SkyAngle Frequently Asked Questions Table
of Contents
How do I chose the proper SkyAngle size for my rocket?Our sizing may be a little different from what you are used to. The enhanced drag characteristics achieved by the unique SkyAngle design tends to defy the old guidelines with respect to recovery. You need to know three things in order to make choosing the right SkyAngle a breeze: 1. Recovery weight of the rocket. For safety margin we consider this to be equal to the pad weight.2. Target descent rate. This is the speed (usually expressed in feet per second, or fps) at which the rocket will fall to the ground. The old rule of thumb was to shoot for a 15 fps rate. This may be a good guideline for low power cardboard and balsa rockets, but we feel it’s too conservative for modern high power rockets. With today’s building materials and techniques, rates between 17 - 25 fps can be acceptable. However, specific factors (rocket design, ground conditions, etc.) have to be taken into consideration upon deciding what rate your particular rocket can handle. No parachute maker or seller can or should make this determination for you. It’s strictly the builder’s call! 3. Capacity of the Chute. Every parachute has a given capacity to decelerate a fall to some extent. What a rocket flyer needs to know is what that capability is. Determining load capacity is the responsibility of the parachute manufacturer. (We’ve found that many rocket recovery companies either have not performed adequate testing on their products or over-rate the results of what little testing they have done. We had each of the SkyAngle models extensively tested by an impartial authority on aerodynamic decelerators so you can make an informed choice with confidence.) The following table organizes the results of this testing in an easy to use format:
Depending on the weight of the rocket in question, a flyer can easily tell what kind of descent he is likely to get with any given SkyAngle using this table. For example, if you have a rocket with a pad weight (fully loaded, with motor) of 6 pounds, you can use a Classic 36 and expect a descent rate of a little more than 25 fps. If you select a Classic 44, the descent rate will decrease to right at 20 fps. Choose a Classic 52 and the fall will be below 17 fps. The idea is to pick the chute that has the load capacity that yields the target descent rate the rocket can safely handle. (Please note these rates were normalized for sea level altitudes and will increase at higher elevations.) Our advice is always to err on the conservative side and deploy a size larger when conditions dictate or when uncertainty exists. For more info, check out Jordan Hiller’s excellent online calculator for determining the exact descent rate of any SkyAngle model with a user-specified recovery weight. How does the cord lock work on the SkyAngle?Our suspension line lock is standard on the Classic and Classic II SkyAngle parachutes. It allows you to adjust the inflated diameter and panel flare of the chute, thus altering its drag profile. By raising the lock toward the canopy, the payload will fall faster than it would with the lock toward the swivel. This feature can be used to adjust a larger size SkyAngle to work with a lighter payload than specified. It can also help minimize excessive drift during high winds. How much space does a SkyAngle take up in a tube?SkyAngle Packed Length PDF file
Why is your balloon cloth preferred as the material of choice in the SkyAngle CERT-3 & Classic II series?We purchase our 1.9 oz silicone coated fabric from the mill as "balloon cloth", which is a generic designation for a specific class of nylon fabric. We find it has particularly desirable rocket parachute properties. It is a zero-porosity, extremely strong ripstop material that’s perfect for the more rugged demands of big or complex projects that may experience high speed deployments. It’s slightly heavier and doesn’t pack as tight as our 1.3 oz. material used in the Classic models, but it is considerably tougher. Initial studies indicate that our balloon cloth actually expands slightly during canopy inflation which somewhat increases the parachute drag profile. I’ve heard your warranty service is second to none. Is it?We believe so, and our customers seem to agree. We warrant all our products for life against specific defects in materials or construction. We’ve even repaired a number of chutes over the years for tears due to snags at no charge! We want every SkyAngle product out there to be in top condition. All we ask is that the consumer pay the freight to and from our facility. See our Legal page for details. How does the swivel aid in the recovery process?All rocketry parachutes may tend to spin. Without a swivel the recovery lines are subject to excessive rotation and entanglement as a result. Inclusion of a swivel will keep your rocket as stable as possible and minimize the chance of reduced chute performance and fin damage. Our swivel assembly is fabricated from heavy duty nickel-plated brass and is incredibly strong. In fact, the 1,000 psi test swivel on the Classic series is actually rated stronger than the 3/8" tubular nylon suspension lines it attaches to! We supply a 1,500 psi version of this swivel on the CERT-3 and Classic II series. This is stronger than many quicklinks currently in use in our hobby. With thousands of deployments out there we have never had a swivel assembly fail. Do you sell direct to the consumer?No. We sell exclusively through a limited number of authorized dealerships in the USA, Canada and the UK. We think they are the best of the best in our hobby. They are an important reason for the success of the SkyAngle and it would be dishonorable for us to compete against them. We at b2 Rocketry are always available to work with you, but we ask you to support one of our dealers when it comes time to purchase a SkyAngle product. Why are your Drag Coefficient (Cd) numbers the highest of any chute on the market?Because SkyAngles perform unlike any other chute on the market. Our extended panels "flare" under load which increases the drag substantially over a standard chute. Our calculations derive from independent testing and quantify this. Coefficient of Drag (Cd) calculations require a reference surface area to compute. In the case of the SkyAngle numbers, only the circular "cap" surface area is used as a reference. If the entire surface area (including the extended panels) was used instead, the resulting Cd would be somewhat smaller. We do it this way so you can compare our drag fairly against that of typical circular chutes. Don’t get too hung-up on Cd’s though. What really matters is the actual descent rates, which in our case are well documented. Do you run tubular nylon around the SkyAngle canopy?Absolutely. In fact, SkyAngle was the first commercially available hobby rocketry parachute with mil-spec, woven flat tubular nylon suspension lines. Every model made since it’s introduction in 1996 has featured a single piece running in a continuous, uninterrupted path outside the canopy. The result is unparalleled strength and support not found in any other brand. Why do SkyAngles spin? How is that an advantage?The spinning property of the SkyAngle is an extremely beneficial characteristic. Basically, the rotation of the SkyAngle results from an "trim asymmetry" that is sewn into the chute which amplifies the natural tendency of the chute to spin. Spinning is load-sensitive with SkyAngle parachutes, which means the heavier the weight deployed the greater the revolutions. Furthermore, SkyAngle spinning is more acute in the smaller sizes than the larger ones. The main benefit of spinning is that it dramatically decreases the unstable oscillation, pulsation and sway often seen in other chutes. There is also evidence that the rotation helps to regulate air pressure under the canopy, which prevents canopy collapse (and eliminates the need for a spill-hole). Spinning plays a small part in the flaring of the extended panels which contributes to drag. Spinning certainly aids in tracking of the chute at altitude, especially when coupled with our contrasting multicolored panels. By integrating our heavy-duty swivel assembly, tangling of the lines and rocket damage is virtually eliminated, as the chute spins but the rocket does not. What’s the advantage of the SkyAngle deployment bag? Is it really designed to bring the nose cone down separately?Precisely. We didn’t invent the free bag concept, but we were first to commercially market it as a system for deployment in the rocketry hobby. It’s a smart, reliable way to ensure an uncomplicated deployment at a low cost. Our bag design envelopes the main chute in a flame-resistant Aramid® fabric while containing the suspension lines for an orderly, untangled exit. The main chute is attached to the airframe shock cord as always. But the bag is tethered to the nose which is equipped with its own chute. The benefit is that, upon ejection, the nose goes its separate way pulling the bag with it. The main is allowed to inflate without interference from the nose, the bag or the shock cord. It’s just about as foolproof as you can get. We recover this way almost every flight now and after hundreds of flights we have never had or heard of a single failure using this approach. This sure isn’t the case with other style bags. They tend to be pulled on both ends simultaneously which traps the main inside like a Chinese finger puzzle, often causing a failure to fully deploy the parachute. |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
