New C5000 build from scratch

[dazzler]

I also cut the openings for the water pickups.

Measure twice, cut once.... well yes please as putting a dremel into the hull is a bit scary afterall!
WaterPickup01.jpg

[dazzler]

Then I spent some time trying to determine how and where to place the motors. Not only had I to create a motor mounting template, I also needed to align everything with the flex shaft. To be honest, this is entirely new for me, so I hope I did it a bit OK....

I used cardboard as a template for the motor mounting plate (from which I will make something out of carbon probably), and since I do not yet have my real motors, I made a dummy motor using some plastic plumbers pipe and aluminum shaft. It has the exact same dimensions as a Leopard 8082 series, but the light weight makes it actually very handy in aligning everything!
UitlijnMotor01.jpg

After I determined where I would put the mounting plate and aligning the flex shaft and all, I cut a piece of brass tubing and bent it just a little (using a blow torch to make it hot first, then it bends very easy)
UitlijnMotor02.jpg UitlijnMotor03.jpg

As it is placed now, it really 'feels' as if everything is OK. I mean the bent in the flex is very limited, everything seems to align great, there's no strange torsion or friction noticeable (the flex shaft turns really smoothly)
On the other hand, I not sure if the brass tube might be a little to short, and putting the motors more to the front using longer pieces of tubing might help to keep water from entering through the shaft? The brass tubing is about 80 mm (3 5/32 inch) long right now.

I'm also thinking I should put my motor about 10 mm more to the front to allow some additional room between the coupler and teflon tubing and install an additional safety clamp, in order to prevent me from loosing a drive shaft should the flex come loose from the coupler (I've heard some stories about that actually happening....)

Advice or comments would be appreciated, The entire setup pictured above is just trial-fitting, nothing glued in place so now is the time to make adjustments if needed!

[dazzler]

Quaestion on rudder setup

Hello,

Does anyone have any experience with the MBP hydraulic rudder?
It has a PTFE tube for waterproofing the assembly, but the hole in the mounting bracket does not seem to align with the dummy cylinder.

Rudder_01b.jpgRudder_01_Montiertb.jpg

As you can see in the first picture, with the PTFE tube inserted in both the cylinder and the bracket hole, the holes for the screw (pivot point) are completely offset.
In the second pictures everything is mounted on the hull, but in this picture the PTFE tubing is not installed as it offsets to hole through the hull...

Either I'm doing something wrong here, or is the design of the bracket not suitable for my setup? I'm considering making my own brackets which have the PTFE hole and pivot holes more aligned....

[TubeNut]

I do not have any experience with the MBP rudder system, the only type I have like that came from HPR when I ordered my 233 way back when, I'd be happy to snap a few pics of his system for you.


On a side note, I would be willing to donate a vacuum pump to you, and get in line for one of these beautiful hulls!

[fweasel]

I'll start with the steering first. The PTFE tubes are not really there for waterproofing, they act as a guide for the cables inside the hull, providing smooth transitions back to the servo mount, more evident when the mounts are set wider on the transom. The PTFE tubes should stop flush with the exterior of the MBP hydraulic mounts, and only the inner cables extend into the dummy arms. The second issue I noticed looking at your setup, is that the length of the black plastic connectors on the ends of your steering cables are long, and take up some of travel potential of your steering system. It appears they will bottom out against the end of your hydraulic arms quickly, limiting total travel. You may need to switch to a smaller plastic end threaded onto the end of the cable.

You've done a very nice job mocking up your motors and mounts. I like to see a little more space between the end of the stuffing tube and the front of the motor collet. I agree, about 10mm might be perfect. It provides more room to wipe off grease during cable installation, allows some alignment relief for the flex cable if the angle of approach isn't 100% perfect in relation to the collet, provides a little wiggle room if you ever need to remove a collet without have to pull the motor first, and also adds a degree of safety in case you use a different collet in the future that happens to be longer. Don't bother with the "cable saver" clamps between the end of the tube and the collet. A clean, damage free cable installed in a quality collet, and tightened properly will not fall out.

Overall, I prefer to keep my motors more rearward in twin builds. I'm not sure the size of your hull, possibly 115 or 138cm, but battery placement and installation room can be an issue if the motors are too far forward. In the 115 sized hulls, it can be really tight to fit a 6S pack into the hull if the motor is too far forward. My point is, think a few more steps ahead into the build process before you settle on a final motor location. Mock up your battery placement at your desired center of gravity setup and see if the packaging aspect of the setup is functional. A cm or two in either direction won't ruin your ride attitude on the water, but can make a huge difference in the serviceability and maintenance of the boat.

[dazzler]

On a side note, I would be willing to donate a vacuum pump to you, and get in line for one of these beautiful hulls!

Thanks for the compliment TubeNut. If the distance wouldn't be that great that might even sounds like a good deal. I'm actually working on a deal with my local fiberglass supplier who might have a good secondhand vacuum pomp available for me...


@fweasel: Thanks for the elaborate explication.

Let's first start again with the rudder:
The tip on the PTFE tubes that should stop flush with the exterior is a good one. This already helps a great deal. As you already say, putting the mounts wider on the transom actually reduce friction on the PTFE tube, but I really don't like the geometry of that setup, as the wider you go on the transom, the more you are actually pulling sideways on the rudder horn instead of in a perpendicular way, which I have learned throughout the years is always better.

So, I made a mock-up transom, trying to sort out the geometry of the rudder setup:

Rudder_newAlign.jpg


As you can see, I've actually placed the mounts as close together as possible, trying to get closer to a "perpendicular" setup instead of going wider on the transom. This also limited the possible travel of the cylinders even further, which is why I put an extra 5mm on top of the "tail" (see red square highlighted - I don't know how this thing is actually called)
I actually like this geometry a lot better than the previous one, and I have no restriction on the travel - as you can see the nut on the rudder horn bottoms out against the metal holder.

There is however some friction left between the metal cable and the PTFE tube, more than I would actually like, but then again not enough to go through all the hassle in creating custom mounting plates... the friction will probably wear off when the metal cable has cut some slack into the PTFE tube

Perhaps the 5 mm spacer can be eliminated when I install shorter plastic black connectors, and I think I can also shorten the brass part of the cylinders to make them fit.


For the second part (motors and mounts):

Space.jpg

It's a 115 sized hull, and with a 10mm gap between the stuffing tube and the motor collet there is about a 13cm gap between the motor mount and transom, leaving about 22 cm in front of the motor and the canopy opening. Most lipo packs I've seen are anywhere between 15 and 19 cm in length, so I don't really expect any big problems here in battery placement, but then again I can be wrong. Judging at pictures from other builds on the forum, I don't think my motors are placed more to the front then in other builds?

[dazzler]

I couldn't resist... I made my own custom brackets, with a better alignment between de PTFE tube and pivot point.

In the setup pictured in my previous post, I needed a pulling force of 1,8 kg (63,5 oz.) on the steel cable to move the rudder from one endpoint to the other, due to the high friction of the steel cable against the PTFE tube caused by the bad alignment.

These are my custom made brackets:
NewBracket.jpg

The geometry remains the same, but due to the better alignment of the pivot point with the PTFE tube there is a lot less friction. With this setup, a pulling force of only 300 gram (10,5 oz.) is required!!!

[fweasel]

Well done. You might even be able to run the tubes into the arms now which would help keep the water of the steel cables.