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

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[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.

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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.

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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/prodimages/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.

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[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.

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[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?

[kfxguy]

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.
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i would not worry with the bracket hanging down. mine sticks down like that on my rivercat. It went 95.5mph (best) with the bracket not hanging down and I changed over to another bracket that does it its posted a best of 97.5mph, So I feel certain its not an issue. In other words, its not worth the trouble of messing with unless you just dont like it.

[TheShaddix]

Oh, a suggestion for your bracket hanging too low... You can just add a little ramp from hull to bracket if you think it'll create drag. Indeed it will create air resistance, question is if it's enough to bother with it. In your case it barely steps out, so I would probably just shave off some more on that corner to smooth it out better. It's not a bad idea to make everything as aerodynamic as possible.

[fidelity101]

i would not worry with the bracket hanging down. mine sticks down like that on my rivercat. It went 95.5mph (best) with the bracket not hanging down and I changed over to another bracket that does it its posted a best of 97.5mph, So I feel certain its not an issue. In other words, its not worth the trouble of messing with unless you just dont like it.

Thank you. It would have been substantially easier, and cheaper, to listen to you and jmscard. Unfortunately I continue to take the road less traveled and find myself dealing with lots of new questions. :) I really like the looks of the KBB rudder and it's going to be an easy swap out if/when I hit something in the water, so hopefully the extra effort will pay off down the road. I paid someone to print me up a custom 3D bracket. Hopefully it works out.

The back dimension (that sits flush with the hull) is 54mm wide by 28mm tall. The piece extends out 42mm and the small piece that meets up with the rudder is 25mm tall by 24mm wide. It's also contoured down from the top so the rudder sits low enough to hopefully meet up with the hydraulic arms. There are holes on the top that are 10.5mm wide and 10mm deep...these will allow me to install a 3mm x 10mm bolt into the hole and connect the rudder. After everything is mounted, I"ll have to either print another top and bottom plate or I will try to find some way to cover up the holes. The holes in the back are U shaped and will hopefully be wide enough to hold some locknuts.

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The mount is going to be printed using carbon fiber PLA material. http://www.proto-pasta.com/shop/cfpla I made it as thick as possible so it should be strong enough to support the load. I'll post some pictures when I get the actual 3D printed design in the next day or so.

[kfxguy]

Thank you. It would have been substantially easier, and cheaper, to listen to you and jmscard. Unfortunately I continue to take the road less traveled and find myself dealing with lots of new questions. :) I really like the looks of the KBB rudder and it's going to be an easy swap out if/when I hit something in the water, so hopefully the extra effort will pay off down the road. I paid someone to print me up a custom 3D bracket. Hopefully it works out.

The back dimension (that sits flush with the hull) is 54mm wide by 28mm tall. The piece extends out 42mm and the small piece that meets up with the rudder is 25mm tall by 24mm wide. It's also contoured down from the top so the rudder sits low enough to hopefully meet up with the hydraulic arms. There are holes on the top that are 10.5mm wide and 10mm deep...these will allow me to install a 3mm x 10mm bolt into the hole and connect the rudder. After everything is mounted, I"ll have to either print another top and bottom plate or I will try to find some way to cover up the holes. The holes in the back are U shaped and will hopefully be wide enough to hold some locknuts.

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The mount is going to be printed using carbon fiber PLA material. http://www.proto-pasta.com/shop/cfpla I made it as thick as possible so it should be strong enough to support the load. I'll post some pictures when I get the actual 3D printed design in the next day or so.

Your on the right track. Keith just let me know the design provides more lift than my hm and it may affect it more than it would on mine. So disregard my post.

[fidelity101]

After two different 3D molds, a lot of grinding and filling, adding some brass 6/32 inserts and some JB weld to hold it all together...here is the finished product. It looks pretty impressive to me! :) The top and bottom of the rudder extension is a thick piece of lexan plastic that was sanded to remove the sheen and then painted black so I can access the internal bolts that hold the rudder in place. It came out pretty well I think. Now I need to install the Leopard motors and ESC's.

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I still haven't tightened down the stingers yet as I'm curious if anyone knows a good starting point for the angle of attack. Should I start at 0 degrees?

[tlandauer]

:thumbup1:
Where there is a will....
Great work!!!!

[fidelity101]

Thank you. :)

Now I'm looking closer at these water inlets and one is already loose. I used an exacto knife and cut marks at various angles before laying in a little jb weld. It seems to be holding so I may just do it to the others as well. If that fails, I'll be carving for a long time trying to get rid of all this carbon fiber filled epoxy.

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[TheShaddix]

From my experience, if they are lose, they weren't sanded enough. I had the same issue on my old boat as I was too lazy and lacked knowledge to prep it. Sand them in all directions with some rough grit (80) to increase grab, degrease both hull and tubing with denatured alcohol. Drill a hole same size as the tube, smear some epoxy onto the tube and slide it through. Wipe off the excess. Use some resin thickening additives to increase strength and make it thick enough to create a nice base for your pickups on the inside instead of having it run off. This way you can get the shape more square and neat. Wait for the epoxy to get a bit thicker before doing that.

I also recommend adding that slanted cut on the tubes so you don't have to grind them down later to match the sponson angle as that doesn't come out as clean. And since yours got loose, the water will get through and at this point you're almost better off redoing them. Adding more epoxy or JB weld will just hold it till you have to mess with them again. If the piping is smooth, nothing will hold it.

Don't need to angle the tubes either like the original ones as the bottom cut out shape (teardrop) is what matters in getting more water in. Mine are vertical and it's crazy how much waterflow is coming out of the outlets even at slow speeds. And you don't really need those nozzles soldered on. That's just personal preference and isn't needed imo. Any 3-4mm tubing will sit tight enough. I've never had mine detach unless you use too small a brass pipe and large hoses.

[tlandauer]

^^^
What he said!
Also, IMO, no matter how well these tubes are epoxied, because it is round and only so much sanding/roughing up one can do, I added a support at the end of the tube. This is a tricky issue: anytime you connect/disconnect the hoses, a
lot of twisting and pulling, shoving is placed upon the joint.
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[fidelity101]

That's a great idea tlandauer...removing the blue water tube is what caused the pipe to dislodge in the first place. If it happens again, I'm going to bend them down and make a wooden support structure to hold them in place. Seems to be an easier alternative than trying to grind out a puddle of carbon fiber filled epoxy. Until then, the JB weld really did the trick as the pipe is locked in place so I'm going to leave it alone until it separates again.

Tear drop shapes have been added to the bottom of the hull where the intakes are. I used the Dremel part recemmended by TheShaddix (Thank you)

Now for the next challenge: One of the stingers is installed at an off angle. I'll have to take pictures tonight, but it appears that one of the stingers is 2-3mm off center meaning the prop is angled out towards the side 2-3mm rather than being straight back and parallel to the sponsons. The portion that attaches to the vertical section of the hull seems to be in the proper place, but the square plate with 4 holes that mounts to the underside of the hull is about 1/8-1/16" to far to the outside of the hull. Do you think the negative effects will be minimal or should I go ahead and fix it now? The correct way to fix it will be to remove the part, add another layer or two of carbon fiber to the inside of the boat, epoxy it down, fill the holes, drill new holes and reinstall. It's going to take a few days to fix it. If the small angle isn't that big of a deal, I might just leave it alone until I can buy some of the JBB stingers and do it the right way. Since I've never installed stingers before, I'm curious how much work that would entail as well as it looks like the copper tube is epoxied inside the hull.

[TheShaddix]

You might want to fix that if it's as drastic as 2-3 degrees. You can find out how much it needs to move to the side in order to get it straight once you unbolt the mount, then all you need to do is shift the holes by that much. I know the feeling, though, as my hpr has a similar issue. The original builder mounted one of the stingers about 3-4mm further than the other, visually it's quite noticeable as one of the props is offset length wise. I completely understand someone making such a mistake as it takes practice to drill precisely, but what I don't get is how one would leave it as it is and be ok with that!

[fidelity101]

The stinger that's visually out of alignment is about 3mm (thickness of the bolt) further to the outside of the hull. I'm going to have to figure out an accurate way to measure the current placement so I can figure out exactly how many degrees it's off but it's noticeable. Unfortunately, it's not far enough out that I can just drill new holes so I'd have to expand the current holes to move it, which might be too wide for the bottom plate to cover up. Hopefully that's not the case but time will tell.

Note: This measurement was incorrect as I was basing the "misalignment" off the distance from the inside hull section to the stinger rather than using a ruler to measure the distance from sponson to the stinger. Looking at the hull, you can see the measurements are different...but that's not the measurement that matters. My mistake.

Left stinger
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Right stinger
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[TheShaddix]

If that's the case, you can always make some CF or aluminum plates to create new bases for your mounts. I guess they have to be thin so you still have the vertical adjustment. Or you can just mount them to the new location, then create a neat fillet with black epoxy to cover the old holes.

The best way to get the angle right is to line up a straight ruler to the sponson and check the stinger is parallel to it.

[fidelity101]

I should have asked for the best way to measure the alignment before putting foot in mouth. The right stinger is 1mm off from the portion of the stinger closest to the hull to the furthest distance out. The other one is 0.5mm off. They look different but I believe that's because one is 1mm in while the other one is 0.5mm out. I think I can probably loosen the screws and move the stingers in and out a bit to make up the difference since it's so incredibly small. Thanks for the ruler tip!

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The next question is, how tight do you make the stingers? There is a circular screw which seems to hold two black plastic pieces on each side of the round portion of the stinger inside the hull. That circle goes in about 2/3rds of the way before it becomes to hard to turn with my fingers. I used a wrench to turn it until it was snug, so now it's sticking out about 1.5mm.

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Since the stinger is 92mm long, the 1mm difference is about 0.6 degrees off. The one that's 0.5mm off translates to about 0.3 degrees off. I think that's acceptable. :)

[TheShaddix]

for the little nut that holds the stinger in its cup drop a bit of locktite as that nut will come lose eventually. As for the angle discrepancy, that's not a big deal. However, if it isn't difficult to get right, then why won't you? If anything, you can drill the holes one step larger and slide the stinger support bases to the right position and get it 100%, you'll be glad you did it knowing it's perfect. I know it would drive me crazy knowing something is offset when I could have done it better. And if your boat ever has any weird turning issues and you try to troubleshoot, you'll know this is definitely not the culprit anymore!

[fidelity101]

I finally have some free time today and I plan on installing the motors and esc's...and I'm wondering if I went with the correct setup. I keep going back and forth on whether I picked the correct gear. I have the 4074 2000KV Leopards with OSE cooling cans, OSE couplers, Swordfish 220A 6S ESC's with data logging (because I wanted data logging).

Now that I have all of the components, I'm wondering if I really should have picked up TP 4050 motors and Swordfish 200A 8S ESC's. Reason being, I've heard that the TP motors are more efficient and the extra headroom in an 8S ESC might be beneficial. Do you think the current setup is the way to go or will I be regretting this configuration if I ever push it to 6S 5000mah packs on each side?

Current props are 1616/3 B&S by dasboata (Thanks Chris!)

I'm not trying to build a rocket ship, SAW boat or anything that will approach 100mph. I'm going to be very happy with anything in the 80mph range. I've had good luck with Leopard motors in the past, but I've also had good luck with TP motors.

For about the same price of my Leopard 4074 2000kv motors and OSE water jackets, I could have picked up the TP 4050 2050kv which has significantly higher power ratings and is 6-pole as compared to 4-pole. http://www.tppowerusa.com/motors/in-stock/tp-4050-2050-kv?limit=100

Will I be ok with Leopard or would the TP motors have been a better choice?

[fidelity101]

Also, does anyone known the dimensions for the KBB windshield cutout? I found a local vinyl cutter that can print some out for me, but I need the dimensions.

[Fella1340]

I have the the top 4050 series motors and they are 4 pole motors. They don't go to 6 pole until you get into the larger 56xx series motors. As far as power, I don't think there's enough of a difference between the two to warrant buying new motors. You have to take the manufacturers numbers with a grain of salt, it's advertising as much as it is fact. I have the same escs as well, I haven't put them to use yet but purchased them based on other people's success with the same combination. Many use the t-180 as well with success, same boat, same motors. You should be good to go. You can always upgrade the escs later if you want to really push it.