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Author Topic: Re: Extreme Wildman  (Read 33543 times)
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Goffa
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Extreme Wildman on M1297W


« on: January 01, 1970, 10:00:00 AM »

Well that enough sanding and test fitting...time to start building!

Holes drilled in payload tube for shear pins and rivets.
Switch band epoxied to coupler.



Kevlar bridle, CRs epoxied onto motor tube with some fillets...more fillets to come later....
Used Wests loaded with chopped carbon fibre...
The CF adds strength and black makes it easier to see what you have done thru the fibreglass






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ARA 126
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ICBM

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« Reply #1 on: January 01, 1970, 10:00:00 AM »

Are you going to use ubolts or eyelets for the attachment points of the shockcords.
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Goffa
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Extreme Wildman on M1297W


« Reply #2 on: January 01, 1970, 10:00:00 AM »

Quote from: 55
Are you going to use ubolts or eyelets for the attachment points of the shockcords.

Wouldn't use open eyebolts
I've got welded eyebolts...but i'll test fit ubolts as well.
Still playing around with how to layout bulkhead components...
Welded eyebolts have been proven on this rocket plenty of times in the states
At 100" and 7kg(excluding motor) its a pretty small and lightweight rocket by 75mm standards...
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wolflair
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« Reply #3 on: January 01, 1970, 10:00:00 AM »

i like ubolts because they spread the weight better but i have also used eyelets both welded and no welded depends on how heavy the rocket is
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Dazza98
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« Reply #4 on: January 01, 1970, 10:00:00 AM »

looks like some tidy work there, not like your shed...lol
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ICBM

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« Reply #5 on: January 01, 1970, 10:00:00 AM »

Quote from: 18
looks like some tidy work there, not like your shed...lol

LOL LOL LOL
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star destroyer
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« Reply #6 on: January 01, 1970, 10:00:00 AM »

Welded eyebolts or ubolts will work fine just make sure the washer you use for the eyebolt is of a nice size to help spread the weight and force the shockcord will have on it during flight.
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RocketballSA
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« Reply #7 on: January 01, 1970, 10:00:00 AM »

Looking real good Goffa Smiley
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Goffa
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Extreme Wildman on M1297W


« Reply #8 on: January 01, 1970, 10:00:00 AM »

Now for the tricky part...the fins.
I have decided not to build the fin can outside the airframe.
I am going to use the internal fin fillet injection method.
This involves:
- sliding the MMT/CR section into the airframe.
- tacking the fins onto the MMT/CR thru the slots
- using the slots and a fin jig to ensure fin alignment
- injecting interior fin fillets thru these holes in the airframe near the fins slots

The key to this method is the use of Wests epoxy loaded with chopped carbon fibre for the interior fillets.
This method is well documented and has been proven over many years for rockets up to N-power.
Using the CF for fin reinforcement avoids the need for tip-tip fibreglassing, fibreglass strips etc.
It also avoids the need to cut the fins slots to the edge of the airframe them patch them later.
Its not better than the fin can method...just different and hopefully will be strong enough!
The big advantage of the fin can method is that you can spend as much time as you like strengthening the fin/mmt joint until you are happy with it.

Sanded all areas to be bonded with 80 grit.
Put some rings of epoxy inside the airframe where the CRs will be then slid the MMT/CR into the AF.
You can also see the injection holes near the fin slots and the motor retainer mount holes on the aft CR



Here is the jig ready for the fins.
Spent many hours making sure that the alignment would be right.
Have had enough of mis-aligned fins for one year!


Next, butter the root edges of the fins with epoxy.
Mixed Wests epoxy and thickened with 406 colloidal silica to get "peanut butter"



Here is the root edge with the "butter". Bit hard to see in the photo.

After all three fins done, clamp to the jig, check alignment and wait to cure.


Interior fin fillet injection is next...
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« Reply #9 on: January 01, 1970, 10:00:00 AM »

Hi Goffa will you be using any expanding foam in the fincan area.
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Goffa
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Extreme Wildman on M1297W


« Reply #10 on: January 01, 1970, 10:00:00 AM »

No, ICBM, Havent got any.
But I've read about a few L3 build projects that use it. Looks like amazing stuff!
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Goffa
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Extreme Wildman on M1297W


« Reply #11 on: January 01, 1970, 10:00:00 AM »

Tacked on fins have cured.
Fin alignment looks good.
Here is assembled rocket so far...

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Dazza98
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« Reply #12 on: January 01, 1970, 10:00:00 AM »

nice looking telescope there goffa.. i mean rocket. see you have been working on the shed clean up...NOT lol i can talk my is a mess too.
with the fins you are just pouring epoxy into the void or did i miss something?
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Goffa
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Extreme Wildman on M1297W


« Reply #13 on: January 01, 1970, 10:00:00 AM »

Sorry, Dazza98. Didn't explain very well. Hope these pictures do a better job.

Here we go with the interior fin fillets (fin to motor tube/CRs).

The plan is to use a syringe to inject fillets thru the airframe holes into the valley where the fin joins the motor tube.
The CRs at each end are the dam that holds the fillets in.
So the idea is to inject the epoxy/CF mixture into the holes and then tilt the airframe up and down so the epoxy flows evenly along the valley.
Then use a pair of spirit levels to make sure the airframe is level while the epoxy cures.
There are 6 fillets: do first 2, let cure then next 2, let cure then last 2.

Set up the airframe on a level workhorse. You can see the holes to do 2 fillets



Mix the epoxy and load with chopped carbon fibre (CF).




Inject via syringe into the holes and tilt airframe back and forth to let it run evenly along the fin/mmt valley


Then level airframe for fillets to cure


The other bonus in using the CF it that it is easy to see the epoxy thru the fibreglass airframe.
Here you can see the 2 fillets looking from the inside thru the the motor tube.
The epoxy has spread fairly evenly along the whole length of the fin/mmt joints.



Here is the same 2 internal fillets looking from the outside thru the airframe.



The CF is amazing stuff. Only takes a little bit to really load up the epoxy.
The first batch I put too much CF and and it was too thick for the syringe.
Injecting the first 2 fillets was pretty scary.
I think my mixture was still a little too thick and I was worried it wouldnt flow along the whole length.
But it eventually did.
Second 2 fillets went much better: got the mixture right and it flowed easily.
Used about 30mL of epoxy/CF on each fillet for a total of 180mL.

So that's the interior fin fillets done.
Pretty happy with the way the fillets turned out in the end after a shaky start.
As long as you have access to the CF its a pretty simple and fast method.
Only thing I didn't like about this method was lack of control over fillet quality.
You only get 1 shot at doing the fillets. If something goes wrong its not easy to fix.

Next is the exterior fin fillets...
 

 
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