FL26 build in Friesland

[Jaap]

A bit hectic day today, but we arrived with the boat on the trailer at around 14:00 hours in the harbour and the launching went smooth and easy and we made our first short trip. Up to the lake (Terkaplester Poelen and Sneeker meer) and from there to our home. Weather looks very good on friday and saturday so we take our chance.
The boat is surprisingly good, more stable then expected, but the bow is a little to high. We have no diesel engine, but an electric 48 V brushless 10 kW motor with a 16 180 Ah LifePo4 cells of 3.2 V. The motor controller is Curtiss. So under full throttle the battery pack has to deliver around 200 Amps but surprisingly the motor takes only up to 127 Amp and makes no more rpm then 850. It should do more so something to sort out this week (I hope). The other thing we need to adjust is the rudder. I think we have to make it deeper, almost as deep as the keel and maybe a little longer. My hydraulic steering pump has to make to many rotations from left to right. On speed (speed?? above 6 km/u (4 mph)) it works fine, but on low speed, which we do her quite often, because of all the small harbors and bridges, she gets out of control. A bow thruster would be nice, but at this moment the bow is too high.
I never had a bow thruster in our other boats, so maybe this one is not necessary too.
Stability is really good, it is still a narrow boat and it runs on the lake very very nice.
Topspeed today was 12,4 km/h on my gps, which takes just over 6 kW power. So we miss a 3,5 kW of power.
Our regular allowed speed is 6 km/h and then the motor takes around 1,6 kW. Is this an eye opener for all this big engine guys .
We do some more boating later this week and I really hope to make a better movie, this one comes straight from an Iphone 5s.
Will be continued....

jaap











https://www.youtube.com/watch?v=ayilmbC ... HdK8OZ2Btg

[icelikkilinc]

The boat looks amazing, you have done an excellent job.

The rudder seems way to high. on that picture with the prop, it seems very obvious that it will not meet the propulsion thus the rudder will not be responsive.

Below pic may better explain what I am trying to say.. the rudder is covering all the water that is thrown at it by the propeller thus more trust on the rudder to be more responsive...

[icelikkilinc]

And this is your propeller to rudder interaction.
The shaft angle seems too much, much as in a displacement.
Your boat looks as more flat bottom to me.
I tried to show with red lines where the propulsion is sent thus seems lost..

I hope I am mistaken by the picture, my 2 cents..

[jacquesmm]

Unfortunately, Icelikkilinc is correct.
As designed, if you draw a line representing the shaft, it goes through the middle of the rudder blade.
Here, it looks like Jaap used a larger diameter prop. This was probably required for optimum efficiency of the electric motor but that required to change the shaft angle and apparently, a deeper skeg. All that is fine but in that case, we also need a deeper rudder blade.
Jaap, maybe your supplier will accept to trade it or somebody may be able to modify the blade.
Look at the plans: the lower tip of the rudder blade is lined up with the lower tip of the prop. That is what you need.
No need to make it deeper than the skeg.
It is not catastrophic, it's fine tuning and part of experimenting with electric propulsion.
Everything else looks absolutely great.

One more thing. Now that we see more pictures, it looks like your boat is still very light. Once you load her with cruising gear, she will be more stable, track better and be less sensitive to the wind.
She will also be faster and run better through a chop once the tip of the bow is immersed.
In the design, I counted on 2 persons plus gear plus ground tackle in the bow. You will get there quickly.
It's better to have too light than too heavy.

[icelikkilinc]

If you were to add a skeg and increase the size of the rudder(that's my setup and very pleased with the rudder response) , you will be adding weight back of the cg. Your bow is already high so just remember to calculate that as well

[Jaap]

Thanks for the nice words, we think that boat will serve us very well for weekend trips around the lakes here. The engine weights some 60 kg and the battery pack 120 kg. That is much less then the calculated diesel and fuel. So I have to bring quite some weight to the front, like a watertank, 12 v batteries for the board system, and maybe move the battery pack to the front as well. If we boat, all the passenger weight is in the back.
Thanks also Jacques and icelikkilinc (the fastest builder of this website ) for the advice. It has been a few years since I builded the keel etc. but I think I builded it according the drawings. The prop is a 15 x 13 to start with. You can set the motorcontroller for max rev etc but I do not have the software (yet!). It is not unfortunately that icelikkilinc is correct , we expected the rudder behavior to be as you described, thanks for the drawings too icelikkilinc; we will use the advice for redesign the rudder, which is a standard Vetus one. I thought (try to remember ) that its measurement are not much smaller then on the drawings.
It was a nice project to do and I am surrounded by friends who spend their whole life in boating. The guy in the browns vest is Dirk de Ridder, our neighbor and winner of the Volvo Ocean and Americas Cup. He was involved in developing of the latest AC boat as well and what is better then have endless discussions about how it would perform etc. We decided to leave it as I build it and go out for a test and improve/fin tune from there on. Dirk was also surprised how wel everything behaved on our first trip. He wants a bow thruster in it, because he installed one himself. I like to leave it out and use the torque of the prop. If Dirk with his 110 plus kg stays on the front tip we still don't have enough weight there. Friday and saturday we have nice weather again and use her a bit and next week back on the trailer and to the winter storage. But so far we are very happy with the stability etc. We got some very nice comments from people who saw us, about the boat. Jacques makes awesome designs for just a few bucks, thanks for that and this very helpful forum!!

jaap

[icelikkilinc]

You have done an excellent job and from here onward it is just fine tuning with the different engine you have and weights etc.
I altered the design and I had to move weights, play with the rudder etc.. It is all part of the DIY.
With your skills and friends, you will get there in no time..

[Cracker Larry]

Beautiful work

[jacquesmm]

Yes, the designed prop is 15" diameter. Your prop and skeg are probably to plans.
Here is a pic from the plans with some dimensions added:

The rudder max. height in inches = 17.4" = 442 mm.
See the line I added from the bottom of the rudder blade to the lower tip of the prop: they are flush.
But they are not in your boat
It could be that you shaft angle is different. You may have changed it to fit the electric motor.

Anyway, it's done now and the best way to improve performance is with a longer rudder.
That means more blade area. In order to preserve performance at top speed, try to get a rudder blade with about the same area than the designed one but longer. that means a thinner blade (shorter chord).

[jacquesmm]

I looked at your pictures again and see much more blade tip clearance (from top of prop to boat bottom), that means it must be the shaft angle.