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Building a large RC boat from scratch

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Old 03-11-2003, 08:31 AM
  #1
fryfrog
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Default Building a large RC boat from scratch

I started out boating with a fairly cheap Kyosho Jet Stream kit from towerhobbies.com. After replacing most of the parts (minus the engine) due to ****ty design, and getting it to a working condition I managed to sink it driving behind a real boat (prop wash sucked it right down). I got a Jet Stream 1000 and it was made far better, but I still find it boring.

For about 2 years now I have been planning and thinking about this boat in my head. Designing it, planning things and considering issues/solutions. But my big problem is I don't really have any experience with building fiberglass hulls, modifying 2 cycle engines or much else. I was hoping I could outline my plans and get some suggestions, ideas and/or criticisms.

The Hull: I want to build a very large, 5' - 6' in length deep v hull. I'm not quite sure on the width ratio for that length boat, but i was thinking something like 1' - 2'. Probably 5' x 1.5'. I was going to build in 3 very strong bulkheads using what a co-worker describes as "hobby plywood", and have a pair of large (balsa wood?) sticks running vertically for motor/radio/fuel tank mount. I want to build a skeletal structure out of balsawood sticks, then cover that with balsawood sheeting. Then I would use fiberglass cloth and fiberglass rezen to coat the entire boat. I planned to sand it all down, paint it a nice purple then mix up a batch of fiberglass resin and put in some glitter, then apply a few coats of that to give it the glittery purple look. What I really want out of the hull is stability and control. My goal is to be able to run along side, in front, behind, etc a real boat running at about 45mph and NOT be thrown about violently by small to medium wake/waves.

The Engines: I want to go with duel engines, 2 cycle. At first I was under the impression that due to the way 2 cycle engines work, makine one counter-rotate would be easy. I believe its possible, but beyond what I want to do. I have read about converting them to electronic ignition to lower rpm speed and weight and increase responsiveness. I've read that most people use line trimmer engines, and i was leaning tward a Ryobi 32cc line trimmer because they are about $100 (and I would need 2), but I have also read that the power to weight ratio of chain saw engines is quite a bit better than from line trimmers.

Outdrive: After coming here, I found those MHZ outdrives and they are almost exactly what I'm looking for except they are in germany. I also suspect they are very expensive and that buying a pair of them would probably be about $300 each. BUT, if I was reading correctly you can get one of them that is GEARED to be counter-rotating (instead of making the engine counter rotate!). One of my main goals in twin engines was to eliminate the torque and odd tendencies of a single engine boat (full size and model rc, they all behave very simliarly). Also, twin engines makes you cool.

Props: I actually have no clue what size prop would go with a 32+cc engine. I have read discussions of submerged vs. surface effect and I think that I want to go with submerged. My main goal is stability, speed being secondary. I don't want to forfiet the control that is lost from running a surface effect prop. Also, different from most people... I don't really think a rooster tail looks cool. I'd rather run fast and fully submerged and not throw off a large roostertail (don't want to soak myself if its driving in front of me in a real boat).
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Old 03-11-2003, 04:18 PM
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RobStagis
 
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Default Building a large RC boat from scratch

At that size, maybe a Dumas PT boat would give you the basics..... While not a true deep-V, it IS a big boat and will take a lot of power.

At minimum, take a close look at the manufacturers' offerings - their specs will give you length/beam, angle of the V (deadrise, I think it's called) and recommended power and weight.....

A couple close-ups of their hull bottoms would also be a good thing, eh?
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Old 03-17-2003, 06:07 AM
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Default Building a large RC boat from scratch

I've done a lot of research over the past few days and come up with a few things...

1.) i stand a snowball's chance in hell building my own hull from scratch, and it would probably be cheaper to just buy one. i am thinking about getting this hull, the 70x14" Apache from Expresscraft.
2.) i don't think modifying a weed eater engine is going to work out well either, so i am looking at a G26 MARINE ENGINE (25.4CC) with a clutch, water pump and possibly a belt drive so i can reverse the rotation of the engine easily (can it be modified to run backwards?).
3.) i want to run submerged, and was hoping to go with a scale outdrive, but they are VERY expensive (though they almost all seem to accomplish the counter rotation bit easily). i was thinking of getting these HBR out... rigs? drives? not sure what its called. i like this hbr because it has twin water pickups (on the rudders), is easily adjustable for prop depth/angle AND can be used surface or submerged.

now i run into a couple of issues. how do i get it counter rotating? i was thinking of just turning one engine around to face the other way and put a belt drive on it so the drive shaft would go UNDER the engine and back (and the rotation is reversed). does this sound feasible? i was also thinking i should do the same with the OTHER engine so that one does not have a mechanical advantage over the other (plus, if i wanted i could use the belt to over drive it).

also, i think 4 rudders (remember, i wanted to do twin) coming from 2 of those HBR things may look... well, stupid on the back of the boat.

how do you do flex shaft/stuffing tube on a submerged drive? i assume that the stuffing tube comes out of the hull (and the stuffing tube is fairly bendable) and lines the cable up with the drive system?

how deep should the props run? assuming the bottom of the hull is the water height, a submerged prop doesn't want to suck a lot of air so i would guess around 1/4th - 1/2" below that? how far apart should the props be? what diameter prop should they swing? what pitch? anything else i'm forgetting? what rpm should i be shotting for on a G26?

any opinions?
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Old 03-17-2003, 01:37 PM
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Default Building a large RC boat from scratch

I'd try Jims Rc boat dock. They talk mostly about the big gas boats, and post a lot of pics to give you a good idea about how things work.
http://home.austin.rr.com/jnissen/rcboat.html
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Old 04-04-2003, 02:48 PM
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Default Building a large RC boat from scratch

Your in Atlanta...come down to the pond and see what people are running. Thats what I did. And I'm hooked now.

Spring Nats are right around the corner (in Atlanta)and you will meet some great guys, and see some wild boats.

http://atlantamodelboaters.com
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Old 04-04-2003, 08:45 PM
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Default Building a large RC boat from scratch

thanks for the link, i just bought this and am looking forward to playing with it. i still want to build my own boat, but i think i need to start with something that works so i know how it should all go together )
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Old 04-04-2003, 08:51 PM
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Default Building a large RC boat from scratch

BTW what part of atlanta are you in?
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Old 04-28-2003, 10:03 PM
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Default Building a large RC boat from scratch

I am glad that you have discovered the extreme perils of trying to build a boat from scratch. Your material list would simply not hold together. I manufacture the only 73" scale Cigarette hull that meets the APBA RC Superboat class rules. 18.5" beam, 18 lbs. dry weight. Hull is manufactured in a single or twin engine configuration. The pictures that I have are too big for this site so email me at newmanre@att.net if you would like pictures. The Kanellos drives are unavailable. I am trying to bring some of the MHZ Merc #6 drives in to try. They do not have counter rotating drives available until May 1 according to the owner. Bob N.
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Old 04-30-2003, 07:16 PM
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Default Building a large RC boat from scratch

Fair warning, the HBR set-up is junk! The guys in Jim's will tell you that. One guy threw his away rather than unload it on some poor fool! If you live in the Hotlanta area, look up Gesse Rand, nice person. Lots of other good Gas boaters in the area that could help you out.
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Old 09-15-2004, 11:30 AM
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Default RE: Building a large RC boat from scratch

Speaking of speedmaster #6 drives. I found these maybe 2 years ago from some company in Australia maybe? They really looked cool. Anyone know where to find them?

-THX
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Old 09-16-2004, 09:34 PM
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Default RE: Building a large RC boat from scratch

Reed valve and piston port 2 stroke engines can be made to run in reverse by moving the flywheel to get ignition timing in the same spot on the other side. Real simple if you remove the flywheel and use electronic ignition. Won't work on a rotary valve engine.
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Old 10-11-2004, 12:58 PM
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Default RE: Building a large RC boat from scratch

You can get the Merc look alikes at www.mhzusa.com
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Old 10-14-2004, 04:12 PM
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Default RE: Building a large RC boat from scratch

so where do you stand now? Homelichtsor basic weedeater or blower engines will probablyy not propel that size hull to the speed you were looking at. A Zenoah g26 wont do it either. The only thing i can see propelling the large apache is maybe ballantine hobbies modified zenoah, www.ballantinehobbies.com, i suggest calling them because i couldnt find the engine on the site but remember seeing it a few month's ago. Your other options are maybe twin Zenoah's or possibly a Quickdraw 35cc or even the 70cc twin would work nice. Unfortunatly for this speed to be achieved, you need a big bank account.
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Old 02-06-2009, 12:34 PM
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Default RE: Building a large RC boat from scratch

I need one of those cig hulls....how can I get my hands on one? Garth
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Old 02-06-2009, 02:36 PM
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Default RE: Building a large RC boat from scratch

You might be limited on left and right hand props. That would be something to look into before you commit to a full build then not find any props for it.
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Old 04-24-2010, 09:00 PM
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Default RE: Building a large RC boat from scratch

Here are some pictures of my first scratch build in progress. It's my own design and I have never built a boat before (though I do haveexperience in fiberglass. Maybe this will give you some ideas.?
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Old 04-25-2010, 06:15 AM
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Default RE: Building a large RC boat from scratch

Nice looking hull you've got there! looks like a very stable design.....almost like one of the tri-hulls I used to go out fishing with. What are your dimensions? With that flange, I assume your working on soms sort of canopy perhaps? Keep the pictures coming, we all love build threads here.
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Old 04-25-2010, 09:19 AM
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Default RE: Building a large RC boat from scratch

Hey there, I hope it will be stable and I hope it won't turn into an airplane and fly off the water. It's totally anexperiment. The dimensions are 45 3/4" X 16" This is just a" "PLUG" to build my mold. The flange is for the access cover and will have a fake cooler seat and center console. there will be a poling platform aft. Thanks for the compliment and I'll post pics herehttp://www.rcuniverse.com/forum/m_9656597/tm.htmSee ya on the water! Doug
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Old 04-27-2010, 05:16 PM
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Default RE: Building a large RC boat from scratch

hi there just wondering if you have the plans for your boat and if so can you post them thanks butman
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Old 04-27-2010, 06:29 PM
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I don't have plans per-say just a drawing on my computer then I scaled the lengthandwidthonconstruction paper. Then I cut templates out of theconstruction paper and simply using scotch tape I tweaked it till it was shaped right, then i untaped it and cut 5mmplywood using the templates, Then I used 5min. epoxy to glue the plywood together, then sheeted it with fiberglass inside and out and started sanding. None of this is tested and for all I know it could end up one totally out of control slide...lol. I will post some pics when I resize them later., Doug
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Old 05-26-2010, 06:37 PM
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Default RE: Building a large RC boat from scratch

 use  a chainsaw engine
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Old 05-26-2010, 07:20 PM
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Default RE: Building a large RC boat from scratch


Quote:
ORIGINAL: juanmoas

use a chainsaw engine
They are surprisingly inadequate for RC Boats. A large amount of work to adapt them - if your serious about it then you will need to water cool it. And you still only have a 4hp motor that wont rev beyond 12k.
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Old 05-26-2010, 07:25 PM
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Default RE: Building a large RC boat from scratch

There are serious set up problems in using a chain saw engine.
For starters, the engine turns the wrong way. This means that you would have to either reverse engine rotation(not an easy rebuild) or run either a chain or gear drive. Either one of these requires alignment to be perfect, again not an easy deal. It also limits your drive options to either a series of bearings with a solid drive shaft or a stub shaft going to a flex.
Noise would also be a problem. Since a standard chain saw uses a spark arrestor instead of a muffler or tuned pipe, something would have to be scratch built to install either a muffler or tuned pipe. A tuned pipe would be the better choise, but now you're looking at serious experimenting to find one that would work. Custom motor mounts would have to be made as well.
Save yourself a load of hassle and headaches and stick with a Zenoah, Sikk, RCMK or similar engine as almost all of the problems have been worked out already
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Old 05-27-2010, 07:47 PM
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Default RE: Building a large RC boat from scratch

Who said anything about a chain saw engine? This boat will have a K&B 7.5 on it.
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Old 05-27-2010, 09:24 PM
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Default RE: Building a large RC boat from scratch

A few posts back, someone else suggested it. JAW and I were just explaning why it's not a good idea
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