Unfolding Hull Panels

Busy day today. Unfolded the chine panels for the 30′ catamaran workboat. Rhino 6.
Used to be I would just plot out the patterns. However, my nearly new Canon plotter that cost about half the price of a Honda Civic quit and they tell me it will be expensive. So for now I dimension the flat patterns.
Leaving HP was probably a mistake.

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More Electric Cat

The second note from Kevin.
“Hi Scott,
Here’s the results with the pulley changes. I will call shortly to discuss.

10/21 Re-test
Installed 18 tooth pulley on QT10 (port), and two 20 tooth pulleys on QT20 (stbd).
QT20 display always shows “Key on” regardless of position, but doesn’t show “hours”.
QT10 display doesn’t show “key” at all but does show “99 hours”

Boat is still very light with no water or equipment etc aboard. Bottom clean.
Running perpendicular to a 14knt breeze in flat water.
Port QT10 running alone achieved 139amps, 1460rpm on power setting 100, going 5.6knts
Starboard QT20 running alone achieved 341amps,1844rpm on power setting 76, going 8.2knts
With both motors running: port got 152amps at 1700rpm, starboard got 353amps at 1875rpm with a boat speed of 8.7knts

Running port only at 100amps achieves 5.5knt
“ Starboard “ “ “ 5.8knts

Running one motor at 50amps gets 4.5 kits
2motors at 50amps each gets 5.5

Running both at 100amps each gets 7knts and when running into the 14knt breeze that was reduced to 6knts.

Reduce pulleys more or re-prop?

Thanks, Kevin”

Building power cat hulls

I took on the job of building a set of hulls for Kurts 28’ power cat design which we stretched to 31’ by adding about 2.5 inches to every station. We upped the stringer size by 30% and glassed with 8oz rather than 6oz but otherwise stuck with the plan and laminate schedule. We used multiple layers of 8 and 10oz to make up biax tapes, i find it makes for easier fairing and allows for tapering the buildup. We did a half-way-to-yacht quality fairing job, primed with 545 and installed cleats, hatches, fuel tanks, and fuel fills. There will be lightweight 25 hp engines mounted on rear transoms. We finished both hulls and shipped to the owner in maine, who is going to build the cross arms and center cockpit over the winter. I really can’t recommend committing to building a boat over the summer in sarasota, florida in a non-airconditioned space, but, in the spirit of running a marathon, and other ridiculously painful ways to enjoy yourself, we did it.  Total build time, including purchasing, hardware, and mounting on a trailer for shipment, was in the neighborhood of a thousand hours. LOTS of pictures after the break-


Continue reading Building power cat hulls

Electrical Install

I was fortunate to get Kevin’s notes from going electric on his 48′ cruising cat.

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“Hey Kurt thought you’d be interested in my notes from my first tests with electric motors. Overall pleased so far, but this is not for most people. The complication is high and needs to be self installed to understand. Actually the motors are easy…Its just the entire system integration that’s hard. I’m off to Europe for a month so won’t get any more info for a while.
Cheers, Kevin

nitial testing motors: All needs redo….Got amps wrong on both motors, need smaller pulleys.

Boat is very light with little equipment and no water etc. Clean paint.
Approx. 14-18knts breeze.
Motoring out into breeze on batts only 7.5knts easy to achieve. Uncertain of total amp draw as port motor not reading shunt. She felt much stronger into the breeze than my old 16hp diesels which I attribute also to the 3blade 18” props vs old 16” 2blades props.

STBD motor (alone) once set is running at power setting 50 achieving 1500rpm @ 250A
Was possible to run 300A+ but dialed down to spec. Scott I screwed up on this one. I had 250A in my head— not 350A per manual. That said, I think I will need the smaller pulley to get the numbers . This highlighted sentence skews all the rest of the numbers on this page of course since everything is based on 250A for starboard and 125A port

Port motor (alone) on power setting 95 got 1300rpm @ 123A (using clamp on amp meter). Scott I guess I need the smaller pulley for this motor to get my 1700rpm and 175A

Running STBD alone at 23A (just above idle) perpendicular to breeze got around 3.3knts which should get just under 10hours on batts alone. But this was in strong cross wind….

Top speed with both motors was 9-9.3knts at 375A…roughly 18.5KW (50v x375a)
So should have about 36m of full power available. This exceeds battery output specs so wouldn’t do this without genset backup. Adding the full 250A from the genset should allow 1.8hrs of full speed before that batts give up. Scott are the motors ok with this if for some unusual reason I wanted to use them this hard? (This question to be adjusted to 350A…)

Did not test amps vs. speed vs. 1motor vs 2motor yet to create efficiency chart.
I suspect 100A on one motor, vs split between 2 motors, will yield higher speed in flat calm but the opposite will be true into a breeze or chopped water. Too be tested.

On the delivery run, when motors were not dialed in, I ran the genset for an hour with the boat cruising at 7.5knts into 10-12knt headwind and saw no voltage drop on the batts. On my old diesels I could have achieved 7knts in the same conditions but they would have been working hard. More typically I cruised at 6.5knts. So very happy with this result but haven’t compared fuel yet.

Setting regen at 100 allowed the props to stop spinning! No shaft brakes needed so far.
This is a big deal for fast boats like mine.

It is very easy to loose settings while adjusting on display. I do not love the displays! Running both motors on one display pointless. Two is much better.

Started testing with 53.5v. Motored out into trades then did 5 or 6 runs back an forth across bay at various speeds. Returned to mooring with 52.5v still in the tank.

Shifting is very different than diesels. Slower response. This makes maneuvering a boat like mine onto the mooring in breeze challenging. I have plenty power but it takes much longer to from forward to reverse. Something to adapt to

Reverse has too much power on both motors! Would like to decrease reverse power. Just a tiny bit of throttle way revs up! Scott any options here? It will be worse with smaller pulleys.

Scott’s performance predictions graph indicate 19kw [my current max output, depending on whether one uses 50v or 53.5v x (123A port + 250A starboard) will push the boat at 8.2knts. Actual speed seems to be 9knts on initial test.
So Scott seems right or better on speed.

Distance, however is poorly predicted simply because 300AH is bad input. Actual available power is only 225AH because batts only receive 90% top charge and cut out at 15%DOD.
My numbers above, 3.3knts @ 23A with 225AH available, indicate a 32 mile range vs. 41 miles on Scott’s chart (corrected for actual AH available). But test was with strong cross wind and run over short distance so better numbers needed.

At 9knts range would be something like 4.5 miles which is very close to roughly 5.25 miles on Scott’s chart corrected for 225AH.

If I had gone with 2x QT10’s I would have had 13kw of max power. Estimating from the chart vs. current actual speed I think my top speed would have been 8knts and somewhat less authority at lower speed.

2x QT20’s probably would scrape a weak 10knts top speed.

Speeds will probably not change much when I load the boat as I have found this doesn’t slow her down much accept in acceleration.

Kevin Millett
Holo Holo Charters

phone: 808.335.0815
physical: 4353 Waialo Rd. Ste 5A, Ele’ele HI 96705
mailing: PO Box 50940, Ele’ele HI 96705

No Internet This Week

Internet out in the office this week.
Building owner blames Comcast and said it won’t even be looked at until Thursday.
My backup, a pantech Verizon 4G modem just failed and replacement won’t arrive until Friday.
So it’s Starbucks or this phone for now. I will work on workstation during the day, then go home to send things out.

Sailing 32 Trimaran

I was just about to splash the 12 foot tri when I got a call from Lloyd Fogg, one of my builders who was at Shilshoe Marina that evening.
They just got sails that day and were  going north with the tide in the morning. One of my 32 foot cruising trimarans.
Could I check everything out? Sure.
A few revisions, but it sails great. Fully instrumented. We were faster than true many times.
Great evening.

sailing little yellow trimaran

Wi-Fi down in office building last Thursday and Friday. Owner gone and his voice mailbox full.
Verizon modem no longer working, probably since last unavoidable win 10 update. Clearly the universe was telling me to go sailing. Little 12 foot tri.  Rudder seems to be a 6% or so 6000 series foil; probably from a Hobie.  Would be very easy to stall.  I was worried about maneuvering.  Nah.  Did great.  I will change lots of the sail handling things, but I am fussy about sail trim.
Delightful to sail. “Does everything it’s supposed to” noted Tim Ryan, also trying it today.

Fiberglass Tariffs

Trump tariffs in place now on fiberglass. That is on fiberglass from China, which means almost all of it.
Scott at Fiberlay noted that as of September 24th the tariff will be 10 percent. On January one, that jumps to 25 percent. Prices at Fiberlay, and surely the others, will reflect that.
Thank you Mr Trump.
Better order your stuff before January.

Wireless Switches

Wireless 12v switches. No need for wires to the lights from the switches. No batteries. On composite boats, and composite tiny houses, this is huge.  No need to cut into the composite to hide wires, nor fasten the wires to the composite surface.  Built in dimmers and smart light sorting too. Around $320 for a kit. I probably spent 50 hours doing and connecting switches on the lunar lander. These would have been a bargain. Only scary part is the switches look like the flush button on my Toto toilet.

Kurt Hughes on Catamarans, Trimarans, and Boat Design