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Stress on crossbar from motor mounts

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(@wanderoo222)
Posts: 43
Lubber
Topic starter
 

I am concerned about the stress that all the motor mount designs I've seen put on the rear crossbar . I've decided on the motor mount design by KeithB posted here viewtopic.php?f=23&t=57851 . I am considering adding an additional crossbar aft of the crossbar between the hulls that the motor mount arm would bolt to . The crossbar would just rest on the hulls in some fashion without actually being bolted to them to allow for flexing. What are opinions about this. The outboard I have weighs 37 lbs

 
Posted : November 13, 2016 6:59 am
Edward Hilliard
(@Edchris177)
Posts: 2531
Captain
 

I've decided on the motor mount design by KeithB posted here viewtopic.php?f=23&t=57851

Edit your post. Click on the button below where you type, that says URL.
That will open up a set of brackets. Copy & paste the full address link inside the brackets, then it will become "live" & all readers can simply click on it.

I am concerned about the stress that all the motor mount designs I've seen put on the rear crossbar

What Breed of Cat?
I have not heard of people having issues with mounting small engines. I once towed 2 kids on a tube, tied to the rear beam of a Nacra 5.7.
There are several videos of towing a wakeboarder behind a Nacra 5.0
Small engines do not create tons of horsepower, & the Cat hulls create little resistance. The boat moves before much stress is put on a X bar.
If I was worried about 40lbs bending the beam while driving through waves, I'd get a different Cat.

Edited by Edchris177 on Nov 13, 2016 - 08:15 PM.

E C Hilliard

Nacra 5.7
Bombardier Invitation

 
Posted : November 13, 2016 2:12 pm
tominpa
(@tominpa)
Posts: 624
Chief
 

I don't think a second beam system could be setup on most cats. The structure does not exist to mount it on the hulls, and tiller systems move both side to side, and aft as you turn. Avoiding interference with tillers and rudders would be quite a feat. Outboard motors need to be planned and mounted to avoid interfering with steering, and closer to center is better to avoid the motor ending up in the water when you heel. I agree with Ed, the rear crossbeam strength should not be an issue.

 
Posted : November 14, 2016 5:42 am
André
(@catmodding)
Posts: 424
Chief
 

wanderoo222 wrote: I am concerned about the stress that all the motor mount designs I've seen put on the rear crossbar . I've decided on the motor mount design by KeithB posted here viewtopic.php?f=23&t=57851 .The outboard I have weighs 37 lbs

Is this the one?
http://cheatabrackets.com/page1.php

If you keep the Bhp around 2/3, stress on the rear-beam shouldn't
be a problem. Anything over it would burry the sterns anyway....

A second beam system seems difficult to me, how does it handle
propulsion/torque, hence rotation without being actually bolted to
the hulls?

I'm thinking about installing a Cheata bracket combined with a
Torqeedo travel 503 on my Tornado.
It has a build-in battery. So no dealing with gasoline and external
batteries. Maybe something for You?

Grtz, A

Edited by catmodding on Nov 17, 2016 - 10:13 PM.

André de Bruin, Amsterdam,the Netherlands
P 18-2

 
Posted : November 17, 2016 9:02 am
(@wanderoo222)
Posts: 43
Lubber
Topic starter
 

Here is the link to the mount design I made for my Hobie Getaway. http://www.hobiecat.com/forums/viewtopic.php?f=23&t=57851

Once I mounted the outboard the crossbeam torqued some then settled. Seems stable but I am still a little concerned about how the up and down bouncing of the boat might put excess torque on the beam or on the hull where the beam goes into the hull. Does anyone know how far the beam goes into the hull on the Getaway?

 
Posted : November 17, 2016 11:46 am
(@wanderoo222)
Posts: 43
Lubber
Topic starter
 

After testing the mount with extra weights it held up fine. The crossbeam appears to extend deep into each hull giving ample support. Nice design.

 
Posted : November 18, 2016 7:19 am