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Elizabeth.mish wrote:In the rules manual, it specifies that shielding is needed around each propellor. For the lift propellor, I put mesh shielding on the top but no underneath the propellor. However I do have a skirt that prevents any parts of the propellor from flying out. Is this ok or do I need to put metal mesh shielding under the lift propellor as well?

Rule 3c says: "All propellers/impellers,including under the device, must have shielding which prevents a 3/8” dowel from touching them". So yes, it's required.

I apologize if this has been answered already.

My kids hovercraft was lifting all 16 rolls of pennies and doing very well. We realized that we had forgotten to put shielding on the bottom of the craft on the lift fan. They added wire screen . . . with holes slightly smaller than 1/4 per the rule. Now the craft will barely lift 11 rolls. I am assuming the wire is blocking air flow, but it suprises me that it is that significant in terms of weight lifted. Has anyone else had this problem . . . . and how have you corrected it? Bigger lift motor? Different angle to the lift prop?

reed303 wrote:

Elizabeth.mish wrote:In the rules manual, it specifies that shielding is needed around each propellor. For the lift propellor, I put mesh shielding on the top but no underneath the propellor. However I do have a skirt that prevents any parts of the propellor from flying out. Is this ok or do I need to put metal mesh shielding under the lift propellor as well?

Rule 3c says: "All propellers/impellers,including under the device, must have shielding which prevents a 3/8” dowel from touching them". So yes, it's required.

It depends on the design of your skirt. I have seen skirts that are only around the edges of the Hovercraft, so therefore if you pick up the device and look at the bottom the propeller is exposed. In that case, yes, you must have shielding of some kind per rule 3c. I have also seen skirts that completely cover the bottom of the Hovercraft except for small holes that allow air to escape. In that case, your skirt is also serving as shielding.

NilaiVemula wrote:

404ic wrote:

reed303 wrote:
S-O Battery policy says:
• insulate the battery terminals and attached wires when not connected;
• do not use bare wire at any time in the construction of your device;
• make sure that all wiring connections are properly insulated

https://www.soinc.org/sites/default/fil ... _18_17.pdf

We've soldered & shrink-tubed some connections, and used wire nuts for others.. You could also use crimp connectors for wire-to-wire splices. The connections to lugs on motors and switches were soldered.

Is it okay if I use electrical tape to insulate the wire connections?

Yes, but most electrical tapes start to melt above 250°F, so make sure you don't have connection points that get hotter than that.

Wait, so to sum this up, alligator cables + electrical tape <250°F should suffice?

Also, am I allowed to use two batteries, both 9v to power different motors? I was planning on having two circuits, one for each motor, each powered by their own 9v battery (this would also need two different switches; is this okay? I checked the rule manuals and it appears to be fine... but I'm not entirely sure).

404ic wrote:

NilaiVemula wrote:

404ic wrote:
Is it okay if I use electrical tape to insulate the wire connections?

Yes, but most electrical tapes start to melt above 250°F, so make sure you don't have connection points that get hotter than that.

Wait, so to sum this up, alligator cables + electrical tape <250°F should suffice?

Also, am I allowed to use two batteries, both 9v to power different motors? I was planning on having two circuits, one for each motor, each powered by their own 9v battery (this would also need two different switches; is this okay? I checked the rule manuals and it appears to be fine... but I'm not entirely sure).

Yes. You should be good on both accounts.

404ic wrote:

NilaiVemula wrote:

404ic wrote:
Is it okay if I use electrical tape to insulate the wire connections?

Yes, but most electrical tapes start to melt above 250°F, so make sure you don't have connection points that get hotter than that.

Wait, so to sum this up, alligator cables + electrical tape <250°F should suffice?

Also, am I allowed to use two batteries, both 9v to power different motors? I was planning on having two circuits, one for each motor, each powered by their own 9v battery (this would also need two different switches; is this okay? I checked the rule manuals and it appears to be fine... but I'm not entirely sure).

I assume alligator cables would be fine, although not entirely recommended. Just make sure there's no bare wires. And yes, you're fine to have 2 circuits. You could also use a 2-pole switch if you want both circuits to be hooked up to a single switch.

Just to make sure, is it okay for the propeller shielding to be soft so that if you pushed with enough force (more than a gentle poke) you could still touch the propeller?

I'm using a very thin and stretchable material and I'm not sure if it will earn a construction violation.

Has anyone ran into any issues using thin mesh-like material as shielding?

EcoDyne wrote:Just to make sure, is it okay for the propeller shielding to be soft so that if you pushed with enough force (more than a gentle poke) you could still touch the propeller?

I'm using a very thin and stretchable material and I'm not sure if it will earn a construction violation.

Has anyone ran into any issues using thin mesh-like material as shielding?

I think that will hinge on the supervisor's definition of the word "shielding." Clearly a thin, stretchable material can prevent a dowel from touching the propeller. I think, however, that the use of the word shielding specifically implies that the covering must protect users from accidental contact with the propeller. If I were the ES, I would apple the rule in that spirit.

If your covering resists (for example) a poke of a finger, then I would say you are fine. If I can poke it with my finger (or the dowel, which is really a simulated finger) and stretch it into the blades, you aren't really providing "shielding."

EcoDyne wrote:Just to make sure, is it okay for the propeller shielding to be soft so that if you pushed with enough force (more than a gentle poke) you could still touch the propeller?

I'm using a very thin and stretchable material and I'm not sure if it will earn a construction violation.

Has anyone ran into any issues using thin mesh-like material as shielding?

Don't buy mesh with several small holes. It's adding a lot more mesh as well, and my hovercraft wouldn't even move forward due to the restricted air flow.
I think it's best to keep the holes as close to 3/8" as possible.

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The benefit from mass score score is based on relative performance, and I wanted to gauge how much mass most people can lift. I can lift the 16 rolls regardless, but the additional mass can cause other complications that can decrease accuracy. As for the accuracy, I am usually within ~1 second and would like to dial this in before states. How do you all compare? And for those of you who use DC motors, have you had issues with your motors eventually degrading? Many friends of mine report them having to replace their motors 2-3 times, whereas I have only had to do so once.


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