Tight Phenolic Liner

[m85476585]

The phenolic liner was very difficult to install in the case for the I600 I flew yesterday (and obviously it was hard to get out). What's the best thing to do if a phenolic liner is too tight? I know with a paper liner you can just peel some paper off. Sanding the phenolic liner sounds like a pain, though.

 

[SpartaChris]

The phenolic liner was very difficult to install in the case for the I600 I flew yesterday (and obviously it was hard to get out). What's the best thing to do if a phenolic liner is too tight? I know with a paper liner you can just peel some paper off. Sanding the phenolic liner sounds like a pain, though.

Sanding is a pain, but that's what I did when I had a liner that was a wee bit too tight. Or you could see if your vendor would be willing to exchange it.

Also, make sure you grease it up before you load it into the casing to help with removal. Might even help with installation.

 

[MarkM]

Yup, sand it. Although I had a friend spend a long time once sanding a phenolic liner for a I285 so as it fit into the casing. Other than having AT replace the liner, I haven't seen anyone use a differenet method than sand, sand, sand.

 

[Donaldsrockets]

Yup, sand it. Although I had a friend spend a long time once sanding a phenolic liner for a I285 so as it fit into the casing. Other than having AT replace the liner, I haven't seen anyone use a differenet method than sand, sand, sand.

Yep, I remember that as if it were yesterday.

It took me about a half hour or so to sand that liner to where it would fit. In fact, it was still tight but I was finally able to push it into position using an expended Pro38 motor assembly.

Getting the spent liner out afterwards was easier, go figure.

If the I285R I just bought yesterday has this problem, I'm really going to lose it!!!

 

[m85476585]

I guess I'll start test-fitting liners at home and sanding them with my belt sander or mouse sander if necessary.

 

[dlb]

:2:another vote for sanding it.
I've done it many times, mostly on a batch of J350's I got about 3 years ago.

Heck it messed me up, got to the field with a new 720 case and try to install a reload EHhhhhhh , figured it was the case, NOPE, the liner, but only after getting another case, Duh! :bangpan:. The good news is, I now have (3) 38/720 cases.:neener:

 

[Handeman]

I had the same thing with a I1299N load. I just sanded it until it fit. I would NOT recommend a belt sander or any other type of powered sander. Just use 120 grit, wrap it around the liner and sand until it fits.

Unlike SpartaChris, I don't lube the outside of the liner anymore. The only liners I've ever had a hard time getting out of casings have been greased and the grease seemed to cook/burn and glue the liners in place where the most heat got through the liner.

 

[deandome]

WOW...I thought it was an isolated incident, but this makes me wonder....

At the Bong NSL, I bought an J500, and the liner wouldn't go in. Sanded a fair amount...still, not even close. So I took it to Wildman, he grabbed another Rouse 720 casing...it went in FINE, but the threads were damaged (new casing)!!

Back to Tim, ANOTHER new casing, 3rd time was a charm! Now, I HAD used the original casing for my Level 2 cert flight...I forget if it was tight or not. But bottom line, the fact that tries # 2 & 3 went in FINE shows there IS a Q.C. issue (or issues, as the one w/bad threads on BOTH ends showed) w/Rouse casings...at least w/the 38/720!!

 

[Donaldsrockets]

Sanding by hand is your best bet. If you try to use a belt sander or the like, you might sand the liner out of round or sand off too much material rendering it completely useless.

BTW, the casing I had trouble fitting that I285R liner into was a Dr. Rocket casing. Rouse-Tech motors were not available at that time.

Fortunately that was the only problem I had. I had one that required just a little bit of sanding and most slid right in with no problems so I think it's mostly a liner issue, not a casing issue.

 

[m85476585]

Mine was a Rouse Tech case. I don't remember the J350 I flew in the same case being tight, though.

I can see not using a belt sander, but I don't think my mouse sander would go through it too quickly, especially with finer grit or dull paper.

 

[Rocketjunkie]

I have 4 38/720 cases. ONE is a genuine Aerotech, the rest are Dr Rockets and Rouse Tech. The Aerotech case is definately tighter than the rest.

 

[JAllen]

WOW...I thought it was an isolated incident, but this makes me wonder....

At the Bong NSL, I bought an J500, and the liner wouldn't go in. Sanded a fair amount...still, not even close. So I took it to Wildman, he grabbed another Rouse 720 casing...it went in FINE, but the threads were damaged (new casing)!!

Back to Tim, ANOTHER new casing, 3rd time was a charm! Now, I HAD used the original casing for my Level 2 cert flight...I forget if it was tight or not. But bottom line, the fact that tries # 2 & 3 went in FINE shows there IS a Q.C. issue (or issues, as the one w/bad threads on BOTH ends showed) w/Rouse casings...at least w/the 38/720!!

I've had this happen before on an AT J500G as well. I tried the load in both my 38/720 case and a friend's case. Then I went back to the dealer and we tried it in one of his cases. It still didn't fit. Checked it against another case, another dealer, and it fit. All three in which it didn't fit were Dr. Rocket cases manufactured within 3 years of each other (Post 2001, but I forget the actual date). The case that it finally fit in was an older Dr. Rocket case from before 2001.

Now, that said, this is NOT a quality control issue on anyone's part. It is an issue of machining tolerences. The lower the tolerence, the higher the cost of the case (its an exponential increase, IIRC). If you get a case from a batch that was slightly below the nominal inner diameter and a reload from a batch of phenolic liners that had a slightly higher than nominal outer diameter, it may require some sanding to fit. Is it annoying, yes, but it happens and sure beats paying the price of a 75/5120 case for a 38/720 case.

 

[blackjack2564]

I've been flying for 7yrs now and ever since I started I have had to "fit" grains and liners. From hobbyline to 98mm.

I have flown AT , CTI, AMW, and at one time or another every one of those brands has had fit issues.

I have walked more L-1's and L-2's through certification than I can remember.
During motor building the first thing I tell them to do is check the grain and liner fit.

The easier it goes in....the easier it will come out.

It's just part of flying rockets that at times you must peel or sand to fit. Sometimes a little, sometimes a lot.

As others have mentioned, if everything were held to the strictest of tolerances, the cost of flying would be prohibitive.

For me it's just part of the hobby, call it rocket science or a pain in the butt, we still just have to do it. Call it a non issue.