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Foiling MOTH tuning


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Recently bought a used Mach 2, and with no local moth sailors in my 'hood am relying on some of you experts for input.   I've watched all the Outteridge tutorial videos, and read the awesome articles by Dan Neri (he also followed up when I emailed him the below, with some great advice-- much respect here)

The short version of my dilemma -- I can pop up on the foils quickly without drama- until the foil pierces the surface and I crash.  The boat just wants to keep climbing (vertically).

dial out some lift, right ?    

Cant quite understand how to get enough flap ‘range’ on the main horizontal.
 
equipment background:
 
- ride height barrel has a range of 40mm of thread, full-open (long) to fully closed (short)
- large ‘early-rise’ foil has a flap range of 0-28mm (moving bell crank fore-aft with my hands, nothing connected)
- I’m beginning per Dan Neri's article from mid-height with the gearing, in the middle of the bell-crank stalk
 
the problem:
 
- wand position doesn’t seem to have very much influence on main foil flap angle
- range of influence seems to be around only 4mm from wand vertical  to wand aft (low-ride/ launch mode), regardless of barrel position or gear height
 
summary:
 
- it seems to me that we’d want the main horizontal to be ‘flaps down’ (28mm?) to generate max lift for take-off, then as the wand drops to a vertical position, would relax itself (via the shock cord assist) forward until the main foil gap goes to the suggested 7mm as an all-purpose cruising / starting point.  this amount of range seems unattainable based on my various input combinations of barrel length, gearing, shock cord tension etc
 
Gearing: Barrel threads Main Horizontal Flap GAP
wand vertical ——> wand aft
 
low on bell crank:
 
barrel open 40mm threads showing.               flap range= 24-28mm
barrel in middle 20mm threads showing.       flap range = 11-18mm
barrel is closed 0mm threads showing.          flap range = 2-7mm
 
middle of bell crank
 
open 40mm 25-28mm
middle 20mm 17-21mm
closed 0mm 7-12mm
 
high on bell crank
 
open 40mm 23-27mm
middle 20mm 17-21mm
closed 0mm 9-12mm
 
Conclusions:
 
Gearing has little influence on flap position.     Existing controls cannot provide for both a flap-down and also cruising orientation of main foil flap without significant manipulation.    
 
I’ve been able to sail the boat ‘low’ and have no struggle getting the boat to lift off and go all the way up.   However, this is when the main horizontal flap is all the way  in down / hi-lift mode and the boat keeps rising until the foil breaks the surface.  And I crash.    The flap on the main horizontal will not retreat to a neutral-camber position, it stays in hi-lift mode.  Unless I adjust it to neutral, then it doesn’t create lift for take-off. I have not tried to sail it with no camber.
 
If I put the foil @ the suggested 7mm ‘open’ position (with wand vertical, barrel mostly closed, gearing in mid-height on bell-crank) and then re-look at the main horizontal flap angle with the wand in launch position, I would only be at 12mm gap for take-off.  Is that enough ?  If so, whey would it be designed to have a 28mm range ?
 
I”m guessing this is not enough camber to generate the lift I need to get my sorry ass up in the air, as it only provides 5mm more foil flap lift than the indicated / suggested 7mm ‘cruising altitude’ per Dan Neri’s well written article.
 
Hoping Phil S and other mothies will chime in here.    Dan Neri's info yesterday was helpful for sure, I'm just trying to glean as much info as I can to be efficient with my practice time / mitigate the swim meet
 
No, there aren't any local moths to sail with where I am currently..
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Have a pop at sitting further forward. Yours sounds very similar to my first of two moth sessions. Inutiitively as a dinghy person you inch back when going quick / feeling concerned! Thinking about it, makes sense that it leads to quick take off and "breach" of main foil.

Most of the good moths look a little bow down most of the time, and they only seem to go back on the rack downwind in breeze, where I assume it may be balanced off with some adjustment of the rudder angle

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Hi!

If you change gearing, mechanically numbers have to like double between low gearing (high on bellcrank) and high gearing (low on bellcrank), I cannot see any reason why what you describe can happen. it is mechanics :)

some mach2 had issues in the bowsprit, but that would imply that the wand would not move correctly in the full range. If your wand goes full range if you go high gearing (low on bellcrank) the damn flap should really move, even that terrible foil you have (I hate the early lift) :D

I don't know well mach 2, I do not know if you can actually increase gearing in the bowsprit as well. Maybe some more mach 2 experts can help

Mic

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its been too long since I've sailed a Mach 2, so I don't know all of the adjustments (and I know that most are modified pretty heavily anyway).  But what you are describing could be caused by a main foil whose top is canted too far aft, causing the angle of attack of the main foil to be too great.   I've seen this happen on the UFO.  Once you were up to lifting speed, the foil would lift pretty much no matter what the wand was doing.  I don't know how much pitch adjustment, if any, you have on the main foil, but if you can, I'd move the top forward a bit and see if that helps the foil respond to the wand more effectively.   You also may simply need more lift (more AoA) on the rudder foil.  If your main foil is lifting and your rudder is not, it will be hard for the flap on the main foil to generate enough downforce to counteract the high AoA on the main foil.    I am by no means a Moth or Mach 2 expert, but foil pitch may have something to do with what you are seeing, provided the wand and linkage are working properly.

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OK you appear to have a linkage problem. Not enough flap movement for control. For newcomers you need lots of movement to get out of bad situations, later you will calm it down and refine where movement happens, especially when you start in waves.

You did not say if you have a bowsprit or the original M2.0 bow mechanism. If you have the bow mech you need to wind the adjuster antclockwise so that the pushrod connection goes to the bottom of the thread, this increases pushrod movement for given wand movement.

If you have a M2 bowsprit I do not think there is anything which can be out of adjustment, unless its been modified or repaired? Check at least that the little crank at the bow is roughly 90deg to horizontal when the wand is half way down, if its too far either way you reduce pushrod effectiveness. Other bowsprits? I'll need a picture.

Check that the "sliders" at both ends of the foredeck pushrod are properly threaded onto the 2.5mm pushrod. You can untread one end and slide it out. the 2.5mm rod slides inside a plastic tube which slides inside a 6mm id stainless tube. Flush it out with water and make sure ts all clean. Reassemble with some locktite and make sure that the screws at each end are horizontal across the boat, also make sure that when the pushrod is at either extreme there is still plenty of slider inside the tube. You should be able to move the pushrod about 20-25mm.

While you are in the area, check that the front of the pushrod tube is still securely attached to the little bulkhead at the back of the cutaway for the bow mechanism. I have seen old M2s where this has broken and the boat becomes uncontrollable just like your description. Fixing is not easy. Gluing Stainless is a problem, but mainly you might find that if this joint is broken, the SS tube has been compressed and most likely bent. Its a rolled tube with a seam weld and its tends to split if bent. The best indicator is that your forward compartment leaks heaps of water. Replacing the tube with a 10mm carbon tube is the best option, use a wrapped fibre tube not a pultruded on, pultrusions split too easilly. Not an easy job. A few have managed it by grinding away each end and threading a new tube along the old tube, then pulling out the old one. Most I know have cut a big hole in the very bottom of the boat and worked from there. Logic is that the bottom is easier to patch and less obvious later. I hope this is not your problem.

I think I understand that your centreboard bellcrank has a vertical stem and sliding pushrod attachment. The lower on the stem the attachment is the more flap movement you should get. All the way down with the bow winderalso all the way down will probably be excessive and the system will lock up if you dive into a wave. this can break stuff. The M2 system is not strong enoiugh for this so you need to back it off until the flap can come back to horizontal without anything bottoming out. 

Now if someone else has not done that check there may be damage in your system. You will see if any pushrod ends have been bent. (not the little 5mm dia link between the bow mech and th pushrod slider, its meant to be bent). If you do not have this little solid SS link but the adjustable old version, you need to ensure that its set correctly, it has to be as long as possible without locking the slider against the bulkhead, and the screws need to be horizontal at each end or it will break stuff and lock up.

Or you have the pushrod tube damage I covered above.

I have heard of rare occasions where the centreboard pushrod tube is also bending. Mostly because the top end has become un attached from the carbon. (There is alot of epoxy foam inside M2 centreboards and this gets soft and soggy and provides no real support, so the tube is really supported only at each end. Its a plastic tube and as long as its not kninked you can reglue the top end trough the bellcrank recess.

OK thats some of the bad things which can go wrong. Check all that and you should have the system working smoothly. You need to have enough shockcord tension so the wand snaps down quickly with some authority. The wand needs to be able to come back to the low riding waterline, and down to vertical with a bowsprit or a little forward of vertical with a bow mech. The flap should be in neutral with the flap back at 45 deg. The trailing edge should go up maybe 6mm with the wand forward and maybe down 10mm with the wand right back. You get this differential by adjusting the cam setting in the bow mech, it moves the point in the wand arc where the max pushrod movement occurrs.

Next check the angle of attach of both your main foil and the rudder foil relative to the hull. Make a ply template which locks over the foil, holds the flap in neutral and holds you smart phone. Turn boat upside down with foils installed. Download a digital spirit level app to your phone. Zero the level on the bottom of the hull just aft of teh centreboard case. Check each foil, the mainfoil should be between 1 and 2 deg +. You can add thin plastic shims in the foil socket for small adjustments. (the tree top pin options at deck level change the AoA by a half degree, but everyone I know only ever uses the front one which is the min available) The rudder foil should be at 0 with the tiller winder in mid range. You can also shim the rudder or you can adjust the gantry.  Look at the M2 site for gantry adjustment method. Look at Damic Design site for template and AoA check technique.

Sorry I do not have photos, I sold my M2 a few years back, but I hope my old memory is reliable. Maybe I will have prompted some current M2 owners/repairers/maintainers to add or correct  something.

Good luck, the moth is a very complex animal, it requres care and attention to detail, you need to enjoy the tinkering, but the rewards when you get it right will be worth all the effort.

Phil Stevo.

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wow.   ok.    now i’m back to thinking I DO need more range, phil’s note interpret as 16mm of flap range.

my bow pushrod doesn’t slide as well as that description - i’m gonna start with that, and see what that does, also inspect the parts leading to the bowsprit (yes I have that), and report back.  

THANK YOU all who replied here.   I’m on it.  Standby

eric

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If its a Mach2 bowsprit with lots of hours, the pins at the bow lever wear and you get lots of slop in the linkages. That can shorten your deck pushrod movement. Lots easier to fix too.

Check how much the wand moves without the flap moving. You may have other worn parts. M2 shop has all teh spares you need.

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2 hours ago, Phil S said:

If its a Mach2 bowsprit with lots of hours, the pins at the bow lever wear and you get lots of slop in the linkages. That can shorten your deck pushrod movement. Lots easier to fix too.

Check how much the wand moves without the flap moving. You may have other worn parts. M2 shop has all teh spares you need.

 

2 hours ago, Phil S said:

If its a Mach2 bowsprit with lots of hours, the pins at the bow lever wear and you get lots of slop in the linkages. That can shorten your deck pushrod movement. Lots easier to fix too.

Check how much the wand moves without the flap moving. You may have other worn parts. M2 shop has all teh spares you need.

wand moves pretty freely now, but max wand forward (vertical) to max aft (lowrider position) results in flap moving only around 4-5mm

doesent seem enough?  

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You need to get something or someone else to hold the flap while you move the wand. If you can move the wand more than a few inches without moving the flap, then you have too much slop in the linkages. Then start looking at each part in turn to find the problems. It could be worn pins or bearings or the more serious things I listed earlier.

The M3 pins in the deck pushrod sliders wear in the middl because they bear on a threaded part, replace them with some plain shank M3 SS screws. If the holes are worn, drill them 1/8in (3.16mm) and put in 1/8 bolts with nuts. Assuming you have a source of SS screws handy.

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