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Building my first fiberglass rocket

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slydoh

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Hi all,

I am level one and having been using PML kits. I am taking the next step and purchased a Wildman Draco EX kit. It's a 4" diameter kit with a 75mm mount mount.

A few questions.

1. I have read build posts and people washing the parts before assembly. I put all the part in the tub and used regular dish washing soap and a wash cloth. I rinsed them all thoroughly. Is one time enough?

2. With a 4" diameter and a 75mm motor mount the centering rings don't have much space to mount an eye bolt or similar. On the PML rockets I have glue the shock cord to the motor mount. I could dremel out some of the centering ring and do the same. Or try the eye bolt - I am worried about the strength of this connection and that it would be right next to the body tube possibly causing a zipper. Any recommendations/ideas?

3. I got a 75mm flanged Aeropack motor retainer off ebay. I like the idea but I don't' have a great set of tools and I'm not a craftsman so I worry about lining up the holes when installing it. So... I found thrust rings which are pre drilled for the Aeropack. One of the diagrams shows the thrust ring attached via threaded rods like an ebay. I was thinking about using this method to also attach the shock cord. But the 4" thrust ring doesn't have enough room for the rods or nuts once the retainer is attached. Does anyone know if/where I could get 10+" threaded bolts that have a flush mount end that would work to secure the Aeropack and get up to the top of the motor retainer?

I am sure I will have more.

Thanks,

Simon
 

Bat-mite

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Don't use an eyebolt -- too bulky. Use a U-bolt. For added strength, you can use two U-bolts and buy or make a Y-harness so that the deployment force is halved on each side.

I would have just gone with a glue-on retainer, so someone else will be along to help with the flanged retainer.
 

jcamhale

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After washing the parts I like to wipe everything down with acetone to remove any residue (I also wipe down with acetone after sanding to remove dust). As far as attaching the recovery harness ,in my 4" with a 75mm, I used an eye bolt screwed into the top of the motor bulkhead. Personally I don't like cutting the centering rings when there is so little material. With the aeropack retainer I would have used the non-flanged retainer and shifted the centering rings and motor mount to allow installation.
 

NateLowrie

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Hi all,

I am level one and having been using PML kits. I am taking the next step and purchased a Wildman Draco EX kit. It's a 4" diameter kit with a 75mm mount mount.

A few questions.

1. I have read build posts and people washing the parts before assembly. I put all the part in the tub and used regular dish washing soap and a wash cloth. I rinsed them all thoroughly. Is one time enough?

2. With a 4" diameter and a 75mm motor mount the centering rings don't have much space to mount an eye bolt or similar. On the PML rockets I have glue the shock cord to the motor mount. I could dremel out some of the centering ring and do the same. Or try the eye bolt - I am worried about the strength of this connection and that it would be right next to the body tube possibly causing a zipper. Any recommendations/ideas?

3. I got a 75mm flanged Aeropack motor retainer off ebay. I like the idea but I don't' have a great set of tools and I'm not a craftsman so I worry about lining up the holes when installing it. So... I found thrust rings which are pre drilled for the Aeropack. One of the diagrams shows the thrust ring attached via threaded rods like an ebay. I was thinking about using this method to also attach the shock cord. But the 4" thrust ring doesn't have enough room for the rods or nuts once the retainer is attached. Does anyone know if/where I could get 10+" threaded bolts that have a flush mount end that would work to secure the Aeropack and get up to the top of the motor retainer?

I am sure I will have more.

Thanks,

Simon
The point of the washing is to remove the mold release on the fiberglass parts. You don't have to wash them though. Wiping the parts down with Lacquer Thinner or Denatured alcohol and some lint free cloth is just as good. I would recommend you read http://www.rocketryforum.com/showth...what-your-government-doesn-t-want-you-to-know as a good source for bonding composites.

Regarding the eye bolt, is it forged? If not ditch it for something else. I like to use 1/4" stainless steel forged eybolts. They are small and have a 600lb rating which is more than enough. Bat-mites suggestion of a U-Bolt is also good. Your thought of attaching the cord directly to the motor mount is also very doable, though I would suggest using 2 smaller lengths of Kevlar that have loops on the end. The kevlar has better protection against ejection charges and this enables you to replace the cord easier. In the end, there is more than one way to solve this problem and any of the 3 would work.

I am assuming you are talking about the SC Precision Thrust Plates? You don't need threaded rod. Just drill 3 holes in the rear centering ring and epoxy in 3 T-Nuts. Then, use standard flathead screws to attach the plate to the centering ring. I am using this method on my L3 with a thrust plate.
 

KenRico

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The point of the washing is to remove the mold release on the fiberglass parts. You don't have to wash them though. Wiping the parts down with Lacquer Thinner or Denatured alcohol and some lint free cloth is just as good. I would recommend you read http://www.rocketryforum.com/showth...what-your-government-doesn-t-want-you-to-know as a good source for bonding composites.

Regarding the eye bolt, is it forged? If not ditch it for something else. I like to use 1/4" stainless steel forged eybolts. They are small and have a 600lb rating which is more than enough. Bat-mites suggestion of a U-Bolt is also good. Your thought of attaching the cord directly to the motor mount is also very doable, though I would suggest using 2 smaller lengths of Kevlar that have loops on the end. The kevlar has better protection against ejection charges and this enables you to replace the cord easier. In the end, there is more than one way to solve this problem and any of the 3 would work.

I am assuming you are talking about the SC Precision Thrust Plates? You don't need threaded rod. Just drill 3 holes in the rear centering ring and epoxy in 3 T-Nuts. Then, use standard flathead screws to attach the plate to the centering ring. I am using this method on my L3 with a thrust plate.
Very well said !

The centering rings will notch easy with a file to clear the flat kevlar glued to the motor mount tube as a bridle . Be careful to mark the tube where the fins will attach to keep it clear . I have had to do some 60/40 attach the strap and miss the fin landing spaces.

Kenny
 

My Gypsy

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I am assuming you are talking about the SC Precision Thrust Plates? You don't need threaded rod. Just drill 3 holes in the rear centering ring and epoxy in 3 T-Nuts. Then, use standard flathead screws to attach the plate to the centering ring. I am using this method on my L3 with a thrust plate.
Something like this...

IMG_2931.jpg


IMG_2933.jpg


IMG_2942.jpg
 

slydoh

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Yes. But the 4" diameter and 75mm motor mount doesn't have that much space.
 

slydoh

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20161012_111924.jpg20161012_111850.jpg20161012_111844.jpg20161012_111720.jpg
Yes the eye bolt is forged. But look at the size left on the centering ring. The Ubolt is the same. I couldn't use any washers and it looks like I'd have to do either before putting the centering ring on the motor mount.
Plus I would like to use a quick link to attach the shock cord. Being so close to the main tube I'm not sure how to make this work. I've glued kevlar to the motor mount long enough to get out of the main tube and then used another quick link to nylon/parachute etc. in my current rockets.
 
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djs

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Given the size of the centering ring, I would just do a y-harness with your shock cord- as long as it's kevlar, not nylon. Please remember that it's entirely likely that your motor will extend past the motor mount, and plan accordingly.
 

slydoh

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And as a reminder. This kit is still sitting next to the bathtub. Nothing has been assembled or decided upon. I could use a different retainer. I do lots of different things. That's why I am asking for your help. How should I do it?
 

slydoh

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Ok. Y harness. Level one newbie.... Do I glue two sides of a shock cord to the motor mount to provide the Y? As mentioned with enough slack to provide for the largest motor....
 

djs

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And as a reminder. This kit is still sitting next to the bathtub. Nothing has been assembled or decided upon. I could use a different retainer. I do lots of different things. That's why I am asking for your help. How should I do it?
You could just leave the parts in your bathtub as a playground for your rubber duckie? :)
 

djs

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Ok. Y harness. Level one newbie.... Do I glue two sides of a shock cord to the motor mount to provide the Y? As mentioned with enough slack to provide for the largest motor....
Yes- I extend them down the sides to almost the bottom centering ring, and epoxy down the whole thing. Shock cord should run under the centering rings (with a notch cut out), and roughly on each side of the motor mount (depending on the fin setup). I would make the length of the harness long enough so that it goes all the way to the end of the body tube- so the "junction" part of the Y is hanging out the end.

Some great instructions can be found here: page 5-6

http://www.wildmanrocketry.com/productimages/instructions/Wildman/Demon4.pdf
 

slydoh

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Thanks and :)- djs....

Cool. I just saw a pic on onebadhawk which had loops for eyebolts/or... so it sounds like just what I did for my level one PML's... Kevlar glued to the motor mount (this time a Y harness) and extend it beyond the main tube. Then attach the rest...

thanks...

Any opinions on the thrust ring/flanged retainer? It sounds like people don't have issues with glued retainers and they have worked for me. This was kinda of cheap and I am kinda lazy.

Simon
 

My Gypsy

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Dennis, what size main tube and motor tube are you using?
4" body with a 54mm motor mount. Looks like you may be able to do it this way. You would need to trim the flanges of the blind nuts on the ID of the CR as well as the OD.
 
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Tonimus

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I had Teddy at OneBadHawk harnesses make me a lead with an eyebolt specifically for a 4" diameter rocket with a 75mm mount. Here's a picture of it installed:



It is hard to see, but there is a single 1/4" eyebolt down there. Plenty strong enough for the weight of an empty fin can with an empty case.
 

jd2cylman

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OK, with a 98mm body and 75mm motor tube, the flanged Aeropack is fine. Heck, it's almost self aligning... No need for pem nuts or other stuff. Place a 75mm motor in the tube to center the Aeropack, drill a hole and thread in a screw. Repeat on opposite side. Do this 6 times. Easy peasy. Just thread the screws directly into the centering ring. I do recommend using a 8-32 tap for this. There is plenty of meat to hold the flanged Aeropack on. As djs has said, get 1 inch flat Kevlar strap and glue it to the motor tube. Make the bridle long enough to reach the top of the body tube for easy connection to your recovery harness. Yes this can be a lot of kevlar, but it's worth it for ease of use. Plus it clears ANY motor length... On my Demon 98 and Wild Thang Extreme, this took 8' of kevlar strap. Use tape on the motor tube where you DON'T want glue while gluing on the strap (think clean tube for when you glue on the fins). As far as gluing on the fins, use a good quality 5 minute epoxy to hold the fins on while you align them. Inject the internal filets.
Do a search here or look at this thread:http://www.rocketryforum.com/showthread.php?55019-How-To-Build-A-quot-Stock-quot-3IN-DARKSTAR-CJ-Step-By-Step
There's no need for filets on the inside of the body tube to fin joint. Just fin to motor tube joint and fin to outside body tube.
Matter of fact, that whole thread is a good primer... Good luck.

Adrian
 
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