Grain Bonding Pro98 6GXL

[Feckless Counsel]

TRF,

Cesaroni recommends bonding grains to liner in all Pro98 6GXL reloads?

Anyone have grain bonding lessons to share? I'm a bit concerned about the process. Being feckless I envision grains seizing half way down the liner. Nightmare scenario.

Feckless Counsel

[troj]

Cesaroni recommends bonding grains to liner in all Pro98 6GXL reloads?

Anyone have grain bonding lessons to share? I'm a bit concerned about the process. Being feckless I envision grains seizing half way down the liner. Nightmare scenario.

If I remember right, they either include the adhesive, or tell you what to use (I'd have to pull out the instructions for my reload and check).

I watched a friend assemble one that requires bonding, and he used a long dowel to help with grain alignment.

-Kevin

[atxcple]

the instructions i have for the 6 grain 98mm N2501 white say only the N10,000 has it included all others your to use 2 oz Gorilla Glue ( lowes sku # 152242, or home depot sku # 837667)

[Jeroen_at_CTI]

Some tips:
- Make sure to test-fit all grains before bonding.
- Get a helper.
- Make sure to un-package everything in advance and lay it out on a clean table.

Some tips for any Pro98-6GXL reload, except for N10,000:
- Elmer's Glue Max (a Gorilla glue knock-off) seems to set-up a bit slower and has lower viscosity.
- Do not wet the grains.
- Work in an A/C'ed environment, or anywhere where it is cool.
- Do not bother using a brush to save some time. Simply squirt the glue around the top half of the grain, and then insert it while twisting. The glue will nicely spread around the grain. As long as 70-80% of the casting tube is covered, it will be fine.
- You can save some time by putting the liner on the table horizontally, and let the top 8" or so stick out past the table edge. Leave any glue that drips on the floor and worry about clean-up later. I use a piece of cardboard on the floor and dispose of that after the bonding.
- Push the grain in about 1" into the liner and install the spacer o-ring. Use the next grain to move the grains already inserted.

I'll be at LDRS and don't mind hosting a "grain bonding work-shop". If there is an interest. We just need a volunteer with any size 75/98 load.

Jeroen

[bandman444]

"Do not wet the grains"

Why is that?

The instructions say to dampen the cardboard coating.

Isn't polyurethane adhesive hydrophilic? It needs water to cure properly.

A workshop would be cool, but even better if you taped it and put it online for others to see.

[Jeroen_at_CTI]

"Do not wet the grains"
Why is that?
The instructions say to dampen the cardboard coating.

There usually is enough atmospheric moisture to cure the grains. Wetting the grains helps in dry climates and speeds up the cure. If you are in a field with high temperatures and humidity, it would be better not to wet the grains.

Jeroen

[Feckless Counsel]

Jeroen,

Thanks for your response. You say do not wet the grains. You mean do not deliberately wet exposed propellant with glue or you mean do not moisten the casting tube with a damp rag?

[bandman444]

There usually is enough atmospheric moisture to cure the grains. Wetting the grains helps in dry climates and speeds up the cure. If you are in a field with high temperatures and humidity, it would be better not to wet the grains.

Jeroen

Great.

Just checking

Thanks

[Feckless Counsel]

Jeroen,

My reload is N3301. So I must use the nozzle carrier, correct?

[Jeroen_at_CTI]

My reload is N3301. So I must use the nozzle carrier, correct?

This reload uses the XL-style nozzle. No carrier required. The only 6GXL reload that uses the carrier is the G3 reload.

Note that the N3301 uses a base grain. All details about the nozzle and the base grain can be found in this document: http://www.pro38.com/pdfs/Pro98_notes_V1.2.pdf

Jeroen

[Feckless Counsel]

Jeroen,

Thanks again for your support. Now suppose I assemble the motor and the launch is scrubbed. How should I preserve that assembly until the next opportunity? That could be up to 4 months later.

[Jeroen_at_CTI]

Thanks again for your support. Now suppose I assemble the motor and the launch is scrubbed. How should I preserve that assembly until the next opportunity? That could be up to 4 months later.

No problem. Just make sure your o-ring grease (any grease you would add) is compatible with the o-rings. CTI pre-lubes the o-rings.

Jeroen.

[Feckless Counsel]

Jeroen,

I plan on using Super Lube high temperature synthetic grease. Should be no problem if you're certain Cesaroni's rings are exclusively Buna-N nitrile rubber Otherwise I'll stick with standard temperature silicone grease.