27th April 2013, 08:15 PM
Foam nose cone
I'm working on a project that there is no commercially available nose cone for. One aquaintence said people carve/sand them from foam blocks. He said they used the ones found at Michael's or Hobby Lobby. The are the right size etc. but usually they are badly damaged by almost anything you could use to cover it with like fiberglass etc. Does anoyone have any suggestions? Thanks!
27th April 2013, 09:17 PM
I have made a styrofoam nose cone for a scratch build I did years ago, I used the blue or pink Dow styrofoam you get at a home improvement store, depending on your size body tube will depend on what thickness styrofoam to get.
I used 2" foam, ruff up the surface and glued the parts together with epoxy, then cut and sand and sand and sand and sand to shape and when you are satisfied with the nose cone shape cover the nose cone with few layers of thined Elmer's wood filler, the more layers the better, paint eats styrofoam, then prime and paint. I hope this helps, if not then look up making nose cones at www.apogeerockets.com
L1 Madcow Patriot
L2 Loc/Percision Doorknob
28th April 2013, 12:35 AM
If I need a custom NC for a particular build, I call the Sandman at www.roachwerksmachining.com. I figure he's forgotten more about making NCs than I ever learned. He's made a few for me (4" Red Max, 4" Hornet, 7.5" Goblin) and I've been VERY happy with pricing, shipping, turnaround times, communication during the process, fit/finish, and flying them.
"For although the nepenthe has calmed me, I know always that I am an outsider; a stranger in this century and among those who are still men." --HP Lovecraft
28th April 2013, 01:34 AM
I've done similar - used 1" blue foam for a 6" nose cone that ended up about 2' tall
Originally Posted by Kehoes23
There's special 'foam safe' glue you can get, too.
I finished mine with fiberglass over the top of everything.
It takes time but that's the part I really enjoy about rocketry!
28th April 2013, 02:34 AM
I have made three (one failed, we'll call that one practice) nose cones using thr blue foam method. I think it was 1/2 foam stacked to make a 5" dia x 12" ogive(ish) tall NC and a 3" dia x 15" conical NC. I glued my stack together with elmers wood glue thats what I had lying around. Covered both nose cones with a couple layers of fiberglass. I am also lucky to have a lathe at home to do this work on. And I second krusty's comment, it does take time but to see the finished product is awesome.
When covering the nose cone in fiberglass use a glass that is fairly flexible so it will fit around the curvature of the nose cone. On my first failed attempt I tried using 6oz glass. It was rather difficult to get the glass to fit the nose cone. On my successful nose cones I have used a lighter, I think 1.5oz fiberglass. It needed a couple more layers but the result was much better.
I attached a picture of my ogive nose cone and my method of spinning the nose cones. Glassing the tip of the conical NC was a pain but I managed to get it. Disregard the black lines its just marker lines from when I traced the stencil onto the glass. Good luck have fun!
L1: LOC Phantom NERRF 5 H125
L2: 3" Scratch Built Neon Dart LDRS 31 J285
"The man who follows the crowd will usually go no further than the crowd. The man who walks alone is likely to find himself in places no one has ever been before." ~Albert Einstein
28th April 2013, 03:37 AM
Your 6 oz was probably a plain weave. Harness Satin weaves conform to curves more easily, and are better for this type of application.
Originally Posted by redsox15
28th April 2013, 04:04 AM
I've made some parts from foam... For instance, the S-II/S-IVB interstage, which is in the first post of this thread... http://www.rocketryforum.com/showthr...aturn-I-F-quot
You don't want to use the stuff from Hobby Lobby-- that floral foam is pretty worthless. Similarly, you don't want to use beaded foam like that found in packing materials... it doesn't sand, it disintegrates...
What you DO want is "closed cell" foam like that sold at indoor lumberyards... if you live up north, you can easily get ahold of foam sheet up to 2 inches thick... This is really the stuff you want-- the thicker the better. It minimizes the number of layers that have to be glued up to get a block the size you need for the cone.
While you CAN glue it up with yellow wood glue, epoxy is a MUCH better choice. Yellow wood glue dries by evaporation of the water in it, and foam is impermeable-- so the water cannot wick away into the sheets of foam as it would move into wood or paper being bonded to allow the glue to dry... the only way yellow glue can "dry" when gluing up foam is for moisture to move from the center of the bonded layer to the outside edges, which are exposed to air, from which the water can evaporate... If the area is large, the glue will harden at the outer edges, and remain wet between the sheets of foam inward from the edges, even days or weeks later. Epoxy cures via a chemical reaction, regardless of the presence of air, and without evaporation, so that's really the material you want to use for gluing sheets of foam together into blocks... using wood glue can cause the block to fall apart during sanding as the outer cured edges are sanded away, exposing the still-wet uncured glue in the center. For small parts its okay, but for larger ones---- Well, epoxy is just your best choice...
I glue a wood dowel into the center of the block, again, using epoxy. This can easily be tightened in the chuck of a drill, which then turns the block. Using various grits of sandpaper, starting at about 60 grit and working up from there progressively finer, you can easily turn the cone to shape and size... just remember you have to "sneak up" on the correct size, switching to progressively finer and finer grits of sandpaper as you get closer and closer to the exact size you want and need. I recommend using a tube coupler glued onto the shoulder for a good fit into the tube when finished... that way you don't have to worry about keeping the size of the shoulder very accurate in foam... you can epoxy the coupler onto the foam shoulder easily, using the epoxy to fill any gaps between the foam and the inner surface of the coupler. Remember, you can always take a little more off, but putting more on doesn't work...
I cut a pattern for the nosecone by drawing the exact shape I want onto cardboard, then cutting it out and cutting the pattern in half along the centerline... that way you get a "negative" pattern in the cardboard when you cut the cone shape out of the cardboard, and cutting it in half lengthwise gives you an accurate shape template to compare to the foam block as you're sanding it, and mark any steps or areas where more needs to be taken off... I've done some pretty complex shapes in balsa using this method... (Ares I/Orion nosecone).
Basically all you need is an electric drill you can clamp to a tabletop, and some 60, 80, 120, and maybe 220 grit sandpaper... the rest is just the time and effort put in to do it. I also recommend some "paint mixing sticks" from the lumberyard to tape the sandpaper to, to hold the sandpaper firm and flat while you work... that way you can turn MUCH more accurate shapes than you can using the sandpaper freehand...
Later and good luck! OL JR
The X-87B Cruise Basselope- THE ultimate weapon in the arsenal of homeland defense and only $52 million per round!
29th April 2013, 12:34 AM
Thank you all!!! I've been out of town and away from WIFI so I couldn't check in (that's hard on me, even though my wife likes it ) I really appreciate the ideas, they are all great. I will try a small test one, then work up to the larger one. If I understand correctly, the fiberglass will not destroy the 2" think blue foam? If not, that is lkely what I'll try..
Thank you all again, great to have the help!
29th April 2013, 01:01 AM
If you use epoxy with the fiberglass, then you're fine -- it's the resin that can eat away the foam.
Originally Posted by sunderll
If you use polyester resin, it'll eat the foam, and you'll have a mess.
Any foam will work; pink, white, blue, yellow....just make sure it's not foam that looks like it's little pills compressed together.
29th April 2013, 01:56 AM
I've mad a large nose cone and an entire rocket (still unfinished) using a method like this except instead of spinning the foam blank, I had a router that followed along a guide and I revolved the blank by hand sort of like a milling machine instead of a lathe. Regardless of the method you use, do yourself a favor and have a shop vac rigged up to suck up the crumbs! I'm still finding bits of blue and pink foam a year later!
Originally Posted by redsox15
The derivative of velocity is acceleration. That's what my 4 year old tells me anyway.
29th April 2013, 05:53 AM
Hey buddy, Take a look at my current build--20 million miles to earth--I'm doing what your interested in and it may help. my first nose was foam with glass overlay---did'nt work as planned and honestly would take a lot of finishing effort---I shifted gears and made a male mold. I have not made the female mold yet-maybe this week time permiting. Anyway, the advantage to this technique -- the finished product is exactly the dimensions of the male plug---which should fit your bt ,just right----food for thought?----H
Originally Posted by sunderll
Anyboby see that caboose go by----I lost my train of thought again!
30th April 2013, 12:09 AM
hey Hornet, sounds good, I've been doing some reading on making molds and plugs and after some family matters and other outside stuff, I'm gonna try some. I know if it works, it will probuce some great cones..