Hello all,
On my jon boat build I'm currently sanding the bottom after covering it in fiberglass cloth. I'm trying to understand when to do the graphite bottom. Do I sand the fiberglass until smooth and then just spread the graphite mixture or do I need to use quickfair or some other material to fair the bottom smooth before putting the graphite/epoxy on?
Being the bottom it doesn't need to be perfect but I'd like it to be relatively smooth and look at least OK. I feel that I should fair it but I'm concerned having the quickfair down between the fiberglass and graphite/epoxy mixture will be bad.
I have cracker larry's and Capt AB's graphite mixtures down and have reviewed it but couldn't find a definitive answer on if the graphite goes right on the sanded fiberglass, or if it needs to be faired first to be smooth?
Thanks all
Graphite bottom application
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Graphite bottom application
Boats restored: 1973 Glastron CV16, 1990 Proline 17 CC, 1993 Bass Boat
Boats built: custom 15ft flat bottom skiff, Soon-to-be-built TX18 (originally dborecky's build)
Boats built: custom 15ft flat bottom skiff, Soon-to-be-built TX18 (originally dborecky's build)
- Jaysen
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Re: Graphite bottom application
The short answer is “yes”.
The long answer is “it depends on your focus”. On my v12 the focus is indestructible (which it isn’t) so graphite right on glass would be ideal. The fairing compounds are softer by design so avoiding them does, in theory, make for a harder bottom.
That said, smooth bottoms move through the water easier. So if you build like I do, like the lines are there for show, then you will want to get the bottom smooth enough to keep the hull efficient.
As to the mixture… try both on a sample piece. Use the one that works. I ignored both and did my own thing. I would not follow my example.
Good luck.
The long answer is “it depends on your focus”. On my v12 the focus is indestructible (which it isn’t) so graphite right on glass would be ideal. The fairing compounds are softer by design so avoiding them does, in theory, make for a harder bottom.
That said, smooth bottoms move through the water easier. So if you build like I do, like the lines are there for show, then you will want to get the bottom smooth enough to keep the hull efficient.
As to the mixture… try both on a sample piece. Use the one that works. I ignored both and did my own thing. I would not follow my example.
Good luck.
Re: Graphite bottom application
I used a fair amount of fairing compound to get my bottom smooth before the graphite. If you can live without it, so much the better, as Jaysen said.
There are only two seasons in Vermont: boating season, and boat-building season.
Completed Paul Butler 14' Clark Fork Drifter
Completed Jacques Mertens FS14LS + 10%, Build Thread
Started Iain Oughtred Tammie Norrie
Completed Paul Butler 14' Clark Fork Drifter
Completed Jacques Mertens FS14LS + 10%, Build Thread
Started Iain Oughtred Tammie Norrie
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Re: Graphite bottom application
Good to know Jaysen. I don't need a show boat finish but want to make sure it looks good while being hard enough to not be worried if I pull up on a sand bar or grass flat with small rocks. I don't think it'll matter much if I hit oysters but hopefully I can miss those for the most partJaysen wrote: ↑Thu Oct 21, 2021 7:56 am The short answer is “yes”.
The long answer is “it depends on your focus”. On my v12 the focus is indestructible (which it isn’t) so graphite right on glass would be ideal. The fairing compounds are softer by design so avoiding them does, in theory, make for a harder bottom.
That said, smooth bottoms move through the water easier. So if you build like I do, like the lines are there for show, then you will want to get the bottom smooth enough to keep the hull efficient.
As to the mixture… try both on a sample piece. Use the one that works. I ignored both and did my own thing. I would not follow my example.
Good luck.
I'll see what it looks like after sanding it down I suppose and then I can make a call on fairing or not. I'll give the 2 mixtures a shot
Boats restored: 1973 Glastron CV16, 1990 Proline 17 CC, 1993 Bass Boat
Boats built: custom 15ft flat bottom skiff, Soon-to-be-built TX18 (originally dborecky's build)
Boats built: custom 15ft flat bottom skiff, Soon-to-be-built TX18 (originally dborecky's build)
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- Joined: Fri Mar 27, 2020 12:23 pm
- Location: Crawfordville, FL
Re: Graphite bottom application
I'm mostly thinking on the sides where the cloth overlaps the tape is what will need most fairing since it's layered there. I plan on doing the sides to be really smooth but that'll be topside paint above the waterline/graphite (I think I marked 4"). Do you think if I just faired the sides that it would bond alright? Almost no one will see the bottom but even the few inches the graphite will cover on the sides will be apparent.
Boats restored: 1973 Glastron CV16, 1990 Proline 17 CC, 1993 Bass Boat
Boats built: custom 15ft flat bottom skiff, Soon-to-be-built TX18 (originally dborecky's build)
Boats built: custom 15ft flat bottom skiff, Soon-to-be-built TX18 (originally dborecky's build)
Re: Graphite bottom application
My .02: The epoxy-graphite should bond fine to the fairing mix, assuming they are compatible products. Same with the fairing mix to glass, though make sure your glass isn't too smooth, I think this caused me some headaches on my transom where the fairing chipped off in a few places. I may have been using some bad acetone to clean the surface, I stopped doing that.wpstarling wrote: ↑Thu Oct 21, 2021 8:57 amI'm mostly thinking on the sides where the cloth overlaps the tape is what will need most fairing since it's layered there. I plan on doing the sides to be really smooth but that'll be topside paint above the waterline/graphite (I think I marked 4"). Do you think if I just faired the sides that it would bond alright? Almost no one will see the bottom but even the few inches the graphite will cover on the sides will be apparent.
Getting the sides fair between the multiple layers of glass wrapping the chine and the single layer covering the actual side was a real chore for me. Same with the area on each side of the keel where it goes from a few layers of tape to the single layer of cloth on the bottom. Filling those gaps and getting a flat surface was a lot of work and it was of the variety that I am not accustomed to, not good at, and do not particularly enjoy. But, in the end, it's all smooth and looks pretty good. If you meet up with any other boat-builders at any point be prepared for them to immediately look at your bottom, it's automatic.
As I've said to the point of a broken-record, what I like best about an epoxy-graphite bottom is that it goes on in one long shot, wet-on-wet, no sanding in between, no 3-4(or 7-10 in the VT Springtime) days of drying in between. If I could do the whole boat like that I would but to date I've not found a way to do this, unless I want a black boat, which I don't.
There are only two seasons in Vermont: boating season, and boat-building season.
Completed Paul Butler 14' Clark Fork Drifter
Completed Jacques Mertens FS14LS + 10%, Build Thread
Started Iain Oughtred Tammie Norrie
Completed Paul Butler 14' Clark Fork Drifter
Completed Jacques Mertens FS14LS + 10%, Build Thread
Started Iain Oughtred Tammie Norrie
- Jaysen
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Re: Graphite bottom application
You can't. I aim for them so to make sure I miss them. If I try to miss them the universe moves the oysters to be directly in my path. If I'm aiming for them the universe clears them out of the way just to spite me.wpstarling wrote: ↑Thu Oct 21, 2021 8:54 am I don't think it'll matter much if I hit oysters but hopefully I can miss those for the most part
You "could" torture yourself and make an alternate fairing compound that is hard. I know it is torture because, just like with graphite, I tried my own thing. Get a little fumed silica and add it to some warmed slow epoxy. You don't want to add so much silica that the epoxy starts to thicken too much. Once you have something a bit runny but no longer clear, use it like a fairing compound. It is a b!tch to sand, but it is hard as rocks. then graphite over that. You heat the epoxy to keep it runny. The problem is that heating epoxy makes it kick quicker so plan accordingly. I eventually took to mixing it unwarmed then warming it as I applied it with a warm water bath.
If you ever need to know "the hard way" to do something... I'm your guy.
- Jaysen
- * Bateau Builder *
- Posts: 6520
- Joined: Wed Aug 05, 2015 7:59 am
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Re: Graphite bottom application
Grey? use aluminumoxide. someone in AU or NZ did that.
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Re: Graphite bottom application
Good to hear. I'll plan on fairing sides/transom and I'll play the bottom by ear depending on what it looks like when I finish sanding it. I need to sharpen the chines still but I've been busy fishing so the boat has sat beautifully upside down for a few weeks now haha.VT_Jeff wrote: ↑Thu Oct 21, 2021 9:16 am My .02: The epoxy-graphite should bond fine to the fairing mix, assuming they are compatible products. Same with the fairing mix to glass, though make sure your glass isn't too smooth, I think this caused me some headaches on my transom where the fairing chipped off in a few places. I may have been using some bad acetone to clean the surface, I stopped doing that.
Getting the sides fair between the multiple layers of glass wrapping the chine and the single layer covering the actual side was a real chore for me. Same with the area on each side of the keel where it goes from a few layers of tape to the single layer of cloth on the bottom. Filling those gaps and getting a flat surface was a lot of work and it was of the variety that I am not accustomed to, not good at, and do not particularly enjoy. But, in the end, it's all smooth and looks pretty good. If you meet up with any other boat-builders at any point be prepared for them to immediately look at your bottom, it's automatic.
As I've said to the point of a broken-record, what I like best about an epoxy-graphite bottom is that it goes on in one long shot, wet-on-wet, no sanding in between, no 3-4(or 7-10 in the VT Springtime) days of drying in between. If I could do the whole boat like that I would but to date I've not found a way to do this, unless I want a black boat, which I don't.
Boats restored: 1973 Glastron CV16, 1990 Proline 17 CC, 1993 Bass Boat
Boats built: custom 15ft flat bottom skiff, Soon-to-be-built TX18 (originally dborecky's build)
Boats built: custom 15ft flat bottom skiff, Soon-to-be-built TX18 (originally dborecky's build)
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- Frequent Poster
- Posts: 102
- Joined: Fri Mar 27, 2020 12:23 pm
- Location: Crawfordville, FL
Re: Graphite bottom application
Yea, i hear you on the oysters moving. I'd rather go out at low tide to see what I'm going to run into vs high tide where it's hidden. I found out the hard way what happens when you mix too much epoxy, it about burned my hand and was a waste of a good bit of epoxy.Jaysen wrote: ↑Thu Oct 21, 2021 9:19 am You can't. I aim for them so to make sure I miss them. If I try to miss them the universe moves the oysters to be directly in my path. If I'm aiming for them the universe clears them out of the way just to spite me.
You "could" torture yourself and make an alternate fairing compound that is hard. I know it is torture because, just like with graphite, I tried my own thing. Get a little fumed silica and add it to some warmed slow epoxy. You don't want to add so much silica that the epoxy starts to thicken too much. Once you have something a bit runny but no longer clear, use it like a fairing compound. It is a b!tch to sand, but it is hard as rocks. then graphite over that. You heat the epoxy to keep it runny. The problem is that heating epoxy makes it kick quicker so plan accordingly. I eventually took to mixing it unwarmed then warming it as I applied it with a warm water bath.
If you ever need to know "the hard way" to do something... I'm your guy.
I'll finish sanding and see but I'll make sure to post what I do in here for future builder's, even if it looks terrible
Boats restored: 1973 Glastron CV16, 1990 Proline 17 CC, 1993 Bass Boat
Boats built: custom 15ft flat bottom skiff, Soon-to-be-built TX18 (originally dborecky's build)
Boats built: custom 15ft flat bottom skiff, Soon-to-be-built TX18 (originally dborecky's build)
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