Boat rebuild - hull depressions

Questions about boat repairs with our resins and fiberglass: hull patches, transoms and stringers, foam, rot etc.
Crooked
New Poster
New Poster
Posts: 4
Joined: Sun Sep 29, 2019 8:44 pm
Location: Australia

Boat rebuild - hull depressions

Post by Crooked »

Hi All,
I've followed this forum for a while now and has some really interesting information. I've always been in to boating of the coast of Far North Queensland in Australia and as my family is growing I have commenced rebuilding an older fibreglass hull, well rebuilding and converting really as this was originally a half cabin boat and I am converting this to a centre console. This hull is from one of the old reputable Australian boat builders who are still around today building similar craft, this one is about 35 years old and it is 18ft long.

I have made a fair bit of progress and I will attach some basic photos once I figure that out but I'm looking for some opinions on whether I should be addressing several depressions that are located forward of the transom on either side of the keel. The keel itself is perfectly flat and this is so for around a foot in the centre, but further toward the lifting strake there is a small depression or hook that extends forward for around 2 feet. Outward of the lifting strake toward the reverse chine it is again perfectly flat. So the depressed area is around a foot and a half wide incorporating the lifting strake and 2 feet up the hull, so an oval, at it's deepest it is around 5mm (so just less than a 1/4 inch). I've included a quick diagram for explanation, the red circle is where the depression is.

Question is given the keel is flat so the hull is not completely hooked should I work at fairing these depressions out of the hull, I did try and push them out from the inside but could not. Or is the potential effect on hull handling to minimal to be concerned with this extra work, I have not used this hull in the water so I don't know if there is any impacts that are noticable. I know hooks can produce handling issues but for these small areas and not including the keel and being only 5mm, would this be an issue?

Any opinions appreciated

Fuzz
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 8921
Joined: Tue Aug 02, 2011 4:23 am
Location: Kasilof, Alaska

Re: Boat rebuild - hull depressions

Post by Fuzz »

Hey Crooked welcome to the fun.
Pictures will be a big help to let the guys give you good answers. If you have problems posting them ask and somebody will help with that. Do you happen to know if this hull has been sitting on a roller trailer for most of its life?

Crooked
New Poster
New Poster
Posts: 4
Joined: Sun Sep 29, 2019 8:44 pm
Location: Australia

Re: Boat rebuild - hull depressions

Post by Crooked »

Thanks Fuzz, I'll try and get the pictures up. It has been sitting on a roller trailer and the stringers were rotted so this is what would have caused the hollows. I tried to push them out from the inside when I reinstalled the stringers but it wasn't successful. Just trying to decide if this will affect performance.

Image
Image
Image
Image
Image

DAYTRIP
* Bateau Builder *
* Bateau Builder *
Posts: 848
Joined: Wed May 31, 2006 10:32 pm
Location: North Palm Beach
Location: NORTH PALM BEACH

Re: Boat rebuild - hull depressions

Post by DAYTRIP »

Hi crooked, nice hull and great work so far. Sometimes builders will put a hook in the chine and/or lifting strake to add stern lift or negative trim. The running surface probably should be flat. Not to say they didn’t intend it but my guess is no. I had the same issue on a 17 mako I redid. Mine was depressed I’ver a two or three ft area. I mapped it out then added glass to the area greater than 1/8 then filled and faired. Really helped the performance. Is the depressed area symmetrical from the keel or only one side? Either way, if you were adding trim tabs I personally would straighten the hull panel at a minimum. Trim with tabs as needed. Keep up the good work!

Fuzz
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 8921
Joined: Tue Aug 02, 2011 4:23 am
Location: Kasilof, Alaska

Re: Boat rebuild - hull depressions

Post by Fuzz »

I think DayTrips advice is spot on. Much better to fix it now than always wonder if you left a bunch of performance on the table :wink:

Crooked
New Poster
New Poster
Posts: 4
Joined: Sun Sep 29, 2019 8:44 pm
Location: Australia

Re: Boat rebuild - hull depressions

Post by Crooked »

Thanks for the advice fellas I have sort of been in two minds. It's a fishing boat and not really used in any flat water, so on one hand if it is a bit slower due to more stern lift then no problems but if it is going to exhibit some nasty habits due to these areas then I would definitely do as you say and fill and fair them.

They are on both sides of the keel and within a few millimeters of eachother in terms of depth.

So I guess I was trying to figure out how much effect they would really have on the hull and if the effort to fair out is worth it. I might be best to just get it done and move on without worrying about them anymore!

Jeff
Site Admin
Site Admin
Posts: 8438
Joined: Fri Apr 29, 2016 12:17 pm
Location: Vero Beach

Re: Boat rebuild - hull depressions

Post by Jeff »

Welcome to the Builders Forum!!! Jeff

Fuzz
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 8921
Joined: Tue Aug 02, 2011 4:23 am
Location: Kasilof, Alaska

Re: Boat rebuild - hull depressions

Post by Fuzz »

It seems like the low spots are bothering you. If so they will always bother you to some degree. There is never going to be a better time to take care of the problem than now. You do not want to have her fully rigged and in the water and then decide you need to fix the bottom. That is just my opinion of course :wink:

Crooked
New Poster
New Poster
Posts: 4
Joined: Sun Sep 29, 2019 8:44 pm
Location: Australia

Re: Boat rebuild - hull depressions

Post by Crooked »

Thanks Fuzz, yeah you are probably right maybe i’m just being lazy. These are big projects and take time and effort maybe i’m just looking at it in terms of reducing the tasks left. But I do want to get it right.

User avatar
BarraMan
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 2164
Joined: Tue Dec 11, 2012 3:44 pm
Location: Australia

Re: Boat rebuild - hull depressions

Post by BarraMan »

Remove the hook now - while you can!

It may not make any difference to performance but you will always know its there - and wonder!

When I built my boat, in spite of my best efforts I had some hook in the bottom at the back towards the transom. I filled it with glass cloth and faired it out so that the bottom of the boat was straight as a die!

I have no idea whether or not it makes any difference - but I now know that the bottom of the boat is straight - as it should be.

If you want to trim the nose down - fit trim tabs! :lol:

Post Reply

Who is online

Users browsing this forum: Google [Bot] and 13 guests