How to add nosecone weight?

[terryg]

One other method you use for variable nose weight, is to use a heavy quick link attached to the nose.

 

[bjphoenix]

I really don't understand those that brag that they didn't follow the caliber rule of thumb, but were successful (I only had 0.25 caliber but mine flew great!). This, especially for heavy rockets, is not a rule I tend to tempt.

How many of these were with short stubby rockets where the base cone hack would be a significant aid to stability? I'm working on a FatBoy right now. I've read about stability issues with it so I created a sim and upsized the fins a little bit to try to gain some stability. I only got 0.25 caliber stability without the base hack. I've found that with longer rockets, the larger the rocket the easier it is to make it stable. A small Estes rocket with 18mm motor has a big percentage of its weight in the back and needs big fins. As the rocket gets bigger the tubes and nose cone get heavier and the CG seems to move forward. I've seen small rockets with stability problems but typically never a mid power or high power rocket.

I've only added nose weight to one rocket and it is a 4" diameter but short and stubby rocket with 29mm mount. I drilled 3 holes in the nose cone near the top, stuck in 3 normal nails with round flat heads, and put in the lead weight and epoxy. It's a 4" diameter cone but you can still see the 3 little flat circles at the end of the nose cone. I worried that if I did this and cut the heads of the nails off then the little nubs could pull out of the plastic if there was enough force on them. I may add a bit of weight to the FatBoy nose cone, I'm still considering an easy way to do that.

 

[teepot]

I put a threaded rod all the way to the tip of the nose cone. Attach a welded eye nut to it with red LocTite. Then drill a 3/8" hole in the bottom of the cone. Off to one side from the rod. I invert the cone in a large plastic glass full of bird seed. The seed keeps the cone vertical and acts like a heat sink. Pour in enough BB's that I think will counter balance the biggest motor that I would use then add JB Clear weld and let cure. I'm conservative on the amount of BB's because I made some cones too heavy when I first started building. You can add more but can't take any out. Then balance the rocket to find the CG. If it isn't enough BB's I add more BB's and epoxy. I've only used skewers or brass rods a couple of times. Haven't had a problem not using them. Balsa cones I drill holes in the base and add BB's and epoxy. When I first started building I used quick links for nose weight so I could adjust the weight. I also tried filling Flower stem holders, they hold water to keep the cut flower alive, with BB's and duct taping them to the shock cord. The quick links would end up being too messy and take up too much space in the BT. Same thing with the stem holders.

 

[Donnager]

How many of these were with short stubby rockets where the base cone hack would be a significant aid to stability? I'm working on a FatBoy right now. I've read about stability issues with it so I created a sim and upsized the fins a little bit to try to gain some stability. I only got 0.25 caliber stability without the base hack. I've found that with longer rockets, the larger the rocket the easier it is to make it stable. A small Estes rocket with 18mm motor has a big percentage of its weight in the back and needs big fins. As the rocket gets bigger the tubes and nose cone get heavier and the CG seems to move forward. I've seen small rockets with stability problems but typically never a mid power or high power rocket.

I've only added nose weight to one rocket and it is a 4" diameter but short and stubby rocket with 29mm mount. I drilled 3 holes in the nose cone near the top, stuck in 3 normal nails with round flat heads, and put in the lead weight and epoxy. It's a 4" diameter cone but you can still see the 3 little flat circles at the end of the nose cone. I worried that if I did this and cut the heads of the nails off then the little nubs could pull out of the plastic if there was enough force on them. I may add a bit of weight to the FatBoy nose cone, I'm still considering an easy way to do that.

I probably have more than my share of stubby stuff: Three Big daddy's (29, 38, and 54mm), a 6" Stinger (75mm), a Mach1 Warhead (38mm), 7.5" Megamagg (54mm), 4" Lotus (54mm), etc.... I also have a good count on short length rockets I wouldn't call "stubby" but are not the best length to diameter ratios (Goblins, for instance). I don't have a good feel on how effective the base drag hack is (in actual comparative use) on, lets say a 29mm 3" Big Daddy, vs a 54mm 7.5" Mega Magg, and the hack effectiveness tends to relate to motor selection and the weight of the rocket flown. For a 7.5" rocket, I'm just not interested in chancing things, will implement design rule of thumb, prior experience, and a little bit of hassle, rather than rely on simmed assumptions.

Don't worry about your nose cone prep. If the inside was scored a little, the pins/nails in the outside will hold the weight still enough. As I said, I usually run 1/8" stainless wire through both sides in two directions. This is a great epoxy anchor and is well suited to hold the nose lanyard, or embed a nose anchor. If the rocket gets big, these wires can be upgraded to 3/16" or larger if needed, and the count can be increased.

 

[BABAR]

I saw someone else (this is not my idea, but I thought it was pretty slick); glue in a wooden bulkhead into the nosecone. He then cut a hole and glued in a prescription drug plastic bottle. He could then vary the inserted weight, and then seal it up with the bottle's cap. I think this was for a Big Daddy, but for your purposes, you might have to scale it up. Although I think even the biggest fishing weights might fit in the larger prescription drug bottles.

I like it.

Does still beg the question, is glue alone sufficient to hold in the BULKHEAD ? You may still want dowels to hold bulkhead.

Also not sure of the failure load on the plastic bottle cap. My mind-sim physics cap tells me a larger bottle might be WEAKER (fail at lower G level or lowe mass) than a smaller bottle.

A mod for more efficiency. Cut the base out of the bottle. Cut the bulkhead hole for the bottle small, sand it so it just BARELY fits. Push bottle through just enough to get a decent fillet on each side of bulkhead. Now you ballast chamber goes all the way forward.

Now you can drop in bbs all the way to internal nose cone apex (the more forward the weight, the greater effect on CG, and the less you need!)

You can put a styrofoam plug in the bottle if you have enough BBs in for a smaller motor without filling the bottle. For larger motor, fill’er up.