There has been an overwhelming amount of interest in BAMA Recovery Systems lately, and this tells me that people are wanting something different in the recovery department. This has led me to think about what can be offered to support demand while focusing on custom, unique, and affordable.
A few things to look forward to in the coming months:
-first, generic shaped chutes will become a thing of the past (unless of course it is a custom order requiring the specific shape).
-Rotating chutes will become available in sizes up to 15ft in diameter
-Current plans will place chutes into 3 different categories; foods, items, and spinners.
-Food chutes will include chutes like the donut chute, the ice cream cone, the marshmallow, the pumpkin, with more to come.
-Item chutes will include unique chutes such as the UFO, the bed sheet, wiggle tubes, and in development are capsules
-Guided chutes will hopefully be coming out next year. This system will guide a payload back to the point of origin (launch pad). There will be a high wind system and a low wind system. If the demand requires, there will be a high altitude system as well.
-Custom chute estimator worksheet/ table
How does this affect you now? Some items have already been eliminated either due to material or time constraints. Cost is/ has gone up on a few products. None of this will have any effect on custom orders.
The fun and easy part for me is sewing the gores together. I prefer the french fell seam, but truly any seam will work with the smaller canopies. I won't go into great details on sewing techniques or machine set up, but if you have questions comment below.
First step is simply joining the gores together.
Next are the hems. I put reinforcement tape in the hem to ensure that in the even of a seam failure the tear does not cause a total canopy failure.
Now the canopy is finished, next will be attaching the lines. I don't have any photos of this step simply because the manner in which I attach was very expensive to set up and places BAMA Recovery Systems' parachutes in front with the smallest possible lines on large parachutes. Some notes though: use a zigzag on larger lines, run the stitches off of the line and onto the canopy and off the canopy and onto the lines in order to have an even distribution of force, and attach on the part of the seam with the most material (this means if you have a basic flat seam to fold the material to one side and sew on top of that not on top of the stitch line).
After or even before line attachment you will create those loops using a finger trapping method. Unsure the marks are lined up and that you secure the insert with either a stitch or by inserting the loop through the insert in a sew-less method.
After the lines are attached and looped comes rigging. The center line will feed through all of the pull down loops and the risers will group the main suspension lines into either 2,3 or 4 groups. Everything is secured by a girth hitch. If you have trouble figuring it out let me know. The joining of the risers and center line can be done with a link, another riser, shock cord, etc.
Cutting lines might be the most tedious part of this build. There are 4 different lines to cut; the risers, center line, pull down lines, and the main suspension lines. The line lengths are crucial and attention to detail is important.
First, decide on how much line you want to sew onto the canopy. Chutes in the sizes listed will do best with sewing 2-4" of line onto them. This dimension will be added to you Ls and Lp lengths. All of the lines have one or two loops on them. The loops are formed by "finger trapping" the line within itself. I have found that loops between .75"-1.25" are the easiest to work with. Basically what you need to know now is that the marking for the loops is 2x the loop size. My loops are .75" so my loop marks are 1.5". Center this mark on the line length dimension so that when the loop is formed it is in half on the dimension mark.
In the pictures you will see how I lay out, mark and cut. I use masking tape on a table or even the floor for longer lines. The end that is sewn on the canopy is the critical end. The other end is inserted back into the lines so it can vary a little but make sure it is longer than 2". If you have any questions ask in the comments.
Pictured are the risers and the pull down lines.
Using the table in the previous post, find the A,B and Hg dimensions for the parachute size you are wanting to build. I will be building the 4ft version.
First step is to make the template. I have found that using poster board is the easiest.
1) Mark a line down the center of the poster board (if the pattern is bigger than the poster board, tape two or three together)
2) Decide your seam allowance. This will depend a lot on how you are going to construct the chute. I usually do a 3/8" rolled (double fold) hem on the top and bottom. To join the gores together I use a 1/2" French felled seam. You can do rolled hems, serged edges, overcast, hot cut, etc. If you need an example and can't find it through google, comment below and I'll add a picture of whatever seam you're asking about. Basically you are going to determine how much extra fabric you will need to make the seams. A 3/8" rolled hem needs 3/4" of material to complete. A 1/2" French felled seam requires 3/4" to complete.
3)Starting from the bottom, mark you required hem seam allowance (3/4" in my case) and draw a horizontal line.
4) On this line, mark the A dimension centered on the center line. From those marks, add your seam allowance and mark.
5) From the horizontal line, measure and mark a parallel line using the Hg dimension.
6) On this new line, mark the B dimension centered on the center line. From those marks, add your seam allowance and mark.
7) Connect the marks. Make sure that the lines extend beyond the top horizontal line.
8) Measure up from this horizontal line the hem seam allowance.
9) Cut out the template.
10) Lay out nylon. Ensure that it is bigger than the template. You can use scissors, rotary blade, or any method that works to cut out. You can cut out individually or all at once. I personally fold the nylon and cut all of the gores at once. Do a final count to make sure you have enough gores cut for your chute.
Bellow you will see my template with the seam allowances shaded. I have marked the A, B and Hg lines. I used a rotary cutter and a ruler to cut out. Weight on the template will help the template and nylon from slipping. The chute will be white and neon pink.
The next few post will detail how to construct a high performance conical chute with the vent pulled down. It is commonly referred to an annular or partial elliptical chute. I have already gone through the designing phase in order to make these instructions simpler. First I will go through some basic terms and dimensions of the parachute.
Quick disclaimer: This tutorial is provided for personal or educational use only. The manufacturing with the intent to sell is strictly prohibited. If you have any questions or would like the ability to manufacture and sell these contact Ben@bamachutes.com.
This parachute is a 30 degree conical with a 25% Do (diameter open) vent that has been pulled down 30%. The Le (effective line length) is 1.35*Dc. The Cd (drag coefficient) is expected to e around 9.7-1.2 when using the Do (diameter open/ nominal) as the reference area.
Do=diameter open or nominal diameter
Dp=diameter projected (not used in construction, but a good term to know)
Dv=diameter of the vent
N=number of gores or panels
A=gore cutout dimension of the lower or skirt portion
B= gore cutout dimension of the upper or vent portion
Hg=gore height as measured from the center
Lp=length of the lines running from each gore at the vent to the center line
Lc=length of the center line
Ls=length of the suspension lines
Lr=length of the riser
Le=length of the overall effective lines (Ls+Lr)
The dimensions given are in feet and do not include seam allowances because of the variety of seams that can be used. The next post will go over template and cutout.
One of the most important factors when dealing with chute selection is the performance. For most, the performance comes down to weight, pack size, and how much it was safely land. In the next few weeks BAMA Recovery Systems will be releasing a budget line of quarter-spherical chutes. Why was this shape chosen?
The construction of a chute plays a big role in the price. This leads to a few chutes that are easy to construct; flat, (uni)conical, spherical. The spherical chute has the best performance out of these three because of high drag and lower opening shocks. But there can be many variations of a spherical chute. A true spherical would be very heavy and not the most efficient (think ball) as a main parachute. As the percentage goes down the chute goes through a range of efficiency.
A three-quarter spherical chute is extremely stable and offers a nice shape, but as a main is tends to be to bulky and heavy. The drag is also slightly lower than that of an optimal spherical design. (example: supersonic X chute) CD: .65-.75
A half spherical chute or hemispherical chute offers a good amount of drag and stability. A lot of the stability comes from the pulling in of the skirt that happens because of the lines. Since the shape is constructed perpendicular to the line of travel, the lines easily decrease the mouth of the canopy. The drag comes from the amount of material used in the chute. This is good for drag, but bad for bulk and weight. CD: .75-.80
Next comes the sub-hemispherical chutes. NASA did a lot of testing to find a chute that was light, packs small, and is stable. This led NASA to test a lot of spherical chutes that ranged from 10% spherical to 70% spherical. The testing showed that for most applications where weight, bulk, and stability were most important, a spherical chute in the 22%-30% spherical range was optimal. This is due to the shape of the constructed canopy to continually push against the lines and open the mouth of the canopy. Modern high-performance canopies follow this shape because of the benefits. Manufacturing was eased by making the canopies poly-conical, but the cones follow the quarter-spherical shape. CD: .85-.95
The release of the new quarter spherical line will begin with 20, 48" orange/white chutes. Then it will be 20, 36", then 60", then 72", all the way up to 96". The prices will be amazing and are set at only $5/ft+$5 to cover shipping and packaging materials. This means that the 48" will only be $25 and the 96" will be $45. These chutes will have the amazing NASA orange/white pattern and will look great clustered.
There will always be a debate on what the best parachute is, who makes it, and why it is the best. But what is the best chute?
There are more factors in chute selection than I care to list, but the main ones tend to be the performance, the price, and the look. Some one would be able to make list of the best price and maybe the best in certain performance areas, but I honestly don't believe that anybody can create a list that will direct you to the best chute. Why is this? Because the best chute is only the best chute for that specific project. This can be very confusing when shopping for recovery items, so ask the manufacturer what they recommend and if they can meet your needs. Here at BAMA Recovery Systems, we try to provide a wide range of product to provide that perfect chute, but we cannot fulfill every need. If we are ever unable to fulfill the needs, we can certainly recommend somebody that can.
In the end, the best chute is the chute that meets all of the criteria for your project. And remember that the only way to get the perfect chute is to ask questions .
The length of the suspension lines is very important and has a huge effect on canopy performance. I get quite a few questions about why lines are so long, can you shorten them, why so many? It can be a little frustrating to untangle and repack long suspension lines (ask about the video on how to quickly untangle lines), but hopefully after reading this you will see that your frustration pays off.
For most parachutes, the recommended line length is 1.2-1.6 times the nominal diameter. For most of the BAMA chutes, the line length is 1.4-1.5. This means that on a 10ft diameter chute the lines are going to be around 15ft long! What if we went with shorter lines?
When the parachute is inflated the lines are trying to straighten parallel to the vertical axis. In other words, the lines don't want to spread out. It is the air pressure inside of the canopy that forces the lines apart. This becomes a battle of forces and physics can be in our favor. *experiment* Take (imagine) a string and attach it to one end of a table. Take the other end and attach it to an elevated anchor on the other end of the table (the longer the table and the higher the anchor point, the better the demonstration will be). The line should be straight and tight. Now starting from the end attached to the table, make the line lay flush on the table as you travel to the elevated anchor. If you anchor is not secured to the table you will notice that it has fallen. If the anchor is tight you will notice that the force to push the line down becomes greater. This is the same action in a parachute. The shorter the lines, the more outward pressure is needed to inflate the canopy to full inflation.
To drive home the point here are some numbers. Using the same 10ft diameter chute, we will get an inflated diameter in the neighborhood of 75% (some canopies are more, some are less). Not accounting for the exact profile and cross section area, that chute would have an inflated diameter of 7.5ft and an area of 44.18ft^2. If we shortend the lines to a point that decreased the inflated diameter by only 5% of the inflated diameter, the chute would have an open diameter of 7.125ft and area of 39.87ft^2. If a q (dynamic pressure) of .5lb is used then the full length lines would have a drag of 22.09lb and the shorter lines would have a drag of 19.94lb. That is a difference of 2.15lb! This is why the line length is so important to the performance of your chute.
Any hobby that involves a vehicle or payload being recovered from the air tends to be expensive. Rocketry is no exception. Larger rockets can end up costing hundreds and even thousands when they are ready to launch. Unforeseen expenses drive the cost up or hurt the budget of another assembly/ system. And though it's always important to take time and design a rocket that fits your budget and performance wants, I continually receive feedback about waiting to plan and design recovery until the very end.
One of the first things that I do when bouncing around ideas about a new rocket is figure out what I want the rocket to do. Do I want fast, loud, high, unique, slow and heavy, carrying a payload, replica scale, etc? Throughout this planning I continually think about performance in the way of strength/ weight and how many times I want to fly it. Eventually I start thinking about landing and the what if's. Should I angle the fins up or mount them higher to avoid a fin hit? Can the fins handle a hard landing? Do I want the rocket to land standing up or on it's side? And I arrive at a "do not exceed" landing speed. I pick this number prior to even ordering the components to build the rocket. It will keep me "honest" later when it comes time to purchasing the recovery components. I finalize how I want the recovery set up, but hold off on ordering the actual chutes.
My heavy hand when it comes to epoxy and fillets tends to add some weight to the rocket before it is complete. A quick paint job can be a lot lighter than a nice glass smooth surface. I wait until final weigh in before placing the order on my chute (or in my case design and build). The "do not exceed" rate of descent that I determined will tell me what I need to order as far as drag. The chute might end up a little larger or smaller than previous estimates, but shop around in a smart way. A lot of people I talk to, look at chutes in simple terms such as what size the chute is. I feel that this would be like setting a food budget, going to the store, and purchasing items based off of the package size and not the contents. Being thrifty, I look at the price per unit to determine the best deal. When it comes to chutes the same can be said. So how much is an ounce/ pound of drag costing you?
No two chutes are the same and the Cd (drag coefficient) only tells you part of the story. Some chutes may seem like a great deal, but you may be paying more per drag than a more efficient chute. A great comparison would be flat chutes compared to hemispherical. Lets compare the two in a 6 ft diameter at 15fps. The flat chute can support ~5.68lbs and the hemispherical chute can support ~6.9lbs. Assuming similar material (1.1 oz nylon and spectra lines) and construction the flat would cost ~$55 and the hemispherical would cost ~$65. This puts the flat at a ratio of $9.68/lb and the hemispherical at $9.42/lb. If these were items in a grocery store you would choose the hemispherical based off of this. Now heavier or lower quality can change these values, but when you compare factor in your need for durability and chute weight. If the weight is not a concern then use heavy chutes in your comparison. If durability is not a consideration, then find chutes that will last just a few times. But in the end, if you are looking for performance don't assume that just because one 6ft chute is cheaper than another that it is the better deal.
*Note: A concept that I am considering is chute rentals in the larger sizes >12ft. These chutes tend to be very expensive and are only used a few times, usually for cert. or university testing flights. The cost would be considerably less than purchasing the chute and would allow people to also try before they buy if they use chutes in that size quite often. Let hear your feedback on this concept and tell me your concerns or suggestions.
After the most recent capsule recovery test performed by SpaceX, I have had a few people asking about clustering. I will address some of the advantages and disadvantages and how to properly cluster.
Clustering can be one of the most exciting things to perform with parachutes. Seeing a mass of nylon sniveling in the air before it fills into 2,3,4 or maybe even 12 parachutes. I remember the first time I watched a military payload get dropped out of the back of a plane. This specific payload had 5, 100ft diameter parachutes that were clustered together. It almost looked as if they inflated in slow motion due to the immense size of each chute. As I watched more and more, I noticed that they parachutes interacted with each other. They looked like they were playing a game where they would just barely bounce together and drift apart and continue doing this until the payload hit the ground. I now have a better understanding of what is going on in clustered systems and I have even designed a few.
-it looks amazing
-more redundancy if one chute fails
-can be more cost effective to buy smaller chutes than one large chute
-entanglements are more of a risk
-there is a small loss in individual parachute efficiency
-bulk/ packing size
-complicated to pack
-will drift with the wind more
If you are wanting a cluster in your project, weigh out the pros and the cons and ask if you feel comfortable enough to pack the parachutes. If you determine that you want/need a cluster make sure that you set up your system for success.
When parachutes are clustered they interact with each other because they are pushing air out of the bottom of their canopy. This will force canopies apart. When the canopies go away from being directly over the center of the payload, they have a slight angle that "spills" more air out of the bottom. The "spilling" reduces the parachute's efficiency by almost 3% per additional parachute added. One way that you can force them together more is to lengthen the suspension lines by adding a riser (shock cord or heavy suspension line). Basic rule of thumb in a cluster is that the line length (including riser) should be at least 1.5 times the diameter of the parachute. Almost every parachute offered by BAMA Recovery Systems already has this length of line and would not need a riser, but if you are not using a BAMA chute check the overall line length. Also make sure that you adjust the drag coefficient in your sim/calculations to reflect the loss of drag.
If you are wanting/needing a clustered systems for you project, whether you are wanting just a look (Apollo 11 commemoration flight) or looking for the performance, ask us first to see how we can help.