4 inch Polecat Goblin Replica - Build Thread

[DabCat]

A few months back I put in an order for a bunch of LOC tubes and nose cones. I've had a Polecat goblin on my wishlist for quite a while now, and with the goblin drag race at ROCstock next weekend, I decided it was time to build one. I cut the body tube to 14.25 inches and used a laser cutter to cut the fin slots out. For the fins and centering rings, I laser cut them out of 1/4" birch ply. I decided to go with a full fin assembly that will slide into the fin slots from the bottom of the body tube to make the internal fillets way easier. The motor mount is an apogee 54mm tube, with an Aeropack retainer from Rocketry Works (Amazing service and great price from them). And the nose cone is just a plan ol' plastic 4 inch LOC nose cone. I plan to update this thread later today, or Sunday with our current progress.

 

[Hobie1dog]

All right Why don't you sell some of these as a kit for us members, since no one else seems to be interested in doing so.... thanks very much for doing this.

 

[DabCat]

All right Why don't you sell some of these as a kit for us members, since no one else seems to be interested in doing so...

I might consider that... maybe in the future if I have extra time on my hands.

 

[Hobie1dog]

it could be like the good old days where there were 28 of these at a drag race.

 

[Hobie1dog]

I might consider that... maybe in the future if I have extra time on my hands.

about two hours ago I was ready to send my local rocketry component vendor an email to see if he could Supply me with parts 2 come out to the kit so that I can make some extra money, being on Social Security and disabled sounds like something I could do.

 

[DabCat]

I made quite a bit of progress today, I glued the entire fin can assembly together. Tomorrow I will do the internal filets, glue it into the body tube, do the external filets, mount the recovery gear, and it's good to go! I will attach all the pictures together and post them after my progress tomorrow.

 

[DabCat]

Here's a picture after gluing the fin tabs into the centering rings:
I used a glass with multiple heavy books on top to hold it all together while drying.

I didn't end up taking any other pictures yesterday, but I did take a few today. Here's my progress for today:

I started with the internal filets;


Once all 4 sides were completed I glued the entire assembly into the body tube. The black band at the bottom is a zip tie to hold the tube slots together;


And as if that wasn't already strong enough, I fileted and laminated the top and bottom centering rings with epoxy;


After that was all dry and done with, I put the nose cone on to see what it's gonna look like finished;


And that wraps up my progress today. Tomorrow I will finish the external filets, and get it ready to fly. That means it's time to start thinking about paint themes... how does a black nose cone, black flames, black fins, and a light blue body tube sound?

 

[James Kobel]

Flames should give it some extra speed

 

[cwbullet]

I sure hope they make this kit again.

 

[Hobie1dog]

thanks for the pictures keep them coming.

 

[DabCat]

Oops! Forgot to update this thread! The rocket is waiting for its final coat of paint to dry. I ended up deciding not to paint flames, and just keep it a simple black and dark blue. I will post some pictures tomorrow.

 

[Hobie1dog]

Wow, great job on it and it now always makes me wonder why do companies that have such a great selling rocket where they sell a hundred of them in a "Group Buy" after they mark them down knowing that there's going to be a large drag race where everybody will take advantage of the group pricing, uses them at a major launch, and then they quit selling the product?
No one seems to ever offer a Group Buy in the rocketry marketing world, why is that?

 

[Banzai88]

No one seems to ever offer a Group Buy in the rocketry marketing world, why is that?

Probably because margins are slim enough that the expected discount on a 'group buy' would probably push the realized profits to zero or negative territory. Doing business like that it makes it hard to pay the rent or keep the lights on.

Composite Warehouse has been doing what amounts to a 'group buy' with deep discounts (sometimes 50% or more) on certain rocket kits every month or so.

In general, the best you're going to get is BF/BS sales.....but if you don't get it then at 'discount' then you're paying for those discounts with 'regular price' throughout the year.

 

[Hobie1dog]

In general, the best you're going to get is BF/BS sales.....but if you don't get it then at 'discount' then you're paying for those discounts with 'regular price' throughout the year.

I contacted mad-cow rocketry and they said that they are not doing any Black Friday sales this year. I have a feeling that there are a lot of businesses that are not going to offer Black Friday sales.

 

[Banzai88]

I contacted mad-cow rocketry and they said that they are not doing any Black Friday sales this year. I have a feeling that there are a lot of businesses that are not going to offer Black Friday sales.

Doesn't surprise me, MC has been "out of stock, coming soon" on a huge majority of their catalog for most of the year, with a good percentage of their catalog having been retired and no longer available.

 

[DabCat]

Day before yesterday we got some primer and paint on it. We also added a few Oz of nose weight to get it stable on a H550. In our rush to get it finished, I forgot to get pictures. Oops! Here it is all finished ready to fly soon.

Today has been a great flying day!

 

[Hobie1dog]

great job on scratch building it, looking forward to the flight report. What range of motors will it use?

 

[DabCat]

The smallest it could fly is probably around a G76 and the largest would be a 4 grain 54mm K or around a K550. So I would say G to K.

 

[user 35280]

The smallest it could fly is probably around a G76 and the largest would be a 4 grain 54mm K or around a K550. So I would say G to K.

How long is a K550 motor and is there room for all the recovery gear in that rocket?

 

[DabCat]

On the pad ready to go! Tigerhawk, I'll answer your question in a bit.

 

[DabCat]

How long is a K550 motor and is there room for all the recovery gear in that rocket?

The k550 is in the aerotech 54/1706 case. It's equivalent to a 4 grain K. I'm not sure what the total length is off the top of my head, but the motor would stick into the nose cone and the recovery gear would wrap around the motor.

 

[DabCat]

It flew amazing on the H550! I was first off the pad and definitely won for my set of pads. The nose cone did separate and came in ballistic from 3k. Thankfully it survived and is ready to be flown again. I will post a video when I get home.

 

[Hobie1dog]

all right

 

[user 35280]

On the pad ready to go! Tigerhawk, I'll answer your View attachment 489994question in a bit.

Where are you launching from in this picture?

 

[DabCat]

Where are you launching from in this picture?

Lucerne Dry Lakebed in California. I'm flying with ROC at their annual ROCstock event.

 

[Hobie1dog]

I do like how the fins are somewhat similar to the Nike Smoke shape meaning you could get fiberglass pre-cut Nike fins as well a pre slotted fibergass air frame and cut it down in length. The Lil Goblin has almost identical fins to the Nike. Then you would have a really rugged tough flyer. Cardboard is such a weak and rather primitive material, but I understand everyone just uses it because it's cheap. I've got 50% of the Estes rockets I have, .all with cardboard issues. The tubing you used, did it require filling spirals?

 

[DabCat]

We didn't bother. The spirals are still visible.

 

[Hobie1dog]

Did you get video of it?

 

[Sooner Boomer]

Sweet build. I like short fat rockets! I've got to think about building one of these, maybe with a 38mm motor mount.

 

[DabCat]

Did you get video of it?

I did. It's mixed in with a ton of other videos. I haven't had the time to go through them and pull out the good ones yet.