Newcomer with a question

[Old School]

Many thanks, gentlemen

[Old School]

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.

[rol243]

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.

[Old School]

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

[CraigP]

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!

[CraigP]

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!

[srislash]

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.

[Old School]

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.

[Old School]

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.

[rol243]

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

[srislash]

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

[Old School]

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.

[rol243]

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 ?

[Old School]

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.

[rol243]

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