Ogive nosecone 8.25 x 2.56" VBR StretchBlobbo

[dtstein]

I wanted to replace the plastic nose cone on my Vaughn Bros Rocketry Stretch Blobbo, and near as
I can tell that would need to be a 8.25" tal x 2.6" (for BT80H) ogive
plastic nose cone. Any idea where I could find this item? The aerotech
nose cones are too tall, and are slightly too wide in O.D.

Thanks.
Dan

[snaquin]

I wanted to replace the plastic nose cone on my Vaughn Bros Rocketry Stretch Blobbo, and near as
I can tell that would need to be a 8.25" tal x 2.6" (for BT80H) ogive
plastic nose cone. Any idea where I could find this item? The aerotech
nose cones are too tall, and are slightly too wide in O.D.

Thanks.
Dan

Dan,

I bought a couple of these from Madcow Rocketry a few months ago for a scratch build I'm working on ..... I have one each of the black and red ones. They are molded in those colors and look great. Mike's a great guy to deal with.

http://tinyurl.com/9dgd9k

.

[dtstein]

THanks for the tip Steve!

[US Hobby Distributors]

The Blobbo in a 24mm version is available at discountrocketry.com. Vaughn Brothers Rocketry Brand is back up and running. More kits will be available soon.

Jim

[dtstein]

THanks for the update. Let me know when all their kits including the Stretch Blobbo is available.

Dan

[US Hobby Distributors]

We are contemplating converting the Stretch Blobbo to either a 24mm with enough motor tube length for the Estes E motor with a sleeve to adapt the Estes D motor or a 29mm mount for Aerotech F-G's. What's you opinion on this?

Jim

[Rocketflyer]

We are contemplating converting the Stretch Blobbo to either a 24mm with enough motor tube length for the Estes E motor with a sleeve to adapt the Estes D motor or a 29mm mount for Aerotech F-G's. What's you opinion on this?

Jim

Mmmm. I vote 24mm for the E9's, as spacer for the E15's, 30's and the 24mm reloads. If you go 29mm, include a 24mm mmt adapter. :)

[dtstein]

I agree with a motor tube long enough to accomodate a BP E. I made one (a SB) from stratch and it turned out very well. I also have a motor adapter to work with D and AP E engines. Its a classic design, and I'm sure it would be popular. I guess the only caveat is you would have to RockSim it to make sure there was still adequate margin for stability.

Dan

[falingtrea]

Don't forget the Aerotech 24/60 RMS case. Or is that already Estes E sized?

[US Hobby Distributors]

Rocksim shows the Stretch BLOBBO center of gravity at .67 Caliber ahead of the center of pressure with the F35. This is better than the .62 Caliber of the shorter BLOBBO with a D12.

On these fatter rockets the short caliber distance is still OK and will produce less weather vaning in windy conditions. Normally short fat rockets tend to weather vane more because the diameter to length ratio is shorter and the rocket is more easily turned by side wind when the rocket is comming off the rod or when slowing to apogee. Having a center of gravity less far ahead will prevent the side wind from easily turning the rocket into the wind.


Jim

[dtstein]

Jim-
did you get a chance to Rocksim stability on the Estes BP E? THis weighs more I think than an AT AP E.

THanks.

Dan

[PaulK]

Rocksim shows the Stretch BLOBBO center of gravity at .67 Caliber ahead of the center of pressure with the F35. This is better than the .62 Caliber of the shorter BLOBBO with a D12.

On these fatter rockets the short caliber distance is still OK and will produce less weather vaning in windy conditions. Normally short fat rockets tend to weather vane more because the diameter to length ratio is shorter and the rocket is more easily turned by side wind when the rocket is comming off the rod or when slowing to apogee. Having a center of gravity less far ahead will prevent the side wind from easily turning the rocket into the wind.


JimThis is interesting - so too much nose weight on a short fat rocket is bad from a weather cocking perspective? Maybe that explains why my 3x18mm fat boy can end up almost horizontal *into* the wind on a breezy day (I added nose weight equal to 2 C6-5 motors). I really should get rocksim one of these days to understand these aspects better :o

[US Hobby Distributors]

Rocsim does not offer any explanantion other than calling it marginal stability. You can go to their e-magazine at http://www.apogeerockets.com/Education/downloads/Newsletter86.pdf and look up the article "Stability of Short, Squat Rockets".

While this does not really address the weather cocking issue, it does state that short rockets are difficult to get to 1 caliber (body tube diameter) ahead of the CP and that marginally stable is still stable.

Adding weight to the fat boy to bring it to 1 caliber would have the same affect as an overstable rocket. You can go the the article at http://www.apogeerockets.com/Education/newsletter05.asp for information regarding overstability.

I believe while the one caliber rule of thumb works in most cases, it does not tell the whole story. A better rule of thumb would take into account the ratio of the length of the rocket to the distance the CG is ahead of the CP.

Taking the length and leverage into account stability can be expressed by percentage of the rocket length this way:
Rocket Diameter X Caliber Stabilty Factor / RocketLength X 100

Under this senario the BLOBBO is
2.6 X .62 / 16.5 X 100 = 9.77%

The distance the CG is ahead of the rocket is 9.77% of the rocket length.

Jim
US Hobby Distributor

[snaquin]

The Blobbo in a 24mm version is available at discountrocketry.com. Vaughn Brothers Rocketry Brand is back up and running. More kits will be available soon.

Jim

Jim

Any plans to make the VB extreme series kits available too? The 24 and 29mm in particular. I loved those kits with the fiberglass fins and hardwood nose cones .....

.

[US Hobby Distributors]

Were still in the process of inventorying and assimulating the stock to start producing the kits ourselves. We should have a Vaughn Brothers Rocketry website up in a week or two.

However, we have some VB extreme 24's with the hardood cones that were already kitted when we obtained the stock. There is also a VB Extreme 54H , a few King Blobbo's and a Wild Thing kitted as well.

Jim

[snaquin]

The Blobbo in a 24mm version is available at discountrocketry.com. Vaughn Brothers Rocketry Brand is back up and running. More kits will be available soon.

Jim

Jim

I noticed a bunch of VB parts became available on the Discount Rocketry site a few weeks ago.

Any hints as to what the next few kit releases will be, and when?

:)

.