CRC High power builds

[CRC]

I agree with the fact they should be able to work while tight if the rail is clean, I'm sure they say to allow it to spin to keep some from complaining about wear & I imagine it would help with binding if some debris got in the rail while out on the field if they can spin.... mine are going to spin anyway.
Hardware store......yes I've found the same thing, I'm a contractor & am known on a first name basis at my Home depot & home hardware, so I'm no stranger to the goodies those stores hold....look at my steel cable idea(crc's mid power build thread) that came directly from isle 21 lol

 

[CRC]

Ok, I went and got some #10 thin SS washers to use as standoffs, they fit perfect & look pretty good too I think, They should work good.

 

[CRC]

Got my fillets done, I used thin layer of CA, then Epoxy over it after it dried, I has to sand the coupler too much for my liking, & it still is a bit too tight, I'll see I guess when my replacement tube arrives. So what you guys think? Did I do anything wrong/bad so far?

 

[DAllen]

I haven't seen anything outright egregious - slightly overbuilt but that's okay. I think I missed the reason but why are you putting the extra stuff between the fins on the fin can?

-Dave

 

[CRC]

I haven't seen anything outright egregious - slightly overbuilt but that's okay. I think I missed the reason but why are you putting the extra stuff between the fins on the fin can?

-Dave

Extra stuff? You mean the epoxy? If you mean the fin can segments, they are stock & part of the scale model.
Here is a pic of inside BT with my baffle style SC mount & gussets epoxied in. And another of it getting ready for primer.
Another queston for you guys, I'll except opinions too Should I use a 9x9 chute protector as well? I got the AT plastic baffle, then my SC mount/baffle plate, is that enough? I'm thinking I should use a chute protector as well, but I dont want to cause a deploy failure by adding "too much" Thanks for your input.

 

[CRC]

I shot first coat of primer & let it dry so I can see the imperfections better, I then did a bit of filling(with glue) then I started paint on exhaust port(what I'm calling it) by painting it black, then with a clear high heat engine enamal.
Queston about vent holes for altimeter in payload section, I drilled 4 evenly spaced 7/64" holes......that should allow altimeter to work eh? Do you think I'd be better off with 1/8"?
Next is wait another day so I can spray another coat of primer, then 1st coat of colour, wait for it to dry, sand then paint again.

 

[CRC]

Also What about vent hole(not altimeter sampling holes) Should I drill one out? do i need to? what size if so? I tried looking for this info but I could not find any solid answers. This rocket wont be flown on anything bigger then a H motor. Really none of my rockets have vent holes, only sampling holes, usually in a payload section, but then again none of my rockets will go more then 3500'

 

[CRC]

So I drilled a 1/8" vent hole in bt, now I just need to know if I should use a chute protector with my baffle(if you can call it that) or will I be ok without it. Better queston will it harm deployment having a chute protector with what I got already? I wanna make a order today so please let me know you guys thoughts about that. TY

 

[nute]

I would say get a chute prorector. Put it on, and if it is
Un scorched then you can take It off and put it on a different rocket. Otherwise, it's better to have it and not need it than end up burning a chute or worse

Nata

 

[CRC]

Good idea Nate, thanks! I'm ordering a 9x9 tonight along with a few hundred in motors, gotta stock up for spring & summer.

 

[CRC]

All right I got this built, now I'm just working on the paint, I'm not using the stock red line decals, I'm painting them on insted.
Queston though about how to I tell where the CP will be if I'm using an H(say H123) I can find on the internet with recomended motors, but not sure with it being modified a bit, the NC,rocket length,fins, bt diameter, all is same but its a bit heavier(not sure if that affects CP) plus I'm pretty sure the H motor would change CP wouldnt it? Any help would be helpfull, thanks

 

[nute]

All right I got this built, now I'm just working on the paint, I'm not using the stock red line decals, I'm painting them on insted.
Queston though about how to I tell where the CP will be if I'm using an H(say H123) I can find on the internet with recomended motors, but not sure with it being modified a bit, the NC,rocket length,fins, bt diameter, all is same but its a bit heavier(not sure if that affects CP) plus I'm pretty sure the H motor would change CP wouldnt it? Any help would be helpfull, thanks

The CP is solely aerodynamic. the addition of a larger motor will not affect it. the addition of larger or different sized fins would. The CG is solely related to weight distribution, and will vary greatly between an F40, and say an I200.
OR can estimate this, but a better way is just to balance it on your finger or in some sort of cradle contraption.

Hope this helps

Nate

 

[CRC]

Yes it does Nate, alot, TY!!! I got CG down I think, I balance it then measure from aft of rocket to balance point, that's what I've been told, CP I know if I changd the dimentions of anything it would affect it, but was not sure if motor size/thrust & weight would affect the CP. Thanks again, I really appreaciate it!

 

[CRC]

Ok so I determined my CP is 46.5" from front(according to rocketreview or/rs file)
I also got some paint on it, as per instructions(OMG yes I'm for first time doing stock colours) but I will add a little of my own touch, just to be diff

 

[nute]

CRC... :surprised:doing a paint scheme...:surprised: stock...:surprised:!!!???? This is madness!!!!
Can't wait to see what touches you add, should be cool!

Nate

 

[CRC]

Ok it's not quit stock, but as close as I'll get.....it's the same colours in same places anyway. I'm calling it done other then clearcoat. What you guys think? I hope it will handle a H when it gets one. I got a F20-4 & a F42-4 for first flight.....depending on finished weight is what I will use.... But it does have a date with a G77-7R then onto HPR assuming we get certified. I placed a small circle decal where CP is, along with other decals I took from my satelite interceptor.
It aint no showpiece, but I say it's good enough to show & fly.

 

[CRC]

Also, yes those are Cranbrook rocket club logo decals I got made from my local print shop, along with red flame decals

 

[bill_s]

Re: Estes retainers, I've been using one w/ a 29/40-120 that doesn't go in all the way due to a thrust block, should be less threads than AT HPR. And this rocket produces extremely high pressures.

Don't you need to leave out the plastic thingie for the cooling mesh also to fit HPR motors? I guess the plastic should be able to handle it though.

The Arcas is beautiful and big, was thinking about getting one except it's almost the exact same weight as 2 rockets I already own.

 

[CRC]

I did some research before choosing to use the estes retainers, one reason is I'll be using CTI reloads when I buy a casing & CTI has a thinner thrust ring the AT, thus CTI fits better with the Estes retainers, as well as the fact they 1/8 the price.
The plastic thingy(AT baffle) does not need to be left out for any motor I'd be using in this, it has a 12" MM tube, but I did leave out the Cooling mesh. I'll also be using a 9x9 nomex chute protector along with my baffle plate/SC attach point.

 

[bill_s]

^^--If that's the case, why leave out the mesh for high power? Or is that just a separate choice?

 

[CRC]

I left the cooling mesh out cause A: the aerotech sumo(a HP kit) does not use the mesh, B: I've never heard of using the mesh in HPR, & C: Wiser more experianced rocketeers told me I should not use it.

 

[rocketgeek101]

Great looking bird CRC! Be sure to let us know how she flies!!

 

[CRC]

Thank you Sabastian! I just weighed it &.....OMG I'm thinking the flying pig might not be an inappropriate name. chute, protector, whole thing WITHOUT motor weighs 729g!!! A little more then I thought & AT's estimated weight(without motor) of 400g
I'm rethinking motor selections now as the recommended motors are all out the window now. Once I add the tracker, beeper & maybe a cam I'll be close to 800g
Anycase maiden flight being on an f20 is out of the queston.
Anyone please answer me this:
F50-4 says 1020g max, while all f20,f23 & F42(4sec delays)all say 680g......is a f42-4 econojet really that much less powerfull then a F50-4?

 

[nute]

Daaaaang!!!
That thing turned out Crazy heavy!!! Beautiful, but heavy!!!
The F50T should only give you about 650 ft. of altitude, if that.
The F42T will be even lower, at closer to 425, if that.
I'm not sure why the F42T has 680g as the max weight. It should be fine in anything up to about 50 oz. (1400gm) That is an ideal figure, giving you just barely 5:1 off the pad. However, in your rocket I would say that the F50T would be greatly preferred, but the F42T could suffice. I'd say the other Econojets really should be out of the question, but interestingly enough it looks like the F20 could theoretically work, given ideal conditions and an 8ft rail. A great way to compare motors is this website:https://www.rocketreviews.com/compare-aerotech-f50t-to-aerotech-f42t.html
The F50 has a much higher sustaining thrust, but only slightly higher initial thrust
Either motor is going to be really slow, and probably on the edge of success, especially if the delay runs long
Nate

 

[DAllen]

is a f42-4 econojet really that much less powerfull then a F50-4?

Of course. Remember that letter designations on our motors incorporate a range of total impulse. Sometimes you will hear someone say "Baby O" which means the motor is on the lower end of the O range of impulse. The NAR has this handy little chart outlining the impulse ranges. An F motor has a range of 41 to 80 newtons if I am not mistaken. People will also refer to motors as being a "50% F" which I believe means that F is half way into the F range or about 60 newtons.

Also, the weight you are citing is also dependent on the number following the letter. The higher the number the shorter the burn and the more energy is used per second. So an F with 80 newtons total that is a F40 means it will burn for two seconds where if that same F were an F80 it would burn in one second. Generally, the faster the burn the more weight it can safely lift. A 5:1 thrust to weight ratio is typically a minimum recommendation. I prefer even higher than that.

Aerotech also accounts for the delay in their weight calculations. Obviously, a shorter delay is better for heavier rockets. All that said, a properly set up computer sim is your best friend...

A handy web site for determining motor impulse is Thrustcurve where you can find all sorts of OOP motors along with the current ones along with corresponding computer files to go into your sims as needed.

At 800g (1.75 lbs) you are in the realm of a G motor really or a high thrust F.

-Dave

 

[nute]

Agree with everything DAllen said. My Aero tech Astrobee D turned out only slightly heavier than that, and I flew it on a G64W and really wouldn't wanna fly it on anything much smaller.
Maybe a a G77 would be better.

Nate

 

[CRC]

Wow, awesome links guys, really helpful!! I like that motor comparison on rocket reviews & also that thrustcurve link is super helpfull since I'm not into the sims yet.
How heavy is your astrobee D Nate?
G77? 7sec delay be too long you think?
Hmmmm now what to do with the f42-4's I got....maybe I'll be able to use them in My ventris once I weight it down with electronics.
So of all the motors I currantly got, the only possible motors I can use(I think) G40-4W, G77-7R & the f42-4 but I dont want a cato so I think I'll stick to F50-4 & above.
Funny thing is 400' is plenty high for a lil c rocket, but for my bigger rockets that dont seem high enough for my peace of mind.

 

[CRC]

So first off, the above rocket(arcas) flies great, I've flown it 4 times with 4 diff motors with all successful flights.

Now it's time to talk about my build I'm about to start.......
It will be a high power scratch built rocket,(my first) with diff size payload bays so I can fly it on G's untill I get certified, then I'll be able to add the bigger,longer, heavier tube for high power use.

Please speak up if anyone see's I may be making a mistake or forgeting something, but I do got most of a build plan I'm pretty confident that I'll be able to cert with if I choose to. All the parts have been ordered.
First a bit of info of what I'm using.
4" aerotech thickwall tubing
38mm motor mount(madcow)
4" HD plastic oglive aerotech nose cone
42" nylon chute
1/4" birch plywood fins
2 payload bays, one small, one large
3 fins
38mm aeropack retainer & 29mm adaptor

Only thing I got sofar is the fin plywood, so here is the shape of the fins I'm using, next is to cut them out & wait for all my parts to arrive.

 

[CRC]

Step one of my High power scratch built rocket now named Optimus Prime is now complete.
3 fins are cut out of 1/4" birch plywood, next is to sand them & wait for other parts I ordered.

 

[CRC]

Most of my parts arrived today in the mail, so the build is moving forward, here is a pic of most of the parts.