RigMaster questions and honest answers

Yes, for every calculation. Sling tension, sling angle, hitch capacity, the angle chart, load weight and the PDF are all worked out on the device, no exceptions. A connection only comes into it for ads in the free version and for buying or restoring Pro — and if you already own Pro, opening the app with no signal doesn't take it away.

No. There is no login and no sign-up. Your saved calculations and settings live on the device, and purchases are tied to your Apple ID by the App Store.

Sling Tension with 2 legs (by angle or by length and height), Hitch Capacity, the Angle Reference chart, Save, History and sharing a saved result as text are all free, with ads. Pro adds 3- and 4-leg bridles, Unequal Legs / CoG Offset, the Load Weight Estimator and the Lift Plan PDF, and removes the ads.

Both. Pick Imperial (lb / ft) or Metric (kg / m) in Settings or from the Units menu in any calculator, and every field converts at once. Lengths are decimal feet or metres, so there is no feet-and-inches entry. Saved History keeps the units it was saved in.

With Pro, yes: the Lift Plan button on Sling Tension, Hitch Capacity, Unequal Legs and Load Weight makes a one-page PDF with the inputs, results, notes lines and Prepared by, Signature and Date lines. Only Sling Tension, Unequal Legs and the Basket hitch sheet include a diagram, and the Angle Reference chart has no PDF. Without Pro you can save a result and share it from History as plain text.

No. RigMaster is an estimation aid for qualified riggers. The sling tag, the manufacturer's data, the crane's load chart and your site's rigging plan always come first, and a competent person makes the call.

Yes. It is a universal app: on iPad it shows the calculator list and the open calculator side by side, in any orientation. On iPhone it runs in portrait only.

The math itself is plain trigonometry: tension equals each leg's share of the load divided by the sine of the horizontal angle, rounded to whole pounds or kilograms. Eyeballing the angle is a common source of error — mistaking a 50° angle for 60° quietly adds real tension. Measure the sling length and height instead of guessing the angle, and the number gets a lot more honest.

It does not block anything. Below 30° the number is still shown, under a red Below 30° — NOT permitted by standard rigging practice. placard. Between 30° and 45° you get a yellow caution, and below 5° there is no result at all.

Because the default Load Type is Rigid, which assumes only two legs actually carry a stiff load such as a beam or a machine base. Switch to Flexible only when the load can deflect enough to keep every leg tight; then the load is shared by all legs.

No. Unequal Legs needs you to know how far each lift point is, horizontally, from the center of gravity, usually from drawings or the manufacturer. Given those distances it splits the load and gives each leg's tension, assuming the hook sits directly over the center of gravity.

No. It documents the rigging calculation only. It has nothing about the crane configuration, radius, boom length, load chart, ground conditions or exclusion zones, which a real lift plan must also cover.

Only as a warning. The choker result is a fixed 75% of the tag rating, and a note reminds you that a choke angle under 120° reduces capacity further and to check the sling chart. The reduction itself is not calculated.

It is volume times a typical published density for 13 materials, so treat it as an estimate. Real alloys, rebar in concrete, hollow parts, contents and attachments all change the true weight. Shipping papers, a nameplate or a load cell always beat the estimate.

Only to show ads in the free version. If you tap to decline, you still see ads, just non-personalized ones. The app asks for no camera, location, photos or other access, and Pro removes the ads.

On the device only, in History, newest first. There is no iCloud sync and no CSV export. Swipe right or long-press an entry to share it as text, and swipe left to delete it.

Open Settings and tap Restore Purchases while signed in to the same Apple ID. If nothing is found the app tells you so. Manage Subscription in the same section opens Apple's subscription settings.

Yes. Text Size in Settings offers System, Large, Extra Large and Huge, which override the phone's text size for reading at arm's length. Appearance can be System, Light or Dark.