Scioly.org

Entomology wrote:Is hovercraft relatively about the same difficulty the same for both divisions? I want to know if my Div B resources and Div C resources for hovercraft are interchangeable.

I have only written a test for/run hovercraft once, but from what I imagine, they are fairly different in difficulty. I helped run and write the test for B division Mentor, and I initially wrote the test for C division. I thought it was a fairly easy test so when I modified it for B division, I changed just a few things, mostly removing the fluid mechanics questions. When I showed it to my coach from high school who I was helping run the event, he pretty much threw out about half the test deeming it way too hard for B division and replaced it with some much easier stuff. Even having removed all of the "hard" questions, the highest score on the test was still less than a 70% and there were many teams who got less than 25%.

For batteries I am considering either 8.4v NiMH batteries or 7.4v LiPos. Which would be better for this event?

ericlepanda wrote:For batteries I am considering either 8.4v NiMH batteries or 7.4v LiPos. Which would be better for this event?

There was a very good discussion with a lot of details earlier. From what I've noticed though, is that the extra voltage and weight from Nimh is good, so there aren't really any downsides.

Ashernoel wrote:

ericlepanda wrote:For batteries I am considering either 8.4v NiMH batteries or 7.4v LiPos. Which would be better for this event?

There was a very good discussion with a lot of details earlier. From what I've noticed, though, the extra voltage and weight from Nimh is good, so there aren't really any downsides. Note: Fixed *some* of the grammar.

From the one and only Antoine_ego:
"A LiPo battery is significantly lighter than a NiMH. The tradeoff is that you can have a maximum of 7.4V according to the rules, as per the voltage per LiPo cell. The biggest problem however, is that if you handle them incorrectly, they have a tendency to catch on fire. Since you are using them with 6th graders, this may not be a good idea.

A NiMH (what I'm using) is extremely heavy. The one I'm using weighs about the mass of your craft. You can probably find a less heavy one though. The good thing is that they are significantly more durable than LiPos, and you don't run the risk of them catching on fire. I suppose they could, but not sure how that would happen. You also can get a greater maximum voltage, going up to 8.4V. Since you are running big fans, that extra 0.8V might be useful."

Ashernoel wrote: From the one and only Antoine_ego:

Geez don't stroke his ego any more, it'll take up his entire username if it gets any larger :p

I'm honestly confounded by this event.
We're using the blower fan from DigiKey suggested by the event, and I just can't get it to really lift. Any suggestions for skirt design? How much slack is recommended, and what types of holes should I be putting in the bottom?

Tesel wrote:I'm honestly confounded by this event.
We're using the blower fan from DigiKey suggested by the event, and I just can't get it to really lift. Any suggestions for skirt design? How much slack is recommended, and what types of holes should I be putting in the bottom?

Maximum lift we found is low slack, almost completely taught with a thousand pores poked by a needle.

Ashernoel wrote:

Tesel wrote:I'm honestly confounded by this event.
We're using the blower fan from DigiKey suggested by the event, and I just can't get it to really lift. Any suggestions for skirt design? How much slack is recommended, and what types of holes should I be putting in the bottom?

Maximum lift we found is low slack, almost completely taught with a thousand pores poked by a needle.

Are you using the same fan most of the people on the forums are using? I got it to work, using a lot of holes on the bottom, but I was only able to support 1 kg or so.
When you have your skirt, is it unsupported, or is there a layer of foam or something similar giving it more shape? I'm wondering it that's my issue.

Tesel wrote:

Ashernoel wrote:

Tesel wrote:I'm honestly confounded by this event.
We're using the blower fan from DigiKey suggested by the event, and I just can't get it to really lift. Any suggestions for skirt design? How much slack is recommended, and what types of holes should I be putting in the bottom?

Maximum lift we found is low slack, almost completely taught with a thousand pores poked by a needle.

Are you using the same fan most of the people on the forums are using? I got it to work, using a lot of holes on the bottom, but I was only able to support 1 kg or so.
When you have your skirt, is it unsupported, or is there a layer of foam or something similar giving it more shape? I'm wondering it that's my issue.

Yea we have the blower fan ~1000 pa from digikey that we used at Loyola. As for supports, we have plastic supports to raise the base about half an inch from the ground. Then we put the skirt taught around there, so there is ample room to create that air cushion. Our skirt design isn't slow enough, so we're looking at how to reduce speed