Standard length
Ballast
- Thread starter cerving
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It has 3.5 lbs of shot at the tip held in with West Systems epoxy and the remainder of the NC is filled with expanding foam, density of the foam was lightened by adding some water to the foam mix, been flying for over 15 years without issue
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So I pulled the trigger and foamed about 4# of BB's into the nose cone. I put a small foam plug in the tip first, because the tip really wasn't plugged with epoxy and I wanted to give the weight a little bit of a "shelf" to set on when I poured it. Learned a few things... some of which I knew but kinda forgot...
1) Foam sets fast. The plan was to mix up the foam (about 120 ml total), mix it into the BB's, then pour it into the hole. I did about half of it because I had to put the mix into smaller cups to get it poured into the 38mm hole... and after the first half, the second half had already started to rise. I tried using a popsicle stick to shovel it into hole, I ended up putting the mix in by hand. Which leads me to the next issue...
2) Foam is messy. It sticks to everything. Everything. Did I say everything? Once I got the foam/BB's into the nose cone, I ended up with a hand covered with sticky foam, I thought, "Oh, I can just get it off with some acetone or alcohol." Nope. Only way to get it off is to let it set and just peel it off. I'll probably be doing that for the next two or three days. What sucks is that I have a completely unused tube of Happy Hands barrier cream... and didn't think to put some on first.
3) Keep an eye on the expansion. I did a test last night with some of the foam that I used to calculate the expansion ratio, and I'm glad I did... it came to within about 2" of the bulkhead. Another small liquid pour and I got it right to the end of the bulkhead, where I wanted it.
So I'll find out in November at ROCStock how this is going to work out... should be just fine.
1) Foam sets fast. The plan was to mix up the foam (about 120 ml total), mix it into the BB's, then pour it into the hole. I did about half of it because I had to put the mix into smaller cups to get it poured into the 38mm hole... and after the first half, the second half had already started to rise. I tried using a popsicle stick to shovel it into hole, I ended up putting the mix in by hand. Which leads me to the next issue...
2) Foam is messy. It sticks to everything. Everything. Did I say everything? Once I got the foam/BB's into the nose cone, I ended up with a hand covered with sticky foam, I thought, "Oh, I can just get it off with some acetone or alcohol." Nope. Only way to get it off is to let it set and just peel it off. I'll probably be doing that for the next two or three days. What sucks is that I have a completely unused tube of Happy Hands barrier cream... and didn't think to put some on first.
3) Keep an eye on the expansion. I did a test last night with some of the foam that I used to calculate the expansion ratio, and I'm glad I did... it came to within about 2" of the bulkhead. Another small liquid pour and I got it right to the end of the bulkhead, where I wanted it.
So I'll find out in November at ROCStock how this is going to work out... should be just fine.
I have used a paper funnel before to pour the foam into a hole with. I just took a piece of printer paper and rolled into a funnel, it is a throw away item afterwards.
- Joined
- Feb 3, 2012
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- 5,566
This would have been a lot easier if the bulkhead had not been there, just dump the ballast/foam in and it's done. With the bulkhead, which was set about a foot deep, I only had a few inches to work with, and it was a hassle even with a funnel (yes, I used one). But, I got it done, and adjusted the weight/CG in OpenRocket... with the K1200-2xJ430's that I'm going to use it has a margin of about 1.11C. With any combination of motors that I'm likely to use it has a margin of at least .6C, so I think it's going to be fine.
