RCU 8th Scale Brushless Hydroplane Build

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KC Andres

Well-Known Member
Joined
May 16, 2010
Messages
49
Hey guys I have a build going on another site but I decided to add it to here, it seems like there is a lot of knowledge on this site and I would appreciate any help you guys can give me on anything. I have done tons of boats both nitro and electric but this will be my first 8th scale hydroplane, and my first electric this big. We will be running with the nitro guys running .67s so the goal is to have a nice fair setup, which we have now I think. I have the registration for the 2009 Oh Boy Oberto and thats what I will be running. I have been an unlimited hydroplane fan for all 29 years I have been on this earth ha. I am on the Water Follies Board that runs the Columbia Cup race here in the Tri Cities and do anything and everything I can involved in the sport of hydroplane racing. So racing scale boats is an easy fit for me. Hope you guys enjoy the build and feel free to add any insight you may have on anything.

P.S.

If some of this is not making sense its because I am simply posting what was in the other forum thread so far, but I am only posting my posts nobody else's, I am trying to avoid posts I made that directly answered other peoples questions so it does not get too confusing.
 
Hey guys this is KC and I will be posting my build of my 8th scale brushless 2009 Oberto for the RCU Club. We will also have a number of other boat builds posted in this thread, including a 2008 U-3 piston hydroplane and a 2008 Elam. Look forward to visiting with all you guys.

Also due to the fact that it took a month to get accepted on here to post we will be starting our posts after lotsa work has already been completed, but we will try and catch everyone up on things we have already completed.
 
Hi guys I am trying to figure out where to start, I wanted to post pictures of the new boat, taking it out of the box and every step after. I think I have a couple pictures of the boat before anything had been done so Ill post those. I am doing the 2009 Oberto from Qatar. Steve at RC boat company came through with the T6 hull for me. The T6 can basically be every hull running currently and in recent years. Steve really impressed me with his Fiberglass work. The boat come fiberglass and carbon fiber, and the glasswork is so nice you can almost just prime and paint the boat with no sanding.

The boat has a lot of the scale features but is not 100% perfect. I think his is closer than any other boat makers boat. I looked at Phil Thomas hulls too but it is not even close to what I need as far as scale for my boat. Steve's has 90% of the scale look I need. The cowling had some issues as far as scale look so we are making a new cowling to go on our boats. Josh with his U-3 is doing a lot of hull modifications to make it even more scale. I am going to go with almost everything Steve did because I trust he did what he did for a reason. The ride surfaces of the boat have some very interesting ideas, not very scale but very interesting. So my plan is to set up the boat to run and run the boat before I even start on the paint job. This way I know if I want to change the ride surfaces or not. Here is a couple pictures of the boat with nothing done.

As you can see in the pictures the boat comes with a swim-step, offset bull-noses, over-sized outside sponson, and many other really nice scale features. Only thing I would change if I could have it redone is the rear shoes dont look scale and the real ones one is shorter and shaped different than the other. Also the front ride pads are not scale at all, but again I will trust his design features and hope it performs well.
 
Ok guys got some pictures of a few of the things I have been working on the last week. As you can see from the pictures I added a block that I can add inserts and bolt my motor mount to. As you can see I will be putting the motor as far forward as I can, close to the radio box/cockpit. The batteries will be in the compartments on both sides of the motor, The 4s 5000 mah 40c batteries that we will be allowing in the club fit perfectly in the compartments that were built in for fuel tanks. The speed control will be going up front in the radio box/cockpit and all wires and waterlines will be epoxied into the wall of the radio box so I never have to worry about sealing it up. In the pictures all I have is the aluminum water tubes epoxied in the wall, the next pictures will include the wires as they are, as of last night completed.

Also in the pictures you can see the skid fin stabilizing bracket got epoxied in the hull. Also you can see the scale rudder bracket that has been welded up and mounted to the boat, I purchased a nice rudder with duel water pick-ups and the scale rudder bracket was designed to fit the rudder. Also as you can see I do not like bolts or screws mounted on the bottom of the hull so instead of mounting my strut to the floor of the boat like most I mounted it to the back inside of the transom, and the strut fits perfectly with just the drive dog ears behind the transom.

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Also as you can see I am trying to cut into the hull as little as possible... I have so far only had to cut two small holes in the boat, one to add a piece of aluminum for one side of the rudder bracket to mount to, and the other to put the skid fin stabilizing bracket in the side of the boat. Everything I have mounted I used two layers of fiberglass and one layer of carbon fiber. Hopefully this will keep me from ever having to get back into these places due to the mounts coming apart. Also the motor mount block was mounted the same.

I am currently debating running my water lines through the engine bay, or through the unexposed hull, for the sake of hiding everything I will not need access to and keeping everything neat and organized. As everyone will see once I get everything in the boat, it will be very organized with no clutter. The engine bay will hold only my motor, and servo.

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Hey there. Sounds like the setup we are shooting for is two 4s 40c 5000mah lipos ran in series. It will be about perfect for a set per heat. We first were planning on running a 10s setup with the NEU 1527 but it was a bit too fast to equal the nitro guys, so it has been changed to the 8s setup and that is about perfect for the speeds the club is shooting for.
 
The scorpion motor was tested but it got way to hot for my comfort and with no way to water cool it I wont be going that direction personally. I think it will be an available option for the club but when it was ran it was about 40 degrees outside with ice cold water and the motor came back after a 2 minute run on a 55mm prop with a temp of 155 and that was after it had about a minute or more to cool down, meaning it was much warmer than that when it was running. The NEU runs much cooler in our testing so ill personally be running that.

As far as the batteries, it seems in the club its somewhere around 15 seconds a lap at full speed, all heats are 5 laps, so the race will be 1 minute 15 seconds roughly, and around a minute mill time. All our testing we have been able to get 2 and a half minutes out of our runs, and the batteries still had some mah left, not much and not much room for error but it seems to work. With the 10s setup we would have had much more room for comfort but it was just too fast and that was with a 50mm prop so not much else we can do to slow it down.

1527 1.5y is what we are running

No we had heard it was a good setup.... the 1y is way too high a kv.... running that motor on 8s would be no different than running the 1.5y on 10s speed wise. The intent was to slow it down. We are trying to make a super safe setup and have it run 55mph to run with the .67 nitros and not have a speed advantage.

the scorpion motor worked it just ran too hot for my liking so ill stick with the NEU, however I think you are remembering incorrectly, when you guys ran the scorpion it was over 150 after some cool down time. 155 was the exact temp after the first reading. Either way thats fine for a brushless motor, but in the middle of a hot summer it will be even higher and heat is certainly the enemy.

As far as the mill period goes the reason it will be ran in RCU is because the club is all about scale racing. The unlimited hydroplanes run a mill period and fight for lanes. So the scale boats run a mill, the mill is just another part of the race. Many of the nitro boats get on the course at the 3 minute mark though and I doubt many of the electric boats will be spending that much time milling. I personally enjoy the mill as much as the race, its all about strategy.

Hey Bob just did some measuring and the boat seems to be right on, Steve did a good job.

Boat total length is 45.25 and RCU allows 43.25 to 45.25

Boat width is 23.25 and RCU allows 19.56 to 23.93

Tunnel varies a little but at its widest it is 11.50 and RCU allows 10.46 to 12.79

Sponson depth is 3.35 and RCU allows 3.04 to 3.71

As far as the Jones sponsons are concerned the small sponson is 5.25 and at the same point on the other sponson is 6.50 ... as you know it the rule book it states that Jones sponsons need to be approximately "1 1/4" difference which is exactly what the sponsons are.

So this boat from Steve follows all the rules and meets all the RCU requirements. As you know we are trying to allow people to get into the club that dont have the experience some of us have to help grow the club. This boat can be many different boats that have available registrations and not everyone can build a boat from scratch like you can. That takes a lot of skill and time. So this is a great option for all those that want to get involved but cannot build their own hull from scratch.

Looking forward to testing in a few months with all the new boats. Hows the progress coming on your guys end with the molding process? Hope its going great cannot wait to see all those beautiful new boats.

I keep hearing that about the scorpion. Maybe it was esc settings or maybe the x455 prop was too much or something I dunno but it got too hot for my liking. The way everything is going right now it seems like the scorpion will be an allowed motor in RCU, along with the NEU and maybe a couple others. The goal is to get as many more people involved in the club as we can and help it grow.
 
Ok guys got some work done, as well as made a list of what is still left to do haha... long list. Right now the plan is just to get everything mounted and in place to run. Then I will work on polishing and making all the hardware look good along with painting and the boat and what not. Since I am making everything from scratch the motor mount and everything else do not look that great now, but when I am done with the boat ready to go they will all be polished up and look good.

I got all the wires and everything ran into the radio box and epoxied up and all the connectors on them. I put brass inserts into the block I glassed into the hull for the motor mount, the inserts are threaded on the inside and outside, the outside so they screw into the hole in the mount and stay, then I can bolt my motor mount to the block. I also got my rudder cut down and in place. Stuffing tube has been bent to fit into place and line up with the motor correctly, I have not glassed the stuffing tube in place yet though. I also got the hole cut out the way I want it in the hull for the strut to fit through and move to the angles that I want it at. Here are some current pictures.

Not much to look at now but it will be nice a purrrrty soon enough :)

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Here are a few new pictures. As you can see I have the turn fin mount in place and the turn fin turn-buckles in place. They are adjustable so if I change my turn fin angle I can adjust the turn-buckles as well. They are also break-away along with the turn fin.

Also got the rear wings mounted, the next pictures will show the rest of the wing brackets as well. As you can see in the other pictures I will be mounting the servo in the engine well wall to continue my theme of hiding as much as I can and keeping everything clean and organized. In the one picture you can see how the batteries will fit right in the side compartments on both sides of the motor. Nice and clean and organized. I decided to go with the castle 240 high voltage as I got a great deal on a new one.

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Glad you decided to post the pics here as well. I have a question, have you checked your CoG with the batteries that far back yet? Just wondering as I have been struggling to get mine in the front far enough to get a desired CoG. Had to add 20oz lead in the sponson tips (10oz per tip) to get the CoG where I wanted it. Let us know!

Mike

ML Boatworks
 
Dave you make a great point.... I actually have been keeping that in mind just as much as I have keeping everything neat and organized. Everything is very easy to access and change as well as being hidden away. The radio box has all wires and water lines built into the wall so I can plug and unplug on both sides. The batteries will easily fit in their compartments and have a latch on the front to lock them in and the wire will be right there to plug and unplug them. I just finished the aluminum servo mount bracket that will fit on the inside of the hole and has been tapped for the servo to bolt on. Very easy to unbolt and bolt a new one in as well. Everything is very easy to access and change out if need be. But very good point that should always be a goal to keep everything accessible.

As far as the skid fin goes yes it is breakaway and the turnbuckles attached to it are also break away, but the buckles break away in the middle with a nylon bolt in each so one side will stay attached to the boat and the other side will stay attached to the skid fin. To put it back together just move the skid fin back down where it goes and put two new nylon bolts in the turn buckles and back in business.

Below I put pictures of my wings mounted and almost done just have to do the adjustable mounts on the back of the top wing so it is adjustable and they will be done. They are held on at all attachment points by nylon bolts as well so they will come off during a crash and not hurt the boat hopefully.

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Also I dunno if anyone can see in any of the pictures a couple of us are building scale trailers to go with out boats. The nitro guys almost all just have box stands that their boats sit in. We got the ok to make these as long as we make a prop guard that attaches to the back and covers the prop in the pits. That will not be a problem. The trailers will look scale and tilt like the real boats as well. I even added drawers into my trailer that fit all my batteries and other spare parts. I think they are a nice addition to the boats. Should be cool when done, I will post some pictures of the trailer progress here in the next few days.

Ok guys I have a dilemma and need some advice. I was planning on running two 4s 5000mah in series making an 8s 5000 mah setup which is what we will be running in the club. I know that we will be doing some milling then 5 lap races. When Bob and Rob were testing this setup they got almost 2 minutes runtime and had 17 percent battery left meaning they could get maybe another 30 seconds before they were completely dead. This is cutting it very very close for a race runtime. So I had planned on running a separate receiver lipo, a 2 cell 2200mah with a BEC to regulate it down to 6v. I just noticed you can buy high voltage BECs I didnt know those existed, they handle up to 40volts, so I can run those off my main batteries and eliminate the need for a separate receiver pack. Since I am already worried about runtime though would adding that draw enough current off the batteries to hurt my runtime even more? I know that when I use to run lipos in my 12th scale for my receiver pack I ran a 900mah 3cell and I could run it for a full day of running a nitro, throttle and steering servos, and I would go to charge it and it would almost have a full charge still. So maybe they do not pull enough current to make a difference. Just wondering if anyone knew anything on this subject or had an opinion.

It was Bob and Rob that tested the scorpion. I know they ran the castle 240 on its stock setting to get a direct comparison to the NEU. I know that even the 7th scale guys run the scorpion so I am sure it works it must just be the settings or something. As far as I have heard so far the scorpion will most likely be an option for the RCU electric guys, I already have the NEU and was more impressed with it so I will just stick with it. Just a guess but maybe the scorpion would do better on higher voltage? I am not sure but maybe that will help it work more efficiently I dunno though.

Yeah I will probably just run a receiver pack. I have had pretty good luck with BECs to this point. I will have to have one either way, either running a low voltage one on my receiver lipo or a high voltage on my main batteries to run the receiver off of them. My receiver can take up to 9volts but my servo is only rated at 6v.
 
Hey Mike....

I checked it with everything in it and it was a couple inches behind my skid fin which is a couple inches further back than I wanted it.... But I have made a number of changes since then, and I am going with what I have done, As soon as everything is painted I will check it again and I will add weight accordingly, or test as is. I have settled with the placement because I am happy with where everything is. It may come back to haunt me later but we will see... I know I wanted it more forward but I will see how it comes out in the end and go from there. One of the other guys going to be running electric has his CG way behind where I have mine and did it on purpose because he wants his boat to float more, he has a gyro on his canard, again we are trying some new stuff and will have to see how it works out.

Glad you decided to post the pics here as well. I have a question, have you checked your CoG with the batteries that far back yet? Just wondering as I have been struggling to get mine in the front far enough to get a desired CoG. Had to add 20oz lead in the sponson tips (10oz per tip) to get the CoG where I wanted it. Let us know!

Mike

ML Boatworks
 
Ok here are a few pictures of the trailer with the boat on it. As you can see it tilts like the real ones as well. I forgot to take a picture with the drawers out but the drawers pull out and the batteries are stored in there along with other spare parts. Since I will be doing the Oh Boy Oberto I made the trailer to look just like the Oberto trailer.

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Yeah I am very optimistic we can get what we need out of the batteries I have a sinking feeling it may be close though. I hope there is room to spare though. I never paid attention you have the 6.6v are you running it on a high voltage servo or standard? I know my receiver can handle the extra voltage but Im worried about my servo. I will be running 1/4 scale servos but its only rated to 6v and dont want to fry it. I dont mind running a BEC its what I am use to. But eliminating extra wires is always a good thing.

Thanks about the trailers we are pretty excited about them. Just a fun little touch and fun to do.

Got my boat weighed today with everything in it and on it. Still rebuilding the cowling and obviously its not painted yet so minus cowling and paint I was still just under 15lbs. That is much heavier than I wanted to be but I guess electrics are heavier than nitro boats right? I mean our batteries, the two 4s 5000 mah weigh right around 2 and a half pounds by themselves. I am going to try a few things to cut a little weight out and once I add cowling and paint I want to be at 16 or under. I will maybe build another boat next season and try and get it lighter but I think I will be happy with 16lbs this year.

I am looking at a couple options to get rid of a little weight. One thing I have a few 1/4 scale servos and I had planned on running them, however they are big and heavy, so I may go with a standard sized servo. If I do I can either go with a high voltage servo and that way I can just run a 2s lipo with no BEC, and the high voltage servo puts out over 400 Oz of torque which is wayyyyy more than I will need. Or there is a cheaper waterproof servo Im looking at that puts out well over 300 oz which is still even more than the 1/4 scale servo. If I go with this second option I am thinking about getting one of the High voltage BECs and then I will not need to run a receiver battery pack at all. I can cut about half a pound out of my boat by going with this option. I am also thinking about building brand new wings and canards and so on out of balsa and carbon fibre to cut down on weight.
 
I went ahead and ordered the high voltage BEC and a standard high torque servo. I will have to test this setup and see if I can get the run times I am needing but I am hoping that will not be an issue.

I will probably be waiting on this stuff for at least 3 weeks so instead of testing then painting after I will probably go ahead and start painting and just test after its painted. Since I am already heavier with this boat then I wanted to be I am planning on running this boat and as soon as its done starting to build another one shooting for a lighter weight.

As far as this boat goes everything is mounted except the cowling and the cowling is the next project. The pictures show the boat with everything on it, but the cowling will be changing, I am cutting the cowling off and rebuilding it from scratch cause the cowling that came with these boats does not look close enough to the real boat to fit my liking. I will build it out of foam, then glass it and pull a mold off it most likely. I may lay up the cowling with carbon fiber and make it thin as I can replace it if it gets damaged. Oh also as you should be able to see in the pics we went ahead and made our own spars out of carbon fiber as the spars that came with the boat were not the correct tear drop shape like the real boats.

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Yeah I assume that is the issue. I already have the NEU so thats what I will run as I like it very much and it runs great. The scorpion is going to be allowed to run in the club and I am sure it will do great as well. We will most likely add a few more, we want to have as many options available to people as possible while keeping the field even.

Quote:

Originally Posted by icelert

It sounds like you didn't have the esc timing set optimally for the Scorpion. If you were using the same timing as the Neu, that might be the reason.

I have been running a Scorpion HK4035-800 on 8S1P on an X457R on a 59 inch long 1:6 scale hydro without any heat issues. Speeds were in the low to mid fifties.

Don't get me wrong though, Neu's and Scorpions to me are apples and oranges. All I am saying is that the Scorpion can be a viable option if setup correctly.

Here is a video I made to show what I mean,



Bryan
 
Ok guys well I have everything else I need to complete the boat ready to run on order and should have everything within the next 3 weeks, some coming from China. So my plan is to break the boat down, already started, and start on body work priming and painting, as well as polishing up all the fabricated parts before they go back on the painted boat. So I will update in a few days when I actually start getting paint on some stuff... Right now I am deciding if I want to paint, then clear and put decals over the clear. I do my own vinyl graphics so I can always change them and update them to what the current Oberto has if I put the graphics outside the clear.

Hey guys,

So got all my paint colors I need, got the rear wings and canard painted. Happy with the colors, I will probably get pictures with paint by next week sometime.

Got the new cowling and salt water scoop from Phil Thomas, the cowling looks quite a bit more scale and seems to fit the boat pretty good. Built a new cockpit to mesh the new cowling from Phil Thomas with the boat from RC boat company. Still a little tweeking to do on it to get it perfect but it is getting close. Got the cowling magnets... they are super strong not sure if I will need 1 or 2 sets on the cowl to hold it down. I am thinking it will be hard to get it off the boat with more than one set.

Since last time I took pictures I ended up moving one of the rear upright wings out about half an inch as they are offset when the boat comes for some reason, looks much better now. Readjusted the placement of the canard as it was off a little bit, about a 16th of an inch but I would have noticed it ha.

So here are a few updated pictures, next ones will probably have some paint on the boat and trailer hopefully.

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KC, the boat looks really good and I am curious as to how it will run. Would you like some dimensions and pictures of the shoes on the Oberto to give them a more scale appearance? I can tell you that the shoes are not the same length so let me know if you're interested. I've been working on redrawing a set of Newton T-5/6 plans to build a gas scale Oberto, so you're welcome to any info I can come up with
 
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