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No secrets, just put a very high pitched prop on and run right up to the limit on the amp draw. I am running an ice 240amp controller with a neu 1521 1.5d and 4s2p. As you know probably, the NAMBA P Sport-Hydro class is limited to 4s, so you have two big levers, amps and props. I will have to go out and look at the prop again to get you what it is, because it's been set up the same way for well over a year. I know it is a custom prop. The standard props just don't have pitch in them to really go fast and you need to start looking at the custom prop makers or learn to do it yourself to get the really good speeds. I am starting to lean more toward the ABC props as they seem to have nice high pitch props with smaller diameters, but I am still getting a lot out of the X-series props although worked over quite a bit. Of course, the other trick, is keeping it on the water once you get to those speeds.
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OK here it is.. It's a octura x-455, Profiled. 5.29" of T.E. Cup, 4.15" of (C.O.B) Pitch, cut down to 53.84mm Dia. Yeah, I know, it get's crazy with the props when you start racing. This one was done up by Mark Sholund. Pretty sure that is the correct one(although I also have a worked over x457), the Ink was barely still readable on the blades and I am not up to taking the prop off tonight. I was running a modified x-452 that was giving really nice speeds and that is all I could handle because of the battery capacity. I was finally able to cram 4000mah (4s2p) so 8000mah which enabled me to prop up to the next level and still be able to finish the race. The trick is you need also need a great motor(Neu) and a great esc to keep it all from blowing up. In a 6 lap (1mile) race I am using up 70% of my batteries. Which are also high quality (dinogy 65c).
I might add, because my club members are reading, you got to run very fast to keep up with Jay Turner, Jim Vaughn and the others who have way more (decades) experience than I. They are making and altering their own props. I have not yet started doing that. I have learned a couple of things to keep in mind with props. The general idea is more diameter equals more amp draw, more pitch of course equals more amp draw. The thrust cone is what you focus on. I have found that if I can go smaller(nothing crazy here) diameter with more pitch in the prop that is the way to go. You can see Mark cut down the diameter of the prop. and increased the pitch. However, like with anything, at a certain point it is a diminishing return. There is also the whole two blade vs. three blade issue as well. Two blades, less amps. I say this, but I am running three blade props on my bigger boats Q and up. I also have found cupping the very tip of the blades tends to yield good results and on the x series cutting down the leading edge of the prop is a good thing. There is my simple non-technical guidelines on props. There are people that can go on and on this topic and I not one of them. The "art" thing is when they vary the pitch of the prop across the surfaces. You see on the prop I am using it has a different pitch near the center and then it pitches up near the tip. To do that you have to invest in the tools and also learn how it all works.
The other "trick" is just a lot of time changing strut heights, trying other props, adding weight, reducing lift... As they say, there are lots of things to get working just right because you have to finish the race to win it.
P.S. I was looking through my notes(I try to record information on my iPhone about each run) I showed 66.1mph on the x455 prop(smooth water, not in a race) on a 6 lap oval course. The Q's are racing up near and around the70mph mark so not much faster. That is why the P-Sport hydro's are so flipping scary, they are just plain small fast boats. My biggest hydro is a Backlash and it is doing around 75mph so you get the idea. The funny thing is there seems to be a wall around the 65mph to 75mph range when it comes to oval racing. I suppose it is the sweet spot where it takes a lot more horsepower to make them go just a little faster, not to mention they tend to want to fly like a plane at that point. Let's not forget you are turning quite a bit as well and if you are hooked up right you are hitting the turns full throttle pretty much.
Of course the voltage limitations for the classes plays a big role as well. If you can't up the volts then you have to up the AMPS to make more horsepower and that means more HEAT. So there you have a stream of thought by a non-engineer. The engineer's are much more precise in their knowledge. I am certain I will be corrected if one of my general theories here is incorrect. Chuckle. I still have a lot to learn on this prop topic, that is why I say if you want to go really fast, find a good prop guy who does know what he is doing and start having them make props for you. Mark is great, but I have also used Andy Brown, Propswest, and Offshore Electrics(while not worked over, they have very nice thinned sharpened props).Last edited by electric; 02-24-2014, 10:43 AM.Comment
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Hi electric
What bellows are you using for your rudder? I purchased a sullervan one and it not long enough to go through the hull. What is of the rudder iin relation the the center of the drive?Comment
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Bazng,
Bellows? Hmm I guess we are talking about the steering linkage boot. Here it is..
http://www.offshoreelectrics.com/pro...prod=ose-80454
There are numerous ways you can do this. I drill a hole in the back of the hull, slide in a 1/4" or 3/16" diameter copper tube that is an inch or two long. On the exterior side of the boat you can have it just a bit more than flush with the hull and the rest of the tube sticks out in the interior of the boat. You then slide the bellows on the inside of the boat over the copper tube and tie it off with a zip tie. If you want to make it with more "bling" you can use stainless steel tubing. Make sense? Before you epoxy it all in place, make sure the servo rod has enough room to move the rudder without binding with the copper tubing. If it does, then go up a bit in diameter on the tubing. I will get you a picture if you need it.
Rudder placement is as close to the prop as reasonable without the rudder making contact with a large propeller when turning. Don't get carried away with the gap being to tight to the prop, give yourself some room to allow for error and "flex". The flex occurs when you wreck and torque rudder into the prop when the servo arm bends or fails on impact. Yes, I have done that on a mono. The prop can do some very good work on the rudder, but they both come out damaged. If you give me some time(probably tonight) I will pull the boat of the shelf and take a picture of the back with a ruler so you can see it all exactly.
By the way, you did not ask me which side the rudder goes on? This is the one that opens some debate. All of my boats have the rudder on the right side. This particular boat had the rudder on the left because it was built by Mike. It works great, so left is fine. I do think I saw Mike had written something where he had converted his view to putting the rudder on the right side, but if you have already drilled the holes for the rudder on the left side don't sweat it. You could email Mike and ask him his opinion to check me on that.Comment
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Along with my GP400 Im doing one of these too...Im rather torn on what motor to use, I have a 1521 1Y (1577kv) I would think the KV is a bit low for a 4S setup. I was considering a 1515 1Y (2200KV) not sure if I can stuff enough mah lipos in this hull to handle the amp draw ....DJTunnels-PS295. Cats-H&M M1 Supercat Daytona rivercat. Monos-DF Cyberstorm HiTech 29. Hydros- Ms K Vac-U-Pickle Custom built 37" shovel 10th scale converted to FE Shadow. Rigger-H&M Evo II. AQ Harbortug recovery boat. Build in progress 37" cf DragboatComment
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Rudder on left makes left hand corrections easier and safer than prop on the right.
Motor, I'm opting for the 1521 1.5D but, just in case I have a 1515 1Y Castle Neu to try.
Nortavlag Bulc Comment
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Here are some pictures of the rear end. Notice there is no zip tie on the bellows! Chuckle, like I said I did not build this boat so I learn something new every day. The tube looks to be 1/4 and the bellow's fits so tight around it is fine I suppose. I will zip tie it to be sure.Comment
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The 1515 1Y is great motor (I have one). It might work even though it is on the small side. You are right, you just have to prop it up slowly and watch the amp draw. I know my 1521 1.5D comes back warm after a hard race and these Neu motors generally run pretty cool. Your 1521 1Y is more of a 6s motor than 4s. If you are not racing then you could run it using smaller MAH batteries that are 6s and it would be perfect.Comment
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Interesting comment on the corrections to the left. I do see that effect now that you mention it. When I correct to the left the boat does seem much less likely to take off or come unglued than other hydro's I have run with the rudder on the right side. Would be nice to have two of the same kind of hydro set up each way to see the effect for real.Last edited by electric; 02-26-2014, 11:12 PM.Comment
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Hey, just noticed your handle, olwarbirds. My brother is a private pilot and is really into the Warbirds and is very active in a bunch of stuff related to that. His friend Rod has a crazy collection of these old planes. Check it out here.. http://www.lewisairlegends.com/aircraft/ Not sure if you are involved in that, just thought you might be from the name.Comment
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On the GP400, here is what happens when it flips in the air about 65mph and lands badly and compresses the cowling. It blew the paint off like nobody's business. It looks like it hit something, but that was just from the impact of it hitting the water that hard. I must have been a good 6 feet in the air before it came down. I have flipped that boat way too many times and not damage it, but this time my luck ran out. I have since put carbon fiber in the cowling and she is all repainted and looking good as new.Comment
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Yes, my handle applies to my first RC passion of warbirds. Nice website, tks for link...nice lookn GP400, Ive already lined my canopy with CF/kevlar....There has been alot of talk about Hydros left or right side of transom for rudder mounting...alot of testing went into Mike L. decision to go with right side mounting on the GP V2 series... we run these hydros clockwise, dont it make sense to have the pivot point to the inside of the turn ? just a thought not trying to start yet another discussion on this topic. I totally trust Mike's designs .....hadnt thought about the 1515 possibly being on the small side, might have to get a 1521 1.5 .... DJTunnels-PS295. Cats-H&M M1 Supercat Daytona rivercat. Monos-DF Cyberstorm HiTech 29. Hydros- Ms K Vac-U-Pickle Custom built 37" shovel 10th scale converted to FE Shadow. Rigger-H&M Evo II. AQ Harbortug recovery boat. Build in progress 37" cf DragboatComment
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Yes, I really don't want to start the circular rudder discussion. Just pick your side for your own reasons and go for it. chuckle. I see hydro's all over the place and some are on the right and some are on the left, and both types are capable of winning. So on this one, to each is own. Like I said my other hydro's that I build are on the right, but two that I bought (GP335, Phil Thomas Hydro)have been on the left and they work fine as well. Whatever the difference, it must be pretty subtle.Comment
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Nice paint job. I am just going to put the rudder just like your. There is a great Kiwi saying if its not f....... dont fix itComment
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