Offshore outboard bracket design question

[bob johnson]

I am building an offshore bracket for my starcraft inboard islander. I have seen many of the brackets and have built mine in solid works( a computer engineering program) but as I look at it... I am wondering WHY so many have draft built into the bottom surface, instead of just being parallel and or even with the original hull. I am keen on this as I have welded large flotation pods to the back of my other boat. they are 24" long! and extend past the end of the motor. this was an issue because they acted like a brake, engaged to slow the boat down .BECAUSE, the pivot point was at the transom where the motor was mounted!!! sooo anything behind the pivot point went DOWNWARDS when the bow went upwards!! For this offshore bracket that will not be the case as the motor will be mounted behind the bracket!! the back side of the bracket will be the pivot point....sooo I am thinking I would not need the bottom of the bracket to be swept upwards at an angle. All I think id need to make sure of , is when on plane the bracket isn't touching the water.....so I am running my prop in clean water that has risen from when it left of the old transom-hull edge!! ( one reason guys can raise their motor mounting with setback devices) this bracket will be full width not just a small flotation portion and then a swim platform.. It was matched to the back of the transom almost full width.

. so am I missing something...will the boat not pivot at the motor mount plane?? I guess even on plane, if I want clean water, Ill have to make sure the bracket doesn't drag... bob

 

[dingbat]

Re: Offshore outboard bracket design question

Surface area = drag. For best efficiency, the bracket should be as small as possible. Swim platforms are separate or completely above the bracket.

The ?pivot point? as you call it, has nothing to do with the boats natural running angle. Not to mention, when you accelerate, the bow rises and the stern drops down even further in the water. Moving the motor further back will change your running angle and exaggerate the stern drop.

[/FONT][/COLOR][COLOR=#222222][FONT=Verdana][URL="http://newimages.yachtworld.com/resize/1/53/65/4345365_20130424084203266_1_XLARGE.jpg%5b/img"]http://newimages.yachtworld.com/resize/1/53/65/4345365_20130424084203266_1_XLARGE.jpg[/img[/URL]][/FONT][/COLOR]
[COLOR=#222222][FONT=Verdana]This is the same model boats as mine with a factory bracket. Look how high the bottom of the bracket is from the bottom of the transom.[/FONT][/COLOR]

 

[bob johnson]

Re: Offshore outboard bracket design question

Surface area = drag. For best efficiency, the bracket should be as small as possible. Swim platforms are separate or completely above the bracket.

The “pivot point” as you call it, has nothing to do with the boats natural running angle. Not to mention, when you accelerate, the bow rises and the stern drops down even further in the water. Moving the motor further back will change your running angle and exaggerate the stern drop.

[/FONT][/COLOR][COLOR=#222222][FONT=Verdana][URL="http://newimages.yachtworld.com/resize/1/53/65/4345365_20130424084203266_1_XLARGE.jpg%5b/img"]http://newimages.yachtworld.com/resize/1/53/65/4345365_20130424084203266_1_XLARGE.jpg[/img[/URL]][/FONT][/COLOR]
[COLOR=#222222][FONT=Verdana]This is the same model boats as mine with a factory bracket. Look how high the bottom of the bracket is from the bottom of the transom.[/FONT][/COLOR][/QUOTE]photo wont come up..... bob