Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

E

Eightyseven550

Cadet
Joined
Oct 5, 2011
Messages
17
Strengthening the floor/Bottom.

I am rebuilding a small sailboat for my dad. (13'-6")
(if you care, the boat is a bench style Flying Junior - FJ / CFJ)

Best way to describe the boat's construction is probably like a fiberglass canoe.
Different shape but same construction.


When I took this boat out, I noticed the floor/bottom flexing.

To solidify the boat I plan an the following.

1. Roughly sand all paint off the floor.
2. Using a thin layer of Fiberglass (Woven Mat) across the entire floor.
Probably in 2 or 3 large pieces. (Left then right side)
3. Repaint the floor with a non skid paint.

I have never done any glass work so I aam open for any help or suggestions.

Thank you,
Andre

P.S.
I am restoring this for him as an upgrade to his current sailboat.
He currently has a Laser, these are not great for taking the wife out on.
(The Laser is the same Laser we've had since I was 3.)
 

Attachments

  • IMG_0608.jpg
    IMG_0608.jpg
    128 KB · Views: 0
  • IMG_0609.jpg
    IMG_0609.jpg
    129.3 KB · Views: 0
  • IMG_0645.jpg
    IMG_0645.jpg
    134.5 KB · Views: 0
  • IMG_0648.jpg
    IMG_0648.jpg
    135.6 KB · Views: 0
  • IMG_0649.jpg
    IMG_0649.jpg
    135.7 KB · Views: 0
RogersJetboat454

RogersJetboat454

Commander
Joined
Jul 9, 2010
Messages
2,964
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

Have any pictures?
Would help people form a more conclusive opinion of your proposal.
 
Watermann

Watermann

Starmada Splash of the Year 2014
Joined
Jan 12, 2013
Messages
13,753
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

Sounds like a great project and a worthy boat. The ole timers here are going to suggest that you sample your decking and supports so that you don't throw money away by resurfacing over the top of compromised or rotten wood. This is normally the main cause of decks being spongy under foot. Yes pics please, we all love to see what the project boat looks like.
 
E

Eightyseven550

Cadet
Joined
Oct 5, 2011
Messages
17
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

Watermann said:
sample your decking and supports / compromised or rotten wood. This is normally the main cause of decks being spongy under foot.
Click to expand...

No "Deck" or "Supports" on this boat. (Just one layer of fiberglass between you and the water)

And it was more of the floor flexing when sailing, not a spongy feeling.
Near identical to stepping into a plastic made canoe that is floating.

(Best way to describe the boat's construction is probably more like a fiberglass canoe)
 
Watermann

Watermann

Starmada Splash of the Year 2014
Joined
Jan 12, 2013
Messages
13,753
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

Eightyseven550 said:
No "Deck" or "Supports" on this boat. (Just one layer of fiberglass between you and the water)
Click to expand...

Oh I see that's where pics come in handy. I would have imagined there were some stringers in the bottom that had wood encased in glass. I think I understand now what your facing. Sounds like your on the right path then with your ideas to prep surface add a layer for strength. I'm sure some glass guys will pipe up with the best solution for you. There are tons of threads here already on the subject or using fiberglass with step by step how to's and pics!
 
E

Eightyseven550

Cadet
Joined
Oct 5, 2011
Messages
17
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

Watermann said:
...I would have imagined there were some stringers in the bottom that had wood encased in glass...
Click to expand...

I actually considered putting stringers in, decided that may be a bit much as I would want to put the mat down over everything anyway.

I would like to just do this once, the right way and know my dad has a sound vessel to take out when he chooses.
 
mwe-maxxowner

mwe-maxxowner

Master Chief Petty Officer
Joined
Jun 20, 2012
Messages
825
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

I do knw, from my research on my runabout restore, you'll have to do more than sand through the paint. You'll need to use a grinder with a 24-36 grit flap wheel to grind through the first layer of fiberglass to "good glass". Nice clean not chipping glass. Then you will be able to fiberglass another layer or two after cleaning up good with a shop vac and acetone.
 
73Chrysler105

73Chrysler105

Chief Petty Officer
Joined
Sep 10, 2009
Messages
407
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

I would use Epoxy as it will be a stronger bond and stiffen the boat. If you wanted to really make it stiffer and stronger use carbon fiber instead of fiberglass with the epoxy.
 
a1964rn

a1964rn

Petty Officer 1st Class
Joined
Oct 18, 2012
Messages
287
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

73Chrysler105 said:
I would use Epoxy as it will be a stronger bond and stiffen the boat. If you wanted to really make it stiffer and stronger use carbon fiber instead of fiberglass with the epoxy.
Click to expand...

I agree, except I would use 1708 biaxial cloth.
 
Ned L

Ned L

Commander
Joined
Sep 17, 2008
Messages
2,266
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

OK, So I guess I'd say 'the bottom flexes', and so the problem with that is what? - Not meaning to be sarcastic. It's kind of like sitting in an airplane and seeing the wing tips flex up and down in turbulance, they're supposed to do that. If they didn't bend they'd break. As for the bottom of your boat, without building in frames and stringers (and by doing nothing but increasing the 'panel thickness') you'd have to add so much fiberglass and resin to stop the flexing that you'd really be adding noticable weight to what is supposed to be a light weight high performance hull. A bit of flexing is FAR from sticking your foot through the hull. The FJ looks to be a pretty well established design and class and therefore the engineering aspects of the design were probably proven out long ago. Unless your particular hull was a 'one off' build by someone who didn't know what they were doing I'll bet it is more than strong enough. - Just my .002.
 
a1964rn

a1964rn

Petty Officer 1st Class
Joined
Oct 18, 2012
Messages
287
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

I would use the 1708 biaxial. It lays easy, and is easy to get to "wet out". One layer will be plenty. I'd get my supplies from US Composites, unless you have a local place that's comparable.
 
E

Eightyseven550

Cadet
Joined
Oct 5, 2011
Messages
17
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

Ned L said:
The FJ looks to be a pretty well established design and class and therefore the engineering aspects of the design were probably proven out long ago
Click to expand...

You're right about that. I may have not mentioned that this is an old boat. (Built in the 60s)
I know boats are suppose to flex, the concern is "How much"
 
Ned L

Ned L

Commander
Joined
Sep 17, 2008
Messages
2,266
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

Hmm. "how much" I can't say, I guess I'd look at it from the perspective that polyester resin never realy finishes curing. Yes, it hardens within a an hour or so as we are all used to working with it, but it does continue to harden even futher over time(years), which is why old fiberglass boats will get that micro-crazing in the resin when impacted & new ones don't. So on that level, the more the resin hardens (over time), the stiffer (and more brittle) it gets. So I suppose today it might actually be flexing slightly less than when it was new (but is more brittle). I don't know if that helps at all.
 
a1964rn

a1964rn

Petty Officer 1st Class
Joined
Oct 18, 2012
Messages
287
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

Eightyseven550 said:
You're right about that. I may have not mentioned that this is an old boat. (Built in the 60s)
I know boats are suppose to flex, the concern is "How much"
Click to expand...

If it flexes to the point that you are uncomfortable with it, then add a layer of fiberglass on the bottom and stiffen it up. If you are comfortable with it, then leave it alone. It's your boat, Your call.
 
Ned L

Ned L

Commander
Joined
Sep 17, 2008
Messages
2,266
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

Yep, that's what I saw when I googled the class. If it were me I'd enjoy it as it was built (unless there is damage that needs repairing).
 
E

Eightyseven550

Cadet
Joined
Oct 5, 2011
Messages
17
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

For now, I am going to grind down and reinforce where the daggerboard (Swing keel) meets the floor.
I am then going to put some non slip mats down on the floor and let my dad sail for a while. If he wants me to reinforce the floor later, I will.
 
Ned L

Ned L

Commander
Joined
Sep 17, 2008
Messages
2,266
Re: Strengthening the floor/Bottom. (Dinghy Sail Boat) - Help Please

That sounds like areasonable plan.
As a note, I believe your boat has a "centerboard" (keel permanently fixed in the centerboard trunk and pivots up and down). A "daggerboard" slides vertically up and down in the trunk by hand and is pulled all the way up and out when not in use (kind of like putting a letter in a mail slot). A swing keel normally implies a much larger boat where some sort of mechanical device is used to raise the large weighted swing keel (think like 30'+ boat with a 500lb swing keel). A centerboard is more of a plate type of affair that can usually be raised by hand.
 
You must log in or register to reply here.
Top