KBB 45" build question/assistance needed

[fidelity101]

I purchased this boat from an OSE member who created a custom rudder solution using a TFL drive meant for a 60" or larger boat. One of the first things I wanted to do was change the rudder back to the Keith Bradley Boats (KBB) type A rudder for 45" boats. As you can see in the pictures below, I ran into a problem and I'd appreciate some help on how to proceed.

Old setup: TFL rudder arm is 70mm back from hull. The actual rudder sits 45mm back from the hull
IMG_3126.jpg

New: KBB rudder arm is 50mm back from the hull. The actual rudder sits 42mm back from the hull.
IMG_3127.jpg

I am not sure about the best way to proceed. If I keep the current hydraulic arms, I will have to create another piece of billet that is 20 mm wider which will push the rudder back an additional 20mm...which would make it 65 mm from the rear of the hull. If I keep the rudder in the same location I will have to either modify the hydraulic arms and/or more likely I will have to remove them completely. The hydraulic arms on this boat, for reference, are 34 mm long from the center pivot point coming off the hull to the end of the black arm.

IMG_3129.jpg

[fidelity101]

Here are some additional pictures of the boat I'm working on. It's already setup very well but I wanted to do a couple of changes. As you can see in the first picture, the billet aluminum block that holds the rudder in place comes down to far...which I'm thinking will have an affect on airflow and I wanted to make it flush with the bottom of the hull. I also want to remove that modified TFL rudder and go with a KBB 45" rudder, which is presenting problems as indicated above. Everything else should be good to go as the TFL Stinger drives look great, the Swordfish 220A 6S ESC's arrived from OSE, I had some Leopard 4074 2000kv motors on hand so I'm using them along with some OSE water jackets. Dasboata is making me a custom set of props, which should be here in a day or two. I'm going to start out with 1616/3 ABC props and I plan on running a 5S 6200mah battery on each side.

IMG_3085.jpgIMG_3086.jpgIMG_3088.jpgIMG_3089.jpgIMG_3093.jpg

I also reached out to Monojeff to see if he could make me a window decal

[TheShaddix]

Your best bet is to create a custom CF or aluminum mount to extend that new rudder. No reason to remove the hydraulic setup as it looks nice and is functional. Another option is to relocate the hydraulic "feet" further outwards so there is more space for them to move with the new rudder. But then you'll have some holes (which you can fill or turn into water outlets). Something like this https://www.youtube.com/watch?v=-Ehu76crTdM

Can you post a pic of those water pickups at the bottom? Something doesn't look right but that could be the angle.

[fidelity101]

The gelcoat was chipped a little when the holes were installed. It looks like they were filled in and sanded smooth.

IMG_3132.jpgIMG_3133.jpgIMG_3134.jpg

I can go with a longer piece of billet aluminum and my friend has a mill so he's going to help me out. The problem with pushing the rudder back is that I'm going to have a longer distance between the rudder and the back of the hull. Does the distance between the boat and rudder have an affect on performance and/or handling? I'm not sure if an additional 20mm would have a negative effect on anything else.

I can move the hydraulic arms out, but there is also a piece of carbon fiber plate installed inside the boat which is guiding the pull pull wires. It wouldn't be that difficult to remove it if needed, but it's in place with an epoxy milled carbon fiber mix...so it's SOLID.

The other small issue to address is the holes in the new KBB Type A rudder are very thin...I'm guessing 1.5mm. The current hydraulic arms have 3mm bolts and the Type A rudder arms don't have enough meat to allow me to drill them out to a 3mm hole. I think I'm going to use bolts that fit inside the rudder arm holes and then I'll use copper tube as a jacket to slide over the bolt and inside the hydraulic arm grips.

[TheShaddix]

You might want to improve those water inlets! At higher speeds the water will just go over those holes with very little going inside. All you need to do is dremel out some teardrop shapes in front of each hole with a grinding bit. Also, the longer distance from boat to rudder isn't gonna hurt it, if anything, it's going to improve your straight line stability, same way as longer drives would, but in turns you might (or not) feel it a bit more sluggish to turn. Since you're not adding too much it'll be ok. If your friend can help you, a longer bracket is your best bet!

[fidelity101]

Thank you! That's the easiest option for sure so I'll give it a shot. 20mm is just over 3/4" which is only 1.7% of the hull length anyway. :) Also, thanks for the tip on the tear drop holes. I'll cut some material away from the front of each hole.

[TheShaddix]

Before you dremel those out, put several layers of masking tape around the holes so in case your dremel bit slips, it won't scratch the boat.

[fidelity101]

Thanks, I'm going to use this as a template.
http://www.offshoreelectrics.com/pro.../ose-80400.JPG

I could always replace the four lines with that pickup, but the current lines are covered by a fair amount of epoxy and milled carbon fiber...so it wouldn't be an easy task. :)

My friend has agreed to cut another piece of billet aluminum if he cant find a properly sized piece. I wish I had a 3D printer...even ABS plastic should be strong enough to support the rudder when it's 54mm thick. The way the KBB Type A rudder mounts, I need to attach the 4 bolts from the block to the rudder from the inside before attaching the block to the hull. That's a great idea as it prevents the screws from backing out, but it also means I'm going to have to find some screws that are the perfect length...the holes inside the KBB Type A mount appear to only be about 4mm deep with 3mm threads.

[TheShaddix]

To get the old ones out all you need to do is turn the brass tubing with pliers to loosen it and it'll then slide out easily. Then just use a milling bit to get the epoxy out. Not an easy task like you said, but could look clean if you added some cf bits to cover it and not just have the tubing go through the hull alone. Can you please post a pic of your current setup on the inside?

[fidelity101]

Here's a few pictures showing the Carbon fiber plate in the back of the boat along with the boat layout.

IMG_3135.jpgIMG_3136.jpgIMG_3137.jpg

[TheShaddix]

Any pics upclose of the stuffing tube section and the water pickups on the inside would help, we can throw in some suggestions if anything can be improved.

[fidelity101]

Lets hope these pictures are a little better. It's a bit cramped in the back of the boat.

IMG_3139.jpgIMG_3140.jpgIMG_3141.jpgIMG_3142.jpgIMG_3143.jpg

[TheShaddix]

Looks good. Use this dremel bit (make sure it's the same diameter as the brass tube). Also be careful not to scratch the hull with the dremel chuck when you angle it low (taping up will help with that). A dremel extension tool is perfect for this type of work too! Align it parallel to the tunnel edge and take your time. Like you mentioned, just match those other inlets that you have.

http://images.lowes.com/product/converted/080596/080596004538lg.jpg

[fidelity101]

Your best bet is to create a custom CF or aluminum mount to extend that new rudder. No reason to remove the hydraulic setup as it looks nice and is functional. Another option is to relocate the hydraulic "feet" further outwards so there is more space for them to move with the new rudder. But then you'll have some holes (which you can fill or turn into water outlets). Something like this https://www.youtube.com/watch?v=-Ehu76crTdM

Can you post a pic of those water pickups at the bottom? Something doesn't look right but that could be the angle.

https://www.youtube.com/watch?v=OO2IqSR9z3Y

I found the above video while searching for the best way to install the KBB Type A rudder. It really looks like the hydraulic arms are further apart and the amount of throw on each side is very minimal. I'm in the process of designing a 3D printed rudder mount as that may be the best option, but I'm curious about the proper rudder placement. My experience with airplanes has taught me that throw is good...and always install linkages 90 degrees. Based on the video, however, that's not the case with boats. It looks like minimal throw and a 120 degree angle between hydraulic arms and rudder arms.

If I keep the hydraulic arms 90 degrees with the rudder arms, is that going to negatively affect the handling? I have the 3D mount designed using Sketchup and I'm about to send it to the printers but I'm holding off until I understand the reasoning behind a 120 degree placement vs. the typical 90 degree placement. Is it just aesthetics or is there a functional reason behind it? If I push them out, I will have to reduce the size of the rudder extension.

[TheShaddix]

The main problem with more angle is drag. The cable will come through the hull at \ / angle, then become | |, so the area where it enters will drag causing your servo to work harder centering the rudder after each turn. Ideally you want a super smooth operation. This can be remedied by having your piping on the inside also angled to allow the cable to continue and curve gradually. But less angle is always better, and ideally no angle is best, but that doesn't look as nice. Another thing, I also use liquid teflon and pour it into the steering tubes to reduce drag. Then use some oil as well. You need to treat your rudder system just like everything else, adding some oil to the hydraulic arms and inside of the tubing when you bring it in for maintenance.

The main issue with boats like MHZ is that they are replicas of the real boat and use the same rudder design as far as location and angles, but since the real boat doesn't use cables, it has no problem with such angle. So if you keep it scale, you end up compromising in this aspect. I like how the arms are mounted on HPR boats due to their longer tail section as you can get the arms barely angled and have zero drag.

In that video there is barely any travel in the rudder arms which is alright for saw runs but isn't ideal for a sport boat as you need to be able to turn the rudder enough when going slow. At speed it's not an issue, but when you need to maneuver the boat at lower speed it won't turn much and will frustrate you in some situations. It's best to have a good amount of travel, but then dial it down on the fly through your controller to minimize it for high speed runs. And another thing is, at those angles the cables end up pulling almost sideways onto the rudder bracket instead of going up and down, so that'll reduce the steering power quite a bit there. The best way is to just find an angle that looks decent and also doesn't cause any drag when you pull the cables by hand.

http://www.hpr-powerboats.ch/images/produkte/hpr_c5008/produkte_hpr_c5008_anlenkung_1.jpg

This is a similar angle to what you got already, I'd keep it similar.

Can you take a pic of the inside of the transom to see how the tubing is mounted?