1st L1 Project - LOC Mini Magg 5.5

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RobertH3

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It looks good - took more time on the guts than I did and added nicer hardware. Mine is sturdy but since I went a little overboard, weighs a bit much. Chute sizing: depends on Cd of the parachute and the weight. Rocketman has a nice table and there are calculators. I shot for 15 fps landing speed and this means my Magg will only fly on lower wind days or with a Jolly Logic unless I need aerobic exercise.
The scary moment for me was pouring the fillets - followed the 'masking tape and spread' with 5 min epoxy and it turned out great. Scare was from thinking about sanding out an epoxy mess-up.
 

DAllen

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I've done similar things to rockets like the aft reinforcing ring for much the same reason. What I do instead is usually cut a length of coupler that fits the tube and basically glue it right where you have that reinforcing ring. The ring you have would work better though without adding a bunch of weight to the wrong end of the rocket.
 

Jozef

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Very nice build. Some thoughts on finishing. CWF thinned and applied with a 2 inch foam brush. Block sanded with 220 then two coats of Minwax Polycrylic satin finish applied to fins and airframe. Block with 320 and apply Duplicolor filler primer and block sand till happy. Nosecone is scuffed with 320 after soap washing. apply adhesion promoter and follow up with filler primer and sand till happy

IMG_6684.JPGYsQmKU3xSOmsszsX4VIHdw.jpg
 

Jozef

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Block sanding process. I get firm foam sanding blocks from an auto body supply shop and cut to desired sizes as needed.

IMG_6694.JPG
 

PromptSupercritical

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Block sanding process. I get firm foam sanding blocks from an auto body supply shop and cut to desired sizes as needed.

View attachment 417820
Very nice. I am working through a similar process. I think I may adopt more of the technique you are using though.
Taking my time either way as I am not in a hurry.

I received my AT 38/480 and 720 cases (yeah!). I also picked up the adapter kit plus the delay tool.
I constructed and Excel chart with all my weights so I can accurately get my all up weight calcs for flight sim.

Last night I ordered an Eggtimer Quantum and a WIFI switch - looking forward to building those.
 

PromptSupercritical

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So I am considering converting the nosecone to an avionics bay with an accessible section in the tip for CG adjustment.
I figure the ET Quantum can ride there and it will help balance the rocket by default.

Thoughts?
 

PromptSupercritical

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Hey what's everyone doing for some sort of elastic shock cord in addition to the standard nylon chute cord?
I feel like there should be an elastic segment to absorb the ejection and chute deploy.
 

Nytrunner

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So I am considering converting the nosecone to an avionics bay with an accessible section in the tip for CG adjustment.
I figure the ET Quantum can ride there and it will help balance the rocket by default.

Thoughts?
Good plan! A common technique is to have a smaller diameter tube through the center of the cone that holds the electronics, and epoxy/lead shot in the annular area outside that tube. You can get a centering ring just past the lip of the nosecone shoulder, and use t-nuts to bolt a removable bulkhead that acts as recovery anchor point, and can hold the sled that the electronics are on.

Hey what's everyone doing for some sort of elastic shock cord in addition to the standard nylon chute cord?

As rocket kits get larger, the pieces' mass gets higher, and the recovery forces get much harder.

Stronger "recovery harnesses" are used instead of "shock cords". Upon ejection the pieces are deployed and slow down in the air instead of snap back/stretching like with elastic cords.

Nylon does have a bit of stretch. Kevlar does not.
You can get a little bit of energy dissipation by taping looped bundles in your cord (look up Z-folding)

Some folks use the rule of thumb where their harness is 5x the length of their rocket.
Others say "10 ft longer than the tallest tree at your field"
I like using tubular nylon 3x the length of the longest section its attached to.

Some folks will put a slightly shorter length of nylon in parallel with their kevlar
 

mbeels

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Hey what's everyone doing for some sort of elastic shock cord in addition to the standard nylon chute cord?
I feel like there should be an elastic segment to absorb the ejection and chute deploy.
I'll second the Z-fold. You can tape entire bundles together, or tape individual Z-folds to help dissipate energy during deployment. It works; if you tape enough segments and you have some segments left with unbroken tape, you know that when the shock cord reached its maximum displacment, there wasn't enough energy left to break those last bits of masking tape. Something to check during ground testing.
 

Jozef

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Hey what's everyone doing for some sort of elastic shock cord in addition to the standard nylon chute cord?
I feel like there should be an elastic segment to absorb the ejection and chute deploy.
Not recommended for high power. Long harnesses in kevlar or nylon are the standard for HPR. 20 feet is adequate for the Minie Magg. The length allows the airframe components to separate and handle any stress. Elastic and rubber bands reserved for LPR. Many use smaller diameter kevlar or nylon for LPR as well
 

AfterBurners

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Rail guides...I'm going with the aero style (black). The white nylon conformal guides fit the tube perfectly, just going to save those for now.
I think the black ones would create more drag. You could always bevel the edges and use a coat paint adhesive spray to hold the primer and paint.
 

Handeman

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Hey what's everyone doing for some sort of elastic shock cord in addition to the standard nylon chute cord?
I feel like there should be an elastic segment to absorb the ejection and chute deploy.
I don't use any elastic on HPR. The key is to not use too large of deployment charges, then you won't have the large shock loads. "Blow it out or blow it up" is counter productive.
 

PromptSupercritical

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Ok no special springy bit...just pure almost unstrechable shock cord with copious Z-folds (that is a good idea...)!
 

fyrwrxz

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I’ve built three, the last two with custom centering rings for (2) outboard 29’s. just have to watch your cp/cg. Avionics in the nose. Next one is 5.5” upscale. Yup, kinda stuck in a rut, but I love these birds. Metal storms look great as the plume stretches out by the vacuum effect from the large dia tube. I use the old school alaly conformal lugs, Just cut one in half and use both pieces spaced out. Good flights, my friend. Straight smoke and good chutes.
 

DAllen

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Elastic shock cords are great for hanging rockets from your basement ceiling.
 
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