Flightsketch mini questions

[bobbyg23]

I received my flightsketch mini today and I have some questions. I have it mounted with shock cord to the nosecone loop as I don't have a cargo bay to put it in. I didn't drill any holes in the body tube yet. Here is the data I got. Not sure if it is accurate.
I am wondering if I need to drill holes in the bt or not. If I do drill holes, will they affect the ejection charge? Manual says you may have to drill 3 holes each 1/16".

 

[BEC]

All altimeters will give better, more accurate results if they can "see" the static air pressure outside the model essentially in real time. That's why you need static ports. The FS Mini has no special requirements in this regard.

The size of holes you need really depends on the volume of the compartment in which the altimeter is riding on its way up. The object is to size them so that there is little time lag between the pressure inside the body (prior to ejection) and outside.

Tell us a little more about your model (and motor). With an apogee around 200 feet and that short of a burn (though the FS Mini's burn time calculations are sometimes right on and sometimes not so much) I'm guessing something small with an Estes A8 for power. The altitude graph also suggests to me a delay that was a little too long and both traces say your recovery was kind of turbulent (tumbling or spinning or something).

Three 1/16 inch holes will not vent enough of your ejection charge to matter unless things are really marginal in your model with respect to getting the recovery system deployed already.

I don't see your flight in the online log, so you must not have uploaded it there, so my comments are based on your screen shots only and not looking more closely.

 

[dlb]

3 1/16 holes work just fine.
I also put mine a bt 20 coupler , for protection. 1 end open the other end sealed.

 

[bobbyg23]

All altimeters will give better, more accurate results if they can "see" the static air pressure outside the model essentially in real time. That's why you need static ports. The FS Mini has no special requirements in this regard.

The size of holes you need really depends on the volume of the compartment in which the altimeter is riding on its way up. The object is to size them so that there is little time lag between the pressure inside the body (prior to ejection) and outside.

Tell us a little more about your model (and motor). With an apogee around 200 feet and that short of a burn (though the FS Mini's burn time calculations are sometimes right on and sometimes not so much) I'm guessing something small with an Estes A8 for power. The altitude graph also suggests to me a delay that was a little too long and both traces say your recovery was kind of turbulent (tumbling or spinning or something).

Three 1/16 inch holes will not vent enough of your ejection charge to matter unless things are really marginal in your model with respect to getting the recovery system deployed already.

I don't see your flight in the online log, so you must not have uploaded it there, so my comments are based on your screen shots only and not looking more closely.

It would not let me upload it for some reason. It just tells me I need to be logged in to upload data. I am logged into the site. Is there somewhere else I need to log into?

 

[bobbyg23]

3 1/16 holes work just fine.
I also put mine a bt 20 coupler , for protection. 1 end open the other end sealed.

Does it matter where on the bt the holes are?

 

[bobbyg23]

Here is the one I have it in now. It is a mean machine turned into a sidekick. This flight was 2 C11-3 engines. Deployment was perfect at apogee.

 

[bobbyg23]

Here is a video.

 

[BEC]

It would not let me upload it for some reason. It just tells me I need to be logged in to upload data. I am logged into the site. Is there somewhere else I need to log into?

You need to be logged into your account from the app (not your browser). Swipe to the right from the startup screen to see where the login prompt is. Unfortunately it doesn’t know if you’re logged in or not and once you do there is no good way off the login screen except to kill the app and restart it (which means downloading your data again). Your data from the last fight will be in the FS Mini until you arm the unit for launch again. It’s at that point the previous flight’s data is wiped.

 

[BEC]

On a model that big, I’d actually use three or four 1/8 inch holes. Ideally they should be down below the nose cone a ways so the air has a chance to smooth out after going over the nose cone/body tube joint. But unless you’re looking for very precise data for the whole flight (as opposed to knowing how high it went) the placement, as long as they are in the body somewhere away from big bumps, is not critical.

Added: I had to go look at your build thread - that is one cool model.

Also, the NAR cert data says the C11 takes nearly 0.35s to come to full thrust....so the FS Mini’s velocity curve and statistics about burn time and such are clearly not so good in this case. https://www.nar.org/SandT/pdf/Estes/C11.pdf

 

[bobbyg23]

You need to be logged into your account from the app (not your browser). Swipe to the right from the startup screen to see where the login prompt is. Unfortunately it doesn’t know if you’re logged in or not and once you do there is no good way off the login screen except to kill the app and restart it (which means downloading your data again). Your data from the last fight will be in the FS Mini until you arm the unit for launch again. It’s at that point the previous flight’s data is wiped.

View attachment 414110
View attachment 414109

Thank you very much. I just uploaded it now.

 

[BEC]

Yes, I see it. I was about to suggest you edit in a title, but I see you did that and put in two pictures as well. Love the liftoff shot!

 

[bobbyg23]

On a model that big, I’d actually use three or four 1/8 inch holes. Ideally they should be down below the nose cone a ways so the air has a chance to smooth out after going over the nose cone/body tube joint. But unless you’re looking for very precise data for the whole flight (as opposed to knowing how high it went) the placement, as long as they are in the body somewhere away from big bumps, is not critical.

Added: I had to go look at your build thread - that is one cool model.

Also, the NAR cert data says the C11 takes nearly 0.35s to come to full thrust....so the FS Mini’s velocity curve and statistics about burn time and such are clearly not so good in this case. https://www.nar.org/SandT/pdf/Estes/C11.pdf

That makes sense then. It is not kicking in until a little bit into the flight. After examining the video on my phone, it looks like a total of 5ish seconds to apogee.

 

[BEC]

Oh...and if you’re going to keep flying the FS Mini just hanging from the nose cone, you really ought to protect it from the ejection gases some. Yesterday evening when I was flying one in a small model (Semroc Astro Jr.) down at the nearby elementary school, I was just folding a square of wadding into thirds and then wrapping that around the FS Mini as I stuffed it into the top of the tube above the ‘chute and shock cord. In a model like yours, where you have lots more room, dlb’s idea of a JT-20 as a sort of protective shell would work. When I fly one in a larger model (BT-50 and up) but in with the recovery system, I put it in a little fleece fabric pouch my wife made.

 

[bobbyg23]

On a model that big, I’d actually use three or four 1/8 inch holes. Ideally they should be down below the nose cone a ways so the air has a chance to smooth out after going over the nose cone/body tube joint. But unless you’re looking for very precise data for the whole flight (as opposed to knowing how high it went) the placement, as long as they are in the body somewhere away from big bumps, is not critical.

Added: I had to go look at your build thread - that is one cool model.

Also, the NAR cert data says the C11 takes nearly 0.35s to come to full thrust....so the FS Mini’s velocity curve and statistics about burn time and such are clearly not so good in this case. https://www.nar.org/SandT/pdf/Estes/C11.pdf

Those holes will not affect the ejection charge then, right? I have 2 other rockets that I plan on putting it into also. Estes SLV and Estes QCC explorer. I will put some holes in those also. Is there a method to getting those hole into the BT? Just drill them or add some CA to harden the edges?

 

[bobbyg23]

Oh...and if you’re going to keep flying the FS Mini just hanging from the nose cone, you really ought to protect it from the ejection gases some. Yesterday evening when I was flying one in a small model (Semroc Astro Jr.) down at the nearby elementary school, I was just folding a square of wadding into thirds and then wrapping that around the FS Mini as I stuffed it into the top of the tube above the ‘chute and shock cord. In a model like yours, where you have lots more room, dlb’s idea of a JT-20 as a sort of protective shell would work. When I fly one in a larger model (BT-50 and up) but in with the recovery system, I put it in a little fleece fabric pouch my wife made.

View attachment 414118View attachment 414119

I like that idea. I will have to do that.

 

[bobbyg23]

There are some weird things on my flight data. I think the holes will make that better next time.

 

[BEC]

The SLV, of course, has a huge payload compartment....so you can put it in there. The trick will be keeping it from rattling around. And of course the payload section will need static ports. For the QCC you’ll want to do the same as for your upscale Sidekick (unless you modded it to have a payload section as I typically do).

As for the ejection charges....three or four 3/32 or 1/8 inch holes will probably not be an issue getting a 12 inch ’chute out of a BT-60 (well, as long as the nose cone is not too tight on the tube).

Funny data hopefully will be improved by having static ports.

 

[bobbyg23]

The SLV, of course, has a huge payload compartment....so you can put it in there. The trick will be keeping it from rattling around. And of course the payload section will need static ports. For the QCC you’ll want to do the same as for your upscale Sidekick (unless you modded it to have a payload section as I typically do).

As for the ejection charges....three or four 3/32 or 1/8 inch holes will probably not be an issue getting a 12 inch ’chute out of a BT-60 (well, as long as the nose cone is not too tight on the tube).

Funny data hopefully will be improved by having static ports.

I have not modded any of them to have a payload section. They are built per the instructions. The SLV has the nosecone glued on so I do not have access to the payload compartment. I will have to take a look at how I can easily gain access to that compartment.

 

[bobbyg23]

Had this flight today with my qcc explorer. Quest d16-6.

 

[Buckeye]

Did your rocket land in a 161 ft deep well?

Edit: I see it landed in water. That probably has something to do with it!

 

[bobbyg23]

Ha. Funny things happen when it gets wet.

 

[Spitfire222]

This is a relatively recent thread, so I wanted to use it to also ask some questions about using the Flightsketch Mini. I used mine for the first time yesterday on three launches. I saved the data locally on my phone, and I can see each of those datasets in the app. The logging in is pretty confusing, as an alert pops saying I've successfully logged in, with no indication that I actually have. I've tried uploading the flight data to the web, after having logged into my account on the Flightsketch website, but I don't see it anywhere, even after the app says upload was successful. The numbers are nice, but I'd like to see the graphs also, as well as have the ability to rename/edit the flight data title and description for future reference. Any help is appreciated, I guess starting with where to find uploaded flight data? Thanks!

Nevermind, I finally found the flight logs on the site. It never occurred to me that they'd all be dumped in one location with a pull-down menu of all users to find your account. I assumed the flights would be listed on your "Accounts" page.

 

[Dane Ronnow]

The trick will be keeping it from rattling around.

I'm thinking of a 1-inch-thick disk of low density foam rubber (think bath sponge) with a slot cut into the side. The Mini slides in the slot after power-up, lying flat, and is attached to the upper shock cord or nose cone with kevlar thread that passes through it and the foam disk.

The foam rubber is porous enough to allow the Mini to sense pressure change, but dense enough to cushion it when the ejection charge pushes it up against the nose cone.

I'll be using this in two rockets—a BT-60, and a BT-80. One disk for each rocket, cut with enough space around the side of it to allow movement of air.

 

[BEC]

That sounds like a pretty good plan.

I'd be interested to see the acceleration values flying it oriented that way. I tend to have mine oriented as if it is standing on edge, usually with the end containing the switch (and the lanyard hole) at the top.

It's too bad the current state of the online flight log doesn't yet graph the acceleration data

 

[Dane Ronnow]

I'd be interested to see the acceleration values flying it oriented that way.

This is from page three of the FSMini Guide: "The accelerometer will detect and correct for the orientation of the altimeter however maximum data range can be achieved by aligning the long axis of the altimeter board with the body axis of the rocket."

Not sure if 'maximum data range' means talking to the app, or data collection during the flight. If it's the first, I wouldn't have a problem with the chip lying flat. If it's the latter, I'll rethink orientation. One inch tall takes a bite out of the recovery gear area, which is where I would place it. Flat, no problem. Vertical? Not crazy about it. Unless it's taped to the side of the tube an inch or so below the bottom of the nose cone shoulder (and potentially a hanging point for the chute and shock cord on deployment), it's going to take up more space than I want to give it. I'm thinking it would involve a 1-inch coupler, capped on one end.

On the other hand, maybe a pouch is the way to go. But a very light, thin one. With that, I would probably tuck it into the top end of the chute/blanket roll with the pressure sensor at the top end, and top it with a foam cap, roughly the diameter of the tube and tied to the recovery package somewhere, just to keep the Mini from banging into the bottom of the cone on ejection. That's a bigger concern to me than how to tie it down.

 

[GalantVR41062]

Mount it vertical inside the nose cone. The hole in the bottom of the cone, and a single or couple vent ports in the air frame will be enough for the baro sensor on the Fs mini.

 

[BEC]

This is from page three of the FSMini Guide: "The accelerometer will detect and correct for the orientation of the altimeter however maximum data range can be achieved by aligning the long axis of the altimeter board with the body axis of the rocket."

Not sure if 'maximum data range' means talking to the app, or data collection during the flight. If it's the first, I wouldn't have a problem with the chip lying flat. If it's the latter, I'll rethink orientation. One inch tall takes a bite out of the recovery gear area, which is where I would place it. Flat, no problem. Vertical? Not crazy about it.

It's the latter. The component on the board that's mounted at 45 degrees to everything else is the three-axis accelerometer, and thanks to the magic of vector addition, having two axes 45 degrees off of the actual main axis of the acceleration lets one get a wider range of values for a given device's physical limits along that direction. So...it can cope with and report a higher G-load from boost that way without "pegging the meter" so to speak.

I have a hard time imagining what BT-60- or BT-80-based model would not have room for the Mini oriented long axis parallel to the direction of flight....but I've been accused of having a limited imagination before. I fly the Mini (in a fleece pouch as shown earlier in this thread) in with the recovery system in models as small as an Alpha. It's a squeeze, but it can be done.

You are right to be concerned about banging it into the base of the nose cone. Even though it uses a pretty rugged carrier for the little coin cell that powers it, users (including me) have occasionally had data truncated and the the best explanation for this is a brief power outage caused by banging the unit into something else. Usually this seems to happen at the ejection event, when all kinds of chaos typically ensues. Here's an example from one of my flights: https://flightsketch.com/flights/1232/. In this case the FS Mini was inside a payload section (along with an AltimeterThree) so what it hit and how hard it it was limited more than flying it in with the "laundry". But I admit in the Nova Payloader I usually just leave a Mini in a pouch and don't restrain it any more. The AltimeterThree would have been below it in the payload section so perhaps it smacked the Mini enough to briefly interrupt power. It only takes a fraction of a second and generally the Mini is powered up and running on landing after this happens.

 

[BEC]

I have not modded any of them to have a payload section. They are built per the instructions. The SLV has the nosecone glued on so I do not have access to the payload compartment. I will have to take a look at how I can easily gain access to that compartment.

Oh.....I missed this before. That's unfortunate, because things are pretty tight with the chute in the relatively short BT-55 section that it lives in. I have never understood any models that look like they have payload sections yet one is directed to glue the nose cone in and therefore seal the payload section. I built an SLV as a proof-of-instructions build and I forgot all about that. I, of course, just friction fit the nose cone on mine.

There was even an RTF called "Loadstar" that came with the payload section sealed up like that. THAT really bugged me.....!

 

[Dane Ronnow]

I have a hard time imagining what BT-60- or BT-80-based model would not have room for the Mini oriented long axis parallel to the direction of flight

I'm still stuck on this idea of using a disk of open-cell foam, slight narrower than the body tube diameter. With the Mini lying flat, I can get away with the disk being 1/2 inch thick, so there's a bit of padding above and below it. If I have the Mini with the long axis vertical, the disk would be 1-1/2 inches thick (again, padding above and below). If I allow 1-1/2 inches of room in the recovery section above the chute, protector and shock cords—which I would do simply to keep the disk from pushing up on the base of the nose cone (it's a loose fit)—I'm pushing everything behind the disk farther back, thus lengthening the body tube and changing CG.

Having said all that, I'm probably getting way too fussy about this. Now I'm leaning toward putting the Mini in a pouch (attached to the nose cone with Kevlar thread) and just tucking it inside the parachute protector as I wrap the chute, oriented in such a way that when the rolled-up protector is slipped inside the tube, the Mini is vertical on the long axis. It should be able to breath with nothing but Nomex cloth between it and the wall of the tube, close to the pressure vents, but packed tightly enough that it won't shift under acceleration. On deployment, the rolled chute package would push the nose cone out before the Mini becomes exposed, eliminating an initial collision between nose cone and Mini. After that, it's just a matter of components bumping into each other on descent. I don't think that would be enough to cause data interruption.

Anyway, I appreciate your input on this. It helps move things forward. Now if I can get out of my head (I spend a lot of time there contemplating problems that sometimes don't even exist!) long enough to build the rocket, I might actually be able to use the Mini as it was designed—to see how high the rocket flies.

Thanks again.

 

[Dane Ronnow]

The component on the board that's mounted at 45 degrees to everything else is the three-axis accelerometer, and thanks to the magic of vector addition, having two axes 45 degrees off of the actual main axis of the acceleration lets one get a wider range of values for a given device's physical limits along that direction.

More than anything else I've read, this helped me understand why orientation of axis on the Mini matters during flight. Thanks.