rebuilding a Dumas 1/8 hydro

[t_hedlund]

Hello

I'm rebuilding a Dumas hydro, I have been told that i should move the radio box head of the motor, so i decided to remove the the cockpit and to make the cowl and cockpit one piece, so that i could get the radio box as far forward as possible, Does any one have any suggestions before i start building radio box ?

 

[Brian Schymik]

One... Make the box a separate unit, not using the side of the boat as the wall of the box, if you know what I mean.

Nothing but leaky boxes come from that....

Brian

 

[t_hedlund]

well thank you i was on the fence about using the side of the hull. Now i will build a seperate box. What thickness plywood would b a good choice for the box?

 

[missbudpilot55]

3/32" works well, some use 1/16" & 3/32", just make sure you seal it well and test it for leaks.

I prefer a tape down lid but it depends on what size the box is that you are building. BTW which Dumas 1/8th scale are you referbing?

 

[t_hedlund]

I haven't decided if I'm going to tape or bolt down the lid. But the one I'm rebuilding is the Miss Atlas Van lines.I'll post pictures of it a little later i just got the hardware, I'm going to lay it out before I go to work.

 

[missbudpilot55]

I haven't decided if I'm going to tape or bolt down the lid. But the one I'm rebuilding is the Miss Atlas Van lines.I'll post pictures of it a little later i just got the hardware, I'm going to lay it out before I go to work.

If you need any patterns or need a copy of the instruction sheet , I have a new unbuilt kit of the boat on the shelf out in the shop.

 

[[email protected]]

I'd go with a tape down lid. Makes for easy access and quick access should you need to make changes or adjustments. Plus the radio box tape is water proof.

Once you build the radio box, mix some 30 minute epoxy with a tiny bit of rubing alcohol. Paint the radio box with it and it'll make it water proof.

 

[t_hedlund]

yeah, i think i'll go with tape i think that will be easy to make.

Bill i could use a copy of the written instruction, i lost mine

here is a picture of it before i cut the cockpit my gallery

Thanks for the advise

 

[t_hedlund]

OK now i have a bunch of questions,

i bought a speedmaster drop down motor mount what is the best way to mount it?

What is the best way to cut the flex shaft?

 

[t_hedlund]

i guess i should specify my question a little more.

on the motor mount, First what size screw should i use from the motor mount to the motor and from the Mount to the size of the hull?

Thanks in advance

Tom

 

[missbudpilot55]

i guess i should specify my question a little more.

on the motor mount, First what size screw should i use from the motor mount to the motor and from the Mount to the size of the hull?

Thanks in advance

Tom

Motor mount to hull 10-32 is generally the size it is drilled for. Engine to motor mount 6/32 or 8/32, depends on what size fits the mounting holes on the engine.

Best way to cut a flex shaft is with a heavy duty cut-off wheel in a Dremel Tool. "Do not solder the end of the shaft once it is cut". If you have a small grinder or a small table top belt sander you can round the cut end off very slightly so it will slide into the flex coupler on the engine.

 

[t_hedlund]

ok, thank you

 

[t_hedlund]

ok i'm looking for a prop for this boat, i have been told a good starting point would be a X457 3 blade. Is this correct?

 

[[email protected]]

ok i'm looking for a prop for this boat, i have been told a good starting point would be a X457 3 blade. Is this correct?

Yup, the Dumas boats like the X-457 two or three blades.

 

[t_hedlund]

ok i'm going to order some x-457 tomorrow,

On rudder postion, the plans call out for it to be on the right side of the transom ( from behind boat) but i've see some boats that have it on the other side of the boat. Which is better?

Also on the flex shaft what is the point of doing the s bend? i have read that if you flex shaft is straight that you will need it , but what is it for.

Thanks again you all are awesome!!!!

 

[Joe Wiebelhaus]

ok i'm going to order some x-457 tomorrow,

On rudder postion, the plans call out for it to be on the right side of the transom ( from behind boat) but i've see some boats that have it on the other side of the boat. Which is better?

Also on the flex shaft what is the point of doing the s bend? i have read that if you flex shaft is straight that you will need it , but what is it for.

Thanks again you all are awesome!!!!

Tom,

Dont know how far you want to take this rebuild, but making the bottom at the transom area one flat bottom will help,(I think I saw from your pictures it has a relief cut in (Dumas design)

Flat bottom strut, center of the hull, with the center line of the shaft about 1" to 1 1/8" to the bottom.

X457 2 or 3 blades work great.

if it is built exactly as the Dumas plans, remove the sponson riding surface back down to the sponson bottom, about 10" from the sponson transom forward, you can leave the remainder there to help launch.

sand smooth and fill as required the new sponson bottom. what you will achieve with this is to drop the front end down so the prop dosent have to lift the rear so high to get a good ride attack angle.

post a picture of what your sponson bottoms look like now, it may help explain.

built over 15 Dumas kits over the years (sport 40 & scale)

 

[t_hedlund]

i was hoping to avoid cutting into the bottom of the hull , but i think that is probably the easiest way to get rudder on it, I have to think about the best way to go about it.

I'll post some pictures of the bottom of the sponson later to night now i have to go the the lake and run the little boat. it has been a while.

Thanks again for all the great information

Tom

 

[t_hedlund]

OK i didn't have time to make it to the lake before i have to goto work. so i took some pictures of the sponson bottoms. here they are gallery

Tom

 

[t_hedlund]

with these changes will the boat be legal to compete in sanctioned races?

 

[Mr. Sport 40]

Hello

I'm rebuilding a Dumas hydro, I have been told that i should move the radio box head of the motor, so i decided to remove the the cockpit and to make the cowl and cockpit one piece, so that i could get the radio box as far forward as possible, Does any one have any suggestions before i start building radio box ?

If you have not put the frame together. make sure all parts are aircraft plywood. depending on what motors you plan on running, I would put the fuel tank in front of the motor, the more simple the plumbing the less troubles you might have.