Rasch Mini Rigger Build Thread

[kacordy]

Ok guys, here we go. I have never posted a build thread. I'm wading into new waters with the 3s so I'm looking forward to some new ideas and support. I just received two new Rasch riggers. The one I'm going to build first is the mini. It's about 15 inches long. I will do a future build thread on the "Hydro 1" My objective is make these legal so I can take them to Europe and run at a national event. To start I want to share some photos and show you how they compare in size to some other hulls. Boats included in the photos are my H&M Mr. Krabs, a CF Raptor, a Renegade and a mini sprint. I want to give a big thanks to Paul Heath in England for getting his hands on the Rasch riggers. Paul has been amazing to work with. I will post the current parts I have soon and we can go from there. Thank you for suggestions.

Allen

[StevenBryant]

Nice little collection you have, love the raptor were did you get that from?


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[kacordy]

[QUOTE=StevenBryant;650207]Nice little collection you have, love the raptor were did you get that from?

That is one of 6 carbon fiber raptors that Brian Buaas designed and built. He owns 3 of the 6. He holds many records including the P-limited hydro saw record at 83mph.


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[kacordy]

Rasch Mini-Rigger Build Questions

More details:

1. Motor LBA2445-3400kv
2. ESC ???
3. Best micro servo for rudder ???
4. Mount rudder to inside or outside ???
5. I was sent a brass tube, Teflon liner, and 4mm threaded wire drive, no strut
With these parts I would assume that they are running the brass tube either
directly through the bottom at an angle so the prop is behind the transom or
they are running the tube inside the boat, it would pop out of the bottom of the
transom??? A not adjustable surface drive unit similar to the Barbwire???
6. Tub bottom is flat from the Transom forward for 10 inches, then rises 1/2
inch in the next 5.5 inches. On a set-up board, what height should the flat
part of the tube be off the board. 1/2 inch ???
7. I have no information on the angle of attack on the sponsons ??? Toe In ???
Toe Out ???
8. From the tip of the sponson back to the trailing edge of the sponson is 5 5/8 inches.
How should the trailing back edge of the sponson be related to the Center of
Gravity ??? Be in front of the CG or behind the CG.
9. The tub and the sponsons are un-drilled for the boom tube mounts and turn fin.
This leaves every dimension, CG, sponson offset, toe-in, toe-out, motor
placement, drive-line angle, ride height, all up to interpretation. Fun, Fun, Fun
10. I have never seen a coupler like this. It has 2 compression fittings on each end.
One for the motor shaft, one for the wire. No set screw for the motor shaft. Very
interesting
11. Does the battery go in front of the motor ??? Or does the battery go behind
the motor ??? The wire drive is 7 inches long which would put the motor in the
center of the hull.

Thank you guys for your thoughts, Allen

[NativePaul]

1, fine.
2. I run a Castle 50 for the logging but have run castle 35 in the past with success both watercooled and uncooled, any 30A+ unit should be fine if Chinese stuff suits your budget better.
3, I have tried quite a few micro servos in minis over the years and swear by Hitec HS-A5076HB.
4, Of the course? Inside, ie, on the right side for running clockwise ovals.
5, I am not sure why you didn't get a strut, speak to Paul, it may have just escaped from the package, I would cut a slot in the back and glue in a piece of carbon then run an ETTI strut, Chris Osman (the designer) did the same but made his own carbon struts. stuffing tube out of the bottom, and strut just behind and below transom.
6, Chris always ran with a positive angle of attack on his tubs for lift, I would guess that 1/2" would be about right at the front, and strut only just below the tub at the back.
7, I went with 5 degrees at the midpoint and no toe on my Hydro1 version.
8, The trailing edge of the sponsons has to be in front of the CoG to keep the prop wet, (I normally reckon on about 10-15% back on the afterplane). If I recall right I asked Chris where the CoG was and he said it is where it is, if you put the motor in with a reasonable bend to the shaft there is not much room for movement.
9, I did warn you they were undrilled, unmarked and had no instructions.
10, I have a MBP one like that, very swish but I have to say I personally prefer a simple grub screw coupler over collets for wires.
11, Battery in front of the motor.
12, It is bigger than 15", they are both designed to have carbon extensions on the front like your Mr Krabs (I lightened Mr Krabs ones and used them for my H1 version), the Mini Hydro class has a maximum hull length of 450mm, so I would make it 449mm long.
z Chris Osman Hydro1 Mongoose.jpg
This is the man behind the machine, Chris Osman with his at the 2013 UK nationals.

[kacordy]

Paul, great information. I will start my layout today. I do have a strut and wire drive from Heath. It appears to be long enough for the Hydro 1, but I only ordered the H-1 hull, fin, land rudder. I will take and post pictures as I go along. Thank you for your detailed help. I'm going to stretch this build out over a month or so because I will have to order some more pieces.

Allen

[kacordy]

Rasch Build

FYI, each sponson ways 25 grams or .85 oz. Tub and lid weighs 85g or 3.25oz

1. Here is a picture of the strut with wire drive and the rudder. The strut is
1 inch long w/o bullet and 1 3/4 tall. It came with the Teflon and Aluminum
Tube. The aluminum tube is much bigger than the Teflon? That makes no
sense? This should work for the hydro 1 but looks a little big for the
Mini? I also received the 7 inch wire drive, Teflon and brass tube. The Teflon fits
snug in this set-up. It might be long enough for the mini. The rudder is perfect.
It's 2 inches tall and weighs 14g or .5oz with screws.
2. I have the CF boom tube front supports.
3. Etti CF motor mount, 6 grams, .2oz, looks like it's for an eco or mono
I might cut out my own with CF
4. I have to research lipo options. The rule states max 110 grams. This Barbwire
battery is 180 grams and way to big. Please recommend brand, Mah
and C rating.
5. I struggle with the thought of bending the stuffing tube and then running
a wire drive through it? I can understand the efficiency of a wire drive if it's
straight. But it's going to have a huge bend in it for it to go through
the hull and then line up parallel to the bottom of the tub and line up with
the strut? Paul does it successfully, pictures in another thread, he uses
a support off the bottom of the tub to the wire for stability and remove
risk of whip?
6. Should I abandon the idea of the wire drive and go with .98 cable.

Thanks, Allen

[NativePaul]

3, Either cut the bottom and sides off the ETTI mount flattening it out to suit the tub or use it as a pattern to drill a sheet of carbon, if you make you own one to fit the tub make sure you drill a big hole for wires to pass through before gluing it in.
4, I assume 3s from the motor's 3400kv, Tenshock and Redzone both do 3s 1700mAh <110g packs, I think they are both marked as 30C, I don't believe they are really that high C, but a 5+ minute run must be under 12C anyway.
5, A wire drive will actually whip like crazy if it is straight, and needs either a light bend or a whole bunch of bearings. I have about 20" of wire in the bigger JAE with minimal bend and 12" of that unsuported after the stuffing tube, which is why I added the support. With a 7" wire you won't need a support, you only need about 2 inches of stuffing tube too, just enough to guide it through the hull, with enough over on the inside to seal with a piece of silicone tube unless the Teflon is tight enough to seal it.
6, I have used 1mm, 1.2mm, 1.6mm wires as well as .98" and .130" flex on minis with sucess, though I don't think i would run 1.6mm wire again.

[kacordy]

Paul, I need to order your recommended 5076 for the mini. Since I need to place a servo order I'm going to get one for the Hydro 1. Is the 5076 to small for the H-1? Or what would you recommend?

Cheers, Allen

[NativePaul]

I believe the 5076 has been discontinued the 5070 has very similar specs but with metal gears instead of Karbonite and higher voltage, I prefer Karbonite if I can get them, and found some old stock in summer, but if you can't find the 5076 anywhere now, the 5070 should be fine as long as you can feed it at least 6v. A Hydro1 will need to step up from a micro servo to a Mini servo, I use Hitec HS 5245MG in mine.

Neither of these servos are waterproof, I mod mine by backing off the screws in the bottom about 1-2mm then starting at the top pulling the case up and smearing silicone grease liberally around the output shaft, then separating the joints in the case and frugally smearing electronic grade silicone sealant into the joints and around the screwholes, then re-tightening. I would recommend waterproofing all your electrics or using waterproof electrics, if you don't want to do for fear of applying too much silicone to the joints and it squirting into the gears when you do it up, most of the radio companies make waterproof servos now, Savox sw0250mg looks to be much better than Hitec's waterproof offering for both MiniH and H1 but it is still 10g more than you need for a MiniH.

[StevenBryant]

The HS5245mg is a great servo to use, however if you are trying to save weight try the Sanwa SRG HR, I use this in my mono 1 and Hydro 1 for several years now without failure.


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[kacordy]

Steve, thank you for the suggested servo. I will look that up.

Thanks, Allen

[kacordy]

I have my booms mounted but not cut or mounted to desired length. I'm trying to figure out where the motor should go. Here are my current dimensions.

1. The overall length is 450mm
2. From the transom, forward to the back of the ride pad is 308mm
3. From the transom, forward to center of the rear boom tube is 267mm.
4. Battery will be 110gm and go in front of rear boom tube
5. Motor is 115g with cooling can.

So how many mm should the back of the motor be in front of the transom?

Thanks,

[NativePaul]

So how many mm should the back of the motor be in front of the transom?

I have no idea, I would guess at 150mm from looking at it, but that is a wild stab in the dark based on looks with no real info to go from

2. From the transom, forward to the back of the ride pad is 308mm

This is almost enough info to help you work it out, the distance from the backs of the ride pads on the sponsons to the prop is the "afterplane" and your CoG should go approximately 10-15% back on the afterplane, so if your strut and bracket puts the prop 40mm behind the transom for example, then your afterplane is 348mm and the CoG should be 35-52mm behind the trailing edges of the sponsons.

Place/tape everything that cant be moved to the hull where they need to go first, like the hardware, bolts etc. Then place things that must be fixed but can move before the build like the servo(at the back for a short pushrod), motor, mount(in the middle of its free space at this stage), ESC and safety loop(although these can technically go anywhere they need to go between the motor and battery to keep the wire lengths down). Lastly place the things that can be moved freely as far forward as they will go which is only really the Battery and RX. Find the COG and work out its percentage of the afterplane like this, if it is between 0% and 10% then things are looking good, move the battery and RX back and check CoG again, if it is more than 15% then you are golden and that is where everything goes. If not, you need to move the motor/mount//ESC/loop backwards or forwards and try again to see if you can adjust between <10% and >15% just by moving the battery/RX. If you cant get it forwards enough you may have to move the servo forward.

[kacordy]

Paul, this is great CG information. I will review my layout and get the CG correct. The leopard motor has a 2.3 shaft. I cannot find a coupler for flex that is 2.3 to .098 flex cable? Looks like I will be forced to use the wire drive that Paul sent me. I need to get a ball bearing strut for the mini. Where is the best source for the strut and the cone that goes in front of it so I can use the wire Paul sent me?

Thanks for your help, Allen