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Thread: Arowana 32" self righting hull

  1. #31
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    Quote Originally Posted by rol243 View Post
    the 4050 i have is a 2310 kv.
    Sorry, but I am now looking at running 6s (two 3s batteries mounted fore and aft) so am thinking around 1330kv.

  2. #32
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    i would be working on something in the 1500 odd kv range running 6s. sometimes it pays to go that little bit higher in size .

  3. #33
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    !500kv would give me around 33,000 rpm. No doubt my son would much prefer that. OSE store showing nil stock for the 1570kv.

  4. #34
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    would it be easier for you to buy the 1570 kv from rcbb ?

  5. #35
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    Quote Originally Posted by rol243 View Post
    would it be easier for you to buy the 1570 kv from rcbb ?
    Pricewise about the same once a cooling jacket is added, although he only has one instock I believe.

  6. #36
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    Building two hulls at the same time is both time consuming and expensive. This shows progress to date with the second hull to the same stage. I am up to the point of affixing the longitudinal rails and completing the install of the stuffing tube. The images show a simple jig I set up to get the shaft square to the motor mount.

    Those attempting a self righting boat may I offer one suggestion, before affixing the top plate on the chamber ensure the vertical plates are water tight. In this hull it was easier to affix the top plate of the chamber before fitting the sideplate, however, finding the source of a leak, right at the front of the chamber proved troublesome, being nearly 0.5 metres from the transom and almost totally dark inside.
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  7. #37
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    I am currently fitting the equipment to the transom and have a question regarding the offset of the rudder. I am using an OSE rudder assembly and a Speedmaster stinger. When fitted, the propellor aligns with the trailing edge of the rudder.

    I am thinking of offsetting the rudder mount centreline 55 mm to the right side of the transom vertical centreline. When the rudder throws full travel to port the rudder trailing edge neatly tucks in front of the propellor so little chance of contact but to ensure adequate clearance I was thinking of using an offset of 55 mm, although it does place the rudder a little far to the right side of the transom (aligning with the outer edge of the right side trimtab). Is it detrimental to offset the rudder too far to the right away from the prop centreline? Due only being able to fit one turn fin, most likely the boat will have predominantly right turns.
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  8. #38
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    What i have found with mono hulls is having the rudder blade slightly behind the prop is better for handling than having the rudder before the prop. another thing to be carefull of is if the rudder is before the prop or even in line with the prop and you should make contact with something in the water which would kick the rudder blade back at the bottom thus making contact with the prop [ OUCH ]. you can position your rudder half way between your stinger and turnfin, just to the right of trim tab.

  9. #39
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    Many thanks. I will position the rudder further to the right than planned to get more clearance from the prop.

  10. #40
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    First static flip test on my son's hull in the bath was a success. The hull simply will not float upside down and flips immediately back upright. I was concerned that my additional float chamber may not have had enough volume. The second hull is about one day behind this hull.

    The test was carried out minus the ESC as I was unsure of the watertight integrity of the hull fittings and even though waterproof to one metre I did not wish to chance fate. The ESC will mount forward beside the foremost battery and simply requires cable ties to secure.

    The CoG is about one half inch forward of "ideal" but I do not think on a 32 inch hull that it should cause too much concern. The loop of water tubing on the transom is merely to seal off the through hull ferrules for the test.
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  11. #41
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    I do not expect much runtime as the flood chamber intrudes on battery location and as the batteries need to be offset to port, space limitations mean that a 3s front and rear is the maximum as there are height limitations as well enclosing within the hatch. The motor does not help either as it is a TP Power 4060 1350kv running 6s (2 off 3s 65C - 130C discharge). The prop in the photograph is a CNC 442/3. I do not know if this will remain on the hull. I need the torque of a three-bladed prop to get the hull up on plane to empty the flood chambers after self righting.

    The ESC is a Hobbyking 180 amp model, which given the potential current draw of the motor may be operating on its limit. I do not wish to over prop the boat to limit potential amp draw.

    Apart from painting the hull, the only work required is to plumb the cooling lines, fit cooling outlets and RC antenna mount, attach the receiver and cable tie the ESC to its mounting. This project has given me a few headaches, the most notable being not knowing if the hull would self right. The original flood chamber as supplied on the hull was too small and leaked like a sieve. Given that the hull cost me around $130.00 including airmail postage I cannot complain. Now I need to concentrate on the second hull (my boat). This will be identical with the exception being a TP Power 4050 1330kv motor running 6s.
    Last edited by Old School; 03-17-2018 at 02:51 AM. Reason: Additional info

  12. #42
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    looking good. you can always give the hull a toss in launch like the glow and gas guys do with there hulls, this will get your hull up on the plain easier if needed. If your doing another mono how about offsetting the stinger / strut to starboard side by approx 3/16 to 1/4 inch as this helps to compensate motor / prop torque so then you should be able to place a battery pack on each side of motor eare for a good balance / cog.

  13. #43
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    I am not concerned with a normal upright takeoff onplane when initially launched , but when the boat flips the port side of the boat will be underwater with the flood chambers full. I do not really see an issue as the TP motors should make easy work of it. Just being a little overly cautious as this is a learning experience for me.

    The self righting ability of the hull requires a port side bias to facilitate the flipping. Thus more weight needs to be placed on the left. A longitudinally stable boat may not self right unless it has a grossly oversized cabin/hatch (look to all the current self righting rescue craft used by the Coast Guard and RNLI organisations). The original Arowana 26" hull had an ugly oversized hatch to help the boat self right. I am extremely pleased with the self righting ability of this hull. The second boat already has the stinger mounted on the centreline and hopefully should self right exactly like this hull. The flood chamber does intrude on the internal hull space and this determines battery size and placement.

  14. #44
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    so have you run this hull yet ? or is this the 2nd hull ?

  15. #45
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    This is the first hull. I only installed the stinger and rudder assembly last night and did a static flip test this morning in the bath tub. The other hull is almost completed, just need to install the rudder and cooling lines.

  16. #46
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    So is it necessary to use more weight on the port side of hull so the self righting works ? i would have thought when the chamber fills with water , the hull then flips back over.

  17. #47
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    Theoretically it is the weight of the water that flips the hull upright, however, other factors come into play like supplying enough water to flip the hull plus the bouyancy of the cabin which helps. From what I have seen self righting hulls are not weight bias neutral and offsetting batteries is needed.

  18. #48
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    One down (just needs painting) and now one more to finish. The first boat is now structurally completed and bench tested. I just need to add a hatch lock for security.
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  19. #49
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    Don,t forget a Turn Fin.

  20. #50
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    Quote Originally Posted by rol243 View Post
    Don,t forget a Turn Fin.
    I was leaving it off for storage as the thing is like a sharp knife wanting to stab everything.

  21. #51
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    Most self righting boats with flood chambers also need weight offset ( batteries normally but sometimes esc also ) to the port side to self right. Sometimes you also need to add stick on weights to the outside off the flood chamber to fine tune self righting.

  22. #52
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    Then there was two. Basically identical except my son's boat has a TP 4060 and my boat a TP 4050. Both running 6s. I have a 442/3 prop on my son's boat and a 'grimracer' 4255 on mine as that is what I had handy. When I get to test, if I like the 3-bladed then I will purchase another for my boat.
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  23. #53
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    Mirror image. does certainly look that way but i must say you have done a fine job on these hulls. well done.

  24. #54
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    Many thanks. No mirror image, look to the different props. There were some trying moments especially in sealing the flood chambers. I have a bare Pursuit hull that I am thinking would make a fine self-righting hull (same hull as the Arowana, but different deck). For that one I will seal each wall as it is added so that I can access the forward section of the chamber. With the two Arowana the additional flood chamber had a carbon fibre lining and as it was pitch black inside it was difficult to see to seal it.

  25. #55
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    Bringing up an old thread that I have finally progressed after several years of neglect. Due to life commitments and a lack of enthusiasm after an extensive build programme with about five or six boats built at the time I finally got back onto this project. The mirror image boat that I built as well, I shipped off to my son but he reported that while a beast of a boat (TP Motor 4060 running 6s with I believe a three bladed prop around 44 mm), it did not reliably self right itself after flipping.

    I decided it was now time to revisit my boat and hopefully overcome the resistance to righting itself. As supplied from the manufacturer the float chamber is woefully inadequate, essentially being less than half the volume needed to self right itself. Added to that the stock factory chamber leaked like a sieve. I taped up the hatch and flipped the boat over in a half full bathtub and noticed that air seemed to be trapped in the additional inner chamber that I had fitted. The two chambers are interconnected so I had thought that the inner chamber would bleed out through the holes in the underside of the hull linked to the outer chamber. I determined that additional holes were needed to vent both chambers and reduce the chance of an air pocket forming and thus inhibiting the ability to self right.

    The end result was that even with both chambers vented of air, the hull would not go the final 1 - 2 cm from the vertical position to turnover and correct itself. The slightest finger pressure was all that was needed so I tried various lead weights in the rear of the outer chamber to determine the minimum weight needed to self right the boat. The weight needed was around 100 gm estimated. The boat then self righted itself every time. Unlike other self righting boats I have seen which take a few seconds to correct, this hull is unstable when inverted and immediately corrects itself.

    While the boat was in the bathtub I decided to test its propulsion. The motor is a TP Motor 4050 1330kv "Y" winding running 6s with a 42/55 Grimracer two-bladed prop. This was the only prop that I had left as in my show of disinterest in the hobby I shipped off all my spares for my son to use as he is a keen devotee of fast electrics. With barely any throttle input the thrust was as much as I would comfortably trust my arm strength. I was amazed at the power of this setup. Because of very restricted space in the boat there is only enough room for two 3300 mah 3s batteries attached to the inner wall of the inner chamber, thus with a powerful motor I guess a runtime would be barely 2 - 3 minutes, but I believe an exciting runtime. A plus is that the hatch is easy to tape up so battery changes would take very little time.

    The hull is still available from the manufacturer but be advised the stock float chamber is woefully inadequate plus will probably leak into the hull. A lot of work would be needed to make a self righting hull that reliably corrects itself. This thread details much of what I did to get to the stage of a reliable self righting boat. I must apologise for the gross misuse of "Miss Geico" stickers. Following is a link to the manufacturer.

    https://www.littohot.com/collections...oat-hull-white
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  26. #56
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    That looks really nice. I believe the hull was suited for a 3S 1 pack setup with a smaller motor in order to have proper weight in order to get it to self-right.

    What is the quality of the hull like? I owned one of those years ago but not a self-righting one. The gel coat was really easy to crack on it.

    Looks like you did a really nice job on it.
    Nortavlag Bulc

  27. #57
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    Ray,
    the hull was well made with an excellent gelcoat. I decided to not even paint it. I cannot believe it was three years ago that I was building it.

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