Adding Nose weight

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Several years ago I stopped using epoxy to bond nose weight when I learned that Gorilla Glue makes a stronger bond with polystyrene or fiberglass, without causing extreme exothermic heat or the need to use mechanical fasteners to secure the nose weight in place.

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I weigh out the necessary amount of Copper BB's, into a paper cup, spray the BB's lightly with water until their wet, pour enough Gorrilla Glue into the cup to coat the BB's, using a mixing stick. Then spray the inside of the NC lightly with water, pour the Gorilla Glue & BB mixture into the tip of the NC, tap the NC to level the mixture and support the NC in a section of BT until it cures, about 1 hour. The water activates the Gorilla Glue and it foams up to encapsulate the BB's, when it cures. The BB's don't come loose.



Also if you need to add additional weight at a later time, just mix up another batch of BB's and pour it on top of the original nose weight.
 
Steve - I usually use these little guys that I get at Hobbylinc

https://www.hobbylinc.com/great-planes-epoxy-mixing-cups-50-r8056

As far as epoxy as mentioned I have some West Systems but one pump from the resin would surely overfill one of these little cups, which is why I'm considering just using regular hobby epoxy like 30 minute BSI and mix in smaller batches and add to it.

Does it make a difference in how long you should wait between each batches?

Do you have to wait until batch completely cures and hardens before mixing and adding additional batches?

As said before Wildman sells mixing cups, but not sure if they are like the ones in the link? I thought maybe they would be made out of the same type of plastic, but maybe twice or 3x the size.

Has anyone purchased the mixing cups from Wildman?

Waiting between batches:
You don't want to wait until it completely cures. If you do, it's only a mechanical bond between layers of epoxy. You want to wait until it's firm but not fully set, also sometimes referred to as the leather stage; then the new layer of epoxy will chemically cross link to the previous.

I bought my first batch of mixing cups from a hobby town years ago. I bought another batch just a year ago from Amazon. I also am frugal and wash and reuse the dressing and Parmesan cheese cups that come with pizza. Those containers are also usually shallow enough to prevent cooking off.

I bought a set of West System pumps, but the ratios were wrong for Aeropoxy, so I cut a piece of plastic tubing that was just the right diameter to snap onto the tube at the top of the pump to reduce the stroke. I had to cut a slot in the side of the snap on tubing so it would work.


[emoji1010] Steve Shannon [emoji1010]
 
On a tangent, I've been having good luck with mortar. Much the same surface prep as epoxy. Mix up the powder and water and schlup it in. Poke it with a stick to settle it. I've also set an eyebolt anchor in it - put a washer and nut on the threads and buried it.

Took the idea from Bill Bertoldi, who says the land use managers up in the UP have asked/told them not to use lead weights. He uses concrete.
 
Waiting between batches:
You don't want to wait until it completely cures. If you do, it's only a mechanical bond between layers of epoxy. You want to wait until it's firm but not fully set, also sometimes referred to as the leather stage; then the new layer of epoxy will chemically cross link to the previous.

I bought my first batch of mixing cups from a hobby town years ago. I bought another batch just a year ago from Amazon. I also am frugal and wash and reuse the dressing and Parmesan cheese cups that come with pizza. Those containers are also usually shallow enough to prevent cooking off.

I bought a set of West System pumps, but the ratios were wrong for Aeropoxy, so I cut a piece of plastic tubing that was just the right diameter to snap onto the tube at the top of the pump to reduce the stroke. I had to cut a slot in the side of the snap on tubing so it would work.


[emoji1010] Steve Shannon [emoji1010]

Tangent on this thread, but I did the same thing with my US Composites pumps! A piece of 1/2" CPVC (i think, anyway, it's been awhile) with a strip cut out of it snaps onto the plunger of the pump perfectly. I switch the spacer from the resin to the hardner so I can diminish the stroke volume the same amount (US Composites is a 1:1 pump, although their epoxies are different ratios). This makes it super easy to mix up smaller quantities.
 
So I have done NC weight a little differently than others in both a 4" Madcow NC and a Loc Precision 5.5" NC. First, I cut off the aft end. Then, I poured melted candle way into the tip of the NC with some twine submerged to help me pull it out. It removes easily if you stick the NC in hot tap water. I then use this to make a mold in plaster of paris. With a mold of the inside of the NC, I melt and pour the desired weight of lead into the mold. I now have a form fitted weight. I have done this with 7 oz and 11 oz weights.

Now, I clean up the inside of the NC with IPA (rubbing alcohol) then score it with 80 grit sandpaper. I wet the inside of the NC and coat the weight with Gorilla Glue (GG) and place it in there. I then put a small bead around the edge. I then drill a hole through the NC and run 1/2" dowel through. I also place a loop of schock cord through to be my attachment point. I then cut off the ends of the dowel, sand smooth and finish off with Bondo spot and glazing compound. The result is very solid, if not overdone.
 
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So I have done NC weight a little differently than others in both a 4" Madcow NC and a Loc Precision 5.5" NC. First, I cut off the aft end. Then, I poured melted candle way into the tip of the NC with some twine submerged to help me pull it out. It removes easily if you stick the NC in hot tap water. I then use this to make a mold in plaster of paris. With a mold of the inside of the NC, I melt and pour the desired weight of lead into the mold. I now have a form fitted weight. I have done this with 7 oz and 11 oz weights.

Now, I clean up the inside of the NC with IPA (rubbing alcohol) then score it with 80 grit sandpaper. I wet the inside of the NC and coat the weight with Gorilla Glue (GG) and place it in there. I then put a small bead around the edge. I then drill a hole through the NC and run 1/2" dowel through. I also place a loop of schock cord through to be my attachment point. I then cut off the ends of the dowel, sand smooth and finish off with Bondo spot and glazing compound. The result is very solid, if not overdone.

Some questions on this- are you melting the lead and casting it that way? I'm guessing yes, or else I'm not clear on the value of the plaster mold? Can you go into more detail about the dowel part too? I'm assuming that's across the chord of the tip, but if it transects the weight, I'm not sure how you get the shock cord loop there...
sounds like a neat and sturdy technique, just not entirely clear on how to do it.
 
My technique only works with FG nose cones with a removable tip and all thread that screws into the tip. I get either wood or washers that vary in size. If using wood i turn it on the latest the to match the inside of the nose cone, the drill a hole through the centre the same diameter as the all thread, then bore out a large diameter hole about 2/3 of the way down the wooden plug, the bore hole gets filled with how ever much lead shot and epxy you need to bring it upto weight but before pouring in the epoxy/shot I insert a waxed steel rod into the all thread hole so when the epoxy cures I can remove the rod and have a hole for the all thread which through the nose cone and with a washer and nut you can secure your wooden and epoxy/shot weight at the tip of the nose, this way you can also remove the weight or add a different weight for different configurations.

with the washers that vary in size from small to large i weigh up the amount i need and start threading the washers onto the all thread going from smallest to largest, I do this with the tip on and the all thread in the nose so I can make sure the washers match the shape of the nose cone, then use a nut or wing nut and just tighten that up against the aft washer so it clamps the washers up against the nose cone and will also clamp the nose cone tip in place.

Could also do the same as CZ Brat suggested and cast a weight out of lead or just epoxy and shot then just drill a hole through it and secure that on the all thread with a nut/wing nut.
 
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I picked up work on this again. I was delayed for awhile. I had to work again. I originally had the nose weight at 24oz, but after I finished with the weight of the epoxy and some additional BB's I came in at 25 oz, which worked out much better.

Here's the following information based on my L2 flight with a J500G-10

Max Altitude: 3091.29
Deployment: 3.08 mph
Margin: 1.35
CG: 27.02 from nose tip
Total Mass Loaded: 84.14 oz

I used BSI 30 minute epoxy and also used a leveler to make sure the nose cone was leveled to evenly distribute the nose weight. I plan on using 2 part foam epoxy to fill the rest of the nose.

And yes I did use a wood dowel through the cone about 3.5" from the tip. You can see the sand marks on the side. I may just send this up in primer and paint it after I get certified and a dozen flights after.

One thing I might consider is having the nose cone and payload section come done under its own chute. Seeing that most of the weight is in that section I would hate to have the two pieces collide. That could cause some serious damage. IDK it's just a thought?

UPDATE: After adding the 2 part foam epoxy the numbers changed again. I was surprised it added a couple more ounces.

Max Altitude: 3088.68
Deployment: 0.64 mph
Margin: 1.50
CG: 26.44 from nose tip
Total Mass Loaded: 86.34

Also here's the RS file

View attachment patriot.rkt
 
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My plan originally was to use plastic snap rivets to attach the nose cone so I could remove it and use my JL altimeter. I didn't think that I would have so much weight in this nose cone, but that's the way it turned out. My concerns now are whether or not these rivets will actually hold the nose cone on the upper payload or would I be better off just to epoxy it on?? Also I used the expanding foam all the way to the top, but I did redrill the holes test fit the first part of the rivet and it seems secure? I know once they are in they are a PITA trying to get out especially if you don't have finger nails.
 
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