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Thread: Newcomer with a question

  1. #31

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    Cool looking boat. There is a lot of good info on here so don't mind asking.

  2. #32

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    While I am awaiting the slow boat from China with my carbon fibre cloth, I have regularly revisited this project making little changes to the interior each time. My first thoughts were to simply modify the hull but still retain the original look of the interior with its plastic mount brackets. Common sense eventually dictated that the entire interior had to be scrapped and start with a clean sheet, regarding placement of motor mounts, servo, batteries and ESC. With everything cleared out I can now look at this project in a positive way.

    My first question is in regards to motor placement. I have secured a 36 series longitudinal carbon fibre motor mount and need to determine its placement as it will be bonded to the shell after the shell interior has been strengthened with carbon fibre cloth. As the motor is relatively heavy should I position the motor longitudinal centreline over the C of G and then allow the batteries (one either side of the motor) to balance out the moment weight of the rest of the hardware (stinger and rudder aft and ESC forward of the motor on the centreline)?

    I am taking the theoretical C of G as approximately 30% of the 'wetted' waterline measured from the stern.

  3. #33

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    its wise to place all gear in the hull and balance c.o.g. from there before the motor / mount is fitted , its not good to place batteries port and starboard in a mono hull as the V of the hull will amplify a bad balance . keep the batteries in front of motor when setting c.o.g. balance.

  4. #34

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    Many thanks

  5. #35

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    Upon receipt of my HK Osprey, I have removed the 3/16" stinger and now modified it to fit the 60 degree sloped transom on this hull. The sloping transom problem has now been overcome as both the rudder mount and the stinger are now modified to fit. Now awaiting carbon fibre cloth to arrive.

    The Osprey had a two-piece flexshaft so this will not be used on this hull. Hopefully, I will be able to salvage the stuffing tube, teflon liner, dog drive and 40 mm propellor from the Osprey to use on this hull.

    Edit: I have removed the stock stuffing tube from the HK Osprey and will fit to this smaller mono. I noted that the stuffing tube is two tubing sizes too small for the stinger strut tube, so have cut tubing to allow the stuffing tube a neat fit inside the strut tube. I will allow approximately 1/4" insertion and seal on final install. I will also fit a Speedmaster rotating bushing to the stinger with a one-piece flexshaft.
    Last edited by Old School; 10-10-2017 at 09:29 PM. Reason: Additional information

  6. #36

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    The slow boat from China arrived this afternoon with my carbon fibre cloth. I quickly set to work and mixed a small quantity of West System G-flex (designed for adhering to ABS plastic after first keying the surface with coarse sandpaper) with some chopped carbon fibre strands and filled the void in the hull as a result of me removing the old skeg.

    Once cured I need to then complete the task of reinforcing the hull. I need to purchase some acetone, white vinegar and disposable brushes. I have never worked in carbon fibre but about fifty years ago I did do a little fibreglassing as part of my apprenticeship. Fingers crossed!!!!!!!!

  7. #37

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    This is my "kit" of carbon fibre cloth. When I lay the cloth the thin tape side will be unseen.

    Edit: carbon fibre now added. I used a West System epoxy formulated for use with ABS plastic (G-flex). The use of white vinegar as a cleaning solvent has been a godsend, saving me a fortune in acetone. For a week or so I have been cutting the bottoms from empty plastic milk bottles to use as mixing containers for the resin. These were perfect. I am happy with the result, but it could have been better executed if I had a little more experience. I applaud those who carry out perfect results on their hulls.
    Attached Images Attached Images
    Last edited by Old School; 10-11-2017 at 11:12 PM.

  8. #38

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    I have hit a stumbling block installing my stinger. The transom is angled at 60 degrees and coupled with a 'vee' hull and the addition of carbon fibre to the interior, I have found that when the holes were drilled for the lower mount holes on the stinger there is no room to fit a nut and washer. The mount bolts enter the hull right where the transom intersects with the floor.

    I have refilled the lower holes in the transom with an epoxy resin and feel that my only alternative is to use self tapping screws on the two lower mounts holes. This is not ideal but what alternative do I have?

  9. #39

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    Drill and tap a backing plate?
    Paul "tug Killer" Upton-Taylor, Cat lover.
    FastElectricBoats.co.uk

  10. #40

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    Quote Originally Posted by NativePaul View Post
    Drill and tap a backing plate?
    Paul,
    I wish that I could however, the threaded end of the mount bolt enters the inner face of the transom right where the lower edge of the sloped transom intersects with the floor of the hull.

  11. #41

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    can you fit Thread Inserts into the existing bottom holes then all you have to do is screw on the bolts.

  12. #42

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    Unfortunately not. I tried last night to enlargen the recess on the inner side of the transom to get a nut in there but to no avail. I have extended the stuffing tube through the transom about 1/4" - 3/8" so this will support the lower edge of the stinger tube, while still allowing some trim angle if needed. I feel the self tapping screws should be sufficient as in reality I have little choice.

    Similarly with the trim tabs. These will need to be attached with self tapping screws for the same reason as there is no way a nut can be fitted to a machine screw mount. Also, I will have to revert to my initial idea of using the simple Traxxas Spartan stock release turnfins as mounting the 'expensive' fins I later purchased will have the same problem. There is just no room at the transom/hull interface to fit retaining nuts - the 60 degree sloped transom has caused me multiple issues.

  13. #43

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    Can you get pics with a flashlight in there to light it up? Maybe someone can see an out of the box solution...

  14. #44

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    How about this. Either use some epoxy metal repair, or build up the area with epoxy glue and when cured, drill and tap the holes you need.
    NZMPBA 2013, 2016 Open Electric Champion. NZMPBA 2016 P Offshore Champion.
    2016 SUHA Q Sport Hydro Hi Points Champion.
    BOPMPBC Open Mono, Open Electric Champion.

  15. #45

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    you do know what a Threaded Insert is don,t you ? these will fix your issue.

  16. #46

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    Many thanks, gentlemen

  17. #47

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    A couple of technical questions please. The photographs show the trouble the sloped transom has given me. I need to source a longer 3 mm securing bolt for the trim angle adjustment. I have simply reversed the original stubshaft to represent the position of the prop as I do not have a replacement flexshaft as yet. The stinger is simply placed in position and is not secured at all.

    My research indicates that a stinger should be 5% - 7% of hull length. I have taken this stinger from my recently arrived HK Osprey (a much larger hull than this one) and at roughly 10 cm from the transom to the far edge of the prop the percentage of hull length is almost 15%.

    With my rudder temporarily in position the far edge of the prop from the transom aligns with the trailing edge of the rudder. I unfortunately had to get an "oversized" rudder as these were the only ones that the mount to the transom could be separated from the rudder support arm (all courtesy of the sloping transom) as the support arm needed to be modified to compensate for the transom angle.

    Should I reduce the length of the stinger? Will an overly long stinger effect performance? I have read that the prop should be mid span on the rudder blade. Is it possible to cut the stinger tube shorter? How does one remove the lead/teflon bushings? I intend fitting a Speedmaster rotating bush so the bushings need to come out anyway.
    Attached Images Attached Images

  18. #48

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    you can still have the stinger / prop coming out past the rudder blade and still have good turning control. the Lead Teflon bushings are ok as long as you keep the shaft stub greased up after each run. to fit the speedmaster bushing you need to have an outer sleeve for the speedmaster bushing to spin in, this is normally done by using a suitable sized brass stuffing tube that goes into the stinger , stinger adjustment will be limited with this speedmaster bushing set up as opposed to using the lead teflon bushings. if you want better quality lead bushings go to a bearing supply shop as they sell them for around 60 cents a piece., when they wear out just tap them out and tap in the new ones.

  19. #49

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    Many thanks. I sourced the 1/4" brass tubing for when I eventually get the Speedmaster bushing.

  20. #50

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    I would have made a box that squares that up and glassed it to the 60 degree transom. It could be an ingress or an external placement. When I'm hit with stuff like that, I start cutting and glassing!

  21. #51

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    Quote Originally Posted by rol243 View Post
    you do know what a Threaded Insert is don,t you ? these will fix your issue.
    I think you're right... Grind off one side of the insert's nail head. If there's room to drill a clearance hole for the bolt, there's room for the threaded insert. Personally, I would have squared it up with a glassed on structure. You gotta be willing to do some cutting and glassing in this sport, especially when in repair mode!

  22. #52

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    You can fit the brass tube into the stinger to facilitate the speed master Bushing. It may take a couple sizes or you may have to lightly drill the stinger to fit the brass. As I guarantee that stinger is all metric. The brass tube does not necessarily need to run right thru as a stuffing tube as this would mix any stinger adjustments. Just Loctite the brass tube inside the stinger.

  23. #53

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    Many thanks gentlemen. My first thoughts were to either remove the transom and refit sitting upright or to build a pod to enable the stinger and rudder to mount vertically. I then decided too much work was involved. Initially this was to be a quick and dirty brushless conversion. Alas, it has become a monster, so perhaps I should have invested a little energy squaring up the transom. Too late now!!!!!!!

    Many thanks on the info on the stinger conversion.

  24. #54

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    Still a long way to go, however, external components now temporarily fitted. The interior is strengthened with two layers of carbon fibre. I need to epoxy (JB_Weld?) the motor mount frames, epoxy the ESC mounting, mount the servo and receiver then balance the C of G once the batteries are sourced. Will need to fit flotation and paint the hull.

    Pity the rudder support arm is oversized but unfortunately smaller rudder assemblies do not have removable transom mounts. As stated earlier, I needed a removable mount so that the rudder support arm could be modified to accommodate the 60 degree transom.
    Attached Images Attached Images

  25. #55

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    Looks good, you have done a fine modification job on this hull and no doubt it will go well once it hits the water.

  26. #56

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    Nothing wrong with that. I like the look of the hull. So what type of batteries are you looking for? One can use wood blocks to make provision for placement of the real thing. Then use fishing weights on the wood to replicate battery weight for CG

  27. #57

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    Thanks gents. This project has been a steep learning curve. My dilemma now is C of G. At present a rough mapping out at a static 30% from the stern. Alas, even with the motor as far to the rear as I would want (motor is actually midspan on the C of G), I need to have the batteries basically aft of the motor. On port side it is not a problem, however, the servo and receiver occupy the starboard part of the stern. The right hand battery will need to be closer to the C of G which effectively rules out its total weight as a counterbalance.

    I would have liked the battery/batteries to be on the centreline, however this is not possible. I hate to suggest it but is "dead" weight acceptable. I realise that it would be parasitic adding unnecessary overall weight, however, if I cannot balance the boat with batteries what alternative do I have please?

    The motor chosen (3660 size 2070KV Brushless Inrunner) will be taken from a Hobbyking Libero that I am expecting any day now and will be run on 4s2p. Battery choice will be critical due limited available room either side of the motor mounting. Most likely will be in the region of two off 4000mah 4s 45C lipo batteries. I need to run through a list of batteries to find a suitable battery with the right dimensions and available locally otherwise expensive shipping penalties are incurred. Airmail shipping companies do not like lipo batteries.

    Edit: with approximately 100 gms lead at the stern I can statically balance, minus batteries, at 33% "wetted" hull length. This would give me a better tolerance to position the batteries if the boat proves to be difficult to get on plane or nose down attitude. The single battery used initially weighs in at around 600 gms. This was a 4500 mah 4s 45C lipo. Thus with the parasitic lead left in the stern, two batteries around 300 gms - 350 gms each may be able to balance out the hull.
    Last edited by Old School; 10-14-2017 at 01:20 AM.

  28. #58

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    it would be better if you could get the battery packs in the center part of hull line as with the packs on each side of center the hull will want to rock left / right as the deep -v hull will allow this, a shallow - v hull can handle this battery position better. isn,t there any room for the batteries behind the motor ? if not can you make some room ?

  29. #59

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    The aft face of the motor is 13 cm forward of the transom. The area aft of the motor is occupied by the locking collet (approximately 3 cm in length and the stuffing tube. There is simply no centreline location for the battery/batteries aft of the motor. The position/angle of the stuffing tube dictates the motor location so this cannot be altered so to keep flexshaft alignment. The servo needs to be located on the starboard side close to the stern so this also would intrude on battery considerations. I do see numerous hulls with side mounted battery packs. No doubt this impacts on lateral stability but given my space limitations it is something I need to live with.

  30. #60

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    could you place the batteries cross ways [ east / west ] over the flex shaft log.?

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