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Old Apr 24, 2008, 10:06 PM
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Mono hull plans for a small 18" boat

I have had a few emails regarding the plans I drew up of the "Little Dumas V" So I thought some of you might want to try this small 18" boat.

If you have photoshop you can open them in that program and they will be the right size when you print them out on the portrait setting on a printer...they will open in plain old Windows XP but the sizes go all wonky...that is why I have included an inch scale with the templates...once you have printed them out just scale them up or down on a photocopier so the inch scale is correct.

The whole boat can be made out of balsa...as the strength comes from the angles and joints forming quite a ridgid hull...either fill the grain with your favourite filler and paint or the model could be covered in heavy weight mono coat...the inside has to be water proofed. We just give them a couple of coats of model areoplane Buytrate or Nitrate dope. One fellow framed it up in balsa then skinned with 1/32 aircraft grade plywood. Most builds are working out approx 7oz bare boat filled and painted...some came out 5oz bare boat.

All the formers 1/8" hard balsa and the rest is 1/16" Balsa...the side stringers are 1/8" bass wood or aircraft spruce.

Once the templates of the formers are the right size trace them onto the balsa and cut them out...the complete framing can be done in a couple of hours. Join the two top halves together then glue the formers to the distances shown measured from the bow.

The whole boat is framed upside down on a flat surface making for a true boat. I have not drawn a 3/4 view as I have limited drafting skills...but here is a 3/4 view all framed up...note the formers are designed not reach the edge of the topsides as the sides go up underneath forming a neat deck line.
Note there is a "U" cut in the 3rd former to accept a stick type battery paralle with the drive shaft...I am using a fullsize servo, radio and speed control on the opposite side of the drive shaft and the balance worked great.

Inside access is by a raised, sliding 1/32" panel.



Here are the fullsize templates...use the directions above to have the printouts come out the right size...that is the hardest part of the build...

Here are the plan files...

http://www.theoaks.ca/formers.jpg

http://www.theoaks.ca/bottom.jpg

http://www.theoaks.ca/sides.jpg

http://www.theoaks.ca/top.jpg

You can reach me with any problems at...

tony@theoaks.ca

At present I am using a water cooled Speed 550 $14 motor and playing with the props to keep the current draw down to approx 14amps. The battery is an Apogee 3 cell 1500 mAh...11.1Volts.

It makes up into a neat boat...Tony Vancouver Island Canada.
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Old Apr 25, 2008, 11:32 AM
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edmonds, wa.
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Is your boat surface or subsurface drive?
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Old Apr 25, 2008, 12:07 PM
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Originally Posted by csr101
Is your boat surface or subsurface drive?
We are at the moment trying both...In mine 3/4 of the prop is in the water when the boat gets on plane...two of the other boats are running with the prop 1/2 way in the water...so far the jury is still out which will be the best in the end...right now the 1/2 submerged is showing the same speed and drawing a little less amps.

Thanks for the interest.
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Old Apr 26, 2008, 10:04 AM
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Winnipeg, MB, Canada
Joined Dec 2004
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Looks great thanks for posting this! I was looking for plans because I wanted to build a small mono, when I printed these plans it came out 75% which is a nice place to start... about 13.5" long. If all goes well I will build a 6"-9" version.. should be a fun project! All my boat will be brushless and lipo. Anyway sorry to but into your post! Looking forward to seeing others build this boat!
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Old Apr 26, 2008, 12:15 PM
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edmonds, wa.
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REWOUND...I have a few plastic props you guy's can try. Various cuts and diameters. Send me an address.

Brian.
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Old Apr 26, 2008, 08:20 PM
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Winnipeg, MB, Canada
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By the way.. how about some pics of the finished boat and the gear inside? Thanks.
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Old Apr 26, 2008, 08:51 PM
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Quote:
Originally Posted by FHHOBBIES
By the way.. how about some pics of the finished boat and the gear inside? Thanks.
...your wish is my command...



above is the full hull with the 3 cell lipo and gear arrangment...the battery on one side of the drive shaft and the radio,reciever and speed control on the other has made for even trim. The foam is for catching the usual few drips of water coming up the stuffing box...I would rather have a few drips of water than putting grease in the stuffing box adding drag.



I use a coat of model dope to seal the wood then a couple of high build car primer rubbed out then a couple of coats of laquer paint wet sanded with 1200grit...then brasso...then a coat of canuba.

above is the hull with an eight cell 2/3A stick.
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Old Apr 26, 2008, 09:55 PM
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Quote:
Originally Posted by csr101
REWOUND...I have a few plastic props you guy's can try. Various cuts and diameters. Send me an address.Brian.
Thanks Brian...

So far I have been using a Traxxas prop that I converted to the dog drive and have been drawing 15/17 amps that has been giving me problems with the Speed 480 motor…this motor will run all day at 10/12 amps but the extra 5 amps has been over heating the armature even with extra cooling.

Reducing the size of the prop reduces the speed to a point were the boat has a hard time getting up on plane but the amps are in the right ballpark. You will notice I have gone to a Speed 550 motor that should handle a bigger prop and the extra amps…it sure is a balancing act getting the right combination that will give you the speed without drawing too many amps…there is a lot to be said for a RTR boat with all the hard parts figured out.


Thanks for the offer of the props! I will PM you my address…I thought I would show you the type of drive I have been using. I run 1/8" solid shaft that I turn a thread onto…quite simple and will post how to do that if anyone is interested.



As I mentioned the prop I have used so far is the Traxxas 36mm cut down to 35mm but is drawing 17amps…in the line up of props I have yet to try starting from left to right is
1. 30mm cut down from the Hammer/Fisherman
2. 31mm uncut from Hammer/Fisherman
3. 34mm cut down Traxxas
The weather last testing day was only 3degrees with a 20knot wind so I have not been able to give it a try.

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Old Apr 27, 2008, 08:19 AM
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Winnipeg, MB, Canada
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Very nice thank you. What do you use for hardware, can we see a bum shot? Of the boat that is, lol. What do you use for a hatch? I think I may start the build today!
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Old Apr 27, 2008, 10:59 AM
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Here is what I have done so far, pics done next to radio for an idea of scale, this is 75% scale of yours. I was thinking of perhaps a 400DF outrunner motor and 3S TP1320 lipos. I have to figure out what hardware to buy... this is where I get lost, lol. Any ideas? I can see wyself making a fiberglass version of this boat! Let me know if you want me to start a new thread on my project or just stay here, thanks.
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Old Apr 27, 2008, 03:35 PM
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Quote:
Originally Posted by FHHOBBIES
Let me know if you want me to start a new thread on my project or just stay here, thanks.
Sure keep it here...I for one would like to see the build...and help if I can.
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Old Apr 27, 2008, 03:48 PM
Lipoly Killer
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Gulfport/Biloxi Biloxi Reg, Mississippi, United States
Joined Dec 2000
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Hardware

The MicroCat hardware is pretty good and is reasonably priced. For what you have, homemade hardware is fairly easy to build. Umi has had a thread on building your own stuffing box so all you need is a rudder assembly and some ride plates.
Frank
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Old Apr 27, 2008, 08:48 PM
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Quote:
Originally Posted by FHHOBBIES
Very nice thank you. What do you use for hardware, can we see a bum shot? Of the boat that is, lol. What do you use for a hatch? I think I may start the build today!
...sure

All pretty standard stuff...cost is a BIG factor for us...young guys with new families and old guys on pensions...here is a break down of the basics.

Balsa for hull...................$12
Paint or mono coat...........$15
Motor Speed 550 Brushed..$14
Speed control GSW600......$17
Rudder.............................$8

Most of the boats are being built for under $60

Here is the aft showing the rudder and the water pickup...the top cover is just a slider made of 1/32 ply...I have yet to find a driver and windshield? ...for the top...I want to give it a different look than a Cracker Box...any suggestions?



You can see here the 3/4 submersion of the prop...some are using the traditional flush with the transom giving 1/2 of the prop in the water...at this stage of the game both are working...if a person had the $$$ a true surface mount prop would be fun to try.



Here is a detail of how the slider goes on.


We are playing with the addition of bottom chine strips to give the boat more grip in the turns...we are finding they really roll into the turn before the side digs in and the boat goes round...a friend jokingly said I could sell advertising space on the bottom.
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Old Apr 27, 2008, 09:24 PM
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Joined Nov 2005
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I'll venture a guess that, if someone had some 1" angle Aluminum(1/16" thick) that one could make a turn fin for not much $$$(and if two or more people chipped in to buy some...). with say an 1.5" below the hull, should plant the boat nicely in the turns .
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Old Apr 28, 2008, 12:36 AM
full time pirate
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The Great White North
Joined Jun 2004
323 Posts
I downloaded the sketched drawings and noticed that they're awfully rough around the edges. I loaded autocad and went over the drawings to sharpen the edges. Am I allowed to post these drawings, and if I am, how would I do it?

Thanks ahead
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