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Hermes: Custom 38mm MD Build

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Who_Cares

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Welcome to my ambitious build!

A little backstory: My name is Caden, I'm 18 years old and this is my first year in HPR. I've recently completed my level 2 certification and ever since I've been anxious to move onto something bigger and better (I know I'm another hot shot young guy).

Below are my goals for this project listed in order of importance from top to bottom (top being the most important). Keep in mind that these goals are ambitious (I want to challenge myself) and they are meant to be. I probably won't achieve all of them, but that's okay because I'm doing this build to learn and have fun.

* = This is my first time doing this
  1. Create a 38mm MD rocket*
  2. Duel Deployment with a drogue and main chute*
  3. Fiberglass the BT*
  4. T2T fiberglass the fins*
  5. Thoroughly document the build and flights*
  6. Designed with the ability to add a booster stage*
I've already created a thread asking what and how much fiberglass I should use. That discussion is here: https://www.rocketryforum.com/threads/how-much-fiberglass-should-i-use.147284/

Hermes will have a GLR plastic nosecone filled with a two part foam and it may be painted with heat resistant paint. There will be a 12" phenolic section and a 36" phenolic section, both section wrapped twice with 6oz fiberglass, with the av-bay, the blue tube av-bay kit sold by Apogee, positioned in the middle of the two sections. Hermes will have g10 custom fins with a clipped delta design. The motor will be friction fit. I have not decided on the parachutes yet.

Below is a picture of Hermes in OpenRocket and I've also linked the OpenRocket file.
Note: The parachutes currently in the rocket are just place holders.

Hermes.PNG


Criticism, advice, concerns, and insults are all welcome and I encourage you to share them so I don't make any major mistakes! For example, do you think I will have a problem with weather cocking with that high of a stability or will it not be a problem with how tall the rocket is and how small the fins are?
 

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timbucktoo

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Weathercocking could be an issue but until you have final weight, CG & a motor installed it's too soon to make any conclusions. Since you are doing a T2T, you'll be adding more weight to the aft end so that will certainly help.
 

markkoelsch

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If it were me I might make the fins a bit larger. Increase the span by about .75”. I understand what you are getting at with the design, and I have built rockets like this.

The other thing you will need is some type of tracking whether gps or rdf. A rocket like this can disappear in a hurry on even moderate motors. Trust me- it has happened to me. I have a similar rocket I built and lost on an AT I300- it was like the rocket teleported[emoji3]. It had a Walston tracker in it that I believe broke lose from the mount and broke. Saw the apogee event and then lost it.
 

captbk

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Unless you are just doing the phenolic and glass thing for the experience, why not jut buy a fiberglass kit? I have both the MadCow Go Devil 38 and Wildman Blackhawk 38 and they are both great kits. I didnt do T2T on either one although some people here have. Good luck and welcome to the forum.
 

Who_Cares

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Unless you are just doing the phenolic and glass thing for the experience, why not jut buy a fiberglass kit? I have both the MadCow Go Devil 38 and Wildman Blackhawk 38 and they are both great kits. I didnt do T2T on either one although some people here have. Good luck and welcome to the forum.
It is partly for experience, but also for the challenge. I just don't find those kits very interesting. I want to have the satisfaction of building my own rocket.
 

Who_Cares

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If it were me I might make the fins a bit larger. Increase the span by about .75”. I understand what you are getting at with the design, and I have built rockets like this.

The other thing you will need is some type of tracking whether gps or rdf. A rocket like this can disappear in a hurry on even moderate motors. Trust me- it has happened to me. I have a similar rocket I built and lost on an AT I300- it was like the rocket teleported[emoji3]. It had a Walston tracker in it that I believe broke lose from the mount and broke. Saw the apogee event and then lost it.
What benefit would there be in increasing the span of the fins?

Luckily, my club rents out radio transmitters for only $5. I'm sure I'll eventually have to put a gps tracker on this, but I might wait a little bit because that's expensive. This build is already way more expensive then a kit.

Right now OpenRocket says this rocket will reach 15k feet on a J228 although that is without the added weight of the fiberglass and some likely unforeseen weights. Do you think it may be a good idea to go drogue-less?
 

blackjack2564

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You may consider using a streamer to help see/'finding it.
I use the pink 1inch tape they wrap trees to mark what gets cut. Stuff is so thin you can get 50ft easily rolled & dropped in fincan. It will lay across top of crops/corn/beans/bushes with out sinking into them like everything else. doesn't weight anything either .Roll of 100frds only 3-4bucks any big box store

Tie it & tape to shock cord....roll end around a pencil & just twist pencil to easily roll up any needed amount. remove from pencil & drop in.
 
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