Re: fsi and apogee Aspire

These and the E5 were the most fun I ever had with FSI motors. Loved 'em
both.

If you do things right they fly fine. Build light and lighter, and make sure
the ride up the rod/tower is stiction free, and get that launch elevation as
close to 90 degrees as you can. I flew many BT-60 3FT based rockets on
these, and had no problems. The only time I did was a light BT-55 based
thing I once built that had fairly small fins and I had the CG just a bit
too far back - someone has great video of it snaking around in the grass,
occasionally breaching a couple of feet up then back to slithering again.
Needed nose weight or more speed off the rod.

Whatever you do though, don't build any rocket for these like you are going
to fly it on F50's or the like. And use light weight fins and don't skimp
too much on the area due to the speed off the rod with these motors. It is
nothing like the F10 at all, which I have flown in very lightweight 2.6"
rockets. In fact it is not even an F7 if you look at the real cert data
versus FSI's data. I believe the real average thrust is between 5 and 6
newtons.

That said, my biggest concern would be the reliability of these after 15
years - they were not the world's most reliable motors although I think I
saw more F100/E60 problems, likely simply due to more of them being flown.
All the examples I flew worked, but they were not old at the time. I believe
Don Carter could elaborate on the reliability issue, for those that remember
that incident in the late '80's IIRC.. ouch :-(

But you may as well fly them! Enjoy, wish I had some.

Mike D.



"DanF" <dafalb2001@xxxxxxxx> wrote in message
news:1155849803.455741.128790@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
In all probability, unless you are extremely lucky, your whole flight
with the F7 motor will be one big arc. Flights with F7's usually go up
about 50-100 feet and then start a really large arc until the parachute
/ streamer comes out.
A lot depends to where you are launching (high humidity areas are
worse) and how much of a breeze there is. Notice that I didn't type
"wind".
Good luck.
By the way, an F10 will take the model up much straiter and higher than
the F7.
Daniel





caheaton@xxxxxxxxxxx wrote:
Well, I think I answered my own question. I created a rocket profile
in WRASP, ran a check of the profile against predictions from Apogee
with other engines and then tried it with the F7. The F7-6 is the
desired engine, with ejection coming about 1 second before apogee
(rocket is traveling around 30 fps at the time, the F7-8 would allow
the rocket to arc over and eject when descending at around 33
fps...ideal predicted delay is 7 seconds). Max altitude is 3580
feet....a little less than the 5468 max design altitude using an F10-8
(the engine the rocket was built around, according to Apogee). This
looks like it might be doable and a way to use up my stock of those
engines.
Launch rod velocity is 27 fps...nice and slow...maybe too slow?
(By the way, the rocket is 29" long and weighs 1.85 ounces empty
according to Apogee.) Now to run out and buy the rocket! :-)
Craig



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