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  #2476  
Old 01-11-2017, 09:27 AM
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daiquiri daiquiri is offline
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Quote:
Originally Posted by Doug Lord View Post
you might be interested in two short commentaries by Tom Speer on the previous page, post 2465 of this thread
There's nothing from T.S. either on the previous page or in the post #2465 of this thread, Doug... A typo?
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  #2477  
Old 01-11-2017, 10:34 AM
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Tom Speer

Sorry! Post 2460, page 164-----last post on that page.
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  #2478  
Old 01-11-2017, 12:20 PM
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Originally Posted by Doug Lord View Post
The ama on this boat is designed for more or less incidental contact with the water-it is not designed to be sailed "on" since it will be flying from a 5 knot breeze on up.
However, I've been curious about the idea of a planing ama for some time and that is why the bottom widens out as it goes aft. For the "normal"(incidental contact) use of the boat I don't need such a wide planing surface but I want to be able to experiment with it hence the wide bottom. I'll be able to play with it w/o using the foil for lift to see how well it works.

My thoughts;
these complicated unique amas add lots of cost, surface area, complication and weight. They were an interesting experiment back when you started this thread years ago, but when foiling was added their function was all but eliminated. You have the original MPX model to experiment with -you could pull off the lifting foils and see how it behaved and checked the self righting. Now that you are creating a second RC model proto for a real life boat, why not go with cheaper, lighter, conventional floats?
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  #2479  
Old 01-11-2017, 12:37 PM
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WOLF---daughter of fire arrow

What can be done after the planing tests is simply to reduce the expanded aft planing area(cut it off) if there is no other reason to keep it there. Testing the planing area on the Fire Arrow would not be as effective as testing it on WOLF. I have a hunch that that planing area may have more benefits-such as roll damping at slow or no speed-testing full size will prove or disprove that. The other elements of the two stage amas are critical to the overall performance of the boat-like the increased height of the center of buoyancy of the whole TSA(two stage ama) . And the TSA shouldn't be heavier than a conventional ama and probably won't be more expensive. However,regardless, it is far more effective for a small foiler than a conventional ama would be.
The concept model of WOLF is not an rc model-it is being built to show what the fullsize boat will look like.
Thanks for the comments.......
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  #2480  
Old 01-11-2017, 06:41 PM
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Wands / Speer

Slavi, whats your opinion of the two posts Tom wrote?
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  #2481  
Old 01-12-2017, 06:57 PM
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WOLF---daughter of fire arrow

Looks like max beam will be somewhere around 16.5' with the limitation being how the amas will fit when folded-will fold to a max beam of 8'. I have to experiment with it some more but I don't think I can go any wider. That will work-its still slightly oversquare. The more beam the better the mainfoil/ ama foil will work when the main foil develops downforce and the ama foil has an equal and opposite increase in vertical lift. I'll get back on it in the morning and see what I can do. Part of the limit is how high the thing sits on the trailer-right now it would be close to 5' from the bottom of the boat.

1/12/17--UPDATE: I may get almost 18' max beam including the planing surfaces. The amas would fold one on top of the other for a total height of about 5'4" from the bottom of the boat. This will be perfect if it continues to work out. I'll ask my sailmaker to measure his trailer which is identical to the one I'll get.
If the beam was proportionately equal to the Fire Arrow beam it would be 18.48'. It all depends on how it fits the trailer......

1/13/17--UPDATE: Going with 18.3' beam overall. Folded that won't fit in the garage(no vertical clearance) but neither will 16' and I won't go that narrow. So, I talked to Scott (sailmaker) and he said he could make a cover for the folded boat which with the 18'+ beam will be 8' off the ground with the boat folded.
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  #2482  
Old 01-13-2017, 06:07 PM
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WOLF---daughter of fire arrow

Updated specs and notes:

LOA 15.458' (4.7m)
---
Beam max-18.3' (5.58m)
-beam folded-8' (2.4m)
-main hull beam on deck: 2.625'(.8m)
-main hull beam at wl: 2.125'(.65m)
-main hull L/B at wl:7.27/1 (planing)
---
Two Stage Ama-11.3' (3.5m)
-ama hull-7.7' (2.35m)
-ama hull beam .58' (.18m)
-ama hull L/B=13.3/1 (planing)
- curved piece-5.7' (1.74m)
- overlap- 2' (.61m)
- two stage ama canted bottom out 12 degrees.
- two stage ama buoyancy(not including crossarms)=252lb(61%)
---
Weight:
-boat-200lb (91kg)
-crew-215lb (97.7kg)
-sailing/flying weight: 415lb. (188.7kg.)
---
Sail Area:
-main + jib= 160sq.ft(14.9sq.m)
- spin/screecher about 150 sq.ft(13.9sq.m)
-pounds per sq.ft./SA:
--upwind=2.59
--downwind=1.34
---
Designed flight angle of heel: 5.5 degrees to 15 degrees. Standard 10 degrees.
---
Main hull flight altitude at centerline: .5'(.15m)---2'(.61m),Standard 1.19'(.36m)
---
Righting moment:
-crew 215 @11'= 2365ft.lb.(3206.5 N/m)*
-boat 200 @ 7.5'=1500ft.lb.(2033.7 N/m)
[b]TOTAL RM=[b] 3865ft.lb (5240.2 N/m)
Downforce from main foil(if used) approx. 1500ft.lb.(2033.7 N/m)
* N/m conversion done from online converter
---
Foils:
-uptip foil in each ama, adjustable AOI and up/down(mostly retractable). tentative AOI-3-5 degrees over twisted foil.
-mainfoil wand altitude control, adjustable AOI(nominal 2.5 degrees),up/down(mostly retractable).
-rudder T-foil, adjustable AOI(nominal zero degrees).
---
Planing surface on lee ama hull is designed to be flat when main hull is just clear of the water(6") and that will occur at an angle of heel of 12 degrees.

-------------



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Last edited by Doug Lord : 01-15-2017 at 05:52 PM.
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  #2483  
Old 01-15-2017, 05:12 PM
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WOLF---daughter of fire arrow

The folding system on this boat will make set up extremely fast since it is only a matter of sliding the inner tube and releasing a latch on each crossarm and then fold. Eric Sponberg helped with the original work on the slide system and came up with the latch on the bottom of the tube. The hinges are glassed and carbonated to the two tubes so that the carbon doesn't touch the SS hinge.
The new tubes will likely be smaller than those shown in the illustration-probably 3"-3.5" OD carbon. And the push-pull rod will go toward the center of the boat. The ama cant angle and position and type of foil are also different on WOLF.

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Last edited by Doug Lord : 01-18-2017 at 05:24 PM.
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  #2484  
Old 01-18-2017, 05:46 PM
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WOLF---daughter of fire arrow / Ama cant angle

The amas on this boat are at a cant angle of 12 degrees and when the boat is loaded and level they are 6"(152mm) above the waterline at the aftmost centerline of the ama hull.
The ama hull is planing and the aft planing surface is parallel with the water when the boat is at an angle of heel of 12 degrees(off the foils)-and the main hull is just above the water.
--
The nominal flying altitude of the main hull on foils is a little over one foot(304mm) at an angle of heel of 10 degrees. At the same flight altitude and angle the ama is 9"( 228mm) above water. The flight altitude and angle of heel are completely adjustable. At 10 degrees the windward ama foil is well clear of the water(and most waves). And that is a big deal when sailing the boat because it means that the foils don't have to be adjusted up and down with every tack/gybe making it much less labor intensive to sail.
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Last edited by Doug Lord : Today at 06:03 PM.
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