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Amateur trying to figure out a hydroplane

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Amateur trying to figure out a hydroplane

Old 04-09-2020, 11:49 AM
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CarrowM
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Default Amateur trying to figure out a hydroplane

As I tend to do, I decided to start off RC boating with the hardest thing possible and bought a hydroplane. I am very familiar with RC cars and stuff, but I have never dealt with boats so I could definitely use any advice that people can give. I traded the guy I got this from a buggy I had laying around for this boat and 3 other hulls so I am just trying to get this one going really well before I start doing crazy stuff with the other hulls.

The boat is a 30Ē Hydroplane with a Tacon 3674-2800Kv motor (what came with the boat and is probably a little fast, but Iím only planning on running up to 4S), a Hobbywing Seaking 180A ESC, a 3/16Ē flex shaft driving a 38mm diameter prop. I donít know anything about the pitch of the prop or anything as the only marking that the prop has on it says TFL 440. I have been testing it on two 3 cell 4000MaH high output batteries because thatís what I have. Also, the center of balance is about 3.5Ē behind the end of the sponson.

Iím not trying to set speed records or race but I would like to be able to drive it around the lake and still be able to haul a bit of ass. Any advice that could get me toward that goal would be much appreciated. The last time I tested it didnít go very well. It ran much slower on 3S than it did on 2S (before I changed the ESC because the other one was failing) and just wouldnít get up on plane. It also sounded like the motor wasnít even working that hard when the throttle was pinned. Iím just not too sure what direction I need to be going to get this boat up and running good.

I'm new on here so I can't post pictures yet, but I will try to earn some points then post pictures
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RURC (04-09-2020)
Old 04-09-2020, 12:45 PM
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I am able to post a couple photos of CarrowM's boat for him.


This is CarrowM's hydro. I know that he feels certin that the prop is not right but neither he nor I are boat guys so we don't know. We are both very deep into cars and he does airplanes and quads also.
The previous set up was with an different Hobbywing ESC (took it out of one of the 1/8th scale buggies) and ran it on 2s and it ran far better than it dod with the new ESC and 3s.

Old 04-09-2020, 03:41 PM
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Just my thought but the 3S batteries will weigh a lot more than the 2S and since they are behind the sponson they could load down the back of the boat. That could keep it from getting up on step. Try it with a 2S. If that works figure out how to move the 3S further forward.
Old 04-09-2020, 03:42 PM
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Another thing to try is using just one 3S to see what happens.
Old 04-10-2020, 01:56 PM
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Default More photos CaerrowM asked me to post.






Old 04-10-2020, 02:24 PM
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Thanks to RURC for posting those pics. I've seen things about the angle and level of the prop being important, but I am just not sure what they should be like.

rgburrill I appreciate the input. I will definitely try getting the center of balance closer up toward the back edge of the sponson. I'm kinda thinking the balance should still be a little behind the sponson so it isn't trying to submarine on take off.
Old 04-11-2020, 03:45 AM
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Okay, I'm not an electric guy but I do know my way around a hydro. That said, I see some problems. Let me kind of go over a few:
1) What the hell are trim tabs doing on that boat? IF the boat is planing properly, they won't be anywhere close to the water so get rid of them, they're useless weight
2) RG is correct, the 3S packs are forcing the rear of the boat down due to the mounting location. This makes it harder for the prop to lift the rear of the boat
3) To go along with the battery location, the battery leads are too long. This causes higher resistance and less power to the ESC and motor.
4) The center of balance should be no more than 1" to 1.5" behind the sponsons. This, again points to too much weight aft.
5) Has that prop been sharpened and balanced? If not, it won't work as efficiently as it should. IF that prop is sized the same as an Octura, it's a 40mm prop with a pitch of 1.4 times length, or 56mm.
6) Have you removed, cleaned and greased the drive shaft? That is something that should be done before putting the boat on the shelf after a day of running. There are several light greases that will work well, just don't use a heavy grease.

That should start you off in the right direction
Just for the record, this is a .67 nitro powered 1/8 scale boat I've been racing the past several years. It's 43" long, 22" wide and weighs in at around 14lbs.

Last edited by Hydro Junkie; 04-11-2020 at 03:58 AM.
Old 04-11-2020, 08:44 AM
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CarrowM
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Hydro Junkie That is a lot of very helpful information. I am extremely familiar with electrical drive-trains so it is all the hydro stuff that I need help with.

1) The trim tabs were an idea to try and help it get up on plane by forcing the rear up at lower speeds then removing themselves from the equation once on plane and not causing any significant drag. It was just a hypothesis that may be completely unnecessary; but hey, you learn by experimenting. It's the same kind of idea with having two smaller turn fins. Since there isn't any racing leagues around me, I want it to keep straight at speeds, but still turn nice each direction. So far that seems to have actually worked.

2) I will definitely be doing some more testing to see what I can do about getting the center of balance within that 1"-1.5" range of the end of the sponson. Not knowing much about hydros, I just haven't been sure how the balance point would effect the performance of the boat. The way I am thinking about it, it seems like having the balance a little more forward would help porpoising and having the weight a little further back keeps from submarining; if this thought correct?

3) I have greased the flex shaft but haven't balanced and sharpened the prop. I'm not even sure if the prop is the right specs. What kind of stuff should I look for in a prop for the hydro? I have read stuff about lifter props and stuff, but I am not entirely sure what that means. What kind of ratio should I be looking for in a prop and what kind of effects does the round or other shaped blades have on the performance of the prop?

I will definitely continue posting about how this process goes while I try new things and see what they do.
Old 04-11-2020, 02:06 PM
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The biggest thing to remember is "Don't try to re-invent the wheel". A hydroplane is a very sensitive animal. You have to be weight and balance conscience with everything you do to it. They are designed to turn right and go fast, nothing else. Have you ever seen an R/C hydroplane actually run? If not, that may be the first thing you need to do is see how they are supposed to behave on the water and then start to work on getting it there. You have to remember, I build and race these things. I have to watch every gram I put into the boats as one gram, in the wrong place, is enough to take a boat that could be a winner and turn it into a boat that plows through the water and. won't get on plane

Last edited by Hydro Junkie; 04-11-2020 at 02:31 PM.
Old 05-13-2020, 09:31 AM
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That looks like a miss vegas hull, as it sits the stut is to deep with to much negative pitch, hull should sit level with both sponsons and strut on a level surface. Ideally should be a 2100kv motor on 4s (2x2s packs in series) with rpm around 30k. prop should work, batteries need to be forward of the motor. boat will try to submarine on start up need to bump the throttle to raise sponson and go. Also rc hydros turn right with one turnfin on rt sponson set much deeper than yours. Good luck.
Old 05-13-2020, 11:07 AM
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Originally Posted by trashcar View Post
That looks like a miss vegas hull, as it sits the stut is to deep with to much negative pitch, hull should sit level with both sponsons and strut on a level surface. Ideally should be a 2100kv motor on 4s (2x2s packs in series) with rpm around 30k. prop should work, batteries need to be forward of the motor. boat will try to submarine on start up need to bump the throttle to raise sponson and go. Also rc hydros turn right with one turnfin on rt sponson set much deeper than yours. Good luck.
Trashcar, I take it that you run electric hydros, If that is correct, nice to know I have someone that might be able to assist me with this boat's issues.
CArrowM, have you had a chance to work on the boat and make any of the changes we've told you to make? As I see it, you have two options:
1) Listen to Trashcar and I as we both know what we are talking about
2) Don't listen to us and have a sporty looking barge
That said, I went back through your response to my last post and found some things that actually worry me:
1) You want a boat that will turn both ways
2) You were trying to remedy issues by throwing weight and money at the boat
You want a boat that will turn both ways, throw that hydro in the trash and buy either a vee hull or a catamaran, Now, at the risk of repeating what's already been said, here is what you need to do to start:
1) Trash the trim tabs and left turn fin. The tabs are usless weight as the rear of the boat is supported by the prop when it's running and the left side fin will cause the boat to barrel roll if you try to turn it at anything close to being on plane
2) Raise the strut so that the prop shaft is parallel to the bottom of the boat and the center of the shaft is even with the bottom of the sponsons. This is probably going to be a bit too deep but it will allow for fine tuning it later
3) Cut the top of the strut off at roughly 1/8" above the strut bracket. This will reduce the weight at the rear of the boat a bit and will also allow for some fine tuning later
4) Remove the battery trays and either move them forward or discard them. Many racers just use Velcro to hold their batteries in place
5) Was that radio install your idea or was it that way when you got the boat? Either way, it has to go as it's an easy way to get the receiver and servo water soaked and cause you to lose control of the boat. That rubber boot on the rudder pushrod was a water seal to prevent water from getting to the radio gear. You need to find a way to protect your radio gear from water, preferably a water resistant box of some sort that is as light as possible
We've told you what to do, it's up to you as to what you actually will do. Give us some updates as it's been 32 days since your last post and some of us are curious
Old 10-19-2020, 12:49 AM
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Anyone know what's happened with this boat? The OP hasn't posted anything since April 11 so I can only assume he's either gotten local help, gave up on the boat or he got mad and left.
Old 10-21-2020, 03:51 AM
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COVID happened. My son lost his job and has not had the money to spend money on the boat. But that is rounding the corner and we are looking to be able to get back into this. As we are in Florida we can run year round.

Also he is trying to finish a retrieval boat for when those things that leave the boat in the middle of the lake happen often. The last time we went out the drive shaft split or something and the prop is at the bottom of the lake and we spent the next 2 hours getting the boat.

But with his funds limited and with life expenses this is on the back burner. However like I said above this likes like it will change soon.
Old 10-23-2020, 12:17 PM
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I'm really glad to read that he didn't give up. That is what normally happens, new boaters find out that the boat actually takes work to get to run properly and they give up and unload it on Fleabay. That said, I was hoping I didn't come across sounding like a demanding person as many new boaters also think they can find everything they need to know on Youtube. If the new boater gets lucky, they might find a video that covers what they need to know but, unfortunately, that's not normally the case.

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