High Performance MPX Foil/Self-righting Trimaran-The Test Model

Surely that wingtiP will cause far more drag than benefit aerodynamically? Not that the drag penalty won't be worth its primary benefit of preventing it going turtle. I think the black was the better choice over the red too.

 

MPX Testing and Development--Wing Tip

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I don't know ,Dennis-for sure-anyway. But the Wing Tip is a better shape than any other buoyancy pod I've seen and Tom Speer says that increasing span is always better-if you can do it-than a wing type endplate. This thing effectively increases span-I think. And I've used a version of this on almost every rc boat I've ever built. However, I think the greatest benefit of this whole set up is:
1) the adjustable gaff tensioner,
2) the adjustable upper outhaul.
Oh, and I like the look of the black Wing Tip as well.......
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PS- in many classes full size or model this would be considered extra sail area. I agree......

 

I agree, but its inefficient draggy sail area compared to the rest of the sail. Perhaps a smooth high block naca section would be the go?

 

MPX Testing and Development-------Wing Tip

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Well, I disagree because it's located at the tip.....

 

How would a smooth foam naca section of a similar planform and buoyancy not give an advantage over a relatively crude block? Just seems like its not fitting with the impeccable design and built work of the rest of the boat. I can't say what the difference would be, but I can say it would be low hanging fruit compared to other work you have done.

 

MPX Testing and Development-------Wing Tip

Gee, I think it looks pretty good. Its very thin and should work well. It's a prototype but, frankly, I can't think of how it could be improved-other than improving the seal between it and the sail which is fair and could be better. Adding thickness adds weight-what I wanted for the proto was the planform you see with the minimum buoyancy(foam) required to prevent a turtle(I hope). It's also designed to move a little side to side thru wind pressure.
It also has to allow adjustment of the upper outhaul and tensioner.
I think the quality of the thing is as good as you could get at this point-I'm very satisfied and think it will work well and I think it looks real good and compliments the rest of the rig.
PS- The shape of the Wing Tip with the foam in it is very streamlined-not a "block" shape at all.....

 

If the tip is a slim symmetrical foil shape and is freely pivoting it will have minimum drag, while at the same time its airflow will help to reduce the sail top vortice, which in turn will reduce the overall drag of the sail.
However if the tip is fixed in line with the hull centreline, it will be at a permanent AOA to the apparent wind. Since this AOA will be greater than the AOA of the sail, its induced drag may be detrimental. Freely pivoting is better and can still allow it to carry out its duty as a flotation capsize preventer.

 

MPX Testing and Development-------Wing Tip

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Paddy, it pivots with the sail.....

 

MPX Testing and Development-------Wing Tip

Testing postponed until Thursday. Good wind but the waves are too big in the Banana River. Just like we had to wait for the right conditions for the first sail we have to have smooth water for the first foiling trials to make sure the foils are set up properly. I hate the idea of sailing in the River with the wind blowing off shore especially knowing the switch is not working right. Rob said it's ok to sail with it but I don't have a lot of confidence in the thing.
I'm going to look around a bit today and see if I can find another location with smooth water. On Thursday, we sail even if it has to be an offshore breeze. We need smooth water for the first time foiling-after that it won't matter.

 

MPX Testing and Development-----Wand Lever Arm

When I designed and built the production F3 I brought it over to show it to Dr. Bradfield and Tom Haman. The one criticism they had was that I didn't make the wand lever arm long enough. Since the boat worked so well I discounted what was said and left it as it was-but I never forgot it. I have the MPX main hull sitting right here in front of me and I'm methodically(to an extent) going over the foiling systems. I remembered that comment and decided I would check the length of the MPX lever arm as a function of the pushrod arm compared to the same on Dr. Bradfields last boat the Osprey 18 foiler. I was there for the launch and took a bunch of detailed pictures. What I found was that the Osprey lever arm was 3.25 times the pushrod arm and that the MPX lever arm was 2.3. So, since I had the room, I went ahead and modified the arm to be the same as the Osprey. The MPX arm was proportional to the F3 arm(s). This increases the power of the spring I am using so that may have to be adjusted during testing.
I'm not sure if this will improve the function of the wand system but it won't hurt it and gives more adjustment options.

Pictures show the Osprey set-up and the MPX setup--old and new:
click ---

 

Nice "remembering" there Doug. Great hearing you referring to Bradfield's work with such respect. I followed his work and got to see Skat (the boat for Phil Steggal) up close a few times.

Never saw anything Sam Bradfield did that I didn't make me smile. Talk about someone being ahead of his time.

 

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He taught me so much and was a first class guy. This is a picture of one of my F cubed "Flyer" tri's that Dr. Bradfield bought to do foil experiments with for Skat. He actually bought two and the second picture shows both the Flyers on the dock at FIT. If you look close in the upper left of the dock picture you can see Dr. Bradfield standing there-gives you a reference for the size of the two models. I spent a lot of time with him while he did the testing and the following winter I designed and built the F3. The last picture was taken on the day the Osprey was launched and was the last time I saw Dr. Bradfield...

 

MPX Testing and Development--First Flight!!!!!!!!!!!

We went to three different places this morning and the last place was where we took the first video. By the time we got it rigged the wind had picked up to between 9-11-too much for the rig-too much for the main alone. This rig was supposed to be reefable but the first system I tried didn't work well so I said to hell with it just to get the boat done. That decision was unfortunate because I knew we'd need it sooner or later. We needed to be able to reef today. I may have hurt the winch sailing in these conditions which were way in excess of what the thing was designed for. The winch is set up for speed ,not grunt and when used in these conditions could strip a gear.
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I knew all that and sailed anyway-she was a handfull because the sheeting system was not working well- but she flew the main hull and foil assisted a lot sailing just on the lee hull and foil*. But a few times when I got control of it she 100% foiled but because she was so overpowered it wasn't constant. But we know now that this 21lb boat wants to fly!!! If the wind had been 5-8 (or I could have reefed the rig)she would have flown the whole boat nice and steady-no ifs ands or buts. Notice the almost pitchpole and recovery! This thing was impressive-and this was just the begining.
* We know that because the ama buoyancy is only seven pounds so when she was flying the main hull the ama foil was working all of the time or the ama and the curved piece would have been totally buried. The few times she flew clear it was obvious.
Here is the video-later today I'm going to have youtube take out the shakiness and I'll add some music maybe:

Note-the shakiness has been mostly fixed and music added to the video

https://www.youtube.com/watch?v=LmXCdAlo4mk&feature=youtu.be

 

MPX Testing and Development----First Flight!

Here are some still shots of the boat- I'm so happy I can hardly see straight!
Tracker says top speed 6mph, average speed 1mph, maximum height 65' minimum height 0. Sooooo, I guess this thing may not be too accurate?

 

I have to admit to having been a bit skeptical Doug, but for the first time in reasonable wind, that was truly impressive.