Help with my first scratch build

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

ToneDeafJunior

Well-Known Member
TRF Supporter
Joined
Oct 11, 2017
Messages
223
Reaction score
106
Location
Charleston, SC
First of all, thank you to those who would like to help. I'm new to TRF. I just completed and flew an Estes Mercury Redstone. First rocket I've flown since Boy Scouts some 35 years ago. I am attempting to build my first scratch rocket and could use some assistance. (I like the looks of the Gabriel iii A/S) I live in a smaller city with only one hobby shop and its supplies are limited. I'm looking online to buy components. Would rather not say the name of the shop. I'm considering 2 x 2.6" tubes with a coupler, 1/8" plywood for fins, nose cone MC-PNC26, shock cord, 24" parachute and a 24mm engine mount to use Estes E9-4 motors. I was told by the online retailer that the rocket will be totally under powered and they suggested a 29mm engine and F motors. Specifically the Aerotech F44. So... The engines are so much more expensive. Are they correct that the rocket would be underpowered with the E9-4? Should I suck it up and go with the 29mm and the Aerotech F44 engines?

Secondly, Do I need to weight the nose cone? I've searched TRF and I see many conversations about weighting the nose cone to limit height and not too many about stability. Would you all suggest I weight the nose cone for my new build? Thank you so much in advance.
 
Welcome to scratch building! Not enough information to advise on motors. We'd need to see the complete design, as there are just too many variables. Have you tried Open Rocket? It's a free rocket design program. As for online retailers, I really like Balsa Machining. I also like Rocketarium, but their shipping can be a little high.
 
Welcome :)

Open Rocket is a simulator so you can play with component locations and mass to see if your design is stable during flight. Apogee Components has RockSim simulator available, and it has a free trial period. Otherwise you need to buy it. It is what I use. Open Rocket is probably the one for you currently, especially at the price of FREE!

Have purchased stuff from Apogee Components before. Great service.
 
Well I'm not afraid to say it: I believe you have provided enough info to confirm that an E9 will *not* be sufficient for that rocket. I think the shop was advising you correctly.

As already suggested: get openrocket, learn how to use it, and get a feel for this stuff before tackling a rocket of that size.
 
I have downloaded OpenRocket and am working on it now. Thank you for the suggestion. Having a hard time trying to add a motor to the drawing. I don't have the options that the YouTube video has.
 
I have downloaded OpenRocket and am working on it now. Thank you for the suggestion. Having a hard time trying to add a motor to the drawing. I don't have the options that the YouTube video has.
Motors are added by selecting the tube you want it to be in, opening the edit dialog box for the tube and one of the tabs is "motor" check the box if you want the tube to be a motor mount and then how far you want it to stick out of the tube. You can then goto the motor cofiguration tab and add motors.
 
I too agree that the shop is probably advising you correctly about the E9 being under powered for your scratch build.

Scratch building is a lot of fun and a great way to learn more about rockets. Just remember that when it comes to thrust and weight ratios, don't worry about the letter designation of the motor, look at the initial, peak and average thrust. The E9 is a good motor for a light rocket you want to get up high. It is not very good for a heavy rocket even if it is an E motor. Usually a D12 will work better then the E9 in heavier rockets. Of course the composite AT 24/40 reloads will give you much more power and thrust and a huge selection of power ranges.

It's all part of what you learn building and flying mid power. BTW, the learning process doesn't stop, it continues up and through L3.
 
I would suggest doing simulations with 24mm motors 1st (AT 24/40) as they might not require nose weight for stability(and they might be all you want for performance). then if they don't work out switching to the 29mm motors. that is the nice thing about flight sims, try it before you start building and save yourself from extra work :).
Rex
 
Back
Top