Goblin 2X Clone

[Thor]

Just back into rockets again. Flew them first during the time frame 1965-1970. My daugther completed a BIG BETTY Quest rocket and that was all it took to get us all hooked, my wife, me and my girls, on rockets again. Building a 2X upscale of the Estes Goblin and have just about decided that a D engine will make my first upscale a lawn dart. I am probably looking at an 8 ounce rocket and that makes me think that an E would even be limited in use in this one. What do you guys think? I am only familar up to the smaller (The Goblin 1X and Cherokee-D) D engine rockets so I am a bit behind the learning curve. I have also ordered the proper shape Nose cone from BMS to complete this one.

I am also doing a 2X upscale on the Estes Boost Glider NIGHTHAWK. Problems I see here is finding a proper lead ribbon for nose weight of the glider and the aluminum sheets for canyard movements.

One other thing I would like to know if possible. Where locally can I find Elmer's FILL 'N FINISH priming paste? This seems to be the product of choice for a lot of people for balsa fin and tube spiral filling.

Thanks! Any info would be greatly appreciated.

[A Fish Named Wallyum]

Are you sure about the weight on the Goblin? 8 oz. sounds like an awful lot of weight for a 2x upscale, unless you're building it like a tank.
As for the Fill & Finish, I've always found mine at Lowes, conveniently in the same aisle where they sell glue. I believe it goes by a different name now, but if you do a search for Fill & Finish, I'm pretty sure we just had this discussion a couple of days back.
The Nighthawk glider sounds like an ambitious project. I have nothing at all to contribute to that discussion except to say good luck and post pictures as you go.
Welcome back to the hobby.

Rocketry Forum thread on Fill & Finish:
http://www.rocketryforum.com/showthread.php?s=&threadid=17919&highlight=fill+finish

[Thor]

I am probably guilty of just what you described. Using 3/16 thick hobby plywood for the fins and a stuffer tube like der V-3 (another Estes rocket with a similar body tube) I am already up to 7ounces WITHOUT the 9-10" Balsa nose cone. YIKES! Bill, I enjoyed your review of the original Goblin size clone in the EMRR's OOP: Goblin reviews. I probably will build one of these too! I kind of like the yellow black scheme like the original but also like the halloween orange black scheme. I found a picture in an old estes catalog that is kind of a yellow/orange color and finally found a spray paint like this one and will paint mine this color complete with Tango Papa 2X decals.

[A Fish Named Wallyum]

I am probably guilty of just what you described. Using 3/32 thick hobby plywood for the fins and a stuffer tube like der V-3 (another Estes rocket with a similar body tube) I am already up to 7ounces WITHOUT the 9-10" Balsa nose cone. YIKES! Bill, I enjoyed your review of the original Goblin size clone in the EMRR's OOP: Goblin reviews. I probably will build one of these too! I kind of like the yellow black scheme like the original but also like the halloween orange black scheme. I found a picture in an old estes catalog that is kind of a yellow/orage color and finally found a spray paint like this one and will paint mine this color complete with Tango Papa 2X decals.

Yeah, it sounds like you're getting into Aerotech territory. The closest thing I have to that is a Centuri Magnum Hornet that I made using an LOC Lil Nuke as a donor kit. That will fly on an F20-7 when the time comes. One of the RocSim gurus on here should be able to point you toward which engine would best suit your Goblin.
I forgot all about the Goblin review. My Goblin has lived a hard life. I'm really close to taking the nose cone and starting over. This is a picture from its latest flight.

[A Fish Named Wallyum]

Make that "I've taken the nose cone and started over". The body was pretty well destroyed due to hard landings and the cone had teeth marks in it from where a dog "helped" me recover it. It's covered with Fill & Finish as I type.

[Thor]

Hey, thanks much for the assist, went to Lowes today and picked up the FNF. Should have contacted you guys earilier. How long is the streamer on your Goblin? Do you favor that over a 12" chute, I hate breaking fins but I hate loosing the rockets worse. I notice the original plans warn about getting the balance point no closer than 3 & 5/8" from the rear on the 1X model. Have you had any problems with stability on your Goblin? It is been way too many years since I flew the scale model to remember. Thanks again!

[A Fish Named Wallyum]

Being that yours is an upscale, I wouldn't suggest a streamer. Maybe a reefed chute. That's what I'll be going with when my 1:1 is flying again.
As for stability, I never had a problem and neither did my Goblin. :D

[CPMcGraw]

Just back into rockets again... Building a 2X upscale of the Estes Goblin and have just about decided that a D engine will make my first upscale a lawn dart. I am probably looking at an 8 ounce rocket and that makes me think that an E would even be limited in use in this one. What do you guys think? I am only familar up to the smaller (The Goblin 1X and Cherokee-D) D engine rockets so I am a bit behind the learning curve. I have also ordered the proper shape Nose cone from BMS to complete this one.

The Goblin just begs for doing an up-size, doesn't it?

See the attached RockSim file...

Go download a demo of RockSim 8 from Apogee.com and play with it for a while. When you get comfortable with it, which doesn't take long, buy the full version (which lets you save your work). Use the component database to try out different materials.

FWIW, that 2X Goblin can be done with TTW balsa fins and still be plenty strong enough without having to resort to plywood. Just do a careful, light-as-possible glassing of the fins, and apply some 1/4" strips of Carbon Fiber underneath the glass at the leading and trailing edges. A low-end F (composite) would fly it nicely.

The nose cone can probably be done by Carl at SEMROC, or by BMS...

One other thing I would like to know if possible. Where locally can I find Elmer's FILL 'N FINISH priming paste? This seems to be the product of choice for a lot of people for balsa fin and tube spiral filling.

Lowes, Wal Mart, Home Depot...

Look in the paint sections...

The trick to using this stuff is to thin it down a bit with water before brushing it on. This helps get the compound deeper into the grain. You may have to apply a second layer, but these typically get sanded off before priming.

Craig McGraw

[Thor]

Or we could go totally crazy with this one? over 7' tall! GOLLY MOLLY!!!
http://home.usamedia.tv/robwegner/images/Golblin8a.jpg

[A Fish Named Wallyum]

HEY! It's not crazy unless you plan to ride in it. :D

[CPMcGraw]

Or we could go totally crazy with this one? over 7' tall! GOLLY MOLLY!!!

Hey, no fair!

You jumped 21 years into the future to snap that photo! :eek:

What did you use, RockSim v15 to draw it? :eek: And you didn't bother to bring us back a copy, either!!! :p

Now, let's see...

That's gotta be at least an 8" tube, probably fiberglass or carbon fiber nose cone...

Punching the numbers now...

This'll take awhile...

Craig

[tbzep]

I did a 2.6" (BT-80 body tube) upscale of the Goblin about 15 years ago and it's still going strong today. It is an awesome demo model for schools because of it's slow and firey launches. I used 1/4" balsa for true scale and a single 24mm motor mount for D/E engines. It flies perfectly with D12-5's in calm air, and with D12-3's in moderate winds where weathercocking comes into play. It recovers with an 18" chute, but I cut the center out of it for faster decent. With the thick balsa through the wall construction, it would probably recover just fine with a 12" chute.

[Ltvscout]

Or we could go totally crazy with this one? over 7' tall! GOLLY MOLLY!!!
Wow, that's a great upscale, Thor!

[Thor]

That BIG one I found on another rocket forum,it certainly is not mine! I am only at the 2X level, never fired anything over a D engine yet. I am having a great time. Hey tbzep, that sounds great, I had wondered if the Ds were enough, I am probably going to configure it to fire both Ds and Es. I appreciate the help and reports. These guys are talking about a 2X DOUBLE stage with 4 Es on each stage! No wonder it is listed in the HIGH POWER section.........crazy!!!Goblin 2X Two STAGE (http://www.rocketryforum.com/showthread.php?s=&threadid=17643)

[Thor]

The 2X is finished except adding decals and after looking at the "decal" threads I think I will buy them from Tango Papa rather than making them myself with an inkjet printer. I have not tried this but it does intrique me. After weighing the rocket in its final form I was astonded to see it went 13.5 ounces, egads. I finally decided NOT to shoot it with an E engine but go to an F. Probably an Aerotech F21-4W I had originally wanted a larger Goblin I could shoot with E engines so I might have to build a 1.5X one with a 2" tube and give a try to making my own cone. The one I bought for the 2X was a little too conical in shape so the next go round I may try making one. This was really fun and a good rocket to get back into rocketry. I have just finished the construction of a 1X clone with a BMS cone that looks right. I was astounded this little D Engine rocket only weighs 1.5 ounces. MAN.......what a screamer!!! :eek:

[tbzep]

The 2X is finished except adding decals and after looking at the "decal" threads I think I will buy them from Tango Papa rather than making them myself with an inkjet printer. I have not tried this but it does intrique me. After weighing the rocket in its final form I was astonded to see it went 13.5 ounces, egads.

WOW! Did you build it out of lead? :D

My 2X weighs in around 7.5 oz without the motor. That's with 1/4" thick balsa fins and a lengthened PNC-80 nosecone.

I built a 2.6" diameter Red Max with 1/4" balsa fins also, but I turned the nosecone for it instead of modifying an existing plastic cone. It's unpainted and is only around 4.9 oz right now. I'm sure it will be close to the Goblin's weight after painting and detailing.

[Thor]

Well, obviously I am not good at building them light. Thickened plywood fins, I think they are 5/32 thick, a 8" BT 50 stuffer tube with THREE plywood centering rings and lots of glue I guess. I has a BT52 stiffner tube over the 50 Engine section. Built much like the Der V-3 construction with an extra centering ring. I was a bit shocked when I weighed it the last time. Perhaps I should call it the Fat Albert Goblin! lol :D I am interested in how you made your cone? Who makes the PNC 80 nose cone? Thanks! Obviously I have a long way to go to correct construction, but I am having fun. THANKS!

[tbzep]

Your rocket should withstand F and G motor flights easily.

If you want to build light enough for D and E motors, just build it with standard BT-50 motor mount/stuffer tube, and use regular cardboard centering rings. Three cardboard centering rings on the mount/stuffer tube will handle composite E motors with ease.

I used 1/4" through the wall fin construction just for scale reasons. The original Goblin had 1/8" fins, so a 2X would be 1/4" thick. The fins are plenty strong to handle a composite E15, but I always fly it on a black powder D12. Considering the size of the rocket, 1/8" inch balsa fins would be strong enough for Estes D and E motors as long as a decent size chute is used. An 18" would be plenty.

The PNC-80K was offered by Estes when they actually sold parts out of their catalog. It's the same nosecone that was in the Phoenix kit. I have no idea if you can buy them seperately now. I've started turning my nosecones for scratchbuilts, so I'm not too worried about availability. :)

Edit: I used cardboard from the kids' boxes of Corn Flakes, Frosted Flakes, etc. to make my centering rings, including the BT-80 sized Goblin, Red Max, and Big Bertha. I just laminated a couple of rings together to make a thicker ring that was still thinner than the cardboard that Estes uses for 2.6" diameter kits. The Goblin has flown with Aerotech E15's so three of these rings with a long motor tube is plenty strong until you get to bigger motors.

[Thor]

Hey tbzep! THANKS for all the good info, looks like I used a double thick wall BT-80 which looks a bit overboard too! I am interested in how you turn your cones. Do you do it on a lathe or use a drill press? Do you start with balsa blocks and cut off the corners to start. I made tranverse measurement on the the original Goblin cone every 0.5" so 10 measurements total to get the profile of this cone. Any sugguestions on making your cones would be appreciated. I am very interested in making my own. Thanks! :)

[tbzep]

Hey tbzep! THANKS for all the good info, looks like I used a double thick wall BT-80 which looks a bit overboard too! I am interested in how you turn your cones. Do you do it on a lathe or use a drill press? Do you start with balsa blocks and cut off the corners to start. I made tranverse measurement on the the original Goblin cone every 0.5" so 10 measurements total to get the profile of this cone. Any sugguestions on making your cones would be appreciated. I am very interested in making my own. Thanks! :)

I usually just measure the length, shoulder diameter, (the max diameter will be the same as your body tube) then eyeball the smaller nosecones. If I'm doing an upscale, I just use the multiplying factor for the new dimensions and start turning.

For larger ones, I do profile measurements the way you mentioned also, but I find that when I have the smaller original cone to look at, I can get the shape pretty close.

I have a Harbor Freight lathe and tools. I wish I had better, but they do a good enough job on nosecones. I bought my balsa blocks from BMS. I don't fool with cutting off the corners of balsa, but I do run hardwood stock down the bandsaw to knock off corners. I'm no expert on turning. I didn't read any books or watch anybody, so I imagine I do everything backwards. Your best bet would be to find somebody local that does woodworking and get advise from them. Lots of cities have woodturning clubs with members that love to help newbies. I live in a rural area, so that didn't help me.

[A Fish Named Wallyum]

I keep hearing about these Harbor Freight lathes. That might be something I look into if and when we move.

[tbzep]

The one I have is from the same casting as the Jet JWL-1236. IIRC, the only difference is that the Jet casting is finished a little nicer and is slapped with a brand name that people are willing to pay double for.

A true woodworking hobbiest would have something better, but if you only plan to turn nosecones and transitions, they would likely tell you that the HF version of the Jet is plenty good for that purpose plus it ain't bad to do some other stuff too.

Here's a link to my lathe...if you decide to buy one, be patient and wait until it goes on sale!
Harbor Freight Lathe (http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=34706)

Here's a link to the Jet lathe.
Jet JWL-1236 (http://www.northwestpowertools.com/lathe/jwl1236.htm)

[Thor]

Thanks for the links tbzep!!! Back to the heavy one I have now, I will be buying some F series motors that use copperhead igniters. What sort of electrical system do these require? I understand from reading some other threads they are hard to get to work right everytime. Any advice on these? Should I buy some extra ignitors too as there are only two igniters included with the two F motors. Also, my 1x Goblin is finished except sealing, priming and painting. I put in a D engine to check the balance point as measured from the rear of the rocket. Estes plans say dont launch with the balance point less than 3 &5/8" from the rear, I assumed that meant with engine in the rocket and wadding, chute, etc, ready to launch. I checked mine at it was at the 3" distance with the engine and about 5" without the engine. Should I be worried enough to add some nose weight? Thanks again for all your help guys. :)

[tbzep]

Copperheads...

I've never had any trouble with copperheads. They need 12v for good ignition. I don't use the Aerotech clip. I take the ignitor and split the copper leads so that they can be hooked up the normal way with clips. Make sure you get the head of the ignitor all the way to the top of the motor and you should be good to go.

You can split the copper leads by taking a lighter and heating the tip (not the end that goes in the rocket!) so that the plastic barrier between the two copper leads melts. I don't smoke, so I seldom have a lighter around. I usually just take an X-Acto knife and peel them apart. It's not hard, especially if you grew up pulling the aluminum foil off the wax paper of Wrigley's chewing gum wrappers. :p

1X Goblin...

You might try a swing test with the rocket fully prepped. It will probably fly as is, but it shouldn't take much weight to move the balance point up to 3 5/8". I would go ahead and add something just to be on the safe side if you plan to launch around other people. If you launch on smaller motors with a light weight adaptor, you probably won't need any weight at all.

I just checked my clone with a D12-5 and no wadding. It balances around 3 3/8". I've always flown it without adding weight.

[Thor]

Since the 2X is really too heavy to get the 4 second delay to work well on a E9-4, I am considering putting a light lower stage on it and running a D12-0 or an E9-0 in the lower stage with an e9-4 upper. The only things that might not make this work well is the amount of space from the back of the main rocket body tube to the first centering ring. It looks to be around 5/8". The other thing is the rocket is the center of gravity is sure to move back some and I wonder if it will be unstable. I would rather run it as a two stage than buy F motors for it. Any comments are appreciated.

[tbzep]

If you make the fins larger than the ones on the sustainer, and still build it light, it will help a lot with the CP/CG situation.

The D12-0 will have a much faster velocity by the time it leaves the launch rod, making it more stable, less likely to tip over, etc. than the E9-0. You might want to run your design through a simulation program to see if it is moving fast enough when it leaves the rod. It will also give you a good idea how big to make your booster fins to know where your CP/CG should be.

[Thor]

Thanks tbzep! I noticed the D12 has a peak thrust of around 30 N and the E9 only 20 N, or there abouts. I dont have a sim program or have any idea how to run one. I suppose the bigger booster fins will push the CP back some by causing more drag? I dont have a two stager so this is a good reason to try one. These would be 25% bigger, would that work?
Thanks! I found this one on another forum.
http://homepage.ntlworld.com/paulhandley/gbb.JPG http://homepage.ntlworld.com/paulhandley/2ds.JPG

[tbzep]

I don't use sims to check stability myself. I use the "That looks about right" formula. It's never failed me! I always fly alone when trying out a new design that might be marginal, so I don't have to worry about my stability testing method failing me. :D I have used sims to predict altitude, just for fun.

As long as you don't use heavy materials and over do it with the glue, those fins "look about right". :) According to your construction method and materials used, it might or might not need a little nose weight.

Yes, the bigger fins will change the CP to your advantage compared to fins the same size as the sustainer. You can also use thicker fins such as 1/4" balsa, but you are probably more interested in altitude than I am. 1/4" thick fins will add considerable drag, but you get to see the D12 burn up close and personal!

[Thor]

I went ahead and bought two F21-4W motors to try this heavy dude out. I still may stage it later. I am hoping to get at least 850' on the Fs.

[sandman]

I just found this thread.

I made the BIG GIANT Goblin nose cone shown earlier in this thread.

It was made for a " Rocketry Forum" member to fly on an EX motor...an L something I think.

The 8.2" diameter cone was made of 2" thick pink insulating foam stacked and glued then turned on a lathe to the correct profile.

It was then covered with two layers of 6 oz. fiberglass and West System epoxy while still on the lathe. (the lathe was covered with garbage bags to keep the drips off)

After the epoxy cured I turned the lathe back on and "trued" it up.

Notice the body seam below the nose cone. His body tube was too short (a Sona tube) and I had to make a straight section on the cone 6" longer to compensate. I left him a "seam line" at the top to seperate the yellow from the black.

And how much??? No where near enough! :rolleyes: I think I made about $1 an hour on that job.

As for custom nose cones. The Goblin nose cone (BNC-55AO) in various sizes from Micro Maxx to 8" monster upscales are probably THE most popular nose cones I am asked to make.

[Snakeman]

Hi there!
that's MY Goblin 8" Upscale.
:D

here's a link to my Level 3 website with some pics and a video, etc.

http://home.usamedia.tv/robwegner/images/L3

Enjoy!

[WiK]

Hi there,

Its nice to see my project appearing here. Thats my rocksim of a BT80 based Two Stage Goblin. Check out this (http://www.rocketryforum.com/showthread.php?s=&threadid=17643) thread on The Rocketry Forum. (http://www.rocketryforum.com) It sims out to around 2300ft on 8 D12s. It is almost finished, and should fly at the end of September. Check the thread for more information and pictures.

Just saying, you might want to include credit with pictures from other websites in the future. I look foward to seeing how your Goblin turns out!

Phil

[Thor]

Well, I decided rather than stage my heavy 2X Goblin, I now have my first two F motors to try it out. Now to figure out how to use these copperhead ignitors. The motors are Aerotech Econojet F21-4W. I put one motor in the mount and weighed it at 16 ounces. Any idea if it will make 800' on one of these? Thanks Craig for all the help you have given me.

[CPMcGraw]

...The motors are Aerotech Econojet F21-4W. I put one motor in the mount and weighed it at 16 ounces. Any idea if it will make 800' on one of these?

Go with the F21W-6 instead -- the 4-second delay is an instant shredder with a 77 fps Dv...

Deploys about 12" pre-apogee with a 12.4 fps Dv. Nice and smooth for this model...

[CPMcGraw]

I put one motor in the mount and weighed it at 16 ounces.

I re-simmed the model with an additional 3 oz of mass, to bring the weight up to ~16 oz. You should still use the 6-second delay instead of the 4. The overall altitude drops to 1200', and the Dv becomes 11.3 fps, with deployment still pre-apogee by about 3".

Enjoy that puppy! :D