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

Fire Arrow Foiler / MPX Foil System Testing and Development

This post and the following four posts are a comprehensive summary of the test videos, performance , specifications, changes, and analysis of the Fire Arrow's foiling performance.

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Testing will resume with much more video as soon as my "crew" Dan is available. The boat is ready and I'm sure ready.

Testing Status as of 11/9/14

It's interesting to note that this boat has been sailed a total of 1 hr 50 min with a total of 26 minutes and 38 seconds of sailing video uploaded to YouTube.
In that very short period of time, a radical foiler design using two different foil systems in a combination never before seen in the history of mankind was taken from light air testing to full flying foiling. This is a sort of Index so that if the reader is interested in reading about development milestones they can do so easily from this page:
Sailing History--( youtube channel: https://www.youtube.com/channel/UC6S7JPG1d2uZ91lqt7ObyIw )

1) First Sail-6/17/14, page 91, post 1356. Total video time: 10:55. Total estimated sailing time:25 minutes.
video- https://www.youtube.com/watch?v=X0AHD34_-8c
video- https://www.youtube.com/watch?v=74KEpcmgCh8
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2) Second Sail/ Foil Assist-6/26/14,page 93, post 1393. Total video time 4:42. Total estimated sailing time: 20 minutes.
video- https://www.youtube.com/watch?v=FF7cy8AoFnU
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3) Third Sail-7/10/14, page 102, post 1522. Total video time:2:58. Total estimated sailing time:30 minutes.
video- https://www.youtube.com/watch?v=LmXCdAlo4mk
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4) Fourth Sail/ Full Flying Foiling-7/24/14, page 106, post 1589. Total video time: 7:48. Total estimated sailing time: 35 minutes.
video(long version)- https://www.youtube.com/watch?v=4YBOEolFqiE
video(short version)- https://www.youtube.com/watch?v=7Mok3d4KiMI


Longest period of foiling=15 seconds-reason: Land
The boat would foil for hours in 5mph of wind or more if radio range wasn't a concern and if land didn't get it the way. She was rock steady in pitch and tended to roll a bit in waves always maintaining full foiling.
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Milestones of Development: (click on page above)

1) Reefing, page 102, post 1527
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2) Ama foil mods, page 104, post 1554,
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3) i-flap description, page 105, post 1561,
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4) Pictures of ama, main and rudder foil mods, page 105, post 1575
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5) Pictures of painted foils, page 106, post 1578,
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6) Summary of changes/fixes before first full flying video,page 106, post 1581,
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7) Changes made since first full foiling video, page 109, post 1626,also see page 111, posts 1659, 1661 and 1662,
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8) Removal of i-flap on port foil, page 109, post 1628 and 1630,
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9) GCD and Reefing, page 109, post 1631,
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10) Cutting mast for reefing, page 109, posts 1633-34,
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11) Updated Specifications, page 110, post 1639,
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12) Pictures of reefed rig, page 110, post 1642
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Fire Arrow Foiler / MPX Foil System Testing and Development

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Here is a list of the modifications made since the First Foiling video on July 24th,2014. Number 10 added 10/17/14. 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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MPX Test Model Specifications---latest update: 8/14/14

A) Name- Fire Arrow

B) LOA-79" (6.58')-including bowsprit

1. mainhull-66.19" (5.52') (The reasoning behind and the story of the added hull length can be found in posts 1177,1187-88,1195-1198)4/30/14

2. mainhull+ rudder and gantry(no bowsprit)- 69.125" (5.76')

3.planing portion of ama=34in. (2.83')

4.ama LOA=50.75in.(4.23')

C) Beam-81.6"(6.8')

D) Mast 103in. (1.75"chord wing mast / 8.58')5/1/14

E) Sail Area:
1. Main+ Mast + Jib= 3390.9sq.in.( 23.5 sq.ft.)5/1/14

2. Main+ Mast + Code Zero= 4087 sq.in.( 28.38 sq.ft. )5/1/14

3. Main + Mast-no jib= 2690 sq.in ( 18.7 sq.ft.)8/14/14

4. Reefed Main + jib= 2796 sq.in ( 19.4 sq.ft.)8/14/14

5. Reefed main + mast= 2096 sq.in.( 14.5 sq.ft.)8/14/14

F) Foils(all foils updated 8/14/14)

1. Main foil area was increased from 50 sq.in. to 84sq.in. which gives it a foil loading of .188lb/sq.in. which is identical to the F3 and equal to about 75% of the total sailing weight. For earliest takeoff the lift from the ama foil is discounted to make sure the main foil alone can lift the boat. Span was increased from 23 to 29" with a 7.6/1 aspect ratio. Initial foiling was done with a mainfoil angle of incidence of 2.5 degrees.

2. Rudder foil area was increased from 26 sq.in to 49.8 sq.in. and is now 59% of mainfoil area with an aspect ratio of 8/1. Span increased from 18.74 in. to 23.25 in.. Rudder foil loading is.106 lb/sq.in. and equal to about 25% of total sailing weight at takeoff. Loading on this foil automatically changes from takeoff to near zero to negative(pulling down). Initial foiling as done with the rudder foil set at 0 degrees angle of incidence. But if you watch the videos you'll see that the boat initially pitches up during takeoff giving a positive angle of attack to the rudder foil before leveling off.

3. Ama foil(s) area is 68.62 sq.in. which will change as it is refined. The effective area(projected) for vertical lift is 52.9 sq.in. or 77% of total area. One foil is still using the i-flap, described earlier, while the other foil has had the flap removed but retains the same projected area for vertical lift. The idea is to test whether or not the foil can achieve early take off as well as the foil with the i-flap-or at least close enough to justify the reduced drag by the removal of the i-flap. The effective aspect ratio of the foil includes both the horizontal component and the vertical(curved) component and is 6.4/1.
IMPORTANT NOTE- In the last 7+ min foiling video it is clear that it would be ideal to have the model foils retractable and that for sure, as always planned, the full size foils will be retractable. But when they are retractable they will also be about a foot deeper(3.375" on the model) which would help in waves when on the foils. Not possible on the model, at least any time soon.

4. All Foils change their loading as the boat speeds up:

a. Mainfoil begins to unload right after takeoff until it's primary function is pitch control(with the rudder) and maintenance of the main hull altitude(boat angle of heel). If the heeling force causes the main hull to rise past the preset wand altitude set point( that is, if the angle of heel increases), the main foil will develop substantial downforce adding to the righting moment of the boat.This is a particularly important feature of this foil configuration.

b. Rudder foil starts with a maximum vertical lift of 25% of the total load(5.28 lbs) minus the pitching moment created by the rig. It will change loading automatically until it pulls down, if necessary. Rudder foil works with the main foil to control the pitch angle of the boat. See F2 above.

c. Ama foil begins to load up right after takeoff until it carries the majority of the load. Ama foil angle of incidence is preset for the conditions apparent at the time of launch. On the full size boat the ama foil angle of incidence will be adjustable while sailing but such adjustment will be very infrequent. Ama foil angle of attack is controlled by the main foil and rudder foil working together. Ama foil angle of incidence is preset in the range of 0 degrees to +7 degrees. Initial foiling was done with the AOI set at + 7 degrees. From the results of the early foiling, it appears that the AOI may be able to be substantially reduced-depending on the comparison tests of the two ama foils-one with the i-flap and one without. Independent pitching of the ama foil is physically impossible since ride angle is controlled by the main foil and rudder foil, again, together.

d. Angle of incidence of every foil is measured in reference to the static design waterline which is parallel to the flight waterline soon after takeoff.

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Fire Arrow Foiler / MPX Foil System Testing and Development

What I expect out of this test model:

Fire Arrow

UPDATED( edited): 11/9/14--. This post will be moved and/or updated as required. The idea is to allow anyone really interested to find all the pertinent info on the boat in one place.
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11/9/14--I'm going to describe what I know now after the first series of tests culminating in full foiling on July 24, 2014. These questions/expectations were first put forward by Magnus Clarke and though the boat hasn't sailed in heavy air yet there are some things that are known now. The original of this
post is on page 88. When Dan and I have gotten more video including in relatively heavy air I will amend my responses today as required.


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These are some "questions" posed Magnus on another forum(with a couple I have added). I think they represent a good idea in that it will allow me to summarize my expectations for this test model foiling trimaran before I sail it. And after I've sailed it.

1) Will boat tack thru 90 degrees or so upwind? on foils?
--I expect it will but I also expect that the boat has the potential to tack on foils as well as to gybe on foils. My previous RC foiler,the F3 design did it in relatively light air according to a report from a friend of another owner.In the first light air video the boat tacked fine,but in the video where she was overpowered, the rudder response was too sensitive and caused "pitch-ups". I corrected that in the foiling video but I overreacted and reduced sensitivity too much which caused tacking problems in the relatively light wind(5mph) with waves larger than would be expected. I think that is corrected now. She definitely would not tack on foils in that breeze especially with the main set so poorly-but I think she could have gybed on the foils but I ran out of time. The boat will definitely foil upwind and was held back in the foiling video by the poor set-up of the main. The boat wanted to fly upwind and she actually did for a couple of seconds as can be seen in the long video at between 1:58 and 2min in: https://www.youtube.com/watch?v=4YBOEolFqiE
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2) Will it foil in a stable fashion downwind above a certain True Wind Speed?
--Yes-above 5-6 knots TWS. The boat should begin to foil at a hull speed of 4.75 mph(4.13 knots). The foil loading and power are better than the F3 that met or exceeded these numbers.
The boat foiled in a 5 mph(4.35 knots) breeze measured with a Davis windmeter. She was very stable in pitch and tended to roll a little in quartering waves.
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3) Much of the the time downwind it should fly on "X" number of foils. And this is the behavior I expect to see.
-- It will fly with three foils immersed, one mostly unloaded, one of them carrying about 80% of the load ,the other 20% of the load. After the boat achieves full flight the main wand controlled foil will be near zero lift(except in it's roll of working with the rudder foil in pitch control) with the majority of the load carried by the ama foil and 20% of the load carried by the rudder foil. I expect that the boat will fly at a 10 degree angle of heel with the ama clear of the water most of the time. The boat should be able to foil upwind.
The boat flew with the main foil, lee ama foil and rudder foil immersed. The setup when foiling was 75% of the load on the main foil and 25% on the rudder foil. She foiled at a 10 degree angle or less. There are a couple of instances when the boat was sailing upwind where the main hull and lee ama started to lift but the wind was so light and the main set so poorly that she didn't foil upwind(Except as stated in #1 above). However, there is no doubt whatsoever that she will foil upwind as I get her (and me) dialed in.
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4) Should do "X" when it hits a puff?
--Speed up with little change in pitch and roll attitude.I expect the same after seeing her foil.
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5) Should do "Y" when it speeds up a lot?
--Generally, the same as #4.Same.
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6) When it gets upside down ,it will.....?
--Piss me off... Seriously, I expect the boat to be very stable in pitch and roll so will sail without masthead buoyancy for the first couple of times.She pitchpoled in the "overpowered" video but recovered. That was primarily due to the rudder when turning downwind. When she was foiling she was rock steady in pitch with a small roll in quartering waves. That roll could be cured by deeper ama foils which would be retractable. Always planned on that for the full size but not going to happen on the model(for a while at least).
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7) It will be very pitch stable because.........
-- Even when the ama foil is fully loaded the wand controlled main foil and the rudder foil work together to control pitch of the whole boat and,therefore, the ride angle of the ama foil. Even if the ama foil was to ventilate, it can't physically pitch down, and the planing ama would pick up the slack(lack of lift).The pitch stability of the boat was quite apparent in the foiling video and will show up even more clearly in upcoming video.
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8) Things I am not sure about as a designer include its behavior in these conditions:
a. bigger waves-the wand controlled main foil and rudder foil are very deep which should ensure pitch control in most conditions. Just what the conditions will be that exceed "most conditions" will be interesting to learn.
b. behavior of the ama foil in near top end conditions- will it ventilate, plane(like a DSS foil) or some heretofore unknown combination of foiling and planing(and ventilating). The ama foil will get critical in it's performance far before the mainfoil and rudder foil do-that's why they are so deep. The effective range of ama foil performance both in terms of speed and waves is a major element of the testing to be done. I want an ama foil on the full size boat that doesn't require a wand or manual adjustment throughout the entire speed range-that's a big ask. We'll see how it goes.
Even though we didn't have"near top end conditions" the ama foil performance was one of the big successes of the first foiling test: the UptiP ama foils worked perfectly maintaining a constant altitude even with different speed and loading. In one picture you can see the ama foil breach the surface with no apparent change in effectiveness. The foils were never adjusted before or during testing that day. I expect that in stronger winds I'll be able to reduce the foil angle of incidence and in the next test the effectiveness of the stb. ama foil with the iFlap will be compared with the port ama foil with just about 3 degrees of washin( positive twist-the opposite of washout on an airplane wing)-and equal area to the stb. foil.
c. I want to experiment with the planing ama by changing the ama foil as well as changing the bottom area(but not the volume) of the ama itself.Still to come.
d. As the designer, I want to see if the ama foil lifts the weight due to heeling moment from the slowest speed to the fastest speed-do my calculations match it's performance? I have concerns in both areas. At slowest speeds the foil may require something like the spring loaded flap to create enough lift,and at fastest speeds may require something like servo(manual) reduction in the angle of incidence. Generally, on my foilers I set the boat up with the angle of incidence of main foil at +2.5 degrees and the rudder foil at zero degrees. The ama is an asymmetric foil but I am still starting at + 3.75* degrees though that may too much. These angles are measured parallel to the nominal static waterline that starts at the bow knuckle and goes to the point where the center of the transom touches water. However, I discovered that if I tilt the boat(F3) back after setting the foils up as above, she will take off quicker. In about a 5-6 knot breeze the F3 would take off in about two boat lengths when set up this way. We'll see what this thing will do.* Actual AOI in the foiling video was about 7 degrees.Discussed in 8b above.
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Additional questions and comments:
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9) The L/B ratio of the main hull is smaller than most tris-in other words the main hull is wider. Why do you expect that it will be satisfactory?
-- The L/B ratio on this hull is close to that of a Weta full size tri and matches a 20' tri I designed and built many years ago. The hull is a planing hull and has about 20% more wetted surface(in seahugger mode) than the "ideal" rc or fullsize race tri main hull has. The model is scaled down from a full size hull I used to have which is the primary reason for the beam. But the most important factor in assessing how this hull will work is the Sail Area/Wetted Surface ratio* compared to my F3 RC trimaran foiler. And this boat has equal to more sail area per sq.in. of wetted surface than that boat does both in seahugging mode and when foiling.Since the boat took of in a 5mph breeze, it is evident that the L/B ratio of the main hull had ZERO negative effect on performance. This is a scale model of a full size "sport" foiler and I would use the same basic hull on a full size version after seeing the performance of the boat in all the videos.
* SA/WS(with Code Zero)= equal to F3 at takeoff(even with the wide planing hull), better when foiling--7/1 seahugging, 16.5/1 foiling.
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10) You've said that the projected sailing weight of this boat is 21.13 lb which exceeds your target weight of 16.688lb. How will that affect the performance of the model?
-- I don't expect it to affect the boat much because the amount of sail area per pound of weight almost equals the same measurement on the F3. The boat has enormous power to carry sail. The affect, if any, may be in very light air, but I don't expect a problem relating to weight and it's actually an excellent test for the ability of the boat to carry extra load. If this was designed from scratch as a racing rc trimaran it could have been built for 11-12 lb. but it is designed as a scale model. At any rate, the boat should be able to perform very well at this loading. I extended the stern of the main hull about 9% to improve pre-foiling take off speed. The boat took off and foiled well in a measured 5mph breeze-enough said!
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11) Full size applications in 60-100 footers?
--After re-watching the MOD 70's and Open 60 tri's under sail I'm more convinced than ever that the wand controlled main foil could be a big aid in allowing not only much better light air performance because of flying the main hull in very light air , but improving heavy air performance by improving pitch stability while also allowing the boat to be pushed harder because the wand controlled(or electronically controlled) main foil can instantaneously develop downforce as a responce to a gust giving more margin(not to mention speed) in tough conditions. In a situation like Virbac-Paprec got into a short while back the main foil might have prevented the capsize. But thats one of the reasons why there is a test model-to see if that is true-which could be a big deal.After seeing her foil I'm more convinced than ever of the potential of this foil configuration on oversquare tri's of any size.
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14) Reefing changed see post 664 for changes. Probably won't affect testing.
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15) Radio Box changed-see post 664. Will reduce size and weight of box. Makes installation of servos now and later simpler. Still allows for ama incidence control and "manual" mainfoil flap control with mounting of servos at ama and main foil servo on aft deck with wires run to box.
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16) Did you know: MPX = Max Power Experimental
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17) See post 1177 for the "bottom job" where the length of the main hull was increased by 5.25".
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18) See post 1178 for more pictures of the model with the rig on it for the first time.
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19) Technical Impressions of the Foiling Fire Arrow:
Above on this page 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 this page as well, 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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E) 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 above on this page). 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 and we will get more video when he is available. Without Dans help, there would have been no foiling video.....


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All videos can be seen on my youtube channel here:
https://www.youtube.com/channel/UC6S7JPG1d2uZ91lqt7ObyIw
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Pictures "A" and "B" as discussed in 19c above:

 

Fire Arrow Foiler / MPX Foil System Testing and Development

Fire Arrow /MPX Foil System

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Note: this was written before the boat foiled!
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Here is a brief summary of what makes the MPX foil system unique and why that is important:
1) The boat has four foils total. On the fullsize version, only three foils are used at any one time. On the model, since the ama foils will not be retractable(at least initially), they both contribute to vertical lift at take off with the majority of lift coming from the main wand controlled foil and the lee ama foil.
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2) Here are the unique characteristics of the ama foil:


See page 73, post 1090 for much more on the theory that applies to the unique ama UptiP foil. It has just been updated with a link to Dario Valenza's experiments on A Class cats with "uptip" foils where he found that the foil will function w/o leeway coupling for heave stability --using the breaching of the inboard tip for altitude control when leeway is low.


a. The Uptip ama foil is designed to only lift vertically(no downforce) and horizontally,
b. The ama foil is targeted to perform throughout the speed range with no adjustment. It is anticipated that the angle of incidence may have to be changed once, as speed increases, if it is changed at all.
c. The ama foil is designed to carry 75% of the weight of the boat with the rudder foil carrying 25%. The ama foil loads up as the mainfoil unloads.
d. The ride angle of the ama foil is controlled by the action of the main foil and rudder foil together.
e. The ama foil was inspired by the new type of foil designed by TNZ except that this foil has a wider range of speed before angle of incidence adjustment might be required.
f. The ama foil angle of incidence of the vertical lifting "L" portion of the foil for the first sail is 7 degrees relative to the static waterline.5/1/14
g. The ama foil angle of incidence of the vertical portion of the foil is set at +2.25 degrees, relative to the boat centerline, for the first sail. This will unload the daggerboard and provide leeway coupling to help with altitude control.5/1/14
h. The main foil angle of incidence for the first sail is +2.5 degrees relative to the static waterline.5/1/14
i. The rudder foil angle of incidence for the first sail is zero degrees relative to the static waterline.5/1/14
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3) The main foil has a flap and the flap angle is controlled by a wand*. This allows the boat to fly the main hull in very light air which is a big advantage for an oversquare trimaran-particularly a tri under 20' which would, likely, not be able to fly the main hull in these conditions. As soon as the main hull lifts off, the boat accelerates to roughly twice windspeed in a 5mph wind. As the boat speeds up and heels, the mainfoil unloads as the wand causes the flap to rise. At a certain point the flap causes the main foil to not produce any lift with all the load automatically shifted to the ama foil. If the main hull rises above this point(about 10 degrees angle of heel initially), the flap will continue to rise causing the main foil to create down force(unless this facility is disabled). When the main foil is developing downforce it is also developing lift to weather, similarly to the lift to weather when a Moth is using Veal Heel(except on this boat it is a function of the "normal" heel of the boat and the downforce on the mainfoil). See post 532 for an illustration of how this works.
* The boat actually has dual wands but they act on a single axle acting as a single wand.The reason for that is to allow the wand to work when the boat is heeled. The lee wand is nearly vertical when the boat is heeled 10 degrees and acts to maintain an angle of heel of about 10 degrees and an altitude of the main hull of about 6". See the sketch below showing the heeled waterlines. Also see posts 512 and 514 for more on the wand system.
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4) The rudder foil is a trailing foil that automatically develops 25% of the lift required at takeoff, then gradually unloads until it begins,again automatically, to pull down.
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5) As best I can tell there is no other trimaran in the world using a foil system like the Fire Arrow / MPX system. Having a wand controlled mainfoil on the main hull and an ama foil that flies the ama(nominally a few inches above the water) with no control input other than that of the surface piercing component of the foil and the effect of leeway on the "L" portion of the foil(however small) will be significant if it works. The whole foil concept will be significant if it works because:
a. it allows an oversquare tri to fly the main hull in light air,
b. it unloads the mainfoil allowing it to become,with the rudder, primarily a pitch control system which controls the running angle of the ama foil.
c. it allows the mainfoil to contribute to righting moment with downforce,
d. it allows the mainfoil to develop lift to weather when it is developing downforce.
e. the deep main foils acting to control pitch prevent the main hull from bottoming out and allow the angle of heel to be varied between approximately 10 degrees and 17 degrees(or a bit more) by adjusting the wand length.5/1/14
f. the planing ama design serves as back up in rough and/or gusty conditions when the foil might be momentarily overpowered.
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6) Speed- Top end speed is NOT the priority of the MPX Foil System-light air speed resulting from the unique ability to fly the main hull in light air is. The MPX Foil System's main claim to relevance are the two lifting foils on the main hull which allow an oversquare platform to fly the main hull when a wide trimaran,particularly 20' or under, w/o these foils would not. To make a 1.2-1.3 oversquare tri fly the main hull (without foils) requires excessive sail area(or wind) and impairs the pitch stability of such a boat . The two main foils work together to provide pitch stability way in excess of any "normal" trimaran and control the running angle of the planing ama and ama foil. The system should work well with a planing ama using foil assist and/or using an ama foil that allows the ama to fly when the main hull does(the current test model configuration).5/1/14
Top end speed is enhanced by the initial configuration being tested which has the light air advantage intrinsic to the system with the added speed potential in heavy air due to the reduced ama wetted surface and the fact that the main foil will develop downforce adding to the righting moment. Further, the foil that flys the ama is designed to support 100% of the boats weight as the boat speeds up, unloading the mainfoil and reducing drag substantially.

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>Preliminary testing has encompassed testing all foils to 3 times their calculated maximum load(estimated 150% reserve above that before breaking).

> Boat was originally designed as a scale test model of an 18 footer based on a full size hull I used to have(donated to a friend).Since the stern extention it is longer.4/30/14

>See post 1242 that confirms the ability of my first foiler design(F3), about 15 years ago, to do foiling tacks and gybes!5/9/14

 

Curved Twisted Surface Piercing T-Foil

This basic foil concept was developed for use on the Fire Arrow to replace the dual wand main foil at least in "sport" applications. See post 1831 on the previous page.
I took the concept and eliminated the center asymmetrical section , for use on the D4Z AC 55RC foiler cat-check it out here:
http://www.boatdesign.net/forums/pr...rnational-ac-62rc-class-51540.html#post712646

 

Fire Arrow Foiler / MPX Foil System Testing and Development

Found a new software I want to explore-it lets you add telemetry to an existing video as I understand it-haven't looked real closely at it yet but I figured some others might want to take a look at it:
http://www.dashware.net/

Update: doesn't look like the iGOTU tracker is supported-I'll have to look into it further.....

 

Re; post 1846

You say in 1hour 50 minutes you have had the boat foiling for 15 seconds. Problem is running out of radio range.

If you are using 2.4 Ghz radio gear and the hull you have your reciever in is carbon then you will have issues with reception. To solve the issue put the receiver aerial on the outside of the hull. No more problems. If however you're using any FM band radio gear the carbon isn't an issue. If using either FM or 2.4GHz correctly there can be no excuse for lack of range. Anyone will tell you that you can sail a rc yacht almost out of sight and still have signal. The only issue is knowing if its coming or going.

So come on Dougie stop making excuses about why after an hour and a half you only have 15 seconds of foiling time.

As for your comments further on the you cant see why 60-70 foot multihulls shouldn't be sailing without foils - once again you fire off a whole lot of waffle that you have no experience in - only 15 seconds of foiling makes you the foiling god - I don't think so?

 

Fire Arrow Foiler / MPX Foil System Testing and Development

15 seconds was the longest single period of foiling on the last video-not the total foiling time for that day. I ran out of time waiting for wind-she would have foiled all day if Dan and I could have stayed. Much more video coming.
I'm convinced that this system would be an advantage to almost any trimaran in terms of pitch stability and in terms of flying the main hull early- particularly to small oversquare tri's. On larger tri's it would allow flying the main hull in fairly light wind as well as providing exceptional control.

from post 1849:
After re-watching the MOD 70's and Open 60 tri's under sail I'm more convinced than ever that the wand controlled main foil could be a big aid in allowing not only much better light air performance because of flying the main hull in very light air , but improving heavy air performance by improving pitch stability while also allowing the boat to be pushed harder because the wand controlled(or electronically controlled) main foil can instantaneously develop downforce as a responce to a gust giving more margin(not to mention speed) in tough conditions. In a situation like Virbac-Paprec got into a short while back the main foil might have prevented the capsize. But thats one of the reasons why there is a test model-to see if that is true-which could be a big deal.After seeing her foil I'm more convinced than ever of the potential of this foil configuration on oversquare tri's of any size.
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The antenna is on the top of the radio box:

 

Foiling Gybes---

This is a foiler built by my friend Chris and is among the best surface piercing foilers I have seen. This boat does three foiling gybes in the course of this video-the first I've seen on any RC foiler since my F3 14 years ago:
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UPDATE:11/26/14-I just noticed that Chris doesn't rely on the hydrofoils for lateral resistance and uses a daggerboard for that and his boat is still one of the best RC foilers around!

https://www.youtube.com/watch?v=YLT3v8KlqxM

 

Hello basil,

Good points, people should show their credentials before talking too much!

So, maybe show us your 15 seconds of your boat foiling

Ta!

 

Doug's talk to foiling ratio is very disproportionate. I'd say it's a draw between him and basil at this point. Chris' boat is really cool though. Elegant and functional. Thanks for that video.

 

Fire Arrow Foiler / MPX Foil System Testing and Development

The difference between basils and your talk and mine is that I know what I'm talking about and you two don't have a clue.

 

Yes I do. Chris' boat is cool.

 

Fire Arrow Foiler / MPX Foil System Testing and Development

Well, everybody is right some of the time but your being right to talk ratio is pretty poor- in this thread anyway.