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Author Topic: Twin Props Fitting "A" Frames How?  (Read 6926 times)

banjo

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Twin Props Fitting "A" Frames How?
« on: December 12, 2007, 01:50:30 PM »

Before I cut great holes in my new hull I would like some advice regarding fitting the A Frames.
(See the picture)
I understand marking up for the prop shaft, I think, but how are the frames best fit into the hull?

Help please...
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DickyD

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Re: Twin Props Fitting "A" Frames How?
« Reply #1 on: December 12, 2007, 02:09:16 PM »

When I do mine I mark their position and profile on the hull. I cut through the hull and jnsert the A frames.then I give them a good dollop of 2 part epoxy resin on the inside of the hull to stick them in and to waterproof.Rough up the inside of hull to provide key for resin. O0
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banjo

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Re: Twin Props Fitting "A" Frames How?
« Reply #2 on: December 12, 2007, 02:20:54 PM »

Thanks for that DickyD,
Its the V shaped bit that worried me, its wider at the top, so will not got through optimum holes futher down, then what to do with the sticking thro' the hull bit??
The prop shaft proper goes "naked" through the bearing in the A frame, the tube stops short of it.
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DickyD

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Re: Twin Props Fitting "A" Frames How?
« Reply #3 on: December 12, 2007, 02:27:05 PM »

Cut them off.
Just leave a short bit for the resin to stick to.
Worked for me. O0
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HS93 (RIP)

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Re: Twin Props Fitting "A" Frames How?
« Reply #4 on: December 12, 2007, 02:30:06 PM »

this how I do them as you are not using solid shafts you need a bit of support.

Peter
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HS93 (RIP)

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Re: Twin Props Fitting "A" Frames How?
« Reply #5 on: December 12, 2007, 02:34:32 PM »

By the way the way  they should only have a single leg on the fire boat.

Peter
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banjo

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Re: Twin Props Fitting "A" Frames How?
« Reply #6 on: December 12, 2007, 02:35:11 PM »

Thats how you did them on your crash boat?
I can understand that bit,
I'll take the length from the side elevation..yes?
and the location as well?
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banjo

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Re: Twin Props Fitting "A" Frames How?
« Reply #7 on: December 12, 2007, 02:36:19 PM »

SH***************t
The man who did them for me said......
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banjo

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Re: Twin Props Fitting "A" Frames How?
« Reply #8 on: December 12, 2007, 02:37:42 PM »

and it cost a rake of money..
shall I cut them down do you think?
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HS93 (RIP)

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Re: Twin Props Fitting "A" Frames How?
« Reply #9 on: December 12, 2007, 02:43:02 PM »

have a look at my PM

Peter
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boatmadman

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Re: Twin Props Fitting "A" Frames How?
« Reply #10 on: December 12, 2007, 02:59:13 PM »

Assemble these and glue with the shaft in place, this way you make sure the alignment is ok.

Ian
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HS93 (RIP)

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Re: Twin Props Fitting "A" Frames How?
« Reply #11 on: December 12, 2007, 03:06:44 PM »

this may help you work out hole sizes without cutting the hull and give you a chance to look at different ways of doing it just a bit of 1mm sheet  this is on my deens hull 24"
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banjo

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Re: Twin Props Fitting "A" Frames How?
« Reply #12 on: December 12, 2007, 03:21:27 PM »

Yes
Thats a good idea.
Thank you.
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HS93 (RIP)

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Re: Twin Props Fitting "A" Frames How?
« Reply #13 on: December 14, 2007, 02:01:51 PM »

a quick sketch of one way of doing it, you may have to rake the legs back a bit to keep the correct angle, just some 6mm  /  1/4 ply glued together with the slots cut first.

Peter
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banjo

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Re: Twin Props Fitting "A" Frames How?
« Reply #14 on: December 14, 2007, 03:37:15 PM »

Thank you for that.
I'm going to do a "dry run" incorporating both these hints.

 O0
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banjo

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Re: Twin Props Fitting "A" Frames How?
« Reply #15 on: December 18, 2007, 10:06:59 PM »

"Lashing " up the first prop is easy...but getting the other to match..Gloom Gloom

 :'(
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grasshopper

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Re: Twin Props Fitting "A" Frames How?
« Reply #16 on: December 18, 2007, 11:30:43 PM »

Make a template to hold the shafts in position on the outside of the hull - Cut piece of stiff card or ply to fit shape of hull with holes for propshaft marked and drilled in correct place and tape to hull whilst epoxy goes off.
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banjo

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Re: Twin Props Fitting "A" Frames How?
« Reply #17 on: December 19, 2007, 02:44:43 AM »

 O0

All help greatfull received...

Cheers Grasshopper

 8)
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Shipmate60

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Re: Twin Props Fitting "A" Frames How?
« Reply #18 on: December 19, 2007, 08:24:25 AM »

banjo,
Firstly drill some strip brass to be a tight fit over the inner propshafts and the width of the propshafts. Put these formers over both ends of the inner propshafts.
I then soft solder some brass strip (at least 2 of) between the outer propshafts. This makes the propshafts fairly rigid and more importantly parallel.
Remove the outer former and open up the hull to a good "sloppy fit". Mark up the "A" Frame holes in the hull, again a good sloppy fit, as previously described bend the legs that protrude into the hull so they are straight through the hull.
Fit the propshafts through the hull to about the right place and slide in the inner propshafts through the outer propshaft and "A" frames.
Lock the brass strip aft of the "A" frames with 2 nuts on each shaft, this should make the whole unit quite rigid.
I then place the motors and couplings roughly in place to ensure that the motors can be lined up when the propshafts are set.
Loosely screw on the props.
Now measure, measure and check the measurements to where you want the props to sit and the "A" frames, ensuring that the shafts are parallel to the keel of the model.
When you are satisfied that they are in the right place superglue the outer shafts into the hull, use the glue sparingly.
Put to one side and let the glue harden and all solvents evaporate, overnight is usually good.
When you return to the model check everything again and check there is no binding in the "A" frames.
If you are not happy with the fit remove the shafts and start again.
When happy with the fit tape over the holes in the hull from the outside with masking tape.
Mix some epoxy resin and run around the shaft exits and "A" frame exits, just a thin smear.
Again let harden.
Now you have rigid propshafts and "A" frames.
Quickly check everything is in place, if it is you can now make them permanent using either P38 or Epoxy.
For Epoxy use a small amount of blutak to hold in the epoxy.
Either bent or cut off the excess "A" frame inside the hull.
This gives a very strong rigid system where I have dropped a model on the props, bent the "A" frame, but all stayed rigid in the hull, so straightened the frame with pliers.
Remove the masking tape and fair in using P38.

Bob
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banjo

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Re: Twin Props Fitting "A" Frames How?
« Reply #19 on: December 19, 2007, 09:31:21 AM »

Bob..

Awesome..

Thanks

 O0
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Shipmate60

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Re: Twin Props Fitting "A" Frames How?
« Reply #20 on: December 19, 2007, 09:41:40 AM »

Hope it helps.

Bob
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banjo

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Re: Twin Props Fitting "A" Frames How?
« Reply #21 on: December 19, 2007, 10:44:09 AM »

How it is so far..:-

Masked off the hull for position marking..

Cut out slots for A Frame and Prop tube..

Note..the prop tube is not planned to extend down to the A Frame

Note the angle on the plan of the prop shaft

Am about to "cut"...extend the slots for the prop shaft futher aft to lessen the angle of the shaft internally....

have located some brass strip, to drill, and use to keep the whole rig "square"

So far so good...

 O0
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HS93 (RIP)

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Re: Twin Props Fitting "A" Frames How?
« Reply #22 on: December 19, 2007, 11:13:25 AM »

did you look at the blog ?a couple of ideas that where on it you can spot a bit of super glue to hold on the plasticard and use the disks to give the correct hight of the shaft for props I make em the size I want with clearance added and you can see how I check to see if they  are both at the same level on the inside.

peter
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banjo

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Re: Twin Props Fitting "A" Frames How?
« Reply #23 on: December 19, 2007, 11:41:23 AM »

Seen...

I'll be doing this too....

Someone could edit all this stuff and make a magic "How to..."

 O0

PS I'll do squares instead of disks, same difference but easier?
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HS93 (RIP)

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Re: Twin Props Fitting "A" Frames How?
« Reply #24 on: December 19, 2007, 12:15:44 PM »

and glue a strut between them to give parallel shafts.

Peter
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