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New to RC with a 63” bare hull - help!

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Old 08-27-2019, 03:42 PM
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WhiteH2O
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Default New to RC with a 63” bare hull - help!

I found a 63” deep vee hull in my dad’s garage that I want to make into an rc boat since I got some lake property. I had an electric rc boat when I was a teen, and have been out of the hobby since, and with the size of this hull, I think gas is the way to build this one to avoid having to buy hundreds of dollars of batteries for 5 minute runs.

I’m not sure what realistic expectations are for a build like this, but I’d love to get speeds in the mid 40s or faster without taking out a second mortgage.

I started looking at power options and quickly found lots of options from $200 to over $500. How big is the difference between the G300PUM for $220 and a J&G 36mm for $513 (looking at Gizmo)? This hull is big and wide, I could fairly easily put in two G300PUMs for a similar price as the J&G, but would maintenance and complexity be made up with that much better performance? There seem to be lots of other options as well between those two options, and I’m not sure what the performance vs cost trade offs are.

As for driveline and rudder setup- what should I be thinking about here? Are different setups based on desired performance? Such as extending the rudder far back from the transom, or is that more for prop clearance? Advantages or disadvantages of one piece rudder strut combinations vs separate prop strut and rudders? Stinger type drives vs struts that seem like they effect prop depth (surface drive vs submerged)? Dual rudder vs single?

Any input and recommendations are appreciated!




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Old 08-27-2019, 06:42 PM
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Okay, first thing's first:
1) Since you haven't been in the R/C world in years, stick with a single drive. Going with twin drives complicates things since you will:
  • double your cost in parts
  • double your maintenance
  • double your fuel requirements
  • double your aggravation when issues pop up
2) I'd go with a known reliable engine manufacturer. J&G, Gizmo and B H Hansen are all known to be reputable and for full service. The first two are more expensive as they sell engines set up more toward performance than a Hansen set up
3) You're looking at getting a specific speed. That means you need to have as little in the water as possible. Forget the double rudders and struts as they both add more drag and reduce the speed your boat can attain. A surface drive "stinger" with a flex cable would be your best bet for reaching your desired speed. As far as the rudder bracket, you only need one long enough to get the rudder past the prop though some will tell you the rudder doesn't even need to be as far back as the prop to be effective.
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Old 08-29-2019, 09:55 AM
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Lots of good info, thanks for that! I had a feeling that dual engines wasn't a great idea for me. I think the biggest part for me is double the aggravation because I don't have the experience to know how to fix issues yet. Cost is another one too of course. I figured that a dual rudder was overkill as well. Looks like a basic build for this first time boat is the way to go.

Could anyone give a little input as to what size and level of modification of engine would be ideal for this build? I'm currently looking at a G300PUM BZ1 from Bonzi. It seems like a good combination of price and power. For just a few bucks over stock, it has a few minor upgrades that seem like it could help push a big hull around. Any better options that I should be looking at?

As I'm looking for running gear, I came up with another question- what determines length of shaft? I'm somewhat assuming that determines where the engine gets mounted (distance from prop to engine), so should I plan on the engine being 1/3 of the way from the end of the transom to try to get the balance point around 1/3 of the way down the boat? I'm guessing the electronics in the rear will somewhat offset the weight of the gas tank in front of the engine. Am I close to being right here? Does 500mm sound like I'm in the right ballpark? Can they be trimmed at all, or am I stuck with the length I buy?

So, as I understand this, I need to mount two stringers (plywood) 5" apart for motor mounting, and a convenient place to put a radio box? Like I said before, this is a completely empty hull. I'm working on a deck and a hatch right now as I try to figure out power, running gear, and electronics.

Once I get enough posts to be allowed to post pictures, I'll start documenting what I'm doing with visual aids...
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Old 08-29-2019, 06:57 PM
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Okay, let's cover a few things that I know, not what I don't:
1) The engine isn't what needs to be at the 1/3rd up from the transom, that's where the boat needs to balance. Moving the engine forward or back is a way of achieving that balance point.
2) The shaft can be cut, but there is something you need to be aware of if you do so:
If you go with a square drive, the shaft can be cut but to do so means you will have to solder/weld on a stub shaft which can be very difficult for someone that's new to boating as length must be within a specific tolerance and welds must be almost flawless
If you decide to go with a round collet drive, cutting the shaft won't be as big of issue, but you need to be sure to cut the shaft long so you can adjust the length.
3) The most common location used for a radio box is just forward of the transom. The reasons for this is that it cuts down the length needed for the rudder pushrod(helps prevent bending) as well as keeping the weight as far to the rear of the boat as possible
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Old 08-29-2019, 07:34 PM
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1. I guess I'll get all the parts and pieces and before I get out the epoxy, I'll play with fore and aft balance to see what works best. I'd assume balancing with a half tank of gas would get the average balance the best.
2. Sounds like a round drive is the way to go. I can make metal stick to metal, (TIG or solder) but sounds like round is just easier in general. Easy choice there- long round drive line in the cart.
3. Easy enough. Radio gear in back.

Thanks again Hydro Junkie. I see you are just about an hour and a half north of where I am (Gig Harbor, WA). I hope to get the chance to see you and some of your boats some day!

Build update: Got a deck put on the hull today. Started fairing in the rough areas on the hull to start sanding tomorrow to make it pretty. I need to come up with a plan for a superstructure and build it. Finally clicked "order" on my ebay cart with assorted drive gear and other random parts and pieces. Also found a 19" hull my 10 year old son is starting to build (that one will be electric). Got a deck put on that one also. Pictures to come when I get my post count high enough.
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Old 08-30-2019, 01:00 AM
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At the moment, I've only got one that's running and it's a 1/8 scale hydroplane.
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Eventually, I should have 8 or 10 boats ready to go. Just a matter of time and money, when I have one, I don't have the other
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Old 08-31-2019, 11:20 PM
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A little progress today with getting a superstructure built. I thought I started this project with a lot of epoxy and micro balloons, but they are quickly dwindling into nothing. Still changing my mind on a powerplant a few times a day, not sure about a paint scheme, and trying to keep myself occupied while waiting for hardware to come. I should have enough sanding and fairing to keep myself busy for a while. Tomorrow I'm off on a work trip, so no progress for a few days.

I think I might be able to add pictures now; let's see...

Empty hull in rough shape, but the price was right. Just have to be careful sanding the outside- only one layer of glass then kevlar. Don't want to sand into the kevlar, because it likes to fuzz.


Deck on and working on getting rid of the wavy edges on the hull.


Working on a superstructure. This is going to use up a lot of micro spheres and sandpaper to make this a usable part.


Not 100% happy, but it will do. Lots of sanding left to do, but its almost starting to look like a boat. Really couldnt stand the primer grey, so a quick coat of black applied. Oh man, it looks so much better in black.
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Old 09-07-2019, 12:26 PM
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You're better off running it without a hatch. Gas engines generate a LOT of heat so it needs to go somewhere.
Compare prices. Great buys on Zenoah's from www.gimzomotors.com and running hardware from Welcome to Zippkits! , both great places to deal with offering 2-3 day shipping to you.
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Old 09-21-2019, 06:19 PM
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Well, I think I have figured a lot of this out by reading up on a lot of different forums and dealer websites.

Since I last posted, I've ordered running hardware and have installed it. I added a few pounds of paint and clear coat- I decided that red with black racing stripes is going to be acceptable. The transom isn't vertical, and has about a 15 degree rake, so I had to bend the trim tabs and make a bracket out of HDPE to make the rudder sit vertical. I have a radio, steering servo, throttle servo, and some other odds and ends. After much research, I have decided on a Zenoah G320PUM from BH Hanson, and I'm just finishing discussing the details and will be ordering in the next day or two. I'll bolt on a ZippKits exhaust once I get the engine mounted and see what header would work best. I still need to order odds and ends like pushrods, water hose, gas tank, gas hose, and figure out a radio box (tempted to use tupperware or similar). A Prather S280 prop is in my shopping cart, but I haven't clicked order yet. I've also been tempted to go three blade Octura Y572/3, but the extra cost is pushing me toward the S280. It would be super easy to change over if/when I want to try something else. I haven't bent the drive line yet since I don't have the engine, and don't know where it will be mounted due to balance, so that gets to wait. I have a clutch and a water pump waiting to be mounted as well. The fuselage has a big vent in the back, but I agree with the previous post that the engine needs more air flow, and I'd rather use the top instead of running it open, so I have some air intakes in progress that will be added soon. Hopefully, it will be enough along with water cooling of the motor and exhaust.

Question- when I start placing everything in the boat to figure out balance- do I do this with a half tank of gas to get an average balance point? With an electric boat, it seems easy to move batteries to change the balance point to find the "sweet spot", but how is this done with a gas boat?

I'll also add some updated pictures. If anyone sees any glaring issues with the build so far, let me know! This is all based on other people's posts on forums, discussions with others via email, and what dealers recommend on their websites.



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