The Great $80 RC Submarine Challenge!

[Subculture]

That was analogous btw.

[wlambing]

Ewwwwww!!!!

[Subculture]

Well if we're into the professions, let's play doctors and nurses, and I've shown you mine.....

[Fishb0y]

So many sea lawyers...

[Subculture]

Well to print this in nylon costs about $20 plus postage. It's a small boat about a foot long, so Bob's worst nightmare, but all the linkages are external, and inside will be no worse than working with a 2" wtc.

That leaves around $50-60 for the rest, so plenty of headroom.

[TuptubBuilder]

It seems my example was poorly chosen. I’m not suggesting the purchase of 100 servos to “legally” comply with the <80 rule. I assume that the “spirit” of the contest is to stimulate the design of a low cost starter sub that meets basic performance standards.

Manufacturers spend millions on R&D and prototypes before releasing a product. Iterations abound. Given my background, my first thought is to produce a working prototype and then cost reduce. For example, use lead ballast for the prototype, then substitute with an equivalent weight of cement for the contest entry.

How deep must you “drill down” in terms of cost?

[Subculture]

I think a degree of common sense should apply.

So to give some examples, no one would buy100 servos to build a single submarine, but they may need to buy a metre(yard) or two of tubing if making a wtc. They may need to purchase ten O-rings rather than one or two.

In short I think a build should reflect the real world costs for new items a potential builder would face if wishing to replicate what is presented, rather than use discounting on large or secondhand purchases to operate under the $80 threshold.

In short, I believe it's important those entering get into the spirit of the competition, which should be to present a realistic boat that can be built for under $80 and emulated by others wishing to do the same.

Over to Bob.

[Schmitty1944]

Correct. Perhaps if a bunch of builders wanted to go in together, they could bulk buy some servos, ESCs and batteries and get the price down for everyone? Only issue would be shipping, which would kill the savings. Shipping $1 worth of servos would cost you $8, and, technically, that is a cost of building the boat, so....

I think this is where the impartial judge comes in. If you bought servos on Amazon prime and they where delivered for "free" do you count the cost of the Prime subscription? ($15 a month or $140 a year). Most states (USA) have to pay sales tax but some don't so does that count?

I think it's reasonable to buy parts cheap such as closeout or surplus items (servos, motors, pumps etc.) but you can't enter a $300 hull and say you bought it at a yard sale for $10. Models entered should be reasonably repeatable for the same cost. Isn't that the whole point of the contest?

Most people will understand the spirit of the contest and hopefully not just look for loop holes in the rules. But ultimately there should be a judge that decides what is or isn't acceptable and assigns a reasonable value to parts who's cost can not be proven.

Could Logan serve as impartial judge?

Jason.

[RCSubGuy]

I think this conversation highlights an important issue. The unit cost of a mass produced item like a 9g servo depends upon the quantity purchased. If I buy a batch of one hundred 9g servos, is the cost of using two for the contest sub 1/50^th of the batch purchase?

Correct. Perhaps if a bunch of builders wanted to go in together, they could bulk buy some servos, ESCs and batteries and get the price down for everyone? Only issue would be shipping, which would kill the savings. Shipping $1 worth of servos would cost you $8, and, technically, that is a cost of building the boat, so....

[TuptubBuilder]

Good question. As 3D printing was used as an integral part of the construction, my ruling would be yes, it counts.

I think this conversation highlights an important issue. The unit cost of a mass produced item like a 9g servo depends upon the quantity purchased. If I buy a batch of one hundred 9g servos, is the cost of using two for the contest sub 1/50^th of the batch purchase?

[RCSubGuy]

If you 3d print tooling to make a fibreglass hull, will that be classified as a 3d printed hull?

Good question. As 3D printing was used as an integral part of the construction, my ruling would be yes, it counts.

[Subculture]

If you 3d print tooling to make a fibreglass hull, will that be classified as a 3d printed hull?

[Subculture]

Probably a good idea- will give people time to gestate the designs.

[RCSubGuy]

Dang it! All you guys living up where water gets hard in the winter are screwing with my contest!

Good point. Shoot. So, do we postpone the whole thing until late spring?

[Scott T]

You may want to change the close date as this is when the water is hard to broach. Sea trials not available to everyone.
Or make it a two-part contest. Build and bath completion. Then Sea trial results.

Contest Close Date:

1. January 31st, 2026

Entry prize if acceptable might be 2-3 sessions of Dive Tribe for completed submarine.