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First time build with the circus circus

Old 11-25-2011, 12:10 PM
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faceplantjae
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Default First time build with the circus circus

Hello, my name is Jason and I am new to the hobby. I was advised to post this thread to show my progress and to seek help if needed. I have purchased the Dumas Circus kit, but will be using it as a template. I was supposed to start this week, but my National Balsa order was damaged when it arrived. I have the jig built and all the pieces traced and ready to be transferred. In the mean time I think I am going to build the kit just for the heck of it. I have decided to go with a CMB .67 engine and will go with accu-tech strut, rudder, and turn fin. Please let me know how you think it is going and any suggestions will be greatly appreciated.
Old 11-25-2011, 03:43 PM
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Default RE: First time build with the circus circus

Please tell me you built the jig with a solid flat top over the whole width to support the middle of the bottom as well as the center framing
Old 11-26-2011, 07:09 AM
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Default RE: First time build with the circus circus

Your not the first one that used the Dumas ply as a template. Birch ply is what is needed to build a hull.
Old 11-27-2011, 09:54 AM
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Default RE: First time build with the circus circus

It's what I've done to build a sport 20 Pak and will be doing the same to build a 1977 Atlas where I have most of the parts already cut out
Old 11-27-2011, 01:41 PM
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Default RE: First time build with the circus circus

Yep you need a good flat surface or your wasting you time & $
Old 12-02-2011, 12:08 AM
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Default RE: First time build with the circus circus

Hello all, I did build the jig with a flat surface. Here is a pic of the jig.
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Old 12-02-2011, 12:27 AM
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Default RE: First time build with the circus circus

Two words of advice:
WAXED PAPER
Old 12-02-2011, 12:32 AM
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Default RE: First time build with the circus circus

Your jig looks great! Do you have any "stops /spacers" up front for the sponsons placement as you have in the back for the transom? I'm learning, thanks V.
Old 12-02-2011, 11:09 AM
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Default RE: First time build with the circus circus

Hey Hydro, I found that out the hard way. had to spend 15 minutes with exacto knife trying to get a sponson inside off the jig. I got bored and decided to put the dumas kit together. I wanted to practice to make the other build go smoother. Already found some areas of the design I need to change. Like extending the sponson insides for the extensions. So far so good. Ill post a pic later tonight on what I have so far. After I put the stringers on and before the nontrips are added on, I will do a little windowing on the bulkheads and stuff to lighten up the frame.

Vasek, Thanks for the compliment on the jig, as I am too just getting into this hobby. I must say that this is fun already. As for the stops/spacers on the front of the jig..... No I do not have any. I hammer T-pins through the sponson insides once everything was square. Also, I added about 6" of extra length to the top decking of the jig to increase my work area. Here are some pics to show what I am talking about. Hope this helps.


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Old 12-02-2011, 11:12 AM
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Default RE: First time build with the circus circus

Here is a pic of the boat so far. This is the dumas kit with the supplied wood and with no modifications in the plans. I am still waiting for my National Balsa issue to be resolved and I will begine that one. The Dumas pieces are traced and ready to be used.
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Old 12-02-2011, 12:16 PM
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Default RE: First time build with the circus circus

Looks good! Thanks for sharing.
Old 12-02-2011, 05:22 PM
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Default RE: First time build with the circus circus

Okay, time to start giving serious advice for the remanufactured kit:
1) As you already found out, the sponson insides need lengthening at the transom. Be sure you add enough to account for the 1/4" transom thickness AND the added length of the extension. You will need to cut a notch through the top of the sponson inside for the transom to lock into as well as through the bottom of the transom
2) BEFORE you start building the remanufactured boat, make sure you can get a cowl from Dumas. IF YOU CAN'T, you will need to widen the engine bay to a full five inches and pick up a cowl from another source. THIS WILL REQUIRE REDRAWING ALL THE FRAMES THAT CROSS THE CENTER OF THE HULL as well as make the front of the cockpit build totally different
3) Use the solid blocks that give the deck it's shape between the sponson inside and engine bay walls as templates unless you plan on bolting the engine mounts through them. This is one place were using a top and bottom stringer will do the job just as well and be lighter. I normally use 1/8X1/4 spruce for this area allowing me to use two sticks laminated for more flexibility. If you prefer to use blocks, you can also remove the material in the center for a similar result.
4) IF YOU CAN AVOID IT, don't put any holes through the engine bay walls. I know the kit is set up to have the radio box aft of the engine but, with today's smaller modern radio gear, if you use that location, it will all fit without going under the deck. Granted, cooling lines will probably be run under the deck but, unlike the huge holes in the radio box, they will be sealed with epoxy when you glue the tubing in place

Hope this helps
Old 12-04-2011, 08:11 PM
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Default RE: First time build with the circus circus

Hello. I called Dumas and they are sending me a cowl. So now I don't have to worry. I have decided to complete this build as the Circus before starting the remanufactured one. I will make that one the 1988 miller high life. On newton marine it looks like it is the same as the dumas circus. I see there are a lot of areas that can be modified. I agree with you hydro about the radio gear. I was actually thinking about putting the parts that I punched out of the cockpit insides, back in and using epoxy to seal that compartment. Then that will be used as the engine bay and I can move the radio gear where Dumas designates for the engine. What do you think? Also I was thinking about not using the sponson ride pads. It seems pointless to have them. Plus they will add weight, increase the ride height, and could pose as a water trap. Is this advisable to leave them out?
Old 12-05-2011, 01:40 AM
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Default RE: First time build with the circus circus

1) Leave the engine forward like the instructions say. You need to keep as much weight out of the back of the boat as possible if you want the boat to have any chance of being able to get up to speed and not drag the transom. Another problem with moving the engine back is you will end up with too sharp of bend(s) in your stuffing tube to allow the flex shaft to spin freely, causing serious drag and excessive cable and stuffing tube wear. If you want to move the radio forward, move it up into the cockpit area.
2) Ride pads can improve performance so I would recommend using pads of some sort. That being said, you don't need to make them as high as Dumas has designed them to be. What you could do is make a few different ride pads and tack them onto the sponson bottom with some sort of easily removed adhesive and then go test them out.
Old 12-05-2011, 01:42 AM
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Default RE: First time build with the circus circus


ORIGINAL: faceplantjae
Also I was thinking about not using the sponson ride pads. It seems pointless to have them. Plus they will add weight, increase the ride height, and could pose as a water trap. Is this advisable to leave them out?
A very timely question! I'm doing some research regarding ride pads myself. My plan doesn't show them, but I was thinking adding them to increase top speed. I'm all ears also.
Old 12-05-2011, 02:22 AM
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Default RE: First time build with the circus circus

@HJ, I guess we posted at the same time do you have any useful links regarding the riding pads & testing?


@FP, just a heads up when you'll be gluing the 1/16" ply onto the sponsons; i've read that putting excessive weights when doing this can make the sponsons "dig in" a bit and people who used tape, pins & elastics instead of weights have a bit faster boats. Not sure to what extent this is a correct assessment, but one has to be careful not to deform the structure.

Cheers,V.
Old 12-05-2011, 04:02 AM
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Default RE: First time build with the circus circus

No links off the top of my head but, through some experience, I can give a little bit of help.
The ride pads actually do a couple of things:
1) Narrows down the contact area with the water. This reduces friction since the whole sponson bottom isn't against the water while at speed. Going too narrow, however, will actually hurt performance
2) Lets you vary the width of the boat's footprint by moving the pad in or out on the bottom of the sponson. Depending on the boat's weight and amount of air under the boat, changing the boat's footprint can make the boat more stable or catch the water's surface and cause handling problems.
3) Lets you change the sponson's AOA without having to do a major rebuild. To put that into standard english, it lets you adjust the sponson's bottom angle over the width of the pad. Too much angle and the pad will slam into the water and act like a car's brakes while too little will have more of the pad and/or sponson's length in the water while running

This is where the experimentation come in. Changing the pad angle, width and how far apart they are placed can help or hinder a boat's performance. Using my remanufactured Dumas Pay'N Pak as an example, I will try to give you what you need to test.
This boat was designed to have a 6 degree AOA by Dumas. This means that the sponson bottom is rising 6 degrees as you go forward from the sponson transom. As built, the AOA was reduced to 3 degrees by me reducing the sponson depth by 3/8"(.95cm) at the transom. By adding pads, I can return the bottom to the Dumas designed in 6 degrees or take the angle to 0 degrees by sanding the pad to a given angle for testing. At the same time, I can test the effects of having the pad right against the sponson inside or, if I prefer, out at the sponson chine to see how the boat reacts. I could also experiment with the pad's width, starting out with a width of 50% of the sponson bottom for example. My plan for the boat is, at this point, starting out with a 1/16"(.158cm) thick ride pad with no added AOA and at 50% of the sponson's width placed even with the sponson inside. If this doesn't work to my liking, I can add AOA by adding shims to the face of the pad and run it again, repeating as offten as I feel is needed
Hope this helps
Old 12-05-2011, 12:03 PM
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Default RE: First time build with the circus circus

That old building frame brings back alot of memories. A Dumas build helps the Winter pass quicker.
Old 12-05-2011, 12:13 PM
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Default RE: First time build with the circus circus

thanks HJ! very informative!

i found a good link on setting up a hydro, though i would share it

http://www.modelgasboats.com/Hydro_Setup_Tips/
Old 12-05-2011, 12:42 PM
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Default RE: First time build with the circus circus

Thanks HJ... Very helpful. I see that a lot in this hobby is trial and error, that is to the person's need. I will play with the ride pads soon. The next couple of days are going to used to window out the bulkheads.
@ vasek, I only use the pins and tape. I tried the weights early on and they dented to wood. Of course this could be due to Dumas's grade of wood, but probably due to the weight.

@AB, this does pass the time very well. And a lot of planning, and detail go into these boats. I don't know why I didn't think of doing this sooner. This is a blast, and I haven't even put it in the water.

Old 12-05-2011, 12:50 PM
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Default RE: First time build with the circus circus

Thanks HJ... Very helpful. I see that a lot in this hobby is trial and error, that is to the person's need. I will play with the ride pads soon. The next couple of days are going to used to window out the bulkheads.
@ vasek, I only use the pins and tape. I tried the weights early on and they dented to wood. Of course this could be due to Dumas's grade of wood, but probably due to the weight.

@AB, this does pass the time very well. And a lot of planning, and detail go into these boats. I don't know why I didn't think of doing this sooner. This is a blast, and I haven't even put it in the water.

Old 12-07-2011, 07:56 PM
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Default RE: First time build with the circus circus

Hello everyone. Here is an update on my progress. I did some windowing of the bulkheads and sponsons, and added all the stringers on the top. Come to find out that it is a lot easier to to do this (even with a dremal flex drive) on the sponsons. So I had to remove 2A and 3A to be able to to it well. Here is a pic of the removal and windowing.
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Old 12-07-2011, 08:17 PM
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Default RE: First time build with the circus circus

Here are some pics after I put the frames back on and when I attached the sponson sheers and chines.
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Old 12-07-2011, 08:21 PM
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Default RE: First time build with the circus circus

Here are a couple more. You can also see that the hole alignment on the cockpit insides, are too close to the top edge. It was fine when I drilled the holes, but when I started to put the front cowling floor together, it cracked. I had to realign them and epoxy it back together. It looks as if the functionality of it is not affected. I would probably suggest lowering the center mark Dumas put on the cutout. Maybe about 1/16th of an inch should work. Let me know what you think of the build so far and if there are any suggestings. Thanks and until next time.
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Old 12-08-2011, 12:43 AM
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Default RE: First time build with the circus circus

Looks really good so far. Two things for your second boat, don't cut the lightening holes with pointed corners, leave them with a radius. Pointed and square corner cuts create stress points that will cause cracking of the framing. If you're not racing the kit build, it shouldn't be a problem. Next, when you get the sponsons built, you can remove about half of the sponson sheer material between the frames. IF you were building the boat with Jones sponsons like the 1989 version using Newton plans, you would have to attach the deck to a narrower area on the top of the sheer. Since the stock build sheer is glued to the top of the frames, you don't need as much so removing some of the material won't affect the sponson's strength or how well the deck stays on the boat

I just looked again at the picture of your frame work and, if I'm seeing this right and it's not just the picture, the glue rail at the top of the right side nontrip framing looks to be curved inward in the middle? If this is so, and I'm not seeing things, you need to pull it loose and re-attach it so that it's straight and shim the frames accordingly as this will be noticable when the nontrip and deck skin is installed

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