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Author Topic: flexing hull  (Read 3143 times)

Willit

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flexing hull
« on: August 18, 2008, 11:28:11 PM »

hi all, bit of a pickle here, I am rejigging my Springer as a harbour pusher (the bantam superstructure looked a bit naff after a while) and have been redoing the steering arrangement.  The problem I have is this.  When the servo pushes or pulls the rudder arm, the whole rudder post moves several mm toward or away from the servo like a big lever.  This very visibly flexes the 1mm ply bottom, and can't be doing it any favours.  Anyone know a cure to this problem?  I have played around with the length of the operating rod and even the position of the servo and I'm reluctant to use the boat with this flexing happening.

thanks

Matt
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Stavros

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Re: flexing hull
« Reply #1 on: August 19, 2008, 12:32:30 AM »

Right then simple cure,put a gusset in from the stern to th rudder post and also gusset down from said post to the bottom to the hull this should cure your problem



Stavros
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Roger in France

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Re: flexing hull
« Reply #2 on: August 19, 2008, 06:35:00 AM »

I am sure Stavros is giving good advice. However, before I did as he suggested I would first add a section of ply with a central hole to take the rudder post, slip it over the post and epoxy it to the bottom. This could be done inside or outside the hull. Make it as large as possible.

I think messing with the linkage is useless as your hull is clearly too flimsy to take the strains applied. Even if you appear to have stopped the flexing by doing as you suggest tiny movements will still be taking place, resulting in eventual, total failure.

Roger in France.
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Martin [Admin]

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Re: flexing hull
« Reply #3 on: August 19, 2008, 07:16:05 AM »

I've found that using a double arm linkage often helps.
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DickyD

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Re: flexing hull
« Reply #4 on: August 19, 2008, 08:13:42 AM »

Fix a plywood brace to the top of the rudder tube.
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Willit

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Re: flexing hull
« Reply #5 on: August 19, 2008, 09:06:03 AM »

Richard has the best quick fix so far.

Thanks for the tips guys.  I'm surprised no one else has had this problem :P
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Arrow5

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Re: flexing hull
« Reply #6 on: August 19, 2008, 02:42:08 PM »

Whip the rudder tube out and glue in a 1"x !.5" block of wood hard against stern and hull bottom , re-drill and replace rudder tube. Wont move again and no leaks either. O0
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Martin [Admin]

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Re: flexing hull
« Reply #7 on: August 19, 2008, 03:11:26 PM »

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toesupwa

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Re: flexing hull
« Reply #8 on: August 19, 2008, 03:37:58 PM »

When the servo pushes or pulls the rudder arm, the whole rudder post moves several mm toward or away from the servo like a big lever.  This very visibly flexes the 1mm ply bottom..

Do you have any bulkheads / bracing within the bottom of the hull?..
As others have suggested, put a block inside the bottom and put the rudder tube through that.. You may also need a block on the outside of the bottom too.
You have got the bottom of the rudder supported from the skeg?...

Something along these lines.. and "no", i dont get any flex at the rudder..

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Willit

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Re: flexing hull
« Reply #9 on: August 21, 2008, 02:47:05 PM »

thanks for all the suggestions guys.  The real problem is that the bottom of the hull is quite flimsy and easy to flex so as Roger in France says it will go one day anyway.  I ran the boat today and all was well.....until I got it out at the end.  It was swimming in water, literally swimming in it.  It was so close to the speed controller too.  For that reason I have emailed Norry about getting a GRP hull.  I have had enough fiddling with this current wooden hull. It was never especially well made in the first place and you can't flog a dead horse.  So a new boat will be built using all the running gear recovered from the current boat.
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