40" BEFU Scale Scarab for sport build thread

[Jesse J]

If you get tired of this kevlar kahuna, let me know, I really like the looks and know it could take some serious speed.... I mean go "rather fast"

When you gonna go run her? Its not quite dark yet (here).

[treystoys]

Thats cool Brian just wanted to help you keep an open mind. I want a video reguardless of how it runs. You may prove us all wrong.

Good luck

Trey

[befu]

Mind is wide open on this one, never done this before!

I will try to run it this week. I may mock up a standard rudder behind the prop for testing also so I have something to compare it to.

brian

[marko500]

Hey Brian what ever happened with this build. I was following it and dug out the hull I had. Still trying to decide what motor to use and still try to keep the costs within reason. Another member here has one of these hulls and we wanted to build them like you were, for fun and to blast through some waves. We were looking at the Castle 1717 motors but I don't know if the hull is too heavy or not. Just wondering what happened and looking for some guidance.

Mark

[tomstoys2]

Hey Brian what ever happened with this build. I was following it and dug out the hull I had. Still trying to decide what motor to use and still try to keep the costs within reason. Another member here has one of these hulls and we wanted to build them like you were, for fun and to blast through some waves. We were looking at the Castle 1717 motors but I don't know if the hull is too heavy or not. Just wondering what happened and looking for some guidance.

Mark

I forgot about this thread.
I'll weigh mine tonight Mark and post a picture. I have about 10 coats of Super Epoxy on it as well. I might just order a 1717 anyway, if it doesn't move this hull I'm sure I can put it in another hull.
Tom

[befu]

It's Alive!!!!

actually got out and ran it tonight. Still the same setup, not much has changed. Ran it on 2s,3s and 4s. I only got an amp and speed reading on 3s. It was running a solid 16mph on 3s at around 25 amps (23 to 27amp spikes) on smooth water.

2s was not good. Not sure I would even call it up on plane. Maybe, but not worth while.

3s made it a bit more interesting. It at least ran.

4s was at least starting to move. Motor has torque. Ran it for several minutes and motor / mount / esc was cold. Batteries were barely warm, mid 70's.

Need to get more data on this one, but a couple of points of discussion:

Levi Rudder: I wanted a scale looking boat, so I went with a levi style drive. It is not a z drive or even semi scale z drive, but it is more scale than a stinger and offset rudder. I also thought it might help control the very unscale rooster tail. Well, I was wrong. It really doesn't look scale, it still sprays water badly and the water spray at one point looked like it was coming from the left side of the rudder, so it is stopping some of the prop spray, but creating some of its own. I think this just means a lot of drag and like others have said, lift at the stern.

Standard Rudder. I think I am going to put a standard rudder on it and see what happens. Will also allow me to run a prop larger than 42mm, which I will need if I want to run on 2s or 3s for slower scale speeds.

Trim tabs. Boat has the standard tendency to lean to the right. The prop shaft is angled to the left to counter prop steer and it is offset to the right to counter prop torque. Also need to play with battery placement since the right side sits slightly lower than the left while at rest, and I should have it the opposite way.

This is a large boat, I will say that. Even with all the issues, I think I broke 20mph already, which isn't bad. My goal is over 30mph with this cheap sport setup and low amperage. That is an $18 motor and $24 esc.

video is uploading to utube now.

Brian

[befu]

video is up

[marko500]

I don't know Brian looks promising so far. We've been debating about motors. We want sometimg to run on maybe 6-8s max. We talked about the Castle1717, a Fiegao 580, and maybe the Littlescreamer outrunner although that one needs a little more battery. Any idea what kind of run time yours could get? I know we have debated putting a gas engine in but wanted the option of more places to run. It's been sitting so long that the motor and battery technology have finally caught up to this size and weight hull. Looks good, keep us updated. It really looks like your close to accomplishing your goals on this build.

Mark

[Jesse J]

nice vid man, like all the perspectives and the live narrative WITH a mug shot.

like it like it.

[befu]

Success on round 2!

sorry about the mug shot Jesse, kind of mean to spring that on people at the end huh? Amazing my wife still loves me and we are expecting our fifth child in January!

Took the U shaped rudder off and put on a standard rudder right behind the prop and went out and ran it today.

First Run I tried something odd. I have a bunch of 3s - 2200 - 20c cheapo lightmax batteries that were $10 each. So I put in ONE 3s-2200 - 20c battery and put it out to sea. It worked! ran a consistent 13.5 mph at 23.5 ave. amps. Kind of odd to see a 40" offshore boat cruising along on plane with a small $10 battery! Could have propped it up for more speed and it still would have delivered the amperage. Kinda cool.

2nd run I put a 5s - 5000 battery in it and ran it. It ran up to 26 mph and amperage went up to a peak of low 60's and ran bouncing around 51 amps. This means it will at least take 6s without a problem, or I could go up to a prop bigger than the x442 on it now. It is definately up out of the water running at this speed.

Have some video to process and post. Boat was really noisy, but when I brought it in I found that the motor had come loose on the mount. That can't help it out!

conclusion: So far this is looking succesful! I can easily run 20mph in a scale like look and the amperage is low. I can run 5s and break the 25mph mark. Seeing how the motor is rated for 70 amps on 6s and the ESC is 90/100, I think 30mph will be attainable on this 40" scarab. Even on 5s everything was nice and cool.
The Levi drive idea did not work out as well as planned Rudder it ran and turned MUCH better. Oh-well, gotta try sometimes. Gotta get it to 30mph and get a video of it running!

First photo is 3s-2200 battery, 2nd is the 5s-5000.

[befu]

Today's videos

3s run


5s run


I discovered after running that the screws were loose on the front of the motor, that is why it was so loud. That and the large hull resonated the vibration, almost sounded like a muffled gas boat!

[marko500]

Brian, how were the temps and what kind of run times you thinking on the 5s setup. Getting ideas for the winter build on the hull I have. Think we're going to go for a little more then fast scale speed, but a decent runtime might also help me decide on a motor.

Mark

[befu]

Added the windscreen tonight, rough but it is being puttied in and smoothed out. hatch cover is also on. Sitting at 5 lbs 4 oz right now w/o batteries, so I will be able to cram a bunch of cells in this thing to weigh it down. Might run it again tomorrow on 5s with a prop bigger than the 42mm. Want to see 30mph!

Not a speed demon, but for a really cheap setup, not bad in a 40" scarab hull.

Mark, the temps were fine. I have an IR gauge at work I will have to grab, but last time everything was pretty cool to the touch. No idea on run time. the 3s-2200 - 20c battery would have only lasted about 5 minutes, but that was slow.

The 5s-5000 with the 42mm prop would probably give me about 5 minutes at full throttle. I have two of those and given that the boat would be slowed down some, I would hope to be able to run it around actually moving for 12 to 15 minutes.

Hopefully I will test it tomorrow. Need a new soldering iron to try 6s as I need a new adapter.

Brian

[befu]

28+mph and counting.....

Very very windy today, but went out and tried it anyways. Still on 5s, but I put a 45mm OSE plastic prop on it instead of the Octura x442.

Ran one 5s-5000 hooked up, but put in 4s-4800 for ballast as I plan on running the 5s-5000 in a 2p setup for 5s-10,000.

Running across the wind so it needed some rudder to point the bow in the correct direction. Eagle tree said 28mph in both directions, amperage spiked to 79 amps and settled in around 62 amps at 28mph. Motor was warm to the touch, but would not burn.

I ran it on and off for 9 minutes and the lipo took 1,994 mAhr back.

The motor connectors are getting too warm, they actually melted the plastic bag the eagle tree was in where they were touching, so need to get some better bullets.

Voltage did drop to 18 volts at speed, so two in P should give more speed as it will keep voltage higher.

30mph with this setup will be reached! This winter I plan to tear out the drive and put in a stearable semi-scale drive. This drive train has a lot of vibration and drag in it. The voltage drop under load is also mph as well as the heat in the bullet connectors, lost power there. 30mph on 5s should work fine, just need to tweak it some. I want that 30 before I finish it over the winter.

Not bad for under a $100!

Brian

[befu]

OK, making up a connector tonight so I can run some more test tomorrow with the eagle tree hooked up.

I plan on running 4, 3s-2200-20c turnigy batteries in, 2p, 2s to result in 6s-4400-20c. Not going to run it for long as that is pushing the aperage on those batteries. Also going to drop back down to the 42mm octura prop.

I will also be able to try the 5s-5000 x2 in 2p and see what it does. Will be interesting to see if the voltage stays a bit higher.

If weather holds, may try a 40mm prop also, the 42mm has no problem pushing it on plane.

then I want to try a 45 or 47mm prop on 2s and 3s just for grins. maybe one 2s-2200-20c turnigy. Gee, where to fit the battery.

I know it is not one of the speed demons that people like to see on this site, but it is a nice looking scale boat.

Brian