C19 Stretch and re-build Progress Report...

To help other builders, please list the boat you are building in the Thread Subject -- and to conserve space, please limit your posting to one thread per boat.

Please feel free to use the gallery to display multiple images of your progress.
TomTom
Very Active Poster
Very Active Poster
Posts: 540
Joined: Thu Nov 22, 2012 10:29 am
Location: East Africa

Re: C19 - Major Structural Issues - Progress

Post by TomTom » Mon Dec 03, 2018 1:56 am

Fuzz thanks - do you guys think that porpoising is a natural problem with an outboard style bracket set up - or is it more of a weight and balance thing.

I am doing my repairs right by the ocean and was thinking I could mount the engine and then stick the console in loose and move batteries, fuel etc around to work out where she sits nicely. I kinda have a clean slate from a weight and balance point of view; but I guess what I am trying to work out is how much is porpoising an inherent risk with outboard brackets and how much of it comes down to the weight and balance thing.

The bracket will definitely be more work to do, so really just trying to work out if I am just borrowing trouble on this one. For me the extension is a no brainer, but I keep doing u turns with the "bracket" idea.



User avatar
BarraMan
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 1611
Joined: Tue Dec 11, 2012 3:44 pm
Location: Australia

Re: C19 - Major Structural Issues - Progress

Post by BarraMan » Mon Dec 03, 2018 3:10 am

I've got nothing for you on this. I have never had anything to do with brackets.

The motor on my boat sits on a jack plate with an 8" set back and an inbuilt 2" lift with a further 6" available from the jack plate.

My boat doesn't porpoise - ever!

Trimming the motor out lifts the bow and eventually results in cavitation. Lifting the jack plate too high also results in cavitation.

fallguy1000
Very Active Poster
Very Active Poster
Posts: 6183
Joined: Tue Jan 12, 2010 12:25 am

Re: C19 - Major Structural Issues - Progress

Post by fallguy1000 » Mon Dec 03, 2018 5:09 am

If you have porpoising worries, can't you alleviate these some by building the bracket at 14 degrees to water?
My boat build is here -------->

viewtopic.php?f=12&t=62495

TomTom
Very Active Poster
Very Active Poster
Posts: 540
Joined: Thu Nov 22, 2012 10:29 am
Location: East Africa

Re: C19 - Major Structural Issues - Progress

Post by TomTom » Mon Dec 03, 2018 7:30 am

If you have porpoising worries, can't you alleviate these some by building the bracket at 14 degrees to water?
yes ... I think most transom brackets are built with more angle so that you have more wriggle room with your outboard settings.

I guess what I am trying to figure out is whether on a boat like this, there would really be any major advantages (other than an extra 16 inches in cockpit length) to a bracket - or whether I am just borrowing trouble!

Fuzz
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 6931
Joined: Tue Aug 02, 2011 4:23 am
Location: Kasilof, Alaska

Re: C19 - Major Structural Issues - Progress

Post by Fuzz » Mon Dec 03, 2018 2:53 pm

Like I said my hull has some designed in rocker. I am sure that has a lot to do with it.
You being able to put the boat in the water to check the balance would be a huge help. Having the motor on a bracket makes the boat feel a lot larger for sure.

TomTom
Very Active Poster
Very Active Poster
Posts: 540
Joined: Thu Nov 22, 2012 10:29 am
Location: East Africa

Re: C19 - Major Structural Issues Now Slowly Getting there - Stretching to 21 now!

Post by TomTom » Wed Dec 05, 2018 12:49 pm

I am about neck and neck with Eric now on his C21 - I thought he was going to buy a bolt on bracket...

I am still thinking about it and then the other monkey on my shoulder reminds me of the KISS principle! The stretch is definitely happening though!!

Fuzz
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 6931
Joined: Tue Aug 02, 2011 4:23 am
Location: Kasilof, Alaska

Re: C19 - Major Structural Issues Now Slowly Getting there - Stretching to 21 now!

Post by Fuzz » Wed Dec 05, 2018 2:14 pm

I have now built one bracket and also installed one on a different boat that was a bolt on.
The bolt on was fast and easy. It was also spendy. All said and done I had $5000 in the bracket.
If I were to do another home built bracket it would be done just like the one I and Daytrip did. I would not trust a home built one that bolts on but I feel different about one built by running the stringers out through the transom. To me the key is the stringers carrying the weight and all the rest just being a bonus.

OneWayTraffic
* Bateau Builder *
* Bateau Builder *
Posts: 891
Joined: Sat Jan 10, 2015 7:13 pm
Location: New Zealand

Re: C19 - Major Structural Issues Now Slowly Getting there - Stretching to 21 now!

Post by OneWayTraffic » Sun Dec 09, 2018 10:50 pm

I would add a gusset to the motor mount if it extends more than a little above the bracket surface.

If you use the same, or greater scantlings as the transom itself, and extend out the stringers, along with a generous fillet and a couple of layers tape between the bracket and transom, I can't see it failing. I am no engineer however.

Christer
Frequent Poster
Frequent Poster
Posts: 155
Joined: Thu Sep 28, 2017 8:40 am
Location: Norway
Contact:

Re: C19 - Major Structural Issues Now Slowly Getting there - Stretching to 21 now!

Post by Christer » Fri Dec 14, 2018 7:10 am

The OcraCoke boats have versions with built-in brackets based on through-transom stringers, and it looks good and seems to work well. It's a Carolina Sportfish style boat like the Bateau CS23/25, but I'd reckon the principle would be the same.

Like this: https://bandbyachtdesigns.com/ocracoke-256-2/

Can't wait to see how this turns out! Best of luck!
8ft dinghy built in 1992, BBV sufferer ever since.

TomTom
Very Active Poster
Very Active Poster
Posts: 540
Joined: Thu Nov 22, 2012 10:29 am
Location: East Africa

Re: C19 - Major Structural Issues Now Slowly Getting there - Stretching to 21 now!

Post by TomTom » Tue Dec 18, 2018 6:40 am

Thanks Christer - yes I had secretly been looking at the B and B boats - though I am not sure if one is allowed to mention that here!

I am not particularly worried about making it strong enough if I extend the stringers through the transom to make the bracket. I think it is very doable.

This bearing in mind I am the guy that drove around unknowingly in a boat that basically had half the stringers not even properly taped to the hull, and half the inner sheathing bonded with a chewing-gum-like sorry-ass excuse for resin for most of the boat's life. I can see how faith in the amateur builder could be lacking sometimes!! But it did serve as a remarkable testament to the design that it still didn't fall apart! I am confident that the hull will be stronger than at any point in its history this time around!!

So I personally think there is probably plenty of strength and redundancy - though I can understand why the designer wouldn't want to stick his neck out on this one!

I guess though, I am still slightly confused how a 10% hull extension plus a commercial bolt on bracket would be given the designers ok, but that a 10% hull extension and then an 18 inch through transom "bracket" made with a stringer extension wouldn't be? I mean I suppose one could say this is closer to say a 15% hull extension - but I don't really understand how the stresses would be different to a 10% hull extension and a bolt on commercial bracket? Anyone following me here?! You are still essentially adding the same amount of length. Maybe I just don't understand how the stresses would be transferred.

What concerns me more is whether I am just borrowing trouble in terms of the boat's performance - will I suddenly end up with a boat that rides totally different, porpoises, is out of balance and has a massive rooster tail! Not that rooster tails don't look cool - but I digress...

I guess I am more worried about my ability to get all the angles correct and end up with something that gains me not only an extra 18" of hull space (in addition to the 10% hull extension) ... but that also doesn't screw up a perfectly good boat!

Post Reply

Who is online

Users browsing this forum: No registered users and 4 guests