1st build, got some questions.

[castellina]

Hi all, I am new to this forum. Ive been doing some research, and I found some plans for a boat online that I'm going to build. My school has a laser cutter, so I will be cutting the pieces for my boat with that. Here is the link to the plans I found online that I'm using. Let me know what you think. http://www.rcgroups.com/forums/showthread.php?t=854832

As far as hardware, motor, etc... I have a few questions.

1. will this rudder and strut assembly be good for me? http://www.offshoreelectrics.com/pro...prod=ose-80085
2. My motor is a venom fireball brushed 15d. Will it have enough power? Will it hold up? Im going to water cool it to prolong its life.


Along the lines of the hull building process, I'm thinking of getting it put together with wood, then fiberglassing over the wood. The wood will serve as a mold, and when its dry I will pull the wood out, and have a pure fiberglass hull... Any objections? Should I make a strictly wood hull? Fiberglass and wood? I would love all the opinions I can get, like I said I have never done this before.

If you guys can think of anything that I should know about before starting the process, or any tips/tricks of any kind please let me know.

Thank you,
Kyle

[Make-a-Wake]

Welcome to OSE!!

Neat little project here. I think a 15t motor is too high, that would be around 30,000 rpms(or so) on 8v. Maybe consider something in the 23-27t range. Also, you cant run a heavy 6 cell nimh in that boat with limited power of brushed. You need to run a 2s Lipo in the 1500-2000mah range for weight purposes.

[castellina]

Thanks for responding so quickly, so what you are saying is my motor has to much power? What would the consequences be of using it? would the boat just be hard to control? Also if I do keep this motor, will a 2s lipo work on it? Or is it only if I buy a different motor?
Thanks, kyle

[Make-a-Wake]

Not too much power, you cant gear a boat as you can a land vehicle which it is intended for. Boats need to stay in a comfortable rpm zone to keep the heat down. Boats and land rigs are quite different, much higher constant amp draw in a boat and no air circulation. You could try your motor, but will need a very small prop which then may lead to cavitation.

[castellina]

Oh I see, it will run at too high of an rpm, causing heat. We will see, if it burns up I'll buy a better motor. I'll keep this thread updated as my build progresses.

Just thought of something, what if I rigged up a fan that would suck air from outside? Would that help at all?
Thanks

[Make-a-Wake]

If you flip it you will suck water from the outside as well..............then possibly sink

[castellina]

true, very good point thanks.

[castellina]

Hey, Im going to cut my pieces for the boat this week hopefully. When I get them ill make sure to post some pictures. Im not quite sure what to do about actually building the hull. Should I make is strictly out of wood? Fiberglass and wood? or use the wood as a mold for the fiberglass, then pull the wood out?
Thanks for the help, kyle

[castellina]

I dont know if you guys are interested but here is what I have so far.

[Make-a-Wake]

We're always interested! Nice work

[castellina]

Thanks, I'll keep posting pics. In the mean time, here's my updated shopping cart list.
How's it look?
Thanks

[Make-a-Wake]

My word...........................a 2860 in an 18" boat? Wow. Stiffen that baby up so the motor doesn't just twist it up. That's overkill on motor................but you wont ever have to upgrade.

[castellina]

I made it 24 inches, and once I finish up the wood part I'm going to fiberglass over the wood. I think that should help quite a bit, and add a little weight to it.
Thanks

[Make-a-Wake]

Oh, I didn't realize that it was 24". That will be a good powerplant, still gonna haul butt.

[NativePaul]

Oops, I didn't just double post honestly officer.

Good luck with it, it is great to see people designing for themselves and actually building their boats. Especially new people.

[NativePaul]

What wood are you building with? If it is ply then just use the wood and seal it with epoxy when finished, if it is balsa, you could do the same or for a little more strength add a single layer of 1oz/square yard wing skinning cloth to the outside. Making glass hulls is a lot of work, and I would advise making a few wooden ones tweaking each version closer to your wants until you are happy with it, before making a plug and mold for a glass hull.

I, and a LOT of people I know run Leopard 2860 3400kv on 4000-4800mAh 3s packs with 30-35mm props, in boats of around that size, it is by far the most popular Mono1 motor. Pick the 2840 jacket for it instead of the 2830 one for better cooling.

You don't need a .150 flex for a 28mm motor, .130 will be fine and with either 1/8th" dog drive if you want to sharpen and balance your own props or 4mm threaded if you want to run CNC props.

What speed and run time are you after? We run for 6 minutes in the low 40s MPH, pulling an average of about 45A, an average full throttle of about 60A and spikes of over 100A, if you are after this speed or more I would suggest a bigger ESC, most of us run 100-120A units, 80A is the lowest I have seen being reliable.

[Make-a-Wake]

I've ran a couple of these without issue..........

http://www.ebay.com/itm/Mystery-RC-1...item2592f661df

[castellina]

Thanks for the interest guys. I'm 15 by the way.
To answer your questions, I'm using ply wood for it. Also I wasn't planing on making a plug, I was just thinking about putting a couple layers of glass on the outside of the wood. To make it stronger and seal it up good.
I'm wanting more run time rather than speed, but would still like some decent speed. It's going to be kind of choppy where I'm running the boat, so I won't be able to go that fast.

Also, I was thinking of buying carbon fiber or plastic props to start off with so I can determine the prop that best fits my boat. When I get it all assembled, I think I will take it to a hobby store and see what prop they suggest for me.

Thanks, Kyle.

[NativePaul]

You will want a 4mm threaded shaft then to run Graupner 2318 carbon props which are pretty darned good and easily the most efficient cheap props available, get the 31mm 33mm and 34.5mm if you go for the 3400kv on 3s.

[castellina]

Thanks for the recommendation, the motor I'm getting is 2190kv and I'm thinking I will run it on 2s 3300mah

[Make-a-Wake]

2s is gonna be disappointing to you. You cant go very big on prop diameter so rpms are your friend, you got a pair of 2s batts to run 4s?

[castellina]

I don't have a battery yet, but Steven Vaccaro suggested 2s with my set up. I don't want to fry anything, but if I can use a bigger battery that will give me more run time I will be very happy.
Thanks

[Make-a-Wake]

I don't know his reasons for suggesting 2s........................you can buy a couple 2s batts and if you don't like 2s just run 'em both in series for 4s.

[NativePaul]

I know you are after runtime more than speed, but a mono this size probably can't cope with prop big enough to make use of a 2860 motor of 2190kv on 2s, as I suspect it would suffer from torque and paddlewheel effects before you reach 50mm. If you really want around 2190kv on 2s it wont be very fast and you will have to really watch your weight to help it get up onto the plane. If it doesn't work it won't be a total disaster though, as Make-A-Wake said you could add a second 2s battery in series for 4s, which would give you around the same RPM as the 3s 3400kv setup I recommended and the same prop suggestions would apply.

[Make-a-Wake]

Yes sir Paul........................2s will be a yawner

Hey castellina, I have run these compacts and they are very good in my opinion. A couple of these in series would work well and not be real heavy(although the 2860 wont struggle on any voltage or weight within reason)

http://www.hobbyking.com/hobbyking/s...Lipo_Pack.html

[castellina]

Awesome thank you guys.

[castellina]

Here's my latest progress.
If I go 3s, how do I know what MAH to get? From what I understand the more MAH the longer run time I will get? So whats the biggest 3s MAH I can get with my set up I posted?
Thanks

[Make-a-Wake]

Ahhhhh, the wonder of zipties.............where would we all be without them.

3s will be a nice middle ground that will be decent in all regards. You can use more pitch on a smaller diameter prop to gain speed and not make the boat unstable.

If it were mine I would run 3s2p as the motor is powerful enough. I ran 3s2p in a 24" Mini Sniper so I am not suggesting something I haven't done myself. This little bit of extra weight will stabilize the boat more(being small) and give you good runtime. Plus it will help to balance it better side to side.

Your question about mah is correct to a degree. The more mah the more runtime in general. However if one runs a 5000mah batt with a 20c rating its putting out 100 continuous amps(5000 x 20/1000) A 4000 40c batt is putting out 160 amps and will not strain as hard so it will have roughly the same runtime, although there is not a set formula, this will be the case "generally"............especially in higher ampdraw setups. Boaters tend to use 40c and higher batts due to the nature of high, continuous ampdraw, land rigs don't have nearly the ampdraw for similar motors and voltage. Realize this however, smaller boats don't "need" big C ratings as a rule, 30c is sufficient, but 40c is better for total battery life and most efficient running of your electronics.

Zippy Compacts I would suggest: http://hobbyking.com/hobbyking/store...Lipo_Pack.html

[castellina]

Yes...zipties are great lol

Should I go ahead and order the stuff in my shopping cart at ose? I just don't want to buy all of it and find out there isn't a battery that will work with it. If you guys think its a good start I will go ahead and order the stuff.
Thanks,
kyle

[Make-a-Wake]

I would get the 40mm water jacket instead of the 30.

I cant even find the strut/rudder you have listed................... Not sure what I think about it............it should work, I am just not a fan and its for a Cat anyways.........maybe someone else will chime in on it