Estes Gamma (#1325) BT-60 Upscale (168%)

One of those classic old nearly forgotten rockets of my youth was the Estes Gamma.





I can't remember if it was my Step Brother, or my Uncle (3 months younger than me) who built it, but I know that it didn't make its way into my collection. In reading a thread over on TRF, I was reminded of this kit. However the reminder was given a patriotic paint scheme (based on the coldpowered Estes Yankee 5). I wanted to see the original, so, I googled it, and found it on a number of sites. That, and that Wizard Rocketry has a clone out there (w/a balsa nose cone). Their clone has a nose cone that resembles the (upscaled) BNC-60Y from Semroc. Just so happens that I have a BNC-60Y. I bought it for my Centuri Spirit of America build, but then later found that I should have been using a BNC-60YP for a better match to the original PNC-50Y.



When I decided to switch my SOA over to the BNC-60YP, that left me with the other NC orphaned. When I saw Wizard Rocketry's version, I saw that their NC strongly resembled the BNC-60Y. In my research, I know that the BNC-60YP would be a closer match for the original's appearance. However, I've got the cone, I have the desire (I wish I had more $$ and time), but my orphan has a home now. The instructions found on YORP are clear, and easy to read, but a bit huge for my computer screen (and printer), so I downloaded them, and uploaded them to my flickr page.



There's no indication of the dimensions of the fins or decals given.



The Original:

Overall Length 20.1"
Nose Cone 4.4"* Estes PNC-50Y
Body Tube 15"
Upper Tube 9.5"
Lower Tube 5.5"
Difference is made up by the fins

Recommended Engines A8-3**, B4-4, B6-4, C6-5

There is no reason, other than to simplify masking for the paint job, for this to be made of two lengths of body tube, when one could do it. I suspect Estes was using scraps from other kits when they designed this one.

*Info found on a quick search. I'll update once I'm more certain
**Recommended for first flights

BT-60 Upscaled (168%)

Overall Length: 33.768"
Nose Cone 7.25" Semroc BNC-60Y (or BNC-60YP)
Body Tube 25.2"
Upper Tube 15.96" ~15 15/16"
Lower Tube 9.24" ~9 1/4"

Difference is made up by the Fins

Powered by C11's, D's and E's. However, Open Rocket isn't working for me right now, so I can't sim it.

Since the upscale's body tube is longer than 18 inches, I'll maintain the body tube joint in the scaled location. I haven't decided if I'll paint it separately leaving the joint unfilled (easier), or fill, mask and paint with the joint smoothed (my preference).

My plans are to make this a single stage upscale (a 2nd stage is possible).

Now, all I need is time, money, body tubes, centering rings, engine clip, parachute, balsa, sleep...

Pointy Side Up!
Jim
.

K'Tesh said:

There's no indication of the dimensions of the fins or decals given..

Click to expand...

I ordered my fins thru Semroc just to round out an order. Of course when they arrived they were twice the size I was expecting. Easily fixed... I could almost hear everyone on the forum chanting 'upscale.. upscale!'

K'Tesh said:

There is no reason, other than to simplify masking for the paint job, for this to be made of two lengths of body tube, when one could do it. I suspect Estes was using scraps from other kits when they designed this one.

Click to expand...

When I built my original three and a half decades ago I still messed it up and put the motor mount in the wrong tube. Had to mask it anyway.

K'Tesh said:

Now, all I need is time, money, body tubes, centering rings, engine clip, parachute, balsa, sleep...

.

Click to expand...

Don't forget the 70's-Fantastic decals!

adrienwapkaplet said:

I ordered my fins thru Semroc just to round out an order. Of course when they arrived they were twice the size I was expecting. Easily fixed... I could almost hear everyone on the forum chanting 'upscale.. upscale!'

Click to expand...

So, what are the dimensions of the fins?

adrienwapkaplet said:

Don't forget the 70's-Fantastic decals!

Click to expand...

I didn't... but I had that figured into the "money" part of the "time, money..." list in my OP.

In most cases when you find a picture of a fin template, it's an actual size that you can print. In your case you needed it up scaled for a BT 60 and I did that for you. Just print the attached PDF file and you should be good to go.

View attachment Gamma Fin 60 Upscale.pdf

Gary Byrum said:

In most cases when you find a picture of a fin template, it's an actual size that you can print. In your case you needed it up scaled for a BT 60 and I did that for you. Just print the attached PDF file and you should be good to go.

Click to expand...

Thanks Gary,

I'll get that printed.

I'm still interested in the original's dimensions as I'm simming it in Open Rocket. I got OR working again yesterday... Had to uninstall Java, then download it again.

Thanks
Jim
.

The root and tip are 1.5" and the leading & trailing edges are 2 - 11/16"

Thanks again Gary!

When I get the chance I'll run it through the sim and see what I can make of it.

Pointy Side Up!
Jim
.

You know....Semroc also makes a BNC-80Y......just saying.


F15s anyone?

paul.nortness said:

You know....Semroc also makes a BNC-80Y......just saying.


F15s anyone?

Click to expand...

But I don't have one on hand...

Here's a screen grab of my simulation of the Gamma (original scale)





[EDIT] Deleted attachment as fins were wrong.[/EDIT]

Are you sure those fins are correct? They sure don't look like the template I made.

Gary Byrum said:

Are you sure those fins are correct? They sure don't look like the template I made.

Click to expand...

I had to download the pdf, copy the image, crop it, change the fin from white to black, then save it. When I tried to import it to Open Rocket, they were over 15 inches long at the root edge. So, I scaled them, and this is the result.

I suppose that the reason that the outer edge's tips look larger than the root edge is the way the program handles 3D foreshortening.

Here's the 2D side view: (it say's Sizzler, because that was what I used to get the nosecone shape, but I can't seem to correct the name in OR)



You wouldn't happen to know the sweep angle and length of the fin mid-chord would you (I don't have a working printer at home). With that info, I should be able to freeform the fins to verify the appearance I'm getting in OR now. I know that the original image of the fin say's that it's 1/8" thick balsa, but I suspect that it was actually 3/32" thick on the original, and am planning on 1/8" thick for the upscale (TTW & papered).




[EDIT] If you are looking to build this upscale, do not use the attachment below, it appears to be the wrong shape. A corrected version will appear in a few more exchanges below.[/EDIT]

View attachment Gamma Fins (upscaled).pdf

Jim, as I mentioned before, the root and fin tip are 1.5". The leading and trailing edges are 2 - 11/16". This would be a perfectly sized parallelogram shape. The leading sweep is 30* from the root. I don't know much about OR but if you took a rectangle drawn to the dimensions I gave you and shifted it 30*, you should have it. Actually this isn't correct. Check out the next post and look at the attachment.

Here's a better example of what happens when you angle a pattern. You can't just shift the angle. The leading edge length must be maintained. Otherwise you'll be stretching it. The attached PDF defines the difference.

View attachment Gamma Fin Dimensions.pdf

Hi Gary,

Here's the way it looks in OR with the numbers I derived from your newest .pdf, plugged in manually (original scale):



To my eyes, the fins still *look* like the tips are foreshortened (and thus wider than the root), but as you can see with the settings the tip cord and root cord are identical.

To do the fins in the previous version, I had to import from image (only available in the freeform fin mode), and thus can't get the tip chord/root chord by numbers. However, I saved over it before checking and can't be sure if the previous version was tweeked or not. In checking the .pdf of the fin pattern, it does look like the tip chord is slightly smaller than the root doesn't it... Oh well, it's fixed now.

Here's the original (botched fins) 3D rendering, and the corrected version (original length):






[EDIT] This is the corrected fin pattern, mentioned a few exchanges ago.[EDIT]

View attachment Gamma Fins (upscaled).pdf

Strange. It still looks like the leading edge is too long, or the root & tip aren't wide enough. When I hold up a printed copy to your OR image, they're not the same. Here's s suggestion. Forget OR and just build the rocket. It's already a proven design. Every time I fool with OR, it just ticks me off and I go back to using Autocad. It's just easier for me. I tinkered with OR a little more this morning before I posted and my settings wouldn't stay put. They kept changing automatically. They looked much like the settings you have, but still, that fin just looks wrong in the OR image. Don't know what else to tell you.

Yeah, K'tesh, What he said.

Why do you need OR?:confused2:

You certainly don't need the software to come up with the design, that part was done years ago. And at the scale you are building, you will have another, albeit larger, LOW POWER rocket. You should not need the help of any software to decide what motors would work, and at that power range it is not like you have a lot of options with delay times. Build it with a 24mm MMT, and then depending on the size of the field and weather conditions, you can choose to fly with a C6-5, or D12-5/7, or E9-7.

Yeah....what he said.......oint:

adrienwapkaplet said:

I ordered my fins thru Semroc just to round out an order. Of course when they arrived they were twice the size I was expecting. Easily fixed... I could almost hear everyone on the forum chanting 'upscale.. upscale!'



When I built my original three and a half decades ago I still messed it up and put the motor mount in the wrong tube. Had to mask it anyway.



Don't forget the 70's-Fantastic decals!

Click to expand...

Yeah! Those Decals are very Shwanky!

Awesome! The #1325 Gamma was my first rocket; back in the 80's. Though I lost the original, I now have four of them: two unbuilt kits, one finished in header card scheme, and one finished in my original's scheme.

Note: it appears that the sims show 3 fins....the Gamma most definitely had 4 fins!

If there is controversy on fin size/shape, I could probably measure the dimensions from one of my Gamma kits I have on hand.

-Eric-

Hi Eric,

Ya' know... My simulation did omit a fin didn't it... D'oh!

If you've got any info that contradicts the previous measurements, I'd be interested in knowing. I'm sure it wouldn't be the first time a rocket with the same name has changed (e.g. Cherokee D (short), vs Cherokee D (long)). I've fixed it in the OR file, however, I'm off to bed, and will have to upload it later.

Do you have any photos you'd like to share w/us? I'd like to see what you did that's different to the stock model.

My progress on this build has stalled tremendously... I've been doing 14 hour days a couple of times each week for the last few (tomorrow's another one), as well as helping my Mom w/some yard work (felling trees) on the weekend, so I'm running close to zero energy.

All The Best!
Jim

Hey Jim, where'd you go? Waiting patiently to see some progress on this project!

In the meantime, I dug out the camera and the Gamma stash.

First up, a pair of Gamma clones. The one on the left is a clone of my first rocket from the 80's: my Dad and I built and painted it when I was a yung'in. Sometime down the road, I found some Estes Viking decals in the trash at a science summer camp, pulled 'em out and applied them to the Gamma. The Viking decals on the clone are from Excelsior. The Gamma on the right is another clone; this one with Stickershock decals. I have the parts and decal set for a 4" upscale, so when Mark did the upscale decals, I had him send me several sets of the 1:1 scale decals (stickers in this case). Pretty sure I used balsa 50Y's from Semroc for both of these.


Next, one of my two unbuilt 1325's; this one with a yellow header. The other I have has a black header.


This one was already open, so I took out the die-cut balsa fin sheets and measured things up. I was somewhat surprised to find nice even numbers and angles...very simple fins!


Keep us up to date, Jim!

-Eric-

ECayemberg said:

Hey Jim, where'd you go? Waiting patiently to see some progress on this project!

Keep us up to date, Jim!

-Eric-

Click to expand...

Hi Eric,

Not much to report...

I've been waiting for VA benefits that I now know will never come. When I finally got some $$, Semroc is currently sold out of the centering rings I need. Today I got an email that said that they're making some, and they'll email me when they're ready.

Until then, all my projects are on standby.

All The Best!
Jim

ECayemberg said:

This one was already open, so I took out the die-cut balsa fin sheets and measured things up. I was somewhat surprised to find nice even numbers and angles...very simple fins!

-Eric-

Click to expand...

Well, this confirms that the fin pattern at YORF is incorrect. When I scaled it up, it was correct on the root and tip, but the trailing & leading edges are 11/16" too long. Great going Eric.

Hi Eric,

As promised... Update on the Gamma Thread.

I glued in the MM...



I glued the fins on recently, however, I haven't filleted them. I still need to glue on the LL, but I'm debating on where to locate it. I'm inclined to do a pair of them, one at the black/white junction, and another between fins... OR install one long one as a homage to the original at the black/white junction.



The nose cone (and forward portion of the body tube) is ready for primer.



I've ordered BT-60 scaled decals from Gord (currently in the mail). Sorry about the delay on those Gord... I hope he sells a ton of them.

I'm still confused about the Gamma's fins. Some weird optical illusion is going on with them. I know that (due to sanding), the root chord is slightly wider than the tip chord, but it doesn't look that way in Open Rocket, nor real life.





Pointy Side Up!
Jim

K'Tesh said:

Hi Eric,

As promised... Update on the Gamma Thread.

I glued in the MM...



I glued the fins on recently, however, I haven't filleted them. I still need to glue on the LL, but I'm debating on where to locate it. I'm inclined to do a pair of them, one at the black/white junction, and another between fins... OR install one long one as a homage to the original at the black/white junction.



The nose cone (and forward portion of the body tube) is ready for primer.



I've ordered BT-60 scaled decals from Gord (currently in the mail). Sorry about the delay on those Gord... I hope he sells a ton of them.

I'm still confused about the Gamma's fins. Some weird optical illusion is going on with them. I know that (due to sanding), the root edge is slightly wider than the tip edge, but it doesn't look that way in Open Rocket, nor real life.





Pointy Side Up!
Jim

Click to expand...

Cool; thanks for the update!

Agreed, that's one thing that always catched my eye with this particular model. The root chord equals the tip chord, yet your mind convinces you that the tip chord is longer. Lookin' good!!!

-Eric-

Ok... worked on the .ork for the original today. I found that the fins were still royally fouled up (thanks again rocketreviews, yet another quality file :/)...

Here's the updated version using ECayemberg's measurements.




It looks far better with that. I'm several thousand miles from my upscale, but I suspect its fins are too long... Thank goodness I never finished that one... I may be able to fix it when I get back.

Upscaling this to a BT-60 should be pretty easy now.