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

Fire Arrow Foiler / MPX Foil System Testing and Development--braggin on the boat!

Below is the updated list of mods made since the last video on July 24th, 2014. I've posted a list of the history of the development of this boat with all the related videos on page 120, post 1787 but I'm going to add another list and that is the things the worked the way they were supposed to-or better. The last video showed some major accomplishments of this design so far:
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A) The boat foiled in a 5 mph wind.
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B) the boat foiled in a 5mph wind at a weight of 21.13 lbs+ with just the main and jib. That is a major accomplishment because the main and jib have a combined sail area of 3390 sq.in. which is 160 sq.in/lb. The production RC foiler I designed 14+ years ago(F3) also foiled in a 5mph wind but she was 8lb with 1668sq.in. of sail or 208 sq.in. per lb.!
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C) This boat foiled using two completely different altitude control systems-for the first time on any size trimaran anywhere, as far as I know:
a. The main hull uses a dual wand controlled flap equipped main foil to help the boat fly in light air and to add righting moment in stronger wind,
b. The amas used a refined version of UptiP foils, pioneered by Team New Zealand in AC34, for the very first time on any trimaran anywhere as of July 24th 2014! My design for the Fire Arrow foils attempted to create a foil that would require little or no adjustment while foiling while keeping the ama flying as the main foil unloaded and the boat sped up. There are pictures showing this actually happening-"A" and "B" below illustrate the ama flying before the main hull while keeping the ama at about the same altitude even when the main hull flew-so these UptiP foils worked under two completely different load and speed cases-can't get much better than that. I think that the ama foils may have to have their AOI(angle of incidence) adjusted down during high speed sailing but we'll see down the line. No adjustments were made to the ama foils while making the last video.
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D) The foil configuration used by the Fire Arrow, as mentioned under altitude control systems above, is a one of a kind with tremendous advantages-particularly for an over square platform: Thanks to the wand controlled main foil the boat will fly the main hull in very light air which would be impossible if one waited for the sail force from the rig to allow the main hull to fly. The significance of that is that the oversquare beam is not a hindrance to light air performance and adds tremendous righting moment in stronger wind due to the very wide platform. But, the main foil isn't finished yet: as the boat speeds up the main foil is unloaded but as soon as it is required the wand controlled foil will add righting moment to the boat equivalent to half the boats weight or more! It does this because as the apparent wind increases and the boat heels a little more the leeside wand reacts by raising the main foil flap and that causes immediate downforce(righting moment).
a. when the mainfoil is unloaded or creating downforce it "works with" the rudder foil in pitch control giving this platform tremendous resistance to pitch excursions compared to almost any other boat.
b. the main and rudder foil together control the ride angle of the ama foil so that it is incapable of any sort of pitch reaction on its own-either up or down.
This was one of the things so evident in the video and one of the great successes of July 24th.
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This doesn't mean the boat was perfect in the last video-I, as well as a few others, have pointed out areas that need work. We haven't sailed in strong wind with the boat working this well and there is plenty of refining to do(see the "mods" list below). But I wanted to take a few minutes and point out the things that were successfully accomplished on July 24th, 2014.
My crew, Coach Dan, is continuing with a winning season (big one last night) and we will get more video when he is available. Without Dans help, there would have been no foiling video.....

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The list of mods below was changed 10/17/14-#10 added.
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Here is a list of the modifications made since the First Foiling video on July 24th,2014. I've included page and post references:
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1) Changed the wand tension system to allow maximum force on the wand when it is down(flap generating downforce).-page 111, post 1662
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2) Painted small black section on hull immediately behind each wand(as viewed from the side) to help the white wand to show up better in the video.
-page 111, post 1661.
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3) 5 full length battens added to main,GCD removed and mast extention added, peak halyard and downhaul purchase increased. -page 109,posts 1631 and 1632.
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4) A reefing system is now incorporated in the rig with a removable mast section and velcro fasteners to hold the rolled up main.-page 109, post 1633-1634 and page 110, post 1642.
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5) i-Flap removed from port foil(still on stb foil) to see if I missed a step in ama foil development by not trying more area before I tried the i-Flap. The resulting foil has the same planform area as the foil with the i-Flap and a few degrees of washin towards the tip. -page 108,posts 1617 and 1618 and page 109 posts 1626 and 1630. Once I have these results I'll either add the i-Flap back to the port foil or remove it from the starboard foil. Then the process of changing the foil angle of incidence,first, and second changing foil area can start-modifying one foil at a time. The focus will be in reducing drag as much as possible within the constraint of light air takeoff which is the main focus of the Fire Arrow project.
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6) Considered adding aero drag reduction measures to the crossarms but postponed that due to a suggestion from Steve Clark,-page111, post 1653.
(While I greatly appreciate Steve's suggestion regarding aero improvements, I disagree with his assessment of the level of success achieved by the Fire Arrow in her first foiling video. My response to that: -page 116, post 1740)
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7) Added experimental endplates to the outboard ends of the partial span mainfoil flap. -page 112, posts 1667 and 1668.
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8) Added mount for a Velocitek Speed Puck to use to calibrate the i-GOTU* GPS tracker used since day one. -page 112, post 1670.
* see picture of the tracker and its installation on the boat page 113, post 1682.
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9) Moved the mast step aft as well as adding a second jib attachment point aft of the original. -see post 1772
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10) Re programmed the rudder so that exponential can be shut off. The programming used in the foiling video had two rudder programming options: either Dual Rate or Exponential but no "off". This was an overreaction on my part to the "over powered" video where excessive and fast rudder movement caused "pitch-ups" and was mostly responsible for the poor tacking evident in the video. The next time there will be Expo +Dual rate and "off".
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So the major experiment for the next test sail is the port ama foil with the i-Flap removed compared to the starboard ama foil still using the i-Flap.
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Pictures-see"b" under "C" above. UptiP ama foils tour de force:

 

Fire Arrow Foiler / MPX Foil System Testing and Development

Here are the basic specs on the boat as she was on her first foiling video:

 

Fire Arrow Foiler / MPX Foil System Testing and Development

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Definitely going to build a version of this foil to test on the boat-relatively simple to build-and, if it works a very cool deal.....
click for best view:

 

Just from memory (of what I think was a forum post from Tom Speer) when you get to working out the details... it might be worth thinking about using a torpedo shape in lieu of a simple fence (but I wouldn't guess you'd be settling for simple anyway).

If memory served there was a picture (by Tom) of the AC72 rudder showing a torpedo shaped fairing at the junction of the vertical and horizontal.

TomH

 

Tom, in this particular application I tend to think a very thin fence would be better to prevent any pressure migration from one section to another. The thing that Bieker used on the AC72 rudder was designed to postpone cavitation, as I remember it-see picture 9 below. Many foilers use some sort of modified structure at the T-foil joint including Moths, the Fire Arrow, Mirabaud:

Pictures, L to R-1-4-Fire Arrow Rudder t-foil and main t-foil joint, 5-decavitator foil, 6-Mirabaud monofoiler foil, 7- Moth foils, 8- Hobie trifoiler foil with fences on leading edge, 9-Bieker mods to Oracles AC 72 rudder, 10- Fences on Hydropteres surface piercing foils:
click for best view-----

 

One for the record

INteresting to consider




edit

Hey - heres the working version

 

Thanks-interesting stuff!

 

I have wondered about foiling technology cross over from sailing to power boats. The example above seems to be a nifty mix of Tri foiler (entire foil pivoting) and wand technologies.

It looked great on flat water. However, I wonder about messy (irregular period) chop. Getting caught in the wrong harmonic frequency could shake a boat to death.

 

Seemed good when it was good, but few spots in turns seemed to drop, like it fell off the pendulum. I think motored your gonna have less stability cause you can veer off the foil anytime, but sail your following a more constant track. Idiots observation from my end at least.

Barry

 

Fire Arrow Foiler / MPX Foil System Testing and Development

In the last video my estimate of top speed was about 10 mph-and Dan backed me up. The Tracker said 6.7 mph and it also said the boat had flown something like 65' high. So I don't trust the tracker but on the next sail I'll take along the Velocitec Speed Puck(which is equivalent to carrying something like another 29 lbs on the full size boat!).
Did some calculations today on when the ama foil may "profitably" ,speed wise, be shifted to a lower AOI(angle of incidence). It looks to be around 9mph, and its fairly easy to tell because you'll see the ama foil break the surface and the ama fly at about 6"-8" of altitude. I remembered a still picture taken the day we did the last video that shows exactly this. Because of my work today I'm more convinced than ever that the boat speed in this picture was at least 8-10 mph.
Can't wait to get sailing again and get accurate speed figures that will greatly surpass these!

 

Fire Arrow II / D4Z AC 62RC proto

I've definitely decided to build a smaller version of the Fire Arrow, but after I complete the 51" AC 62 prototype. The way it's going to work is that the smaller Fire Arrow will use the same main, jib, mast, main foil and ama UptiP foils that will be tested on the proto cat. The cat is already built- just have to add rig and foils.
The smaller Fire Arrow will be 6' wide with a 4'(or so) main hull. I'm hoping that I won't have to cannibalize the big boat to do it.* Talked with the sailmaker today and he's ready to go-we'll meet next week to get the sails on the way. I put the new mast partially together today. And I will start on foils soon. The great thing about these little boats is I won't need help getting them in the water(knock on wood)-but will still to get video. But at least I'll be able to take them out sailing to practice-something I can't do now. And practice is whats going to make foiling tacks and gybes possible.(besides excellent boat design, of course....)
As soon as Dan becomes available again we'll get more spectacular video of the big boat.
*no cannibalization of the big boat until testing is complete, if ever.

D4Z-

 

Fire Arrow II

I compared the "new" smaller Fire Arrow with a Mini 40 trimaran built to the max beam of that rule. Just shows how much an artificial restriction on beam can hurt trimaran design.......
Mini 40-
--4' hull length
--4' beam
-- SA=9.72 sq.ft.
-- Weight =6.5lb.
-- .67lbs per sq.ft.SA
--Max RM=11.89 ft lb.
--Max pressure before reefing/depowering=.376 lb/sq.ft.
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Fire Arrow II
--4' hull length
--6' beam
--SA=12.5 sq.ft.
--Weight= 7.5lb
-- .6lbs per sq.ft.SA
--Max RM=21.6 ft.lb.
--Max pressure before reefing/depowering=.46lb/sq.ft.

 

Fire Arrow II

I moved from Orlando to Cocoa Beach about 8 years ago and brought a lot of stuff with me, but I threw away a lot of stuff as well. I got very lucky this morning and found the original hull/deck mold for the D4Z as well as the original ama mold for the F3. Those two molds will allow building the Fire Arrow II very light! In addition I found the original main foil and daggerboard molds for the F3 foiler which will save a bunch of time on the D4Z/AC 62RC prototype and on the Fire Arrow II mainfoil.
The mainfoil mold works for two main foils and one rudder foil-so rudder foil area is one third of total mainfoil area(and ,of course, rudder foil loading is much less than mainfoil loading).
The foil molds use a neat system that worked well when I was producing the F3 because it allows the foil and flap to be laid up at the same time and allows the mylar flap hinge to be inserted during layup resulting in a complete working foil +flap!

Left is the current Fire Arrow original main foil and Right, the original F3 foil molds. Both use the offset, partial span flap that allows for a thin foil w/o any flap binding under load:

 

Rudder Placement on an RC Foiling Catamaran

I posted this question in the aero-hydro forum as well because I feel it is as applicable there as it is here:
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I'd like some input on the two choices I have:
1) place the rudder under or behind each hull-on an rc boat ventilation is not the problem it is on full size boats but loss of pitch control is so the better position on an RC boat having two rudders seems to be behind the hull because:
a. it's simpler to adjust rake angle for the rudder hydrofoil,
b.it increases the "footprint"( distance between the quarter chord of the main foil and quarter chord of the rudder foil).
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2) hang the rudder in the center of the boat behind the rear crossbeam. This reduces drag a bit but weight probably isn't less than #1 because of needing to build the structure to mount the rudder.
Retracting the windward foil is likely to be the fastest solution but on an rc cat it is expensive requiring a top of the line, fast (RMG/Guyatt) winch to do the job and would require a rudder t-foil in each hull like the AC 72's, GC32's and Flying Phantom.
On the other hand if the two main foils are wand controlled and left in the water, it seems that the center rudder would work fine. It would be the same configuration(but narrower overall) as my F3 foiler.
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I'd appreciate any thoughts on this to help me think it out.....

Pictures-1)-RC trimaran foiler with two wand controlled main foils and single center rudder, 2) Flying Phantom-using retractable main foil with two rudder foils:

 

Fire Arrow Foiler / MPX Foil System Testing and Development

I've been working on a way to adjust the wand length by radio and figured it out today. Could work on any RC boat using a wand altitude control system to increase altitude downwind and reduce it upwind. A similar version could work on a full size boat as well, probably.
click--