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Edit as of finishing the rocket - It took TWICE as much clay weight to make ROCKSIM happy as provided. Please note I did not fly the rocket stock preferring to put some faith in ROCKSIM's CP calculations. So it might have flown just fine. I simply was not willing to find out. We have tools like ROCKSIM, we should be informed by them when possible. With a D12 ROCKSIM showed virtually neutral stability. Did I build heavy? I papered the fins (no CA) adding 16 grams or so to the fins overall mass (~4gms/fin). However the fins are long and the added mass spread out. Nothing else odd was done cept a engine hook. And removing that from the sim made almost no difference in the CG.
I am letting you know this so you can make an informed decision yourself.
Note: I am not saying ROCKSIM is flawless. I am saying I'd rather be conservative. Tools like ROCKSIM probably were not around in the 90's etc... when some of these kits were initially designed. And if they were, they were in there infancy.
BTW: ROCKSIM says 13.1 inches from the tip, VCP which goes WAY back, says 14 inches from the tip!
I have a lot of TLP kits in the backlog. This one looked simple enough. And I have Sandman's decals. :horse:
First thing I did is survey the parts and weigh them. With all the yammering and grief I've read about TLP, which of course I ignore cuz I enjoy building them :wink:, I decided to first weigh the parts and do up a ROCKSIM file. That is attached. I found that with the supplied 20gms of nose weight, given where ROCKSIM believes the CG will be, it's neutrally stability with a D12. If I move the shock cord and the chute forward by moving the supplied bulkhead forward 24mm, things are back to stable. But that is a tad too close for me.
So I'll be keeping a close eye out on the final CG. The rocket should only weigh 4oz (~100g) or so w/o motor. So it's no tragedy if I have to add another 5 or 10 grams of nose weight. For mods I only intended on papering the fins and adding a 30cm of kevlar. It will still move on 24mm loads.
BTW: I took the Mad Cow and a scratch built Hawk ROCKSIM file and they all correlated pretty close. CP is 57-60% of the way back from the tip. So it's no wonder it needs mass in the nose (unless you stretch it more).
TLP Hawk 1.6
View attachment TLP-Hawk.rkt
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