Dual Engine DF Vortex34 Build

[CraigP]

MOTORS

I have the motors ready to go in the boat. On the first Vortex, I noticed an extremely loud whine coming from the boat at full throttle. I figured it was drive line related, with the usual suspects, bad shaft alignment, bad grease, stuffing tube kinked when bending in the radius, bad or loose motor/shaft coupler. None of these were a problem... I even sanded down my flex shaft thinking the wind on it was rubbing on the stuffing tube, no go. I actually went too far on that, and had to replace it!

What I found made sense once I found it, isn’t that always the case. The Vortex is a great hull, so much room to put parts just where you need them. But it IS a hollow shell, with not one cross frame in it. As such, it can resonate like the body on an acoustic guitar. I noticed on fine examination that the epoxy glueing the stuffing tube to the hull had little tiny stress fractures in it. I’ve seen this type of structural failure before. I’ve done quite a few FEM analysis on failed structures, usually motor related. Resonance vibration can be a real show stopper. So I glued an aluminum plate in the bottom of the boat using slow curing marine epoxy. The plate acts as a dampener to the resonance buildup. Worked like a charm, no more noise! So I decided to forgo that trip down the rabbit hole and incorporate a motor mounting plate into the dual design. This plate eventually gets glued in, so all angles have to be double and triple checked.

I fabricated the motor mount rails, attached the the motor plate with 3, #2 flathead screws per rail. I used 2mm socket head screws to mount the rails the the motor mounts I bought on OSE. It’s a very solid affair. Those are 5mm to 0.150” OSE couplers with thrust bearings on each motor. I got my X442 matched prop pairs from Chris (dasboata) and they look great! I’ve been keeping a tally sheet on the gram weight of the components going into the build. I’m actually on track for about 10lbs, very happy with that! Still waiting for ESC’s to arrive... It’s getting pretty close!

[flattrack]

Hey Craig, why do you want more AoA on starboard side? Seems like the increased lift would be counterproductive when racing an oval course turning always to starboard.

[CraigP]

The turn fin has a tendency to tact down the right sponson hard, so having less angle on the outside forces the sponsons to share the load better. All hydros scrub speed when turning. Many concentrate on going screaming fast on the straight, but race water can force you to back off and not use it. I like to gain speed by cornering faster, so I set up for that more than straight line speed.

I had a real knowledable fellow also explain that hydro turning shares similarities to alpine skiing, namely Giant Slalom. High speed turns are accomplished by tracking hard on the downhill ski, while letting the uphill ski just ride by applying all the pressure on the downhill ski. The sponsons are similar, the boat will track and turn better if you can plant the outside sponson, which equates to the downhill ski. Interesting parallel... And even with a very low CG, there is also some roll steer. The lower AoA on the left side fights the boat’s tendancy to roll or climb right.

Many don’t agree with this, but I don’t mind! That’s my thinking, take it for what it’s worth. Thanks for checking out the build!

[Fluid]

I thought the starboard side had a higher aoa.




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[CraigP]

Oops, typo! You gotta type fast, or the freaking site times out on you! I fixed that on edit, thanks Jay...

[Beaux]

Looking good. I've got mine just about together and finished painting.

[CraigP]

Painting.... The thing I like the least.. I wish I had a good compressor and air gun, but I have to struggle with cans... To heavy flow, orange peel, runs and flat not taking the paint. I’m going to run mine without paint at first, then maybe I’ll get fired up to get through that! I do want to paint this dual hydro the paint scheme of the ‘85 Executone, it was my brother’s first ride... The first Vortex is done up like his GP-55 boat, it’s my avatar...

[Beaux]

I've had good luck with O'rielly's Dupli- Color it's lacquer , There is a clear coat also. It works really well.

[Beaux]

I built a turbin cowl, and tail feathers for mine. It looks pretty cool. I'll run a build thread in a couple of days.

[CraigP]

I've had good luck with O'rielly's Dupli- Color it's lacquer , There is a clear coat also. It works really well.

Is that in spray cans?

[CraigP]

MOTOR/ESC PLATE

I built this integrated plate that also strengthens the bottom and eliminates resonant vibrations from the drive line. There is a single in/dual out Opto Board in between the the ESC’s. That eliminates ground loops and keeps the noise out of the control section of the ESC’s. The motor wires were shortened coming from the two T-120 ESC’s. This is ready to be epoxied into the boat...

[CraigP]

RIDE PADS

I got the main runners of the ride pads done. I epoxied underneath and used brass, #2 Phillips flathead screws to hold the aluminum while setting up. I like the finished look! I still have to put the aluminum front shingles on...

[Brushless55]

MOTOR/ESC PLATE

I built this integrated plate that also strengthens the bottom and eliminates resonant vibrations from the drive line. There is a single in/dual out Opto Board in between the the ESC’s. That eliminates ground loops and keeps the noise out of the control section of the ESC’s. The motor wires were shortened coming from the two T-120 ESC’s. This is ready to be epoxied into the boat...

looks good man!

[Beaux]

Yes it is spray cans. Also on this Vortex I'm building I used acrylic urethane it is automotive base coat clear coat, detonator yellow the same color as my dodge challenger from O'rielly's. The spray can is very forgiving, and it covers really well.

[Beaux]

Should I do my ride pads like yours is the stock ride pad not enough?

[CraigP]

Should I do my ride pads like yours is the stock ride pad not enough?

I’ll try that paint... gotta be better than Lowe’s! The stock ride pads, in combination with the “Delta wing” structure, running from the center section over to the sponsons, will produce a lot of aero lift. Some counter this problem by using air dams under the boat. But air dams, as the front of the boat lifts, starts to create high turbulent air flow over the leading edge of the dam. It starts to buffet. You’ve been in an airplane and they drop the flaps to the landing position and you feel the airplane shake until it slows down? It does that on the boat. The other problem is my two Vortex’s both measured 3.8 degrees of AoA on the sponsons. At that angle, the front is going to launch upward in rougher water. I choose to address the problem by changing the ride pads. As to the additional air that the deltas cram under the boat, I’ll put in a wing with reverse lift on the front. That wing will divert some air up and over the top of the boat. If the boat continues to climb, the reverse lift function on the wing comes into greater play, and I have my wing designed to create 3.5 to 4lbs of aero force driving the boat back down to the water. It’s cool to watch, it literally “flies” the boat back down! I have much experience designing wing sections, so it’s something I’m comfortable with. There are many opinions on this, so you have to go with your vision on how you see the boat running... If you want to change the ride pads, I presented some detailed information on this build.

[CraigP]

BATTERY PLATE

This is the Battery Plate. I put the batteries on this plate, because as the picture shows, they are arranged to go into the boat sideways, to better distribute the boat about the beam CG. This distributed weight helps to damp out sponson walking, something I’ve talked about before. In this position, the batteries go out across the sponson wells, and need to be supported. This is all lightweight aluminum and actually added very little weight. I made some fences to hold the batteries in place, just in case the boat experiences a hard stop. The fences are attached to the plate using #2 flathead Phillips machine screws, 18-8 SS. This plate will be epoxied into the boat.

Also, because there are no frames in the boat, the sponsons move pretty freely from each other because nothing is there to tie the structure in. This plate provides that structural support.

[Beaux]

Thanks for the info, I built a wing for the front of mine also.

[CraigP]

Thanks for the info, I built a wing for the front of mine also.

I believe that’s the way to go... the biggest reason is to keep excess air from getting under the boat in the first place. It’s hard to deal with too much air, once it’s there. Some work on the side air traps. Others use air dams. I like diverting some air up and over the top! BTW, the Vortex has 6.5 degrees of AoA on the tunnel, which is high. So that wing is really needed IMO...

[CraigP]

CAP BANK

We had a great discussion on Cap Banks and wiring issues with dual motor applications. I made this Cap Bank. It has 7200uF of capacitance and is built onto copper plates. I bonded a piece of fiberglass board underneath and let the epoxy come up through the copper rails. I applied some more epoxy on the top as well. The small wire with the connector is power to the external UBEC. The connector is waterproof, it has small silicone wire seals in it. It was made for automotive applications. The ESC’s attach on either end using 5mm bullet connectors. The batteries are hard case with 5mm female connectors. I’m expecting no more that 90A a side, so this should carry the current well. I tried to make everything as even and mirror image as I could, so all those little electrons behave and play well! The Cap Bank is attached to the Battery Plate.

[CraigP]

STEERING COMPLETE

I got the steering in and complete. I really like using the aluminum ball ends available from OSE. It makes the steering so tight. The servo is a HiTech HS-646WP, a high torque output unit. I made an aluminum mounting bracket for it and epoxied it to the bottom. I also used an aluminum servo arm, to keep things tight...

[CraigP]

I got the Motor/ESC Plate mounted in the boat. I have it bolted in right now. I plan on testing the boat first, then epoxy it down if everything proves to be good.

[CraigP]

Battery/Cap Bank Plate

I got it bolted in and same as the Motor Plate, I want to run it before I commit to its final position and epoxy it in. Right now, it’s mounted in the middle. I’m guessing that I won’t need to pushed to the port like the single engine Vortex. But if the left sponson picks up under hard acceleration, it will be easy enough to move it over a bit.

[CraigP]

Stuffing Tube Detail

I’m running 0.150” flex shafts to keep the drive line friction down to a minimum. I think it will hold up fine, coupled to 3650 motors... On final shaft lineup, I ended up with the motors pushed up a bit to make all the angles work out. I had about 1” of unsupported shaft and was concerned about that possibly whipping around, so I made a nested tubing “bearing” to support it better, while leaving enough space to get a rag on the shaft and clean any grease off before it gets into the coupling. Those are OSE 5mm/0.150” couplers, they are nice units!

[larryrose11]

looking good!!
A bling idea:
polish the aluminum plates, perhaps a translucent powder-coat over the top.

[CraigP]

That would look sharp! But it will have to wait, I have everything Lock-Tite down right now. This thing is getting close to throwing it into the water! I got water lines and final electronic installation, including the antenna. I’ll run it with no paint and just tape the hatch down, I’m getting itchy to see it go! I want to paint it the ‘85 Executone paint scheme, so I could get the plates powder coated while I’m painting. I have UL-19 vertical fins to mount on too...

[CraigP]

Final Ride Pad

I got the aluminum on all ride pad surfaces. I’m so happy to be done with that! It was far easier than what I did on Vortex #1, but it’s still a lot of work. But it’s one of those things that you just love to see, each time you run it!

[Beaux]

Looking good, I like the shaft support good idea. I have one that needs that.

[srislash]

Engineering beauty Craig, engineering beauty! Looks good.

[CraigP]

Thanks Shawn! It’s been a bunch of work, but soon that will be over and I can just enjoy. I plan on running it for the first time this weekend if the weather holds up. If it all goes good, then I tear it down, get it painted and waterproof the hatch for no tape. I’ll be getting a video of it and post that. I still have water lines, mount Recv, BEC and wire it up. The Opto Board works great! I fired up the motors on the table this weekend, super smooth on the throttle.

Oh, I want to seal the back of both struts too. I’m going to document that to have a complete build thread. Paint, still a bit freaked out about that! It’s NOT something I dig a lot, if you know what I mean!