Plastic nose cone question

[Dane Ronnow]

I'm building an altimeter bay in the nose cone that came with the Aerotech HV Arcas kit. To do that, I'm following the same process I did on my MPR scratch build (also a 2.6" dia.), using sheet polystyrene from Hobby Lobby (Evergreen). But neither CA, nor Testor's 3501 (orange tube) will stick to the Aerotech cone, both of which tested well on my previous build.

Here's a glue test I did for that build using an Apogee PNC-66A polystyrene nose cone, and the adhesives pictured, numbered on the cone as 1) CA, 2) Tamiya (plastic weld), and 3) Testor's 3501:



All three adhesives worked well. I chose Testor's for that build because it took more bending to break it loose.

Here is the same test done this evening, minus the Tamiya, with the Aerotech nose cone, numbered 1) CA and 2) Testor's 3501:



An hour later I tested it. Both pieces just fell off. Neither CA nor Testor's even touched the plastic on the cone. I went back and did another test with the Tamiya, thinking it might need liquid weld, but that had the same result.

The altimeter bay latch will have two flathead screws that will hold the assembly to the nose cone, so having it fall out is not a problem. But I'm curious as to the differences in the two plastics when it comes to adhesion. The Apogee cone is clearly styrene. It behaves just like the sheet styrene. It bends a little, then breaks.

The Aerotech cone is a different type of plastic—HIPS maybe? I can squeeze it a half inch easily. If I were able to do the same to the Apogee cone—and I couldn't because it's harder—it would break.

I guess the bottom line is, has anyone glued something to an Aerotech Arcas-type nose cone using something other than epoxy, and had it stick?

 

[rharshberger]

I'm building an altimeter bay in the nose cone that came with the Aerotech HV Arcas kit. To do that, I'm following the same process I did on my MPR scratch build (also a 2.6" dia.), using sheet polystyrene from Hobby Lobby (Evergreen). But neither CA, nor Testor's 3501 (orange tube) will stick to the Aerotech cone, both of which tested well on my previous build.

Here's a glue test I did for that build using an Apogee PNC-66A polystyrene nose cone, and the adhesives pictured, numbered on the cone as 1) CA, 2) Tamiya (plastic weld), and 3) Testor's 3501:

View attachment 528952 View attachment 528953 View attachment 528954 View attachment 528955

All three adhesives worked well. I chose Testor's for that build because it took more bending to break it loose.

Here is the same test done this evening, minus the Tamiya, with the Aerotech nose cone, numbered 1) CA and 2) Testor's 3501:

View attachment 528956 View attachment 528957

An hour later I tested it. Both pieces just fell off. Neither CA nor Testor's even touched the plastic on the cone. I went back and did another test with the Tamiya, thinking it might need liquid weld, but that had the same result.

The altimeter bay latch will have two flathead screws that will hold the assembly to the nose cone, so having it fall out is not a problem. But I'm curious as to the differences in the two plastics when it comes to adhesion. The Apogee cone is clearly styrene. It behaves just like the sheet styrene. It bends a little, then breaks.

The Aerotech cone is a different type of plastic—HIPS maybe? I can squeeze it a half inch easily. If I were able to do the same to the Apogee cone—and I couldn't because it's harder—it would break.

I guess the bottom line is, has anyone glued something to an Aerotech Arcas-type nose cone using something other than epoxy, and had it stick?

Its probably polypropylene, nothing sticks well to that and most solvent glues dont work well on it either. Generally in these type cases I use a mechanical locking method (for nose cones I put a bulkhead just on top the shoulder of the NC, the main diameter of the nose cone meets the shoulder and a bulkhead/centering ring inserted sideways and rotated on top the shoulder is nice and snug.

See the John Coker video about how it works if you haven't already seen the video.
http://jcrocket.com/plastic-nose-mods.shtml

 

[Initiator001]

AeroTech nose cones are molded in polypropylene.
Not much will stick to that plastic.
I sand the part with coarse sandpaper and use 30 minute epoxy. That's still not 100% guaranteed to work.

 

[Dane Ronnow]

Thanks. Screws will work.

 

[Dane Ronnow]

Generally in these type cases I use a mechanical locking method

Here's a pic of the altimeter bay on my other build:



That flange on top is glued to the cone with Testor's, but the screws would hold it in place. So I'm good with no glue.

 

[Dane Ronnow]

@Initiator001, @rharshberger - So on polypropylene, what's the process for painting? Sand, then adhesion promoter, then paint?

 

[rocket_troy]

One thing you might want to try for an adhesive is hot melt glue - BUT you'll need to heat the application of it well beyond the stick guns typically used to apply it. Well, you apply it onto the PE or PP with the applicator gun, but then you need to further heat it with either hot air (250 deg C say) or mix it around with a soldering iron so as to create a partial weld with the substrate. Then obviously apply to the piece to be bonded before the glue cools too much.

TP

 

[Dane Ronnow]

@rocket_troy - Good idea, but too much trouble for this application. Other than acceleration, there's no stress on the bay.

 

[rharshberger]

@Initiator001, @rharshberger - So on polypropylene, what's the process for painting? Sand, then adhesion promoter, then paint?

Sounds like you have the plan for painting...word of caution though. The paint will stick with adhesion promoter, but not well enough that masking tape wont pull it off some.

 

[Dane Ronnow]

The paint will stick with adhesion promoter, but not well enough that masking tape wont pull it off some.

I'll keep that in mind. Thanks.