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Crazy Jim's Gone Banana's
Jan 17, 2009
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Savannah Ga
I just finished this build and one of the priorities for doing it was to build it in such a way that was simple, easy, no use of power tools ''most'' of us don't have and for the first time builder of a fiberglass rocket. The WILDMAN XTREME 4 is a 3in motor tube and designed to fly on J- M motors.

Try to eliminate jigs and measuring required for shear pin, rivets, rail button locations. Keep it simple and FUN. Eliminate all the aggravation and hassles that keep many fliers from trying fiberglass. So if your one of these keep your Eye on this build, it will be very different from most others!.

Even though it is a Level - 3 capable kit, if done in this manner it will be a flight worthy, rather simple build, for even the newbie. All these techniques be used to build any SIZE glass rocket up to 8in. [And I only say that because when you get bigger, some strange things begin to happen which may or may not come into play]

You will note the sequence of the build may seem "out" of order by normal standards, why it was done this way will become clear. Mainly it saves time and measuring.

Also to Fred: sorry to hear of your Cherry Bombs demise and I had already started mine and named it before reading of yours. Hopefully I will fare better!

The parts: this kit comes with everything other than the chute, motor retention and railbuttons, also a complete altimeter bay with sled are included, even shear pins and rivets. I got this photo off the web and can't remember where, if it's yours let me know and I will credit you. [Rocketry Planet ]

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The first of 4 items making this kit "unique" among most kits:

1 The airframe tubes are spiral wound rather than wrapped glass.

2 The fincan tube is 56in long rather than the standard 48in included in all other kits. [as far as I know] Making flying large M motors much easier!

3 Comes with the manual on CD with plenty of pics, and easy to understand procedures.


4 LIFETIME guarantee against failure of any kind due to components! If built as I am going to do, with the "INJECTED" internal fillet style of build. You will Not be able to rip the fins off. Of course this does NOT cover recovery failures! LOL

You may have heard of injecting the fillets, but I will show how to do it properly.....step by step...in a clear, concise and easy to understand way. If you do not understand anything I'm doing, or have questions about the build, please feel free to ask.

No question will be considered silly or stupid, no matter how trivial it may seem to you! There are many ways to build a rocket, but this one is one of the best to accomplish a LIGHT weight, strong and functional rocket, that will stand the test of time.
If I can abuse a rocket the way some of you know I do....and it stands up....I must be doing something right.

When done, this Xtreme Wildman will fly on any commercial motor made to date, with NO need for any nose weight or other types of fin re-enforcement. No tip to tip, no strips of glass, no cutting the rear of airframe to re-enforce the fin to motor mount with glass strips and sliding the assembly in.

Other standard Wildman features are: The included [2] 26ft lengths of TN and all eyebolts, threaded rod and nuts, washers and recovery harness [4500lb 1in Kevlar strap.]
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Hopefully you will be able to build one, pretty much by just looking at the photos. They are all marked and labeled for measurements. If you like them, save the photo's for a future build of yours.

I have built a rather large number of high power rockets, and why it took so long to think of this time saver is beyond me. But finally the light bulb came one.

Right off the bat I used the slotted fincan to mark and measure for: rivet location .....shear pin location...vent band vents location. Had I built the fincan first it would have been impossible. Sooooo...............

First slide the coupler into the slotted end and mark through the slots for all 3 avbay rivet locations.
Then the NC for shear pin location [all 3]

These photos clearly show the spiral wound tubes and couplers also.


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Insert the marked NC into the payload tube , transfer all 3 marks for shear pin location.

Push NC tight into tube and use 5/64 bit to drill all 3 holes through the tube and NC for shearpins. [ 2-256 nylon screws known as shearpins]
They should be located 1 and 1/2 inches back from edge of tube.

Extend the 3 lines on coupler by using a drawer or straightedge.


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To center the 2in vent band on the coupler which is 12 long:

Mark 5 and 7 from one end.

Slide band over coupler and extend marks from coupler for vent locations [3]

After marking sand coupler and inside of band with 80 grit where they will be epoxied.

Apply epoxy and with a twisting motion, [to evenly disperse it] put vent band into position. Make sure to wipe any epoxy of your tube, you want it very clean so when assembled the tubes fit tight. Not bumping up to a small fillet!


You want the vent holes between the rivet locations, thus preventing turbulence from the rivet heads from interfering with the vent holes. This can cause problems with accurate altimeter readings if they are inline.

To do this rotate the vent band so marks on it, are centered between marks on coupler. [should be above the epoxy step]

The photo was taken before gluing thus it slipped from centered position ,but note how all lines are positioned.



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After epoxy has cured:

Mark center of vent band in all 3 positions for vents.
Drill vents using 1/4 in. bit.

Insert coupler part way into payload and transfer lines onto tube for rivet location.
Mark 1 and 1/2inches back from the 3 locations.
Push coupler tight into tube and drill for rivets using a 5/32 bit.


I forgot to mention this for the shearpins also....

DO THE RIVET HOLES ONE AT A TIME...drill hole, install rivet, move to next and repeat, finally the third.
If you try to drill all 3 first then install the rivets, your chance of success in aligning them ,drops to slim or nothing!!

If you are so inclined, make a key mark [to aid in assembly] by drilling into the joint between the coupler and vent band. Half hole on each side, it only need by deep enough to be seen through several coats of paint. In the photo I darkened it with a sharpie to high lite it. If you don't like this method, use your own.

Pretty fast and simple way to do your shearpins, vents and rivets all in one swoop! Don't no why it took me so long to figure this one out, but me LIKEY !


Thank you for this truly excellent build thread!

I'm just finishing up a 3" Wildman right now, but the 4" model is hanging on the shop wall waiting for attention. I'll definitely put your ideas to good use.
While at it, will drill the airframe vents to bleed of internal pressure.

These vents will prevent premature separation of Nose cone from payload and payload section from fincan due to the internal air pressure becoming higher than external.This being caused by rapid acceleration during flight, and pressure variences at different altitudes.

Higher internal pressure will want to force the separation of components in order to equalize with the out side. [Think ears popping when traveling up and down in the mountains]. This often overlooked step has been the downfall of many a rocket!

Drill hole [1/8 bit] 12 in. from either end of payload.

Drill same 16in down from TOP of fincan tube.


The Extreme Wildman comes with a Y shaped recovery harness that attaches to both sides of the motor mount. Need to Make 2 notches on opposite side of ring for straps tp pass through. Here's the easy way......

First lay a section of strap across the center of a Motor Mount Centering ring [MMCR] and mark a line on both sides of strap.

Transfer marks to inside of ring and sand or file notches.
Stand MM on end, stuff harness into tube.
Leave 6-8 hang over each side.

Slide notched MMCR down tube, sandwiching the straps . Ring should be 1/4 to 1/2 in from top of tube.

Strecth out the harness full length, making sure bothe side are = and there are no twists in strap. Adjust if needed.

Tack ring on with CA and stuff harness back in tube to prevent getting glue on it in next step.
Mix epoxy and smear some on tube under straps.
Push straps into epoxy.
More epoxy on top of strap. [Encapsulate it]

Repeat for other strap.

Make a small fillet of epoxy on top of CR. SMALL fillet!!! just enough to seal any gaps between CR and tube.

A large poured fillet will be done later, once the MM assembly is installed in fincan.

Just want to seal it so when poured the big one won't leak all over inside the tube.

Sand each side of fin slots outward to a distance of 1/2 inch....with 60-80 grit. To aid in fillet adhesion later. Much easier to do before fin installation.

Measure 4in. from each end of slot for injection holes to do internal fillets.
Do this on both sides of all 3 slots.
Center of holes should be 1/4 in. from edge of slots.
Use 1/4 bit for holes, they need to be large enough for the syringe tip to enter.

These holes will be hidden when the external fillets are done. Keep them to tolerances shown.

Make SURE the holes are clean. If needed reach inside of tube and sand off the fuzzies, that may be left from drilling.

A large dowel or piece of PVC pipe wrapped with sandpaper will do the trick.
[Actually this should be done on the AVbay vent holes also to make sure your air samples are less turbulent.]

If left,...... when the carbon fiber/epoxy mix is injected.....the fibers will collect on them clogging the holes, making injecting difficult if not impossible!


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Hey Jim
A word of caution you may want to add to this build thread is.
"When drilling any size hole in spiral wound material always back it up on the inside." This stuff splinters badly if this is not done.
Thanks for the nice build thread.
Excellent build thread Jim.

Agree using the pre-cut slots as a jig for other things is a nice bonus.

Hey Jim
A word of caution you may want to add to this build thread is.
"When drilling any size hole in spiral wound material always back it up on the inside." This stuff splinters badly if this is not done.
Thanks for the nice build thread.
Yep splinters when drilling. FYI Hawk Mountain Extreme 2 spiral wound splinters very badly. Start with a small pilot hole and step up the bit size. Also go easy on drill pressure.
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I've had some success using a single-fluted drill bit. It doesn't totally get rid of the splintering, but does keep it to a manageable level.
Hey Jim
A word of caution you may want to add to this build thread is.
"When drilling any size hole in spiral wound material always back it up on the inside." This stuff splinters badly if this is not done.
Thanks for the nice build thread.

Actually I did not encounter this problem. [SPLINTERING] Just some fiber fuzzies in hole. But I use an old hand powered twist drill , hand me down. Good point however. Maybe using the low speed setting with power drills would help. I can see where a lot of downward pressure would cause the innermost layers to splinter badly. I always drill slowly and when the bit breaks through, back it in and out several times to get as clean a hole as possible.
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Time for the Motor Mount assembly.....
......but first fit your motor retention the rear CR. In my case an AeroPac was fitted on an extra wood CR, marked and removed. Wood was just easier for me, due to all the screws needed to fit the flange. I did not use the inserts, just the bolts threaded right into the wood.
Use and fit whatever you need.


After fit and measure, the rear CR is tacked with CA on MM tube 1/2 from rear, [leaving room for AeroPac] The type of retention you use will determine the distance from rear of tube the CR is located.

There is nothing worse than completing a project, only to find your motor won,t fit due to a small overlooked error. It is advisable to use a motor during dry fit, just to be sure!

In this case....dry fitting revealed that the mounting bolt heads had to be ground a tad, to clear the side of airframe tube.



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During the next few steps, you will be injecting the internal fillets for fins. The fins MUST fit TIGHT to the motor tube, and the CR's must fit snug to he top and bottom of fins. You are creating a dam so the injected epoxy can NOT LEAK under the fin or around the joint between the top and bottom of the fin and centering ring!
To do this the MM assembly must be pre-fitted out side the airframe.

Slide the MM tube and CR's into the fincan and position so you can trace through the slots onto the MM tube. This will aid in lining up the fins outside the airframe. Number each slot and fin while fitting to assure everything goes back smoothly when glueing and there will be no leaks. Now remove from airframe.

Stand the marked MM tube on end, and position the 3 fins in their appropriate locations. If your middle cr is snug fitting , it will hold them in place. If not an extra set of hands will be needed to help. Once you are satisfied with the fit, tack the CR in place with some superglue [CA].

Tack only, do NOT glue. You may need to adjust. Remove the fins, insert the MM tube into airframe, line up lines drawn on tube with the slots and insert fins numbered to match their numbered lines [slots].

fin numbered.....slot numbered....line on mm numbered....
.........this will provide the perfect fit needed so there are NO leaks. This is the step most overlook when injecting and end up with a mess. A few minutes of proper prep and all will go very easily!

Remove the assembly from the airframe and do a fillet on the TOP of middle CR to prevent any leaking. fill any gaps between the tube and top of rear CR .



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This method has been in use and tested for many years now. When properly done, NO other type of fin reinforcement is needed. No tip to tip glassing, no internal glass strips or any other type of reinforcement. Simply inject the mixture of chopped fibers [carbon or kevlar] with epoxy and the bond is strong enough to withstand the forces any commercial motor can generate during flight. PERIOD. ENOUGH SAID, it works! This configuration has been successful on rockets up to N impulse class motors, and is guaranteed for the life of this rocket!....................

Also NO NOSE WEIGHT IS NEEDED for any motor flown, that will fit ! When Built without modification.
Fin mounting:

First some type of guide is recommended. I used a simple guide downloaded of the net and mounted on a 1/2in section of scrap plywood.
4in hole cut with jig saw.
1 by 2 scraps of wood nailed along side each fin line.[take into account the thickness of fin and space wood accordingly, NOT tight to line]
A c-clamp will hold fin in place or simply a weight wedging fin to wood bar.

There are many types of jigs and guides available, a little research will yield a functional one. OR if confident enough......eyeball it.


Tacking on the fins:

Epoxy is scooped up with edge of applicator and spread on edge of fin, much like buttering toast.

Take care not to get it all over sides of fin.

A small dollop of glue where the fin will make contact with CR's will keep injection leakage from happening here.

Once fin bottom is "buttered" carefully place in proper slot and push in tight to MM tube, to set into place.

Repeat process for remaining 2 fins, check for alignment, clamp to jig, let cure.

JB weld was used ONLY to aid in seeing the small amount in photo's. Any thickened epoxy is fine for tacking, we are just making a seal for injecting.

One of the great things about glass tubes:
You can shine a light through the tube side and by looking down the MM see if you have everything tight and where it belongs, any gaps will be readily visible. [This last photo was done after first set of injections, show the fillets also]



Rocket must now be in horizontal position to do internal fillets.
Make sure your level front to back and side to side, or the epoxy will not flow out evenly. Shim to level if needed


Mix enough epoxy and chopped carbon fiber for 2 fillets......this will be 2 and 1/2 pumps is using West or similar system.

You can see it does not take much carbon fiber to load the epoxy when finally wetted out. [ pile about the size of dime]

It is best to mix resin and hardener first... 1 minute...then add the fibers and continue to mix till even consistency...about another 2 minutes.

Inject 10ml [full syringe if using one pictured] into each of the 4 holes.
2 for 1 fin and 2 for the other.
There should be 1 more syringe full [10ml] of epoxy left, divide it in half for each fillet.

A little more or less will NOT matter, nor whether you put it in the front or rear holes.
Inject slowly, there is only 1/2 in. clearance between airframe and MM tube.
When sticking the syringe through the hole, it is easy to almost hit the MM with the tip.

Injecting rapidly will cause a BIG back splash off the MM and all over the inside of airframe.

Take your time, your already saving tons of it [time] any way, by using this method.

Remember: clean holes or fibers may collect on fuzzies and cut tip at a 45.

Now tip airframe UP about 45 degree angle to help disperse epoxy evenly.

Then down the same.

If you peek into the motor mount tube you will see it flowing and help gauge the length of time tilt is needed.


One set of fillets complete.

After you have finished injecting both fillets, make sure airframe is level to aid in getting even fillets. [my antique level]

Also wipe any epoxy on outside with finger in glove to even that out.

Repeat above steps to finish other 2 sets of fillets.



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While the fillets are drying, time to finish the avionics bay.

Place the larger BP on eye bolt, making sure you have sanded surfaces to be glued. Spread a few drops of glue, then add the smaller BP. You can repeat on other eyebolt, or stack other large BP,some glue, smaller BP and clamp tight with a nut.

If you do all 4 on 1 eyebolt.......DO NOT GLUE ALL 4 BP"S TOGETHER!!!!

After cured:

Mark and drill holes for tie rods.

1/2 in. from edge of LARGER bp and use 1/4in. bit.

You need to stack all together to get holes to line up.

While doing this, drill holes for you ejection charge leads. [1 or 2 depending on whether you use 1 or 2 altimeters]

1/8 hole will be perfect for E-match lead wire. If using terminal blocks or other means, size your holes accordingly to wire gauge.