Fire Arrow Foiling Trimaran Test Model - Page 3 - RC Groups
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Aug 18, 2014, 05:33 PM
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Fire Arrow


I just finished the reefing system on the model. Very simple: loosen the downhaul,
outhaul, vang, peak halyard and luff wire, remove the 20" mast section, re-assemble the mast, roll the sail(retained by velcro strips), and re-attach and go sailing. Makes it easy match the conditions up to about 1 lb/sq.ft. pressure.
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Oct 13, 2014, 05:09 PM
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Fire Arrow-- new type main foil


The main foil, with dual wand controlled flap, is unquestionably the best for performance. But since this is a scale model of a "sport" boat and not a scale model of a race boat, I've been trying to see if I could come up with a surface piercing main foil that could somehow be designed to produce downforce before the main foil flys due to heeling force- to further simplify the foil system.
Right after takeoff, whether the main foil is a surface piercing foil or fully submerged wand controlled foil, it begins to unload with more and more of the load taken by the ama foil. That's all automatic. And the characteristic of the boat as it speeds up is to pitch down. My use of the asymmetric center section is to take advantage of the fact that an upside down asymmetrical foil will generate vertical lift(an airplane with an asy wing can fly upside down) with the right angle of attack and that while upside down it will generate downforce with a low positive angle of attack or zero positive AOA, while the inboard sections* of the symmetrical foil are at zero degrees angle of attack producing no vertical lift-all this when the boat is at max pitch down.
Whats hard in studying this is to remember that the heeling force is increasing as the boat speeds up and pitches down. And that the heeling force unloads the main foil.
---
At max pitch down there is a symmetrical foil and asymmetrical foil cruising along right next to each other ,separated by fences. The symmetrical foil is at zero degrees AOA and so is the inverted asymmetrical foil. Because an asymmetrical foil can generate vertical lift at zero degrees AOA, it can generate downforce when inverted at the same angle of attack!
So I guess I think it's ,at least, worth a test.....
*which are the only portions of the symmetrical foils that are immersed at that point.
Oct 14, 2014, 06:27 AM
Thomas Armstrong
Doug: This idea is brilliant! The only downside I can think of is that as speed increases the added drag would be higher. But worst would be not flying, right?

After looking at the physics, I immediately thought of using it on a monohull... as the high-lift areas at the tips may even provide righting moment! (the windward tip would be out of the water, the leeward side providing the righting moment)

Any reason why a foiling RC monohull is impossible?
Oct 14, 2014, 09:40 AM
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Quote:
Originally Posted by tarmstro
Doug: This idea is brilliant! The only downside I can think of is that as speed increases the added drag would be higher. But worst would be not flying, right?

After looking at the physics, I immediately thought of using it on a monohull... as the high-lift areas at the tips may even provide righting moment! (the windward tip would be out of the water, the leeward side providing the righting moment)

Any reason why a foiling RC monohull is impossible?
=====================
No reason whatsoever*! The thing that may be hard to understand with the new foil is that at the time the boat has pitched down so that both the outboard symmetrical sections and the center asymmetrical section are at zero degrees angle of attack the mainfoil is 100% unloaded.
And the asymmetrical foil will lift at below zero AOA. So when it is upside down it is creating downforce at zero degrees. The biggest problem I see is in waves-where the foil maybe jumping between crests etc. But the only way to know for sure is to test it fullsize-but I can't do that so I'll probably make a model version of the foil and test it. The simplicity is the motivation-if the foil works like I suggest it will ,that eliminates the complication of dual wands-which is a big deal-especially on a full size "sport" version of the boat.
------
A foiling keelboat is very possible-in fact there is a video haunting the internet showing an rc monohull with a canting keel "sort of" foiling.
The rough sketches below are backed up by calculations showing the boat will foil well. To make an rc version first you have to have a way to generate lots of righting moment with low drag. See the "Trapeze Power Ballast System" on the Melges24 RC below. IF you have the sail area and righting moment weight is not a great concern. For light air takeoff you need around 200sq.in. per pound of boat weight(F3), though the Fire Arrow just broke the mold for that by flying with 160 sq.in per pound in a 5 mph breeze! It's all a question of power and righting moment -a self righting foiling keelboat is well within the realm of possibility!
30' Foiling Keelboat rough sketches:
Last edited by DLord; Oct 14, 2014 at 09:50 AM.
Oct 14, 2014, 11:00 AM
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I'm confused, isn't the Fire Arrow foiling on just the amra foil at ? sq. in's with the main foil and rudder at 0 degrees?
Oct 14, 2014, 11:41 AM
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Surface piercing main foil (with downforce)


Jim, as soon as the main hull flies(due to the lift from the wand controlled main foil flap) the main foil begins to unload until most or all of the load is carried by the ama foil with the mainfoil and rudder foil acting together to control pitch. However, the faster the boat goes the greater the heeling force so at some point the wand causes the mainfoil flap to rise creating downforce.
The new foil theoretically does the same thing as the wand except with no moving parts--IF it works.
Oct 14, 2014, 01:29 PM
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So, does that mean it is flying on 16.5 sq. inches?
Oct 14, 2014, 02:56 PM
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Fire Arrow Foiler / MPX Foil System Testing and Development


The ama foil uptip portion + daggerboard segment(total immersed at speed)is about 40 sq.in., the main foil with the flap is about 84 sq.in and the modified foil would be about 84 sq.in. I don't remember the foil areas exactly but that's pretty close. Why, just out of curiosity? If you need precise figures I'll look it up.
Oct 14, 2014, 03:38 PM
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I was just double checking my numbers, I came up with .133 at 80% of 7.00 lbs for my main foils.
Oct 14, 2014, 04:01 PM
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Jim, that's pretty low-you might be able to reduce area a bit. For the F3 both main foils came to 34 sq.in. at a nominal sailing weight of 8lb. 80%=6.4lb so foil loading at take off was .188lb./sq.in.. She would take off in just under 5mph of wind with 1668 sq. in of sail. Remember that on a Bradfield type foiler, foil loading increases right after takeoff due to righting moment being generated by the foils.
On the Fire Arrow at takeoff the mainfoil loading is 75% of 21.13lb=15.85lb/84=.189 lb/sq.in..
You can have a much higher foil loading after takeoff with no problem. With 90% of the load on the ama foil ,loading is 90% of 21.13=20.82/40=.52lb/sq.in..
Last edited by DLord; Oct 15, 2014 at 11:28 AM.
Oct 16, 2014, 04:36 PM
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Quote:
Originally Posted by tarmstro
Doug: This idea is brilliant! The only downside I can think of is that as speed increases the added drag would be higher. But worst would be not flying, right?

After looking at the physics, I immediately thought of using it on a monohull... as the high-lift areas at the tips may even provide righting moment! (the windward tip would be out of the water, the leeward side providing the righting moment)

Any reason why a foiling RC monohull is impossible?
============================
Found a still picture of the canting keel boat flying and a youtube video where it flies for a couple of seconds:
Canting Keel RC Yacht beginning to foil (1 min 29 sec)


There is also a picture of my microMOTH which sort of foiled as well-very difficult to handle-no foiling pictures. Used a movable ballast system:
Oct 16, 2014, 05:30 PM
Thomas Armstrong
That video is simple incredible!!! Stunning.
Oct 31, 2014, 08:58 PM
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The surface piercing mainfoil with downforce(SPuD)( post 32 above) needs to have a way to adjust the center upside-down asymmetric section independently of the outboard twisted sections. This is not a "mature" idea yet, but basically the hollow daggerboard will be fixed to the center section so the AOI of the center section can be varied by angling the daggerboard fore and aft(moving the bottom fore and aft for testing. Then the outside , twisted sections will be adjusted when the boat is set up on the table or maybe I can make a jig to allow adjustment at the sailing site. I'm leaning toward refining the concept so that the whole foil is laid up at one time, including the fences and pivot rods.
I think I can do it-we'll see.
Nov 11, 2014, 10:28 AM
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Fire Arrow Hydrofoil Trimaran


There is a comprehensive summary page up on boatdesign with links to all videos as well as technical details and analysis of the boats foiling performance so far(much more to come) : http://www.boatdesign.net/forums/mul...36058-149.html
Last edited by DLord; Dec 29, 2015 at 03:15 PM.
Nov 28, 2014, 08:16 PM
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Fire Arrow Foiler / MPX Foil System Testing and Development


This is a set-up I used on all my production RC models, but by the time I remembered it, it was too close to the first sail so I postponed installing it.The set-up allows any RC boat to point higher than if they use the "conventional" jib boom pivoted at about 20% of the chord of the foot aft on the boom. I used it in racing before I started producing models and it gives two or three degrees improved pointing. I'm hoping to get the Fire Arrow to tack on foils(almost impossible with her weight so I'm told) and the only way it will be remotely possible is to improve ,where possible, every aspect of her upwind set-up. The problem is adding the Hoyt jib boom after the fact and I may wait until I test the boat with the mast step moved aft(already done) to see if that is an improvement. So far, the only way I see to install the Hoyt jib boom involves surgery and will not be adjustable. But I'm thinking a lot about it so I may come up with a better solution.
The Hoyt jib boom acts as a vang as well as permitting the forestay to be on the centerline and changes the jib shape advantageously when eased. It really works well.....


Picture 4 shows the typical rc model set up and the way the Fire Arrow is set-up now:
click for best view---


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