Quantcast

Big and built to fly low

The Rocketry Forum

Help Support The Rocketry Forum:

cyberwollf

Active Member
Joined
Nov 2, 2015
Messages
28
Reaction score
0
About to start ordering parts for a new scratch built. My goal is for it to be ~8 inch airframe, taller than me for some "presence", and i'd like it to fly on a CTI 38mm 3 grain (going to be pushing it, probably have to be a 4 grain). I'll probably only fly it a few times a year, and have no interest shooting it to the moon. Something low and slow as a crowd pleaser.

I was looking at a LOC Bruiser kit, but I have a CNC, 3D printer, and other tools so I'll build from blank airframe. Looks like LOC 7.6 airframe is out of stock on their site so I'll shop around after Christmas money is in hand. I certainly wont be glassing it to save weight. Hope to have it under 10 pounds.

Whats the minimum safe altitude for something this size with motor eject and chute release? 1000ft?
 

MaxQ

Tripoli 2747
Joined
Jan 18, 2009
Messages
4,416
Reaction score
59
Location
Central Viginia - USA
About to start ordering parts for a new scratch built. My goal is for it to be ~8 inch airframe, taller than me for some "presence", and i'd like it to fly on a CTI 38mm 3 grain (going to be pushing it, probably have to be a 4 grain). I'll probably only fly it a few times a year, and have no interest shooting it to the moon. Something low and slow as a crowd pleaser.
I was looking at a LOC Bruiser kit, but I have a CNC, 3D printer, and other tools so I'll build from blank airframe. Looks like LOC 7.6 airframe is out of stock on their site so I'll shop around after Christmas money is in hand. I certainly wont be glassing it to save weight. Hope to have it under 10 pounds.
Whats the minimum safe altitude for something this size with motor eject and chute release? 1000ft?
Minimum safe altitude ?
It's all relative. Whatever it takes to get the recovery system out, which has a lot to do with your delay, and how high do you want to go.
This one was pretty big, and very low and slow, a large nine foot rocket, flying on an H100.
700 feet max. with a six second delay....
Trick was the lightweight (6lbs. of paper and foam) and the short delay.

I think your local LCO will have some opinions.

[video=youtube;rkIMvfyQoaM]https://www.youtube.com/watch?v=rkIMvfyQoaM[/video]
 
Last edited:

rstaff3

Oddroc-eteer
Joined
Jan 18, 2009
Messages
11,759
Reaction score
14
My 8" sonotube L2 bird went to 1500' on a J350. Big, fat and ugly! But it got me my cert ;)
 

cyberwollf

Active Member
Joined
Nov 2, 2015
Messages
28
Reaction score
0
Minimum safe altitude ?
It's all relative. Whatever it takes to get the recovery system out, which has a lot to do with your delay, and how high do you want to go.
This one was pretty big, and very low and slow, a large nine foot rocket, flying on an H100.
Trick was the lightweight (6lbs. of paper and foam) and the short delay.

I think your local LCO will have some opinions.

[video=youtube;rkIMvfyQoaM]https://www.youtube.com/watch?v=rkIMvfyQoaM[/video]
Love it. That's pretty much what I am going for. I'll stick with HPR airframe for now, but am intrested in a large foam MPR in the future too!
 

burkefj

Well-Known Member
TRF Supporter
Joined
Jan 27, 2009
Messages
3,285
Reaction score
729
A loc V-2 7.5" will fly to around 1000' on a J-425 38mm su, I've done a ton of foam structured scale missiles from 6 to 10" diameter that weigh 4-6 pounds and fly well from 500' to 1000' on H-128's to I-200's...depends on what you want to do. My avatar rocket is 8" diameter and 75 ounces ready to fly and goes to around 400' on H-97's.

Frank
 
Last edited:

cyberwollf

Active Member
Joined
Nov 2, 2015
Messages
28
Reaction score
0
A loc V-2 7.5" will fly to around 1000' on a J-425 38mm su, I've done a ton of foam structured scale missiles from 6 to 10" diameter that weigh 4-6 pounds and fly well from 500' to 1000' on H-128's to I-200's...depends on what you want to do. My avatar rocket is 8" diameter and 75 ounces ready to fly and goes to around 400' on H-97's.

Frank
Do you have a link to the build technique?
 

burkefj

Well-Known Member
TRF Supporter
Joined
Jan 27, 2009
Messages
3,285
Reaction score
729

cyberwollf

Active Member
Joined
Nov 2, 2015
Messages
28
Reaction score
0
Awesome work! I might have to order some foam instead :) you only used foam safe CA? I couldnt really see from the pics, how well does the skin seam comeout? Just a little filler?
 

ThirstyBarbarian

Well-Known Member
TRF Supporter
Joined
Feb 11, 2013
Messages
8,628
Reaction score
1,231
I started gathering supplies for something similar last year around Easter --- NC was going to be a giant Hobby Lobby Easter Egg. I was planning to use foam core CRs and a cardstock skin. I ran out of time and lost momentum on the project, but I'm still interested in finishing it. Maybe this spring.
 

cyberwollf

Active Member
Joined
Nov 2, 2015
Messages
28
Reaction score
0
What's a good source for depron? 6mm for rings and spar; 2mm for skin? Any thoughts on depron vs XPS?
 

burkefj

Well-Known Member
TRF Supporter
Joined
Jan 27, 2009
Messages
3,285
Reaction score
729
Unfortunately depron is dead, the mfg changed the process and it is no longer flat and so the importer is not bringing it in.

However I think flitetest waterproof foam board may be a good replacement for structures, I'm getting some in to evaluate. It's 5mm but may be good for centering rings and stringers.

I've looked at cellfoam 88 but it is very brittle. MPF and XPS seems very soft to me and not as structurally strong. Dollar tree foam board may be ok for internal structure if it does not get wet.

For the skin, I'm not sure right now what a good replacement is, eps is way too soft. XPS may be ok for heat forming for skins, or cardstock type paper may be a good alternative. I was never 100% happy with the thin depron skins, it is soft, but it was lightweight, it worked for me and when I covered it with some vinyl/monokote it was robust enough, and it did not require any waterproofing.

What's a good source for depron? 6mm for rings and spar; 2mm for skin? Any thoughts on depron vs XPS?
 

cyberwollf

Active Member
Joined
Nov 2, 2015
Messages
28
Reaction score
0
I assume even a veil shell layer of FG negates the whole point of foam? Hmm I was reading RC forum guys saying XPS was the closes to depron...
 

burkefj

Well-Known Member
TRF Supporter
Joined
Jan 27, 2009
Messages
3,285
Reaction score
729
It all depends on the weight you can achieve.
Mpf is the best we have but it is not even close to depron, I think it is junk, soft, not uniform thickness, not smooth finish. I jut got my flitetest foam board, it isn't perfectly flat, and has waves, ca wont glue to it, and it will crease instead of flex but it cuts nicely and is stiff. You'll have to use hot glue to stick to it which is heavy and you have to scuff to paint to it. It might be ok for internal structure, ill have to try it.

Frank


QUOTE=cyberwollf;1647844]I assume even a veil shell layer of FG negates the whole point of foam? Hmm I was reading RC forum guys saying XPS was the closes to depron...[/QUOTE]
 

cyberwollf

Active Member
Joined
Nov 2, 2015
Messages
28
Reaction score
0
It all depends on the weight you can achieve.
Mpf is the best we have but it is not even close to depron, I think it is junk, soft, not uniform thickness, not smooth finish. I jut got my flitetest foam board, it isn't perfectly flat, and has waves, ca wont glue to it, and it will crease instead of flex but it cuts nicely and is stiff. You'll have to use hot glue to stick to it which is heavy and you have to scuff to paint to it. It might be ok for internal structure, ill have to try it.

Frank


QUOTE=cyberwollf;1647844]I assume even a veil shell layer of FG negates the whole point of foam? Hmm I was reading RC forum guys saying XPS was the closes to depron...
[/QUOTE]

Yuck, that doesn't sound like fun at all... Well maybe back to my original 10lb LOC tubing plan lol.

Please post up when you find a suitable substitute, I would love to try a rib and skinned foam rocket. I used to love balsa and monocoat back in my RC days.
 

fyrwrxz

latest photo
Joined
Jun 6, 2011
Messages
6,580
Reaction score
55
Well, Bryce (can't think of his screen name here) did an "M" to 600'-that was impressive and a little scary, but mostly impressive.
 

KenRico

'Just the Tip'
Joined
May 31, 2011
Messages
2,722
Reaction score
35
Well, Bryce (can't think of his screen name here) did an "M" to 600'-that was impressive and a little scary, but mostly impressive.
That was Bandman444

Here you are hugging the rocket

Kenny

1481694263903.jpg
 

rstaff3

Oddroc-eteer
Joined
Jan 18, 2009
Messages
11,759
Reaction score
14
Dollar tree foam board may be ok for internal structure if it does not get wet.
Well, I have tried the dollar store foam board a few times and have been disappointed. I find the Elmers, or equivalent, from a craft store to by much better. Both is stiffness and the surface paper is better. 40% coupons are your friend. YMMV
 

RocketFeller

Well-Known Member
Joined
Sep 15, 2009
Messages
1,185
Reaction score
72
I built a Big and Built to Fly Low rocket with a group of middle school students last year. It is 12.75" diameter and 122" tall with a 60" fin span. It is about 46 pounds on the pad. Our first flight was on a K3800 research motor and we made ~800'. Our second flight was on an L850W and it reached ~1920'.

IMG_0488.jpg

IMG_0670.jpg
 
Top