Big, Lightweight Rocket Made of Rigid Foam Insulation

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Onebadhawk
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ThirstyBarbarian said:
After sanding I glued the fins into place with lamenting epoxy. This shot is actually taken after a mistake was corrected. I wanted the fins to be a bit more rigid so I papered them with Avery label paper before gluing them into place. It did make them more rigid, but it was heavy, and it also did not adhere very well and started to peel off. I removed it all before this picture.

You can also see the rail buttons and the electronics bay in this shot.

View attachment 381448
Click to expand...
Like it, like it alot. One question though, any laments?
 
Some of you newer TRF members might have been wondering, "Is Thirsty really one of the cooler folks on this forum?"
Well now you have your answer, and proof to back it up.

s6
 
manixFan said:
Neat project, I like the idea of a big, lightweight rocket like that. I found this archive link to a technique the Vastaas brothers used:

https://web.archive.org/web/2005111...rtv/arsenal/bradrocs/napkin/napkinrocket.aspx

They built another rocket along the same lines:

https://web.archive.org/web/20021203203025/https://vatsaas.org/rtv/arsenal/bradrocs/black/black.aspx

Their goal wasn't light weight but still some of that info may be useful.


Tony
Click to expand...

I think that the next project, I want to try a hot wire cutting technique like these guys used. I’d like to make some kind of guide for the cutter like they used. It looked like it worked well, and you can make some complex shapes. I’ve also seen some big lathe type setups for sanding.
 
stealth6 said:
Some of you newer TRF members might have been wondering, "Is Thirsty really one of the cooler folks on this forum?"
Well now you have your answer, and proof to back it up.

s6
Click to expand...

Lol!

Don’t let him fool you new members!

Thanks, Stealth!
 
ThirstyBarbarian said:
I leave the lamenting to the epoxy!

Going back, I see a few Autocorrect goofs, but I might just leave them as Easter Eggs for others to find.
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Autocorrect is the source of much hilarity, should be mandatory (with me being the exception since I can't stand it;))..Assuming you're speaking of the hotwire setup with wood profiles and a mandrel? I've yet to try it but looks like a fantastic time, mess and labor saver.
 
Wallace said:
Autocorrect is the source of much hilarity, should be mandatory (with me being the exception since I can't stand it;))..Assuming you're speaking of the hotwire setup with wood profiles and a mandrel? I've yet to try it but looks like a fantastic time, mess and labor saver.
Click to expand...

The great thing about Autocorrect is that it doesn’t leave you with an obviously misspelled word — it provides a perfectly spelled incorrect word that completely changes the meaning of what you wrote! I like the ones that create an unintentional sexual innuendo, or “Autoerotica”.

I do want to try the technique with the Hotwire cutter, wood profiles, and the mandrel. I think there are a lot of creative possibilities.
 
My experience with foam (just like what you used) started with me gluing stacks of foam with epoxy for a nose cone project. At the time epoxy was the best glue for the job, until I heard about Glidden Gripper which is a bonding primer and sealer. Unlike epoxy, the “Gripper” is water based which makes for easier clean-up.

The problem with either epoxy or nearly any other adhesive, is that it’s not wise to spread your glue across the whole surface of the foam you’re using. Most any adhesive is going to leave a really thin wafer of glue that shows up when you are turning it or sanding it. The solution was to spread glue more to the inside of the foam and not all the way to the outer edge. Leave yourself at least ½ inch of bare unglued foam so that, when you sand it, you are no longer sanding that hideous wafer of glue. Easy to spot on this foam cone I turned.

upload_2019-5-1_10-33-41.jpeg

It’s nearly impossible to hide that wafer unless you gouge it out. I accidentally discovered a foam filler that works really well at patching up dings and flaws and sands perfectly. Works great!

upload_2019-5-1_10-35-25.jpeg

If you are still pondering about glues, there’s a great video that compares adhesion strength on this very same foam.

 
Gary Byrum said:
My experience with foam (just like what you used) started with me gluing stacks of foam with epoxy for a nose cone project. At the time epoxy was the best glue for the job, until I heard about Glidden Gripper which is a bonding primer and sealer. Unlike epoxy, the “Gripper” is water based which makes for easier clean-up.

The problem with either epoxy or nearly any other adhesive, is that it’s not wise to spread your glue across the whole surface of the foam you’re using. Most any adhesive is going to leave a really thin wafer of glue that shows up when you are turning it or sanding it. The solution was to spread glue more to the inside of the foam and not all the way to the outer edge. Leave yourself at least ½ inch of bare unglued foam so that, when you sand it, you are no longer sanding that hideous wafer of glue. Easy to spot on this foam cone I turned.

View attachment 381539

It’s nearly impossible to hide that wafer unless you gouge it out. I accidentally discovered a foam filler that works really well at patching up dings and flaws and sands perfectly. Works great!

View attachment 381540

If you are still pondering about glues, there’s a great video that compares adhesion strength on this very same foam.

Click to expand...


Thanks for the info, Gary! I welcome any advice on adhesives, fills, coatings, paints, tools, or techniques.
 
Pretty much anything anaerobic (aka pricey) that won't eat foam should be fine for gluing things together. Aeropoxy light is a fantastic filler, but again it simply is not cheap. I see the most common mistake being people using things that air dry in the obvious absence of air. Canned spray foam insulation being the most common...
 
Gary Byrum said:
Hey Thirsty, you ever use one of these? It's a scraper that seems to work rather well in sculpting Styrofoam.
Click to expand...

I haven’t used one of these. I think there are a lot of tools and techniques used by model train enthusiasts to build the towns and landscapes for their trainnsets. And foam is used by some sculptors, set designers, sign makers, and the people who make large-sized advertising artwork for things like trade shows. I’m going to do some research on it.
 
rharshberger said:
Surform is a brand of those rasps/ planes iirc. They work well for quick material removal but leave a rough/pitted surface.
Click to expand...
True. But the thing is, all of it can be sanded after you are done sculpting. Of course, if you have a lathe, you can do the same thing using the turning tools and they too, leave the same rough surface. I made sanding blocks and some of those thin foam sanding pads to finish it off.
 
Thats correct, and i use altimeter fir deployment only, you are right, these just hang at apogee..

rharshberger said:
Frank has several "foamies", and they are cool as hell, iirc he has 29mm "stuffer" tubes that are actually the airframe with centering rings every so often. Near the nosecone is a larger (4"?) payload bay for recovery gear just under it between the center tube and the outer skin is a altimeter bay for electronic ejection. I have seen them fly many times, and man is it cool!
Click to expand...
 
ThirstyBarbarian said:
Thanks for the info, Gary! I welcome any advice on adhesives, fills, coatings, paints, tools, or techniques.
Click to expand...

My two cents: To cut the circles, perhaps cut the center of each first with a holesaw or Forstner bit. Then fasten a piece of tubing or dowel of the same diameter as the hole to your circle cutter, in place of the pivot point. Shouldn't wander as much when cutting the outside.

I assume you peeled off the plastic vapor barrier from each side of the foam before gluing. (Some foam may not have that vapor barrier but all the stuff I've used had it on both sides.)

To cut down on weight slightly, cut a much larger hole in every other circle before gluing, maybe?

Home Depot lists 2" thick extruded sheets for $29. (1" is $20). Lower cost and it cuts your work in half!

And now I have something else to try for a large rocket! Thanks!!

Best -- Terry
 
If you have any new residential construction in your area foam is free. We used to scrap most of the cutouts from windows, doors gables, etc. 1/2" is pretty much the standard though. Every once in a while we'd get people that'd stop and ask for stuff, always told 'em take all Ya want. Made my job easier...
 
ThirstyBarbarian said:
The great thing about Autocorrect is that it doesn’t leave you with an obviously misspelled word — it provides a perfectly spelled incorrect word that completely changes the meaning of what you wrote! I like the ones that create an unintentional sexual innuendo, or “Autoerotica”.
.
Click to expand...

It’s really a beaut with medical voice recognition

There is something called a “transitional vertebrae”, most common at the junction of the lumbar spine and sacrum.

I keep dictating “transitional L5 vertebrae”

Keeps coming back “transvaginal L5 vertebrae”

MOST of them I catch in the proofreading......
 
burkefj said:
Thats correct, and i use altimeter fir deployment only, you are right, these just hang at apogee..
Click to expand...

I cut a spot for an altimeter bay in the side, and getting the electronics figured out is going to be the next step. I’ve never done electronic deployment, so it’s new for me.
 
prfesser said:
My two cents: To cut the circles, perhaps cut the center of each first with a holesaw or Forstner bit. Then fasten a piece of tubing or dowel of the same diameter as the hole to your circle cutter, in place of the pivot point. Shouldn't wander as much when cutting the outside.

I assume you peeled off the plastic vapor barrier from each side of the foam before gluing. (Some foam may not have that vapor barrier but all the stuff I've used had it on both sides.)

To cut down on weight slightly, cut a much larger hole in every other circle before gluing, maybe?

Home Depot lists 2" thick extruded sheets for $29. (1" is $20). Lower cost and it cuts your work in half!

And now I have something else to try for a large rocket! Thanks!!

Best -- Terry
Click to expand...

I think there are a few ways to lighten it even further. Maybe larger holes on some of the rings, or larger lightening holes drilled parallel to the motor tube. In the Peak of Flight article, the author used lightening holes. That’s what actually gave me the idea for the cluster motor mount.

This XPS foam does not have a plastic vapor barrier or foil radiant barrier. EPS foam often does, and the other heavier white foam which name escapes me often do have it.

I do want to find a source for thicker sheets. My local HD does not have the 2”, but some of the stores may have it within a reasonable drive.

For tools, I think I’m going to move on to Hotwire cutting tools. Rotary tools, drills, scrappers, sanding, they all create a ton of lightweight dust. And this dust is very affected by static electricity, so it’s weird to clean up. There’s probably no way to avoid sanding, but a lot of cutting and boring of holes could be done with the Hotwire tools.
 
Been away for a little while. Heart stopped pumpin on the table during one of my back RF treatments. So I'm doing some catching up.
On the other hand, wife's biopsy came back positive. She has cancer. :(

Very Nice Indeed Thirsty!
I hope I can finish up some of the couple dozen rockets needing primer, paint & decals this summer.
And make a few maiden flights.
 
Wallace said:
If you have any new residential construction in your area foam is free. We used to scrap most of the cutouts from windows, doors gables, etc. 1/2" is pretty much the standard though. Every once in a while we'd get people that'd stop and ask for stuff, always told 'em take all Ya want. Made my job easier...
Click to expand...

I’ll keep an eye out for that!
 

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