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Old Jun 20, 2014, 09:16 AM
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United States, FL, Cocoa Beach
Joined Jan 2010
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Fire Arrow(MPX Test Model)

This is just to introduce those that may not know about it to a long term project that is about the Building, Testing and Development of an RC Test model of a 19.5' sport hydrofoil sailboat. The purpose of the model is to test several different ideas but has evolved to initially test a new kind of hydrofoil system for trimarans.
The purpose of the system is to allow an over-square trimaran to fly the main hull in light air. To accomplish that the main hull has a wand controlled main foil with a 30% flap and a rudder foil. Each outside hull is equipped with an UptiP foil which is based(loosely) on the breakthru foil design by Team New Zealand in the 34th America's Cup. These foils are different than the TNZ foil in that they are designed to have a very wide range of speed before angle of incidence(rake) adjustment is necessary and they have some other differences as well. There are actually two different but similar foils to help test differences in foil design.
I'll be glad to answer any questions.....
More information can be found here: http://www.boatdesign.net/forums/mul...-36058-88.html
I've started testing the boat and it's very first sail in extremely light air was 6/17/14 and it went very well. See the tracker screen shot below that shows a top speed of 3mph(2.6knots). Wind speed was 3-4mph( 2.6 -3.48 knots).
Here are the Specs of the boat:
======================
MPX Test Model Specifications---latest update: 5/9/14

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=4087sq.in.(28.38 sq.ft.)5/1/14

F) Foils:

1. Mainfoil(wand controlled flap)-Span=23.75in., Area=39sq.in.

2. Rudder foil-Span=19in., Area=29sq.in.

3. UptiP ama foil(one used at a time,except at takeoff)-Span(from bottom of ama- a surface piercing, soft "L" configuration)=16.5in., Area(from bottom of ama)=45sq.in.; varies with speed and load.(Inspired by the TNZ AC 72 main foil with refinements that allow it to behave as a surface piercing foil with(with or without leeway coupling) a wide speed range that- hopefully- won't require manual angle of incidence adjustment while sailing.)5/1/14

G) Weight- 21.13lb. 5/1/14

H) Foil loading at takeoff*(80%= 16.9)=.190lb/sq.in.(F3-.188)(lighter=better)5/1/14
* windward ama foil+main+leeward ama foil=22sq.in.+39sq.in.+28.125sq.in=89.125sq.in. at takeoff.

I) SA/Lb(21.13lb displ ) with Code Zero=193.4sq.in.,with main +jib=160sq.in(F3-208.5)(more=better)5/1/14

J) SA(incl Code Zero) per sq.in. of mainfoil group area(89.125sq.in) at takeoff=45.85 sq.in./per sq.in.(F3-49 sq.in/per sq.in)(higher=better)5/1/14

K) SA/WS(with Code Zero)= better than F3 at takeoff(even with the wide planing hull)--7/1 seahugging, 16.5/1 foiling.

===================================
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Old Jun 20, 2014, 09:23 AM
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United States, FL, Cocoa Beach
Joined Jan 2010
169 Posts
Fire Arrow- an MPX Test Model

First sail was on Wednesday the 17th of June in really light air. Hereis some video:
MPX First Sailminus jib! 009 (8 min 44 sec)

[youtube]74KEpcmgCh8[/youtube]
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Old Jun 20, 2014, 04:26 PM
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United States, FL, Indialantic
Joined Jul 2008
105 Posts
rc sailing

Just an fyi there is a good sailing club very near you that meets in Wickham park
on Wednesdays and Saturdays at 10am several good builders there as well at the back lake. I am a member but up north for the summer. would be a good test lake the lake is 8ft deep.
Mike

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Old Jun 20, 2014, 05:28 PM
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United States, FL, Cocoa Beach
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Quote:
Originally Posted by ktm500mx View Post
Just an fyi there is a good sailing club very near you that meets in Wickham park
on Wednesdays and Saturdays at 10am several good builders there as well at the back lake. I am a member but up north for the summer. would be a good test lake the lake is 8ft deep.
Mike

===============
Thanks, I called somebody about that place and went down there. Nobody was sailing when I was there but it seemed like the north lake was shallow a long way out. I couldn't tell much about the south lake but the place is really beautiful. The biggest problem for me was that it seemed like parking was a long way from the lakes. However, a police officer drove out on the grass while I was there?
Is it ok to drive up close to the lake and unload? Thanks for the post.
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Old Jun 26, 2014, 06:44 PM
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United States, FL, Cocoa Beach
Joined Jan 2010
169 Posts
MPX Test Model

Sailed in wind that overpowered the boat since I don't have an effective reefing system. I was looking for 6-8 and got 9-11mph. This video isn't very good and future videos will be much better. As of today we (Dan the video guy and me) flew the boat for the very first time. It was the first sail in foiling conditions and I probably should have waited for the new heavy air main or for better conditions, but my patience ran out and we sailed. Something in the sheeting system broke making controlling both sails difficult-I'll check on what it was tomorrow. These were tough conditions for this boat in it's present configuration but she did just fine. The youtube video is being edited to remove the shakiness which apparently takes a very long time. Last time they did this they screwed up the audio-I'll add music when the editing is done.
MPX Foiling-Foil Assist- Flying Main hull- Over Powered (4 min 42 sec)
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Old Jun 27, 2014, 06:04 AM
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Cleveland
Joined Aug 2002
283 Posts
Rudder wand time???? LOL
Not a bad start Doug!!!
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Old Jun 27, 2014, 08:05 AM
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United States, FL, Indialantic
Joined Jul 2008
105 Posts
wickam park

if you come in via the main gate the ranger station will be on your right make a right at the stop sign and follow this road all the way towards the back of the park
once you pass the dog park about 250 yards on your left is a parking lot with a small pavilion with parking close by you will know your in the right place if you see two docks and the clubs marks out in the lake.
Mike

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Old Jun 27, 2014, 08:54 AM
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Joined Jan 2010
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Quote:
Originally Posted by ktm500mx View Post
if you come in via the main gate the ranger station will be on your right make a right at the stop sign and follow this road all the way towards the back of the park
one you pass the dog park about 250 yards on your left is a parking lot with a small pavilion with parking close by you will know your in the right place if you see two docks and the clubs marks out in the lake.
Mike

-------------------------
I owe you an apology-I was thinking of the sailing site off Hibiscus-not Wickham
I'll go check it out. Thanks!
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Old Jun 27, 2014, 08:56 AM
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Joined Jan 2010
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MPX Test Model

Quote:
Originally Posted by JIM CALDWELLA View Post
Rudder wand time???? LOL
Not a bad start Doug!!!
----------------------------
Right! A little tuning and she'll be fine......
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Old Jun 28, 2014, 10:34 AM
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Quote:
Originally Posted by ktm500mx View Post
if you come in via the main gate the ranger station will be on your right make a right at the stop sign and follow this road all the way towards the back of the park
once you pass the dog park about 250 yards on your left is a parking lot with a small pavilion with parking close by you will know your in the right place if you see two docks and the clubs marks out in the lake.
Mike

==============================
Went down there today to take a look and it seems real good. Shallow quite a ways out but one of the guys pointed out the deep water. Perfect spot for no-wave testing. They were racing Solings and looked like they might race IOM's later. Parking is a long way from the cabana dock area but apparently you can drive on the grass-two guys were parked right next to the cabana.
Thanks for reminding me of this place. A friend and I demonstrated a couple of America One spinnaker boats there around 1996. Though my memory was of a smaller lake?
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Old Jun 28, 2014, 10:51 PM
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United States, FL, Indialantic
Joined Jul 2008
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wicham park

the close parking is for disabled sailors, regulars guys are about 75 feet from the structure. current schedule is 9 am rg65 class at 10 am soling's and us 1 meters
racing all on Saturday. Rich is the name of the commodore and Dennis is the name of the treasurer.
Mike

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Old Jun 29, 2014, 08:53 AM
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Quote:
Originally Posted by ktm500mx View Post
the close parking is for disabled sailors, regulars guys are about 75 feet from the structure. current schedule is 9 am rg65 class at 10 am soling's and us 1 meters
racing all on Saturday. Rich is the name of the commodore and Dennis is the name of the treasurer.
Mike

=================
Thanks!
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Old Jun 29, 2014, 07:14 PM
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MPX Test Model

Some interesting technical facts: based on the boat sailing in 9-11mph wind
and flying the main hull. Boat is an oversquare platform and the full size boat would require about 17mph of wind to fly the main hull w/o the main foil-which will allow the main hull to fly in as little as 5mph of boat speed(6-7 mph wind speed ,estimated). One of the main functions of this design is to use the mainfoil to fly the main hull BEFORE it would on the basis of just wind pressure.
MPX Test Model:
1) Heeling moment at 11mph wind about 45.2 ft.lb.( .48lb/sq.ft pressure on 23.54 sq.ft @ 4' )
--
2) Heeling moment at 9mph wind about 29.2ft.lb. (.31lb/sq.ft. pressure on 23.54 sq.ft @ 4' )
--
3) Righting arm with both the ama and the ama foil supporting some of the weight= 3.04'.
--
4) MAX RM of boat with ama and the ama foil supporting the weight required to fly the main hull: 3.04 X 21.13= 64.24 ft.lb
--
5) Ama buoyancy 7lb
=====================
Conclusions:
A) At 11mph wind and boat weight of 21.13(discounting rudder foil loading) :
--1-So vertical lift required of ama + foil for this HM= 45.2ft.lb divided by 3.04=14.86lb (so even with ama submerged ama foil would have to generate 7.86lb of vertical lift).
---
--2) Vertical lift required of main foil at this wind speed=[21.13-14.86]= 6.27lb
------------------
B) At 9mph wind speed and boat weight of 21.13(discounting rudder foil loading) :
--1-So vertical lift required of ama + foil for this HM= 29.2 divided by 3.04= 9.6lb (with submerged ama ,foil would have to generate 2.6lb of vertical lift)
---
--2) Vertical lift required of main foil at this wind speed =[21.13-9.6]= 11.53lb.

====================
This, coupled with the video is conclusive proof, beyond a shadow of a doubt, that the foils worked in arduous conditions and that they allowed the boat to fly the main hull in conditions where it would not have been able to do so otherwise. Which was and is the central rationale for the MPX foil system.
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Old Jul 02, 2014, 12:18 PM
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Canada, AB, Calgary
Joined Oct 2012
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Hi Doug,

Good to see it on the water and it looks great.

To my eye, it looks like the rig pumps a bit when the boat bounces in waves. I can't see what you have for shrouds, but you may want to have a set of lowers and a set of uppers. The reduced pumping would give you more consistent forward drive which will help achieve a steadier foil.

Look forward to more testing and videos.
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Old Jul 02, 2014, 01:39 PM
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United States, FL, Cocoa Beach
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169 Posts
MPX Test Model-Problems Identified and Solved

Thanks, CF! I hate to admit it but you're 100% right-it was just an act of blatant carelessness on my part-its easy to adjust the shrouds and I simply failed to do it. The shrouds are spectra and adjusted with a bowsie or a miniature turnbuckle or both.
======
Heres a list of the problems and solutions at this point. Everything on the list will be fixed by the next test sail( I hope):
----------
MPX Testing and Development------Problems and Solutions
----------
Here are the problems encountered in the last test sail-part of which is shown in the video:
1) Dynamic Pitch-up's: there were two dynamic pitch ups where the bow jumped up during a turn. Both those and the almost pitchpole were caused by abrupt rudder movement. In the one captured on the screen shot below, the hard rudder movement threw the boat completely clear of the water except for elements of three foils. Amazing power to do that on a 21lb scale boat. Solution is probably to enable dual rate and or exponential on the transmitter, though with practice a smooth turn could probably be learned.
--
2) Vang and downhaul--the gooseneck slides on a vertical rod. I tied the downhaul to the gooseneck so as the vang was tightened the gooseneck tightened the downhaul. This was a bad idea that worked poorly. Solution: de-couple the downhaul from the gooseneck and fix the gooseneck so that it can't move down(or up for that matter). Done. Added a cunningham grommet for the downhaul . Increased the purchase of the downhaul to 8/1.
--
3) Peak Halyard and GCD-Gaff Control Device is the thing sticking up above the gaff to which the peak halyard is attached-line stretched. Solution: converted to spectra and increased purchase.
--
4) Sheeting system-line from the jib side of the drum jumped off because, under a lot of load, the sheet induces slack at the drum. This actually makes me happy-I was afraid I might have stripped the $380 winch! Solution: add a block with a spring to that side of the drum so slack never happens. Note to self: never subject the winch to loads outside its design range-reef, switch rigs or don't sail!
--
5) Rig slack. This happened because I didn't tighten the shrouds enough for those conditions which allowed the rig to go fore and aft a lot which allowed the top of the main to have undue influence on the pitch stability of the boat as well as screwing up the set of the jib. Will discuss the matter with the crew(that would be me) to see to it that the shrouds are always tightened.
--
6) Being overpowered:
a. I dodged a bullet this time by not ruining the sail winch-it is NOT set up for the load found with a 9-11mph breeze+boat speed+ waves and the full rig. Will go with the SA limits I know and use the windmeter to make sure I've got it right.
b. Will design and build a new #2 rig instead of reefing the original main*. The reefing system I used on previous boats won't work with the rotating wing mast.
I was mighty impressed with the way the boat handled the fact that it was overpowered and sailing in big waves(for the model) so I want a rig that will hopefully allow sailing in almost any condition. Removing the jib in those conditions wouldn't help-too much wind for the main only.
* This will be expensive and take some time. In the meantime I have an old rig for a much smaller boat that I may use. Will at least have entertainment value when the mast snaps like a twig......

====================
Next test sail will be in wind between 5 and 7 mph*. The designer(that would be me) says the foils should work in those conditions and the boat crew(me again) has been warned to not repeat the joyriding in unscripted conditions!
*I tend to use mph and not knots because the wind pressure table I have is in mph and the foil lift formula uses mph(ft/per second). If you want knots divide mph by 1.15.
Stay Tuned........
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