Going for the F Record

[James Keller]

Hey all,
With NSL West coming up, and it being an optimal time to attempt a record, I want to give the F record a shot. Initial sims make 12,000ft seem possible, the current record is just over 10,000ft so a little room for error. Here's the plan and current progress.
Airframe
The airframe was wrapped with 1 layer of 5.7oz carbon fiber around a 29mm spent DMS motor. This will really only be used to attach the fins and tailcone to. This will not span the whole length of the motor and the motor will be used to couple the NC and airframe together. The tailcone will be 3D printed and the fins will connect the 2 (half the fin on the tailcone and half on the airframe.) The airframe has been wrapped but not finished.

Fins
The fins will be Biconvex, made of a 0.05" carbon fiber sheet that I laid up out of 5.7oz CF. They will be machined with my CNC router. I am still trying to dial in my technique but currently this works okay. Hopefully I get around to doing this tomorrow.

Tailcone
The tailcone will be 3d printed out of PETG and will be attached to the airframe via the fins. I'm considering doing some sort of "thermal" coating. While I'm not sure this is necessary, it surely can't hurt. Any suggestions on the coating would be appreciated.
Nosecone
The nosecone will be made of 2 layers of 6oz S-glass is a similar fashion to @watheyak method, instead of a fancy fiberglass mold I 3d printed a mold and filled it with concrete. The finish isn't nearly as nice but an initial test piece is promising. With maybe another hour on the backend it looks fine. Given I don't foresee myself making a ton of 29mm NC it will be just fine. The tip of the NC is 3d printed with a thread insert. This will be held in place by the Ebay which will have a nylon 1/4-20 bolt. Fingers crossed I will be making the nosecone this Sunday along with finishing the airframe. Below are the pictures of the test piece and the mold.

Electronics
A blueraven, 2 screw switches, a featherweight Gps and 2 150mah batteries are housed in the nosecone plus about an inch. I tried like hell to cut out the extra inch of shoulder(or the airframe that is apart of the nosecone but isn't the "curvy" bit) and house it all in the nosecone but I couldn't quite get it to work in CAD. The 1/4-20 bold mentioned above will be held in place with plenty of JB weld.

Recovery
Pseudo dual deploy will be used for this flight. The first charge will break configuration and the second will be used to push out a 12" chute which will be housed in the NC. 300lb Kevlar will be used to keep the whole thing together. While this is overkill the weight that it is adding is only about 5 grams which from my CAD designing I believe I can spare. However, if push comes to shove this is what is going first.
Tower
The tower will be made of 1/2" emt conduit with 3d printed plates. It will be 10ft tall in an attempt to allow the rocket to get going as fast as possible to minimize the effects of wind. The parts are almost finished printing so the plan is to finish this up tomorrow.

I think this is everything! I will add more pictures and progress as it happens. For anyone who may have read my last build and is curious about my L1 progress, I built a simple 4" rocket and flew it on a baby H with great success at Tripoli Hartsel, and have gotten certified! Now that that's over I can return to overthinking and overbuilding!

 

[boatgeek]

Very cool! What motor are you using?

And I assume that you couldn’t go to 24mm and still fit the electronics?

 

[darrenf]

Does this mean you're coming to LDRS?

 

[MClark]

Make more than one complete with electronics.
To break record the flight needs to be perfect, a wiggle out of the tower or off vertical will cost 1000’s of feet. Be able to do more shots until it works.
The opportunity to launch is the difficult thing to have.
I used to hold the F record when much lower.

 

[bad_idea]

For anyone who may have read my last build and is curious about my L1 progress, I built a simple 4" rocket and flew it on a baby H with great success at Tripoli Hartsel, and have gotten certified! Now that that's over I can return to overthinking and overbuilding!

Congrats on the L1. Good luck with the record shot.

 

[James Keller]

Very cool! What motor are you using?

And I assume that you couldn’t go to 24mm and still fit the electronics?

Using the F10(which is what @Adrian A used in the current record), I looked briefly at 24mm motors and it appeared they were worse in everyway. Since the burn time of the F10 is so long it really is the best. And it would be impossible to fit electronics in the NC of a 24mm so I would add length as well.

Does this mean you're coming to LDRS?

No this will be at NSL west. At LDRS ASL I'm not sure the record is even beatable.

Make more than one complete with electronics.
To break record the flight needs to be perfect, a wiggle out of the tower or off vertical will cost 1000’s of feet. Be able to do more shots until it works.
The opportunity to launch is the difficult thing to have.
I used to hold the F record when much lower.

Yes I forgot to mention that I am building 2 rockets. It truly is insane how perfect the record @Adrian A set, I guess that makes me insane for trying to beat it!

 

[Adrian A]

Using the F10(which is what @Adrian A used in the current record), I looked briefly at 24mm motors and it appeared they were worse in everyway. Since the burn time of the F10 is so long it really is the best. And it would be impossible to fit electronics in the NC of a 24mm so I would add length as well.

No this will be at NSL west. At LDRS ASL I'm not sure the record is even beatable.

Yes I forgot to mention that I am building 2 rockets. It truly is insane how perfect the record @Adrian A set, I guess that makes me insane for trying to beat it!

Good luck! It's fun to have other people going for these records too.

 

[James Keller]

Not as much progress as I had hoped to make today but still on track. I completed the tower, the bottom pieces are friction fit to the emt conduit and they have 3/8" all thread in the connection points to stiffen the 3d printed parts. The middle pieces are attached using sheet metal screws into the conduit. This is plenty ridged for anything that can fit into a 29mm airframe.

I got both airframes cut to length(their tiny) they each weigh around 2.5 grams. Also got the fins cut out, and have figured out how I will shape them. Initially I was going to use my CNC Router but after an hour or 2 of trying to dial in settings and processes I felt the fins and tolerances were to tight. So I have shifted to using a 3d printed block that allows me to sand the fin down without sanding to far(I will attach pictures tomorrow). I tried it on one fin on one side and it appears to be very promising.


Tomorrows goal will be to shape those fins and make one of 2 nosecones.

 

[watheyak]

Super cool!

I'm excited to see how the 3D printed mold works out. I think the next molds I make will be 3D printed.

Good luck with the record!

 

[James Keller]

Super happy with todays progress! I got the fins shaped, I ended up making 12 and picking the best 6. While the jig I made isn't fool proof, it does work pretty well. The shape of the jig doesn't allow me to sand past where it needs to be. Then the mirror of it has the contour of the fin so it holds it in place properly(picture below). Not sure how well the picture shows it but they turned out pretty good.

After prepping the fabric and everything for the nosecone, I figured I could use the leftover resin for fin fillets. I did an .15" fillet on them which is super tiny but is just over 7% of the root chord. This also meant installing the tailcone. They are still very rough and have not been sanded much at all. I want to get a coat of resin on the whole thing before I get to crazy sanding though.

As far as I can tell the nosecone layup went okay. We will see tomorrow. I didn't feel like changing gloves multiple times while doing the layup so there are no pictures of the layup. I'm going to try to demold the nosecone tomorrow and layup a new one as well. That way if they don't go well I have time to make more.

The last thing I did was fiddle around with some electronics. I'm going to ditch the screw switches and go with some magnetic switches instead. Also I am leaning towards using double side stick tape to hold the altimeter and gps to the sled rather than screws. It's going to make life so much easier this way. If anyone has done this before with good or bad results please let me know.

 

[bad_idea]

Also I am leaning towards using double side stick tape to hold the altimeter and gps to the sled rather than screws. It's going to make life so much easier this way. If anyone has done this before with good or bad results please let me know.

I've used Apex servo tape to hold Eggfinder Minis in nose sleds on low/medium acceleration flights, but I wouldn't use that particular tape for high-G flights. Recently had a high speed crash in which the Eggfinder came free of the sled, not really a surprise.

I've not used it yet, but I have some 3M 5952 VHB tape I plan to use for higher-G flights. The downside of it is that I gather it's nearly impossible to remove. People who've used it have told me of adhesion surviving lawn darts.

 

[kjhambrick]

@James Keller --

Your sanding guide is pure-D genius !

One Q: how do you sand the first side and avoid oversanding while the opposite side is still flat ?

Maybe I am missing it ?

Thanks !

-- kjh

 

[James Keller]

I've not used it yet, but I have some 3M 5952 VHB tape I plan to use for higher-G flights. The downside of it is that I gather it's nearly impossible to remove. People who've used it have told me of adhesion surviving lawn darts.

Interesting, I think I may got this route and heat shrink around the electronics so nothing gets potentially damaged. Thanks for the help.

@James Keller --

Your sanding guide is pure-D genius !
View attachment 646140
One Q: how do you sand the first side and avoid oversanding while the opposite side is still flat ?

Maybe I am missing it ?

Thanks !

-- kjh

Thanks! The other side is more of the same but instead has a flat bottom(see below). I had to go through about 5 iterations of prints to get the fins to stay in place properly and get the right tolerances on the fins, but with enough patience they turn out pretty good.

 

[James Keller]

Progress and setbacks...
Nosecones have been made! The 3d printed molds worked as okay, and with some refining could work really well. The first attempt the bladder popped shortly after I went to bed so that one got trashed unfortunately. I laid up another one shortly after, and that one went really well. I again had some bladder problems where the first one popped again pretty much immediately. I replaced it and that one was fine. The second nosecone went even better. No issues with the bladder that time, so I'm not sure why I had problems initially. Some tips I learned is, have removable alignment pins. Especially with the smaller sizes having them be removable allows you to line the "ears" up much more easily. ALWAYS have some sort of metal backer. The 3d printed mold actually broke in half when I was initially testing because I didn't have a metal backer. And the more clamps/bolts you have keeping the mold closed the better. Overall, I made 4 NC out of one mold and they have decent tolerances. Again not perfect but given the amount of time I put into the mold I am pretty happy. I also 3d printed the NC tips, took a few test prints to get the settings just right. They get a metal thread insert so I have solid threads for the ebay bolt. I printed a little guide to know how much NC tip to chop off. I think I may have overestimated how much I needed to cut off. So I added probably 3 extra grams in the tip, but it really isn't that big of a deal given its at the right end of the rocket.









I also cut the electronics bay out of G10 and the bulkhead. Went to start assembling it and wanted to connect my new featherweight gps to my phone and that went down hill fast. As soon as I plugged in the GPS to the battery the voltage regulator(I think) almost immediately caught fire. I very promptly unplugged the battery. I checked the polarity and everything seemed to check out. Not sure what happened but I sent an email in to Adrian and I am waiting on a response. I think its repairable fingers crossed. Going to have to figure out what to do in the meantime. Worse case scenario I think I can probably buy one from him at NSL and slap it in.


The plan going forward is tomorrow I am going to finish the ebay, nosecone, and start polishing everything. Then Friday I will work on recovery and deployment testing. With any luck I'll be done at a reasonable time on Friday.

 

[James Keller]

Not sure what happened but I sent an email in to Adrian and I am waiting on a response

Turns out I'm just a royal idiot. For some reason I assumed since the blue raven could be powered by a wide range of voltages so could the GPS which is not the case. So PSA do not use a 2s with a featherweight GPS.

 

[James Keller]

Tomorrow's the day. The rocket is done and I am pretty excited! I am going to launch as early as possible tomorrow. The rocket weighed in about 10-15 grams over optimal mass which was slightly disappointing but I am still sim well over the current record. She may look a little ugly but she is very smooth.

 

[kjhambrick]

She may look a little ugly but she is very ...

BEAUTIFUL !

 

[James Keller]

Close but not quite. Can out of the tower perfect and had a nice straight boost for about 5s. At about 5s the rocket did something. Not sure quite what but you could see in the smoke trail it did a roll maneuver or something. GPS altitude report 9286ft, which is just about 100ft below the current record. Current guess is fin flutter but until i get home and take a better look at the blue raven data I'm not sure. Charges were a little hot and I ended up loosing the bottom half and the motor. I took the 300lb shock cord which had about 10 strands and stripped 6 strand out. I think this resulted in less than 40% of thr strength and this resulted in the breakage. Held off on launching its sister because it was more or less doomed to the same result. I'll do a better and more complete update when I get home. But given that even with the major "event" and losing all that altitude and I still was only 1000ft away I do think breaking through record is very doable.