Is there a max weight for the payload to hit the ground safely? I'm looking at a dead drop of about 2.5-5 lbs.

There probably is a max weight, but I will have to test that out and get back with you. Construction and durability of the parachute would not be a problem to handle 5 lbs. or more; however, it is the amount of air that can be contained within the parachute (drag) to lower the object at a reduced speed for landing safely which is in question. Off the cuff this size parachute is designed to handle ounces and probably not pounds. The calculator here: rocketreviews.com/index.php indicates that 5 oz. would require a 25 inch chute to slow to 10 feet per second (fps), which is probably what you need. I think 15 fps would be the speed an object falls without any parachute drag. Until I can test this out, I don't have a definitive answer. If you wanted to test this out for yourself you could easily take a plastic trash bag, cut a 24 inch circle from it and tape on 3 shroud lines at 6 spaced points from any string or heavy thread, and test different weights with it to see how much impact there is upon landing. The surface area of the chute to weight of the object ratio is what you are looking for. I will try to get back with you when I have time to perform some tests, but I am thinking this chute might be limited to about 6 oz. If you check out the link below you will see how complicated this can get from a math standpoint: van.physics.illinois.edu/qa/listing.php?id=2095

Where do you get those black fins in the instruction video?

If I am understanding your question correctly, the black fins in the video are balsawood fins painted black. We used to sell these 8 years ago before we release our screw-on red plastic StratoFins. You can make your own fins from a variety of materials like balsawood, coroplast (corrugated plastic), gift cards, cardboard, etc. The challenge is attaching them to a plastic soda bottle. Certain glues work, but it is messy and they are not removeable or transferable to another bottle once that one wears out so there is a down side.

Doing an egg drop from 4 stories for school, I am planning on construction a Soyuz to hold the egg, do you think this parachute would do its job?

Shouldn't be a problem for the egg. The 24" chute is rather large and will handle a fair amount of weight for a soft landing, but there are limits it all depends on the weight of your rocket. I have launched a 2 liter soda bottle with StratoFins attached, 2 keychain type video cameras and some weights to balance it out and the 24" StratoChute brought it all down gently. Not sure what the exact total weight was, but somewhere around 6 oz. I think. A typical size Large egg weighs about 2 oz., which is about 0.5 oz. more than the larger keychain camera I used. If you need to cut some weight you could use a Medium or Small size egg and shave off 0.25 - 0.50 of an oz. Keeping your rocket build as light as possible will be the trick.

How do they work and attach?

Parachute attachment requires either the StratoFins or your own glued on fins to a soda bottle. The shroud lines loop around each fin (total of 3), run along the side of the bottle, and are gathered together with a supplied cable tie. For further details check out the PDF instruction sheet:dl.dropboxusercontent.com/u/31996993/launcher/Parachute_Instructions.pdfNo additional hardware (no timer needed) is necessary for deploying the parachute. The way the parachute deploys is using gravity and it works most of the time, but not 100% of the time. The big factor is wind. The less wind the more likely it will work. The parachute is loosely folded up under the nose cone, which is not attached to the bottle. The air pressure against it on launch keeps it in place until it reaches apogee. As the bottle turns the nose cone falls off and the parachute deploys. What happens when it is windy is that the wind pushes against the nose cone as the bottle is turning at apogee. If the nose cone does not fall off, then the rocket nose dives into the ground. The beauty of the fins is that without a parachute the bottle just gracefully tumbles to the ground once the nose cone falls off. You never want to attach the nose cone to the bottle as this will just make it nose dive like an arrow. Also, what helps a lot is making sure that the rocket is heavier toward the fin side than the nose cone. Some people add additional weight (washers) which is fine, but don't add them past the center of gravity as it forces it to nose dive to quickly at apogee not giving enough time for the cone to fall off and the parachute to deploy. Weights are not required, but are optional or used to balance the bottle. Please check out our brief videos on how all this works: Shows the fins, parachute and launcher in action:youtu.be/jGixGWDSre4 Fin vs. no fin comparison:youtu.be/X2GJLsdAGwYKind regards,DonRelationshipware LLC

Product Dimensions	60.96 x 60.96 x 0.3 cm; 18 g
Fabric Type	Rip-Stop nylon
Is assembly required	No
Assembly time	5 Minutes
Number of pieces	1
Batteries required	No
Included components	Canopy
Import designation	Imported

24" Red Rip-Stop Nylon Parachute for Water or Model Rocket

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