Delta Force 28 Pathfinder

[hughb]

I bought this hull from OSE some time ago, but recently found the mojo to build it up.

The fibreglass hull is fantastic, strong and solid especially when compared to other cheap hulls. However as is the norm, I've inlayed carbon fibre along the seams and over the tunnel.

In the transom area there is thick (roughly 5mm) hard foam to strengthen this area, but I made an extra transom piece from 0.5mm carbon fibre plate to give something solid for the rear hardware to screw up to. This was glued using West 105+206 with milled fibreglass to thicken the mixture and clamped in place to ensure a solid bond to the transom. Resin and chopped carbon fibre was also added to the tips and the centre on the tunnel.

I used 2-part polyurethane foam to fill in the bow area, however I have used to much as it came all the way up to the hatch opening. While making the bow incredibly strong, this foam is surprisingly heavy and has upset the weight distribution. After much deliberation I've decided to carve much of it out with a Dremel, hopefully it will come out without much hassle.

Also I blueprinted the ride pads making them flat, lots of sanding and a bit of bondo. Then primer and yellow paint to seal it in.

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[hughb]

I've used the sticker set for the Proboat Miss Geico 29, they fit perfectly for this boat. Though the Miss Geico scheme is often done, the striking look is what got me into fast electric boats.

Motor is a TP 4050 2310kv, planning on 4S using two Revolectix 2S 5000mah batteries in series. Also using a Swordfish 220A ESC, is this overkill? I've got it mounted way down the back to help balance the boat as current COG is about 50% from the rear, but with the plan to remove a lot of the foam maybe I can place it in the more usual location in front of the motor.

What prop sizes do you guys think would be suitable for this boat? What kind of ready to run weight should I be aiming for?

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[fweasel]

Looks really nice

[hughb]

Thanks fweasel.

I've removed as much foam as I could be bothered, but left it in the centre to strengthen the top deck.

Also I painted up the windshield, looks like a boat now. Sprayed some clearcoat on, and will do another coat tomorrow.

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[ray schrauwen]

Nice boat! Lots of power!!

[properchopper]

Hugh,

I'll take a shot at suggesting a prop based on a somewhat similar build I did for a customer - A slightly larger Mean Machine with a TP 4050 2200 KV motor on 4S. For blasting around I supplied Mitch with an Oct M545. You can see the results in the vid. Based on your slightly higher KV you might want to start out with an Oct M445 or similar and go from there - one minute runs & check temps.
Nice build

https://www.youtube.com/watch?v=m2rt6sH8jwE

[HTVboats]

I have been experimenting with the DF28 cat and Mean Machine 29 for spec heat racing and overpowering them for 2 lap records. I shortened a DF28 one inch to set "N" records. My conclusion with many hours racing and 2 lap testing neither corner well enough at high speed. The bigger the motor over a 1515 (40X74) the slower the times were as your corner entry was way beyond the cornering capability. I give the DF the edge on not blowing over near as easy at speed.
With your 4050 I would as suggested use an M445 or M545. Others to try the CNC 444/3 here on OSE and 1716 and 1717 ABC's. Stay under 46mm diameter as you just lift the hull into a blowover. An 1817 would be very fast but your into a possible heat issue. M445 and 1716 are safe.
Mic

[hughb]

Thankyou guys for the kind words and advice regarding props. When I return home next week hopefully I'll have some time to finish the boat and give it a blast!

[hughb]

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Well I'm a bit disappointed. Got the boat done last night and took it for a run today. Best I got was 68km/h (according to RCM Telemetry), honestly I was expecting much more. The boat appeared to be running very wet, and having trouble getting the nose up to air out. I was using a generic 443 prop S&B (that's what I had available currently) , and had the strut depth set for the centreline of the prop shaft to inline with bottom of the sponsons. Strut angle was slightly positive to try and get the nose up. I've weighed the boat and it comes out at 4kg RTR, this seems rather heavy?

Temps for ESC and motor were approx 40*C, however the Revo batteries felt warm at 55*C according to temp gun. I thought perhaps the throttle wasn't getting 100% (similar to the issue with Spektrum radios), but according to the logs I was getting 100%. I am using a Futaba 4PLS radio. If I have to change the max throttle how do I do it, the throttle range setting on the Swordfish program is greyed out and cannot be altered, it say it is "444uS".

I'll include screenshots of the logs in the following post to see what you guys can make of them, to my newbie eyes I'm not totally sure of what I'm reading.

[hughb]

Here's the logs:

Current.jpg

RPM.jpg

Throttle.jpg

Voltage.jpg

[Jesse J]

I’d probably try propping up. With such a heavy boat and the cog so far forward, she likely needs more umph to get her bow out of the water and get some air packed in the tunnel. Check temps often (30 second intervals) while trying larger props, but I suspect you will start seeing torque roll with much more diameter.

Also raising and tilting the strut (up on the back of the strut) will help settle the rear and allow larger props, and hopefully raise bow too.

Are you looking to race oval or saw? What are your goals/application with this project?

Your graphs are almost legible..

[HTVboats]

Propeller, Propeller, Propeller try a 3 blade to increase lift and hookup without going to extreme larger diameters. A CNC 442/3 or 444/3 available on OSE or find a high rake 1815/3 ABC. Your carrying a lot of weight forward.
Mic

[hughb]

Thankyou for responses. Sorry for the low resolution of the log pictures, I took screenshots but when uploading them onto this site for some reason they reduced to only 20kb each.

Ok I'll mess around with props including 3 bladers. Im trying to remove further foam out of bow to reduce weight and bring COG aft.

[hughb]

oh and sorry Jesse to answer your earlier question its just for sport boating not racing, and ideally I'd like minimum 60 MPH, which I believe should be realistic.

[hughb]

I did some extensive testing today of different props (from what props I had) and cell counts. For each change I ran the boat for under 2min, brought back in and checked the live RCM telemetry as well as data logs from ESC. Results are below:

4S
(For the 4S testing I only had one set of batteries, 2x2S in series so by the end the voltage was down to 3.7V per cell)

CNC 40mm/2: 63km/h, 255A, 3654W, 30-37K RPM, 35*C

448/2: 74km/h, 255A, 3514W, 28-33K RPM, 33*C

443/2: 65km/h, 219A, 2903W, 25-28K RPM, 33*C

6S
(I know it's a high kV motor [2310kV]. Each test was on fully charged batteries 2x3S)

CNC 40mm/2: 78km/h, 255A, 5673W, 38-42K RPM, 40*C

443/2: 89km/h, 255A, 5436W, 35-43K RPM, 35*C

The specs for my TP 4050 are as follows:

Max Amps (A):237

Max Volt (V): 25.2

Continuous Power (W): 2350

Max Power (W): 5000

Max RPM: 60 K

How does this relate to the reading I got from the data logs? For example, the max amps is 237A, is that how many it will draw, or how many it will safely handle? All my runs (beside one) the max amps was capped at 255A, is this too much for the motor?

And the max watts for the motor is 5000W. Is that the max power the motor should be able to produce, or the max that can be safely run through it? Both 6S runs produced approx 5500W. Will this extra power output kill the motor?