I500 Submin (iHop)

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Brainstormz123

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This week, I realized I have an I500 and don't want it anymore, so what better to do with it than send it really really hard this weekend. I forged some fiberglass fins to surface mount onto the case, and have a resin printed nosecone and avionics bay for the flight. iHop is the name because it has an I impulse motor and "hop because it's gonna hop off that pad". This first picture is when I did a test printed PLA nosecone.
1693375862516.png1693376436531.png1693376458454.png

Some info on the fins:

I made both forged carbon and forged fiberglass fins in the same size. The carbon ones were noticeably stiffer than the fiberglass, but fiberglass looked cooler, so I chose to use the fiberglass fins. The fin molds are printed in PLA and then composite strands and epoxy are mixed into the mold and then squeezed really tight a la easycomposites (). These turned out really well, and there is a groove in the fins in order to do inlayed almost "tip to tip".

1693376108635.png1693376316565.png1693376447987.png

This is a printed tower modified off of @Model_rockets really epic tower using electrical conduit. It mounts to a 1010 rail at the top and bottom with the conduit connecting them together. I don't own a long 1010 rail to test fit it, so I printed tiny little pieces just to make sure everything aligned.
1693376626723.png1693376642268.png1693376653589.png1693376664802.png

This here was my first openrocket sim, the rocket was designed to be really really lightweight, and I think I did a pretty good job doing it in reality. Expected to be firmly in the mach 2 range and around 10000 ft in altitude when starting out.
1693376702055.png

As for electronics, I have a custom flight computer I designed that I may fly on its first flight. It's called "Sparrow" and was designed to fit in an 18mm coupler. It has a built in 433mhz RDF beacon in order to track.

Capabilities:
4 channels
200g 3 axis Accelerometer
16g 6axis accelerometer + gyro
barometer + temperature
flash for logging things
buzzer
LED
Built in RDF 433mhz beacon (will require external wire whip antenna)
Headers for future GPS and better telemetry expansion as a stacked board (didnt feel like cadding those)

Dimensions: 16mm x 37mm (0.64 x 1.4in) Pictured with an 18mm Estes motor below
1693376828862.png1693376838730.png

I wanted to do the inlayed tip-to-tip on these fins since the fiberglass is just really weak at least compared to carbon and I am fairly worried about flutter, given it will be very fast very low down. I gave a "pseudo-prepreg" technique a try for these. The steps were to cut a fin template out of paper, then put a sheet of mylar, a layer of carbon, wet out the carbon, place the second sheet of mylar on top, place the template on top of the sandwich and cut out the shape. Then remove the top layer of mylar, place the cut shape on your fins, press it into place, and finally remove the final mylar layer. This helps to make sure you dont tear/separate the fibers on the sheet when doing the layup.
1693376932820.png1693377689181.png

All 3 layers on picture before cleaning up:
1693377752708.png
 

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Photo after cleaned up and clear coat. Feels very smooth even although the photo looks like there are voids at the end:
1693377940374.png

Here I resin printed my nosecone after the test fit using this resin (https://formlabs-media.formlabs.com/datasheets/2001340-TDS-ENUS-0P.pdf). Its very smooth and strong, but my printers volume is limited (Anycubic Photon M2), so I needed to print it in two parts and epoxy them together during the cure process. I dribbled some of the resin in there from printing, stacked the two parts, and cured it with liquid between. I can't deform it with my hands so it feels fairly solid.
1693377987754.png
 
Here is the rocket when I first put it on the scale. 662 grams total liftoff mass (582g of that is motor) fully integrated. Theres around 20g of nose weight cuz I was sussed about stability. Real sad I had to add mass. I really wanted to send it as hard as possible, but it was marginally stable so I needed the nose weight to feel comfortable.
1693378097261.png

This here is my final simulation and it is ready for flight this Saturday at the Friends of Amateur rocketry site. Should really disappear.
1693378162511.png
 
I want to hear your guys feedback on this rocket. What would you have done differently/where do you think the failure points would be. I have some really low fidelity simulations but they are accurate where it matters (center of mass/pressure accurate, masses accurate). My goal with this rocket was not to optimize altitude, but acceleration, so it is super lightweight everywhere and that's the only goal. 60g of non-motor weight is pretty solid in my opinion.

I considered printing a boattail out of phenolic micro balloons and resin, which I have done successfully before as a nozzle. I considered also making it a longer diverging section because the I500 looks silly and is probably losing a lot of efficiency. 1693378480138.png

Decided against the boattail because it was more mass and reduced stability for benefits I didn't care about (more altitude). I only want this thing to go really fast really quickly, so altitude is just a negative
 
The "parachute" for this rocket is just a 10x10in square of nomex I tied 8 shroud lines to. Assuming a cd of around 0.5, this should bring the empty rocket down around 10 m/sec. Nothing on this rocket besides the electronics should be reusable anyways, so touching down faster than expected really isn't a problem. Using nomex as the parachute material means I don't need to worry about exhaust gasses melting anything which is why I did it. Theres enough recovery volume, but the disadvantage of that is its heavier, allows more air through, and takes up more space than nylon.
 
This "parachute" is exceptionally low quality, and I had no idea what a good assumption for a cd would be especially with the porous nature of nomex. Earlier this morning, I conducted a drop test where I connected a 25gram weight to this parachute (total descent mass of 31g) and dropped it from 40ft. It descended at around 10 ft/second from this height (4.018 seconds of descent).

1693419410570.png

Plugging this value into the drag equation below, I get a Cd value of 0.9 with the area of my parachute (81 in2).

1693419536733.png

This should take my rocket down at around 15 m/sec. This is fairly fast, but I don't want to walk very far to recover this tiny rocket and I think it can take it. It is almost equivalent to hitting the ground dropped from the same 40ft, and I feel like it would survive that onto dirt.
 
I think screwing with the divergent section is considered EX stuff, and wouldn't be allowed, except for at Tripoli EX launches, or, in your case, if you are flying with FAR, they are probably cool with it. Also, coming down fast under a small parachute is not only for the re-usability of the rocket, but for the safety of the people and objects on the ground. Again, at FAR, probably not a big problem, as it's pretty remote, and people are used to 'duck and cover'. (I've been there a few times for some EX classes and looking at getting a Cal-Pyro license around 20 years ago)

I think it's a cool concept. The phenolic nozzles that AT uses do erode, so if you make a larger divergent section, try and match the material with something that erodes the same amount. Let us know how it flies, and I wish you the best of luck. I worry that the 'forged' fins might be low on the fiber/matrix ratio, but it may be 'good enough' for a single flight.
 
Regarding the descent speed, its still not that fast at 15 m/sec, and I also don't really expect it to get that far into the flight lol.

I think it's a cool concept. The phenolic nozzles that AT uses do erode, so if you make a larger divergent section, try and match the material with something that erodes the same amount. Let us know how it flies, and I wish you the best of luck. I worry that the 'forged' fins might be low on the fiber/matrix ratio, but it may be 'good enough' for a single flight.
As for the forged fins, the mass/density/volume of the fins points to a fiber:resin ratio around 65:35, so its actually really good, even better than I could do with a layup/vacuum. They are pretty floppy on their own, but I cant deform them at all with the carbon layer on top of them. The carbon ones I made were very nice as well, and a similar 60:40 ratio.
 
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This week, I realized I have an I500 and don't want it anymore, so what better to do with it than send it really really hard this weekend. I forged some fiberglass fins to surface mount onto the case, and have a resin printed nosecone and avionics bay for the flight. iHop is the name because it has an I impulse motor and "hop because it's gonna hop off that pad". This first picture is when I did a test printed PLA nosecone.
View attachment 600970View attachment 600974View attachment 600976

Some info on the fins:

I made both forged carbon and forged fiberglass fins in the same size. The carbon ones were noticeably stiffer than the fiberglass, but fiberglass looked cooler, so I chose to use the fiberglass fins. The fin molds are printed in PLA and then composite strands and epoxy are mixed into the mold and then squeezed really tight a la easycomposites (). These turned out really well, and there is a groove in the fins in order to do inlayed almost "tip to tip".

View attachment 600972View attachment 600973View attachment 600975

This is a printed tower modified off of @Model_rockets really epic tower using electrical conduit. It mounts to a 1010 rail at the top and bottom with the conduit connecting them together. I don't own a long 1010 rail to test fit it, so I printed tiny little pieces just to make sure everything aligned.
View attachment 600977View attachment 600978View attachment 600979View attachment 600980

This here was my first openrocket sim, the rocket was designed to be really really lightweight, and I think I did a pretty good job doing it in reality. Expected to be firmly in the mach 2 range and around 10000 ft in altitude when starting out.
View attachment 600981

As for electronics, I have a custom flight computer I designed that I may fly on its first flight. It's called "Sparrow" and was designed to fit in an 18mm coupler. It has a built in 433mhz RDF beacon in order to track.

Capabilities:
4 channels
200g 3 axis Accelerometer
16g 6axis accelerometer + gyro
barometer + temperature
flash for logging things
buzzer
LED
Built in RDF 433mhz beacon (will require external wire whip antenna)
Headers for future GPS and better telemetry expansion as a stacked board (didnt feel like cadding those)

Dimensions: 16mm x 37mm (0.64 x 1.4in) Pictured with an 18mm Estes motor below
View attachment 600982View attachment 600983

I wanted to do the inlayed tip-to-tip on these fins since the fiberglass is just really weak at least compared to carbon and I am fairly worried about flutter, given it will be very fast very low down. I gave a "pseudo-prepreg" technique a try for these. The steps were to cut a fin template out of paper, then put a sheet of mylar, a layer of carbon, wet out the carbon, place the second sheet of mylar on top, place the template on top of the sandwich and cut out the shape. Then remove the top layer of mylar, place the cut shape on your fins, press it into place, and finally remove the final mylar layer. This helps to make sure you dont tear/separate the fibers on the sheet when doing the layup.
View attachment 600984View attachment 600986

All 3 layers on picture before cleaning up:
View attachment 600987

Awesome project, any chance you can share a link to the tower?
 
Awesome project, any chance you can share a link to the tower?
Attached are the cad files for my 38mm submin tower using these electrical conduits (https://www.homedepot.com/p/1-2-in-x-10-ft-Electric-Metallic-Tube-EMT-Conduit-853428/100400405). This tower is heavily based on @Model_rockets tower, so a lot of credit to her. She has a writeup on the tower here (https://docs.google.com/document/d/1wkuK2sJ9ZAtBeEdFznTZdBiznUY5W8WaoCECNlkreA0/edit?usp=sharing). Another friend (u/maxjets) on the r/rocketry discord server has created a parametric generator for the endcaps if you want to use different conduit/diameters of this tower. That can be found here (https://discord.com/channels/723644976638066845/724382619206418655/1142965109807910974). What I did is just add mounting points to a 1010 rail so it can be slid onto a normal launch rail.
 

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Wow @Brainstormz123 !

Thanks for sharing your build !

Especially the link to the Easy Composites LTD video.

And I really like your "Sparrow" and your fins !

How thick are the fins after doing your almost tip-to-tip inlays ?

Have you flown the Sparrow yet ?

If so, do you have any data you could share ?

Enough distractions !

Good luck tomorrow and please let us know how it goes !!

-- kjh
 
Wow @Brainstormz123 !

Thanks for sharing your build !

Especially the link to the Easy Composites LTD video.

And I really like your "Sparrow" and your fins !

How thick are the fins after doing your almost tip-to-tip inlays ?

Have you flown the Sparrow yet ?

If so, do you have any data you could share ?

Enough distractions !

Good luck tomorrow and please let us know how it goes !!

-- kjh
Hello, thanks for compliments! These fins with the inlayed carbon are the same thickness as the outside wall (2.5mm at its thickest). The carbon layer didn't add any thickness to the fins. What I find most interesting about the "forged" composite stuff is that you can get a lot of detail. Here are some pictures of some fins I made for an H13 build I'll work on after the I500 flies. You can see how nice detail is preserved. These are 1mm thick at the inlayed part and 1.5mm at the thickest (around the edge).
1693588896903.png1693588903747.png

As for flying the sparrow, this will be its first flight. I have used the software logic for deployment on other flights before and test ran it on around 100 flights of data I've compiled to make sure that it should work. I attached all my flight data below if anyone wants to use it themselves. Here is some flight data from some other computers I've run before (custom1 in the attached zip file, there's 2 others in there too of my previous flights)
1693589175402.png
 

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Was not able to recover the rocket. RDF wasn’t working post burnout, probably separated from the shock cord and fell off or broke in half or something. Was able to eye track to apogee where the charge went off maybe 2ish seconds post apogee (I set my computer to deploy at 1.5 seconds after apogee to be a backup). Looked like the eggtimer apogee never deployed, probably outside the flight profile.

I followed the rocket to touchdown on parachute with my eyes, drove out to where I thought I saw it land, and wasn't able to find it. Green parachute and black rocket really isn’t the play in the desert I guess.

All in all, a great flight. I got what I wanted out of it (maximum giggle) and lost one eggtimer apogee (which I wanted to get rid of anyways) and a flight computer that costs under $10 assembled. 10/10 fun project
 
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Too bad the rocket didnt come back. Looks like it was a fun flight.
Everything looked like it went fairly nominal with the exception of some spiraling on the way up( not sure what from). Looks like it landed successively and fully recovered, hopefully someone finds it and brings it back
 
Was not able to recover the rocket. RDF wasn’t working post burnout, probably separated from the shock cord and fell off or broke in half or something. Was able to eye track to apogee where the charge went off maybe 2ish seconds post apogee (I set my computer to deploy at 1.5 seconds after apogee to be a backup). Looked like the eggtimer apogee never deployed, probably outside the flight profile.

I followed the rocket to touchdown on parachute with my eyes, drove out to where I thought I saw it land, and wasn't able to find it. Green parachute and black rocket really isn’t the play in the desert I guess.

All in all, a great flight. I got what I wanted out of it (maximum giggle) and lost one eggtimer apogee (which I wanted to get rid of anyways) and a flight computer that costs under $10 assembled. 10/10 fun project
I really appreciated your thread because I learned about forged composites.

Forged fins might be a better way for me to get where I want to go with my fins.

I like to build diamond-airfoil fins from wood, glass and epoxy but that means a lot of sanding and the fins always need to be 'tuned' after I am done with them.

I don't have a 3D printing system ( ??? yet ??? ) but I am wondering now if I can make a mold for my fins from one balsa fin shaped the way I want it and then I could end up with three or four identical fins without all the sanding and tuning !

And I really liked your idea of inlayed almost tip-to-tip -- what a great way to add the strength without spoiling the airfoil !

EDIT: I can't find a composite 29mm Ogive Nose for sale so ...

I've also been wondering if one could forge a nosecone as two longitudinal halves with tabs to join the halves and with an inlay area to reinforce the joint ?

Did you start out with the Easy Composites LTD Forged Carbon Fibre Development Kit ?

It seems like a good place to start but maybe you have a better recommendation now with some experience behind you ?

Thanks again @Brainstormz123

-- kjh

p.s. thanks for the Standardized Flight Data.zip file !

Its some really boring data but useful for testing out computer logic

I've not gone thru ALL the directories for all the different flight computers but on project on my back-burner is to convert a bunch of old AltAcc utilities to work with modern Altimeters.

Were all these from real flights which were subsequently converted via the ConvertToStandard.py script ?

I recognize the different altimeter models except what are the 'AlexFlights' and the 'Other Flights' ?

Thanks again !
 
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I really appreciated your thread because I learned about forged composites.

Forged fins might be a better way for me to get where I want to go with my fins.

I like to build diamond-airfoil fins from wood, glass and epoxy but that means a lot of sanding and the fins always need to be 'tuned' after I am done with them.

I don't have a 3D printing system ( ??? yet ??? ) but I am wondering now if I can make a mold for my fins from one balsa fin shaped the way I want it and then I could end up with three or four identical fins without all the sanding and tuning !

And I really liked your idea of inlayed almost tip-to-tip -- what a great way to add the strength without spoiling the airfoil !

EDIT: I can't find a composite 29mm Ogive Nose for sale so ...

I've also been wondering if one could forge a nosecone as two longitudinal halves with tabs to join the halves and with an inlay area to reinforce the joint ?

Did you start out with the Easy Composites LTD Forged Carbon Fibre Development Kit ?

It seems like a good place to start but maybe you have a better recommendation now with some experience behind you ?

Thanks again @Brainstormz123

-- kjh

p.s. thanks for the Standardized Flight Data.zip file !



I've not gone thru ALL the directories for all the different flight computers but on project on my back-burner is to convert a bunch of old AltAcc utilities to work with modern Altimeters.

Were all these from real flights which were subsequently converted via the ConvertToStandard.py script ?

I recognize the different altimeter models except what are the 'AlexFlights' and the 'Other Flights' ?

Thanks again !
Im not too sure about the feasibility of forged carbon to make molds of things like nose-cones, but there are almost certainly better ways to do it (standard split molds, or my favorite, male mold with soller sleeving on top. I can find you videos/writeups on some of these processes if you are interested.

Regarding what I bought, I had laminating epoxy from doing layups before, so I just purchased some mold release from my local hardware store along with chopped carbon from ebay. https://www.ebay.com/itm/1137191881...Oc2QeCvSJq&var=&widget_ver=artemis&media=COPY

I also user a later of vasoline along with mineral oil as a final “last resort” coating to help release the molds.

As for the flight data, all of it is real data that I converted to a standardized format. The Alex Flights are custom computer flights that I had made and tested (name is Alex) and the other computer flights are files I found with unknown origin.
 
Bummer you couldn't recover it!

Love the forged fins. I really want to know how they might hold up to a high mach flight, and what can be done to increase the density of the part.

And I'm obviously a fan of the tip to tip I layup. When I did mine way back when, I used a Cricut to cut the inlays to make them fit perfectly on the recess. But in practice that's only moderately successful. I'm curious how you trimmed yours after the fact, and were there any voids to fill?
 
Bummer you couldn't recover it!

Love the forged fins. I really want to know how they might hold up to a high mach flight, and what can be done to increase the density of the part.

And I'm obviously a fan of the tip to tip I layup. When I did mine way back when, I used a Cricut to cut the inlays to make them fit perfectly on the recess. But in practice that's only moderately successful. I'm curious how you trimmed yours after the fact, and were there any voids to fill?
Well if you wanna know how they hold up, this flight definitely was above mach 2 (sims said mach 2.5, but there was a bit of spiraling, so probably mach 2) and the rocket kept going straight after burnout so probably the fins held on.

As for trimming my layup, i wet out the cloth and cut it before i put it on, so there was nothing to trim. Did not have any voids either. Mentioned the procedure in a message above.
 
IMG_3332.jpeg
Sorry, I should have been more specific. Like in the area circled above, where there is a gap between the recess edge and the fabric. Did it just get filled with epoxy during the layup?

Those areas drove me Nuts mlon the rockets I have done with a recess, not to mention all the work involved in getting them smooth afterward.

Your method seems to have taken a lot less work than my method, so I'm curious!

I was literally Taking a break from working on this exact process when I found this thread. It's awesome work. Love to see envelope busting techniques like this!
 
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View attachment 601795
Sorry, I should have been more specific. Like in the area circled above, where there is a gap between the recess edge and the fabric. Did it just get filled with epoxy during the layup?

Those areas drove me Nuts mlon the rockets I have done with a recess, not to mention all the work involved in getting them smooth afterward.

Your method seems to have taken a lot less work than my method, so I'm curious!

I was literally Taking a break from working on this exact process when I found this thread. It's awesome work. Love to see envelope busting techniques like this!
Ah yes, that area I filled with epoxy when I did a flood coat over the fins. Didn't make that mistake on the other fins tho by just getting better so it wasn’t that big a problem
 
Im not too sure about the feasibility of forged carbon to make molds of things like nose-cones, but there are almost certainly better ways to do it (standard split molds, or my favorite, male mold with soller sleeving on top. I can find you videos/writeups on some of these processes if you are interested.

Regarding what I bought, I had laminating epoxy from doing layups before, so I just purchased some mold release from my local hardware store along with chopped carbon from ebay. https://www.ebay.com/itm/1137191881...Oc2QeCvSJq&var=&widget_ver=artemis&media=COPY

I also user a later of vasoline along with mineral oil as a final “last resort” coating to help release the molds.

As for the flight data, all of it is real data that I converted to a standardized format. The Alex Flights are custom computer flights that I had made and tested (name is Alex) and the other computer flights are files I found with unknown origin.
Forgot to mention, the blue fins were fiberglass from us composites since colored dye doesnt show up in carbon really
 
This build has convinced me to star looking into homemade compression molded parts more. I think that there's potential to further optimize them by using pieces of fabric and tows of carbon to have more oriented fibers in key locations, instead of the largely random fiber orientations that you get with just chopped carbon.
 

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