need some guidance, first hydro build

[ls1fst98]

picked up an r2 hobbies swifter hydro bare hull for dirt cheap ($1 off ebay)

my plan is to run 4s....not sure if 2s in series or one 4s pack or 4s2p... a lot hinges on my few questions.

1) how do you determine COG on a hydro?
2) i have a castle 1516 2650kv motor, a 120a seaking esc or 180 esc, would this be a good choice?
3) can you use standard x series octura props?
4) was thinking of using the AQ UL-1 hardware with this build since its already black and will fit my theme.

R2 swifter.jpg

[nichismo]

Center of gravity on most hydros is anywhere from .25" to 2" behind the back heel/transom of the sponsons, (obviously depending on size) so generally, a good place to start would be to aim for the end of your turn fin bracket and go from there.

For most applications, two packs to get the desired cell count is usually more applicable given how reliant hydros are on the COG to perform well, and having the option for a parallel setup has its obvious advantages as well. However, we need to know the exact specs/dimensions of the hull you are using to give more accurate recommendations.

Im not too familiar with Castle motors aside from the 2028, so I cant really speak for the motor you listed. However, that is a pretty high KV, and the respective ESC you listed also is rather powerful, I imagine if the boat is anywhere near 25-30" that power setup may be a little too much for the boat to handle (i could be wrong). The popular UL-1 2030kv motor and 60amp ESC is a very very good setup for pretty much all boats this size and would go perfect with 4s lipo configurations, just something you may potentially want to consider.

No reason not to use X series Octura props, I have both 2 and 3 blade X450s for my 1/8 scale, and an x455 3 blade.

[ls1fst98]

Awesome, thanks. After I got the baot in hand I can not fit a 40mm diameter motor, so I do have some aq 1800kv and 2030kv motors as well as some 2150kv.

The boat is just shy of 26" long, 13" at the widest point, 7" wide at transom. Transom is 1.25" tall

[JimClark]

Probably closer to .75 in behind the back of the sponson

Sent from my SM-G900T using Tapatalk

[785boats]

I had one a while ago & ran a Proboat 1500kv motor & the 45A ESC for our Restricted class. With an X645 prop she moved along quite nicely.
So your 2030kv motor with a 440/3 blade or 442/2 blade would make this hull fly.
Here's a vid from a couple of years ago dueling with a Whip. Both had the same setup. Held it's own in my opinion. We were both just testing new boats.
The hydros start at 2:20, but you might enjoy the mono's at the start in our little Boondall Bullring.

[ls1fst98]

Very cool, thanks for the info and sharing the video! Always love watching. Does the hardware from the ul1 make a good fit? Won't be too big on the boat?

[785boats]

I'm sorry I can't help you with that question. I've never used that hardware so I'm not familiar with the size of it.
mine had the hardware already installed.

[T.S.Davis]

It's a 2s boat. Spec power is too much.

[Fluid]

I agree with Terry, 2S is probably a better choice although an experienced boater could run 4S or even 6S with the right motor and prop. Our club runs a "spec" 2S class with specific budget motor and prop, a popular and very competive class. As propped the boats run in upper 40s for one mile heats; propped up mid-50s.

.

[T.S.Davis]

Lehner Basic 5000XL if you can find one. 2s with a 435/3. Weeeeeeee.

A cheap option would be a Fieago 7s......ish on 2s.

[nichismo]

Curious how spec power is going to render the OP incapacitated in driving the boat if its just about the same size as a UL-1 (I mean this 100% as articulated, no way trying to imply anyone is incorrect, im still learning). I know this is like darn near blasphemy from other topics ive read here on OSE, but for my current build with a CT13s, I am running a TFL 4074 2200kv on 6s (yes high RPM to say the least) and its very fast and yet control is magnificent, and this is 31" boat at just under 6lbs. However im sure the design of the sponsons have influence in this case.....

[785boats]

It is just 1" shorter than the UL1 & runs fine on 4s.
The yellow one in the video ran at 77klm (47mph) with the 1500kv motor in oval race trim.
I have another one that I'm testing at the moment with a 3660 2310kv motor & a 437/3 blade prop & she flies quite well on a 4s 5000mah pack (2 x 2s). No video yet.
The only problem with this one is that the moulding is way off in the sponsons. Both sponsons have anhedral in them at the ride surfaces & the left sponson really ploughs in when she corners. You might want to check yours. I'll be making some ride pads to level them out soon.

[T.S.Davis]

Never mind. Sorry I interjected.

[nichismo]

^^^

you gotta be kidding me......

[T.S.Davis]

You get input from experienced guys and immediately discount it.
Jay wrote a book on FE. Its always the same though. Questions get asked. Guys with limited experience answer the questions and argue with any conflicting opinions. Gets old.

Eventually the experienced guys we'll stop interfering. No worries.