use some heat to stretch the sprue to the desired thickness, then glue (using something like Tamiya Thin) this into the grooves, and upon the complete setting of the glue, sanding it flush.

Anybody ever use leftover sprue from a plastic model to fill a gap like these? Got any other method for filling gaps you'd be willing to share? Photos would be appreciated.

Pointy Side Up!!!
Jim

 

[Dugway]

I just sand with 80-100 grit sandpaper and then fill the grooves with CWF. Prime/sand/repeat like the rest of the rocket. I've never had the filler fall out without the nosecone being so damaged that there were new places that needed filling!

 

[afadeev]

I've spent a little time with the sandpaper today cleaning up some nosecones. Some of them have some nasty grooves where either the mold halves came together, or swirls from a poor injection/cooling process. This got me thinking... How to fill the grooves before sanding them out? I don't have any filler putty (such as Squadron Green or White Putty). Previous experiments with CA were unimpressive (to say the least). So how to do this?

Really? How so?
My default approach is to fill them with thick (aka gap-filling) CA, let it dry a few hours, and then sand.
This takes care of the problem 95% of the time. The other 5% I either fill it again with another layer of CA, or a layer of 3M Bondo.
On super-delicate LP-model, I fill with Tamiya Putty (white), but that one is reserved for special occassions, as it's pricey.

What about stretched sprue? The idea would be to use some heat to stretch the sprue to the desired thickness, then glue (using something like Tamiya Thin) this into the grooves, and upon the complete setting of the glue, sanding it flush.

If the scars are really deep and so is the nose cone, consider scuffing the area and applying a layer of epoxy?

I will see if I can find some photos and add them to this thread later.

HTH,
a

 

[Steve Shannon]

Baking soda can really add bulk to CA. It becomes hard very quickly. The baking soda acts as an accelerant to the CA. Practice with it.

 

[David Schwantz]

Scrape the seam, groove, with new exacto blade to level surface. Then prime and sand is my preferred method. I think the sprue thing would be way much work. Also, where do you find compatible material. and what glue would hold?
But sure doesn't hurt to give it a go. Post pics.

 

[Jay Rairigh]

I use the Bondo Glazing and Spot Putty for plastic nose cones (like so many here do), thinned out with acetone.

It seems to sand at about the same rate as the plastic whereas I believe with CA or epoxy, even CWF, you could get issues with the different rates of material removal when sanding.

One tube has lasted for years. Easy to work with, though smelly...

 

[DaHabes]

I use the Bondo Glazing and Spot Putty for plastic nose cones (like so many here do), thinned out with acetone.

I do the same. I thin it with enough acetone to paint it on with a brush. Goes much faster that way. Dries fast and can sand the same day. Can easily do a second application for really deep gouges if necessary. Then Rustoleum 2X filler/primer and a light wet sanding with 320 or 400 grit.

 

[Trident]

Really? How so?
My default approach is to fill them with thick (aka gap-filling) CA, let it dry a few hours, and then sand.
This takes care of the problem 95% of the time. The other 5% I either fill it again with another layer of CA, or a layer of 3M Bondo.
On super-delicate LP-model, I fill with Tamiya Putty (white), but that one is reserved for special occassions, as it's pricey.



If the scars are really deep and so is the nose cone, consider scuffing the area and applying a layer of epoxy?

I will see if I can find some photos and add them to this thread later.

HTH,
a

I also use CA. I got the idea from Chris Michael’s rocketry blog. I use the little bottles of medium CA from the Dollar Store (two bottles for $1). The secret is to sand it as soon as its possible to sand, usually an hour or so for me. If you let it fully cure, you are going to utter some really bad words trying to sand it.
I’ve found that even on big “HPR” nose cones, 2 coats usually works. If seams are really deep, just kept adding coats, sanding after each coat. For Estes-types of nose cones, I find two applications, sanded after each, fills the seam. Unlike putty, which can pop off on some plastics, I’ve found that the CA sticks with no issues. I do wash the nose cones before filling the seams, but nothing beyond that, like cleaning with alcohol or other solvents.

 

[DES]

Squadron Green, or the Bondo solvent based glazing putty. If you don't have either of those, a good scuffing and epoxy I suppose, carefully dribbled on and scrapped off with a knife blade to just fill the crevasse. But you are going to be much happier with a filler putty you can sand, like the Bondo glazing putty. Not Bondo body filler in the can. Bondo glazing putty in the tube. Get it at the auto parts store.

 

[K'Tesh]

Just for anyone who doesn't know... I'm in China. There are no auto parts stores that I've been able to find in the nearly 6 years I've been here. Searching for Bondo yeilds nothing even related to automotive products. Filler primer? HA!!!

CA is something I can do... For those who use it, do you let it cure naturally, or hit it with kicker (I've got some BSI stuff that has been sent to me here), the domestic CAs I've found are pretty useless.

 

[DES]

Ah, then we need to get more inventive. The epoxy might still be a choice, but soften it up with a sandable filler, perhaps chalk, talcum, or fine wood dust. I think I'd try and cook up a styrene based filler. Shave some of your plastic sprue, dissolve it in acetone (lacquer thinner) add a little bit of talc or plaster powder until it has a paste consistency. Probably have to grind it a bit with a metal or glass rod on a glass or ceramic tile to get it smooth.

I've never had any luck or joy sanding CA. It is usually harder than whatever you are gluing, so you abrade the plastic while the CA is pretty much untouched.

If you do use CA as a film forming filler, you will probably need to use a kicker. Cure is very slow in thick films on low energy surfaces such as plastic without moisture. it will just sit there for a long time. Until you touch it with your fingers....

 

[Steve Shannon]

Just for anyone who doesn't know... I'm in China. There are no auto parts stores that I've been able to find in the nearly 6 years I've been here. Searching for Bondo yeilds nothing even related to automotive products. Filler primer? HA!!!

CA is something I can do... For those who use it, do you let it cure naturally, or hit it with kicker (I've got some BSI stuff that has been sent to me here), the domestic CAs I've found are pretty useless.

Lay down CA then sprinkle with baking soda. That accelerates it and provides a filler.

 

[Jay Rairigh]

Just for anyone who doesn't know... I'm in China.

In that case, try some ground up fortune cookie mixed with the sauce from a decent Kung Pao chicken. I've not used this method, but it's worth a try.

 

[K'Tesh]

In that case, try some ground up fortune cookie mixed with the sauce from a decent Kung Pao chicken. I've not used this method, but it's worth a try.

Fortune cookies are American... So is Chop Suey... However, 宮保雞丁 (Kung Pao chicken) is really Chinese. I can't tell you all how much I miss American Chinese food... Much of what we enjoy in the US isn't found all over China. The US mostly gets recipes from the southern portions of China, whereas I'm on the East coast... Where they have lots of fish (which I can't stand).

 

[Jay Rairigh]

Fortune cookies are American... So is Chop Suey...

I'm not surprised by any of that.

 

[David Schwantz]

In that case, try some ground up fortune cookie mixed with the sauce from a decent Kung Pao chicken. I've not used this method, but it's worth a try.

I tried that once and it melted the plastic

 

[Cape Byron]

Tamiya Basic Putty. Smells bad, dries quickly, sands well.

 

[afadeev]

CA is something I can do... For those who use it, do you let it cure naturally, or hit it with kicker (I've got some BSI stuff that has been sent to me here), the domestic CAs I've found are pretty useless.

No kicker, as it only acts on the surface. If you tried sanding CA post kicker application, the inner gooey layer will come out the whole thing turns into a mess.
Let it dry just long enough for the CA layer to solidify and become sandable. But don't leave it overnight, else it will turn into rock.

Sanding nose cones with a hand-held sanding plane does the trick for me (I have 3, preloaded with 80 - 240 - 400 grits):
https://www.amazon.com/Amazon-Basic...39QF?source=ps-sl-shoppingads-lpcontext&psc=1

 

[Lord Rory Gin]

Fortune cookies are American... So is Chop Suey... However, 宮保雞丁 (Kung Pao chicken) is really Chinese. I can't tell you all how much I miss American Chinese food... Much of what we enjoy in the US isn't found all over China. The US mostly gets recipes from the southern portions of China, whereas I'm on the East coast... Where they have lots of fish (which I can't stand).

Don't eat the bats! .
I'm part-Chinese myself and the best authentic Chinese food - is from Vancouver!

I haven't used either Bondo or CA on plastic cones. But I have sanded the cones with medium sandpaper and then extra fine conformal sanding foam then used automotive sandable primer and another round of medium/extra fine.

 

[K'Tesh]

Don't eat the bats! .
I'm part-Chinese myself and the best authentic Chinese food - is from Vancouver!

Not a problem... I'll stick with the grasshoppers (actually they taste pretty good, (just like potato chips)).

I'm quite fond of the food I found in Beaverton. Sherwood also has a pretty good place. Of course the best I ever had was at home. While we lived in Hawaii (1972-1975), my mom took lessons from Titus Chan (who was the chef at the Hilton Hawaiian Village at the time, and seen on the PBS TV show ""Cooking the Chan-ese Way"). Mom's recipes are just plain AWESOME!!!

I haven't used either Bondo or CA on plastic cones. But I have sanded the cones with medium sandpaper and then extra fine conformal sanding foam then used automotive sandable primer and another round of medium/extra fine.

Problem with that is, sometimes the grooves are so deep, you end up flattening out the nosecone quite a bit, and all to often thinning the plastic quite a bit.

 

[jqavins]

(I've only read through post #6 so far, and lunch time is over, so I have make this quick.)

All I've had to do up until now is sand groves out. It leaves a little - well, not a flat, but a reduced curvature for a little way around where the groove was. So far I haven't encountered grooves deep enough for that to be noticeable without a seriously critical look.

For deeper grooves, my inclination would be to fill with whatever is the appropriate glue for the material. If it's a polystyrene (PS) nose cone, use glue for PS models, which is actually just more PS in a volatile solvent. Use like you would use CWF on tube spirals; thin (with acetone) if necessary, squeeze it into the groove, then sand after it's dried. If it's no PS, but some other plastic with a compatible glue available, use that glue the same way. If there is no compatible glue, e.g. for polypropylene, then you wouldn't get a sprue to stay put anyhow.

 

[Bat-mite]

I'm not surprised by any of that.

Apparently there is a legend behind the name "chop suey." Chicago mobsters would sometimes "take over" a restaurant after hours to use as meeting places. So, one time they went into a Chinese restaurant. They wanted food, but the owner had nothing left. In a panic, he gathered all the leftovers and mixed them together. He told the mobsters it was "chop suey." They were happy with it. Soon, people all over town were asking for "chop suey," so Chinese restaurants all started coming up with a version of it.

Don't know how true this is.

 

[jqavins]

(OK, I'm caught up.)

It seems people are talking more about thickening than thinning, at least for epoxy and CA. Obviously, for the plastic glues of the chemical weld type, thickening can be done by adding shavings of the same or a compatible plastic (the opposite of thinning by adding the same or a compatible solvent).

I know Acetone works for PS, though it's not what is in old-time Testors Red; that might have been MEK or xylene or some combination. I've read many places, and experienced myself, that acetone works for ABS, and I've read that some ABS predissolved in it makes a good glue for ABS pieces. I don't know, however, if either of those glues, PS in acetone or ABS in acetone, is good for the other. And come to think of it, I wonder what you get if you dissolve both materials in the same batch. (Does it summon a demon?)

Also, I've recently been told that acetone doesn't always work with all things that are called ABS, because many have fillers or copolymers that prevent it. I've made good joints in what I'm pretty sure are APS parts using acetone straight, and they've held up well.

And finally, I've never had chop suey. I've had almost everything you'd expect in a rice house, like everybody else, and I have my favorites, like everyone else, but I've never had chop suey. Maybe I'll try it then next time I have a chance. (Does it summon a demon?)

 

[Pappy]

i've been mixing elmers white wood filler with a little water, thinner for brushing on balsa filler, thicker for other stuff. for gouges, i spread it on with a little palette knife like i'm patching drywall. sand, primer, sand.

 

[kuririn]

I've tried thick CA on the seam between the nose cone and the cardstock "witches' hat" on a TLP Exocet nose cone. This after reading how Chris Michielssen uses thick CA to fill the seams on plastic nose cones. It works, but Squadron or Tamiya putty is easier, less work sanding to contour. But hey, gotta use what you have on hand.
Before CA

After CA and sanding

After primer and sanding

And after painting

my mom took lessons from Titus Chan

My mom and I used to watch Titus Chans' local cooking show on PBS. We got a kick out of his jokes. This was years before Martin Yan's national cooking show Yan Can Cook. Very similar.