Sunfish Repair help

Thread starter #1
Hello everyone, newbie here so please be patient with me. I just bought a 1973 sunfish for $200 with everything. Couple of issues of course. She's heavy but I'll be installing some vent ports and trying to dry her out. I did a leak test and she did really well. Found two major leaks. One on the bottom of the hull almost below the cockpit and the other at the bow handle, the screws are loose.

This is my first boat so I don't have a lot of experience with repairs. But hey at $200 it should be a good learning experience all around. My questions are these,
1. How do I tell if there is fiberglass damage underneath the gelcoat? I watched a video by laser and they said to look for "white" fiberglass. Then you sand until you've gotten rid of the white and start over again.

For example do I still have fiberglass damage here?

Should I keep sanding or can I start rebuilding?

2. I also have a few spider cracks that radiate out, but during my leak test they showed no bubbles. I can just widen these out with a dremel and gelcoat right? Should I sand them down and see how far down I go to make them go away?

These are all in the same general area of the bottom of the boat. I think someone must have dropped the boat on this side.

I only had a leak coming from here, but as you can tell I've all ready cut out the offending crack and widened it out to start the repair. I am only going to use a small strip of carboard as I have the foam block to use for most of the hole to secure the fiberglass patch. I just need to bevel it out with the orbit sander so I can do the layers.

Thanks y'all in advance. If by the way you are anywhere near Durham NC and want to swing by and help someone get in the water soon let me know. I'll take all the help I can get. I am thinking of going ahead and putting in an access hole on top while I have the hole on the bottom and drying out the boat. She's pretty heavy and needs some drying out I am sure.

Gotta dry out the boat before you start to apply fiberglass/filler etc. See extensive threads on method. It ain't fast, think months.

Sounds like you have a good handle on things already. The first picture shows damaged fiberglass.

Spider cracks can be widened out than apply epoxy filler over cracks, remove excess, sand when dry and then gel coat. Don't worry about how deep they are, they most likely go through the entire gel coat. You might try Epoxy and Microballoons for filler. I've found it very easy to work with, sands great. Some use Marine Tex but I've found it very expensive.

Post some pictures of your gel coat method. I'm going to make another attempt at gel coating my SF this spring.
Thread starter #3
I guess I'll keep sanding the ding in that first picture and thanks for confirming my approach on the spider cracks

I think I am going to dry it for a month and see how far I get, then do the repairs and get out on the water. I'll finish drying her next winter when I can let her sit for 3-4 months. For now I just want to do enough to get into the water and play.

Anyone else?


sailing addict
I have repaired several sunfish and those cracks in the second and third pictures are quite common... i find that they appear mainly in four spots... two on each side of the boat... you will find that they will simply reappear if you do not do a strong enough repair... these cracks are caused by the hull flexing and hitting the corners of the cockpit within the boat... you seem to have a handle on it as i would recommend using a dremel to grind them out as you say... just grind until the crack is no longer visible... there are several products you can use to fill in these cracks... i personally use and highly recommend everlast everglass... also red cream hardener it is easier to work with than the blue hardener... also DO NOT use marine tex... it flexes and will only further the problem and will hide the damage which is continuuing to reak havic within your boat... bondo is also another product which i would caution you not to use, it is often times waterresistant not waterproof may cause you more problems in the future. Good luck with your repairs... and nice find with the 200 dollar fish.
Thread starter #5
Thanks for the tips oceanfish. Looks like sometimes you get lucky and sometimes you don't. $200 was about right for a fish some some serious issues. At least I got a good set of spars, mast, sail, rudder + tiller, and daggerboard. I opened up an access port above just aft of the coum(? splashguard)) it was soaking wet inside. I weighed the boat and it tipped the scales at 260 lbs!!! Yikes.

Also the foam blocks on the port side were loose. The foam block from the rear had actually slid completely forward and is in the front of the hull. I've now opened up access ports at the stern of the boat and at the bow so I can have access to the foam blocks, the backing blocks (they of course are all rotted), and can vent the boat. I dropped a heat gun in the middle port, a shop vac to the back port and left the front port open and pretty much ran that for the last two days. Most of the foam blocks at least now feel dry to the touch, one of them is being pretty stubborn but the boat still feels really heavy. I really don't want to work on reattaching the foam blocks until I get the boat down to at least somewhere under 160. I have no idea how long that is going to take coming from 260.

Here's a view:

You can see the heat gun hanging down inside. The foam block on its side that you see behind the mast tube is actually the one from the port side and rear of the boat. I'll actually need to reinforce all of the blocks as they are all a little loose. Here's another look towards the bow.

Here you see the two foam blocks on their side. A small gap above the foam block on the right (although there is expanding foam on the other side of that block and it is in fact the most secure of all the blocks, feels solid). You'll also notice the missing attachment block for the cleat, which I still haven't found fishing around with my hand inside and the rotting attachment backing block for the pulley. The bow handle attachment block just crumbles in my fingers. If you want to see even more pictures inside visit my picasa page.

I can't leave the heat gun and shop vac running while I am at work because the heat gun needs to hang inside the boat by some duct tape rigging I concocted. I just don't trust it long term without some intermittent supervision. So I've now set up a heat lamp at the front of the boat pointing down on some black trash bags on top of the boat with a hole for the bow port. I also taped up the middle port, and left the back port open. No fan. I'm just going to let that sit during the week and run my shop vac/heat gun set up on the weekends when I am around the house doing chores.

The damn boat is too heavy right now to carry it in and out of the garage easily. Hopefully if the weather gets warmer around here I can wrap it completely in black bags and let it sit in the sun. I'll have to build a little dolly for that as I don't have a trailer. At least I can work on the underside of the boat while it dries inside. I'll just have to work on my back. Good thing I bought that shop dolly for under the car work.

I was really hoping to avoid at least one of these tasks but it looks like I got myself a handful with this one. Hey at least it was only $200. I'm learning a lot this go around. I was really hoping I could be in better shape before putting in the water but I may just get as far as I can, make the hull repairs for leaks and set sail until I can dry her out for 4-5 months next winter. In the meantime I'm keeping my eyes open for another hull or full boat at the right price.
if its any consolation, I think I'm in similar shape with my Sunfish, although I didn't get as lucky with only a $200 price tag. I've been sailing it on and off for a while, but never really found an easy way to weigh it, although I've long feared it was overweight. I finally got around to cutting in some inspection ports this fall, and my fears were confirmed - block were soaking wet, standing water inside, and some of the foam blocks are loose, similar to yours. I blogged about it (with some pictures) here: I cut 2 holes in my Sunfish

over the winter, I am storing it in my dad's barn 2nd story - I've put a cheap window fan on it, and ran it for a few months, although it's off right now. I'll probably turn the fan on full time in a few weeks and hope to get her as dry as I can by early spring, when I can tackle some of the repair work. I think I've heard putting a single small wattage bulb inside the hull can help - I thought about getting one of those auto repair trouble lights with the cage around it, and maybe a 60W bulb and using that. I too wouldn't leave a heat gun on un-attended.

one bit of good news - even though my boat has been quite heavy, I have gotten some great days sailing it... probably just doesn't go as fast as it could, though. for this sailing season, maybe just get done what you can, leak test it to prevent it from getting any wetter, and sail when you can, and then dry it out completely next winter.

good luck, and keep us posted on the gelcoat & fiberglass repairs. I have some of the spidery-looking cracks similar to your pics above, and would love to know how your repair goes.



Member Emeritus
I really don't want to work on reattaching the foam blocks until I get the boat down to at least somewhere under 160. I have no idea how long that is going to take coming from 260.
I've been sailing it on and off for a while, but never really found an easy way to weigh it, although I've long feared it was overweight.

I think I've heard putting a single small wattage bulb inside the hull can help - I thought about getting one of those auto repair trouble lights with the cage around it, and maybe a 60W bulb and using that.
Did you read this?

Sunfish KB & FAQ (Found at the top of the page)
Repairs and Upgrades​
How to dry out a wet hull​
Thread starter #9
I'm curious what people's thoughts are on the heat gun approach. I'll see how it compares to the modified "light bulb" approach I am taking. The heat gun/shop vac seems to have worked relatively well for such a short time frame -- 2 days. I am pretty sure it had all the principles described in the FAQ file. Hotter air was exiting the port and a steady supply of fresh air being forced by the shop vac over the blocks. I will tell you the air coming out the front port was warm and very moist.

I know I'll need to wait at least a month before seeing any serious differences. How well do you think the heat lamp shining down on the black trash bags will work? Would it be better to put a bulb inside one of the port holes? I'm thinking the heat lamp will give me more heat and create a better temperature difference. Sort of like windline's recommendation for drying out a boat. Which is basically a modified full black trash bag approach. I am just making the solar power with a 250 w heat lamp.


Member Emeritus
Wayne, I have read the file. In regards to weighing it - the last time I tried it (a couple years ago), all the edge pressure on my $10 POS bathroom scale broke the dang thing.
You can use two bathroom scales, one at each end, and just add the readouts.

Those aren't gelcoat cracks, they're stretch marks.

You can use two bathroom scales, one at each end, and just add the readouts.
Yeah, I figured that... but I don't currently have 2 bathroom scales. The dial scales are about $13 (each), so I can try to engineer some rigging to hold it up balanced or just buy 2 of them. Or, maybe just borrow a bathroom scale. We'll see.



Member Emeritus
I'm curious what people's thoughts are on the heat gun approach. . .
There are two areas you are working with at one time...

1) you want to get the moisture that's osmosed into the flotation's cells to re-vaporize (gently)

2) you want the atmosphere outside the flotation to be drier so there's an imbalance that will coax the vapor back across the cell walls.

The trapped moisture will vaporize more quickly when it's warmed, but you don't want get things so hot you make steam. That would pop all your closed cells creating open cells.

Once the moisture has crossed the cell membrane to the surrounding atmosphere, you want to move the moisture laden air away from the flotation block's surface and replace it with a new layer of dry air to keep the process going in a continuous manner.

Remember, inside the flotation blocks, this same process is being repeated from cell to cell to cell..., that's why it takes time.

Constant warmth and consistant air flow is the key to drying speed. It doesn't need to be too hot or too "windy", though. That's why computer fan air flow and a heated garage work so well.
I have tried different ways of drying out hulls, in Florida with our heat, this is pretty straight forward, remove the bow handle, attach a shop vac to the bow handle holes,
open the drain a run it for a couple of days.
When they are real bad, I take the hull out to a sunny area, cover with black bags and run the shop vac there. Using this method, dropped the weight of this boat from 140 to 124lb.
To weigh them, I use 2 bars with bracket and hang the fish from a rafter or support, then drop it onto a scale.
Good luck with the repairs.


I'm curious what people's thoughts are on the heat gun approach.

I had a 60watt bulb in my SF while upside down, it stayed on all day and night for a long time. I found a brown area just above the bulb, and it was slightly visible from the outside. It was a burn, so be careful. As others have said, slow and easy, it takes time to thoroughly dry it out, but it will dry out.
Also, using up electricity with a high wattage item, seems wasteful, a regular bulb, and a fan set up, should do it, again, you don't have to rush things.
If your SF weighs 260 lb. it is approx. double it's manufactured weight, therefore your packing about 130 lb. of water. I can't comprehend that the foam and the fiberglass laminate could hold that volume of water without looking like mountain of mush. The drying process could take forever. Getting those foam sponges out altogether might be the ticket, and then the drying process would be rather short. The hull and deck are single skin fiberglass, there is no coring therefore there is nothing in the hull/deck that would hold any significant amount of water. Getting back to your repair work, If you see any white areas within the laminate, that indicates either damage which has seperated the glass strands from the resin or glass strands that were resin starved at the time of manufacture. Remove this material and re-glass. If you are repairing an area that has completely penetrated the laminate, try to bevel out an area 12X the laminate thickness in order to do a proper repair. In other words a hole in a 1/4 inch laminate would require a 3 inch diameter bevelled area to glass in. Even though you only paid $200.00 for your SF I'm sure you would like to be sailing her as soon as possible. Good luck.
Once you cut a hole in your boat *shudder* drying it out should go pretty quickly. When I dried mine out, I just attached a small fan to one of the deck ports, and left it on. It dried surprisingly fast (completely dry as far as i could tell within about 6 days).

When repairing fiberglass damage, I used this:

I had some fairly serious holes that the Bondo kit worked perfectly for. I haven't had any problems with those old leak spots.
Thread starter #17
Well I've actually managed to get her down under 200 lbs. I modified my approach and it really seamed to help. I put the heat gun facing the intake of the shop vac and then just turned the shop vac and heat gun on. Really started to speed up the process. Although now I found another boat at a great price and that only weighs 130 lbs. I mixed and matched the parts because some stuff off the old boat was in better shape then the new boat I just picked up. Although the parts on both boats were in good to great shape. I just had the chance to be really picky so I was.

So I think I am just going to part the boat out or see if somebody wants to take on finishing the project. Everything but the sail is in really good shape, well of course the hull has it's issues. If interested in any parts PM me.
I have just taken on the same project. I purchased a 1982 SF late last summer for $200 w/ trailor. She is very solid and in great shape. I had to purchase a new sail since the mice had made one heck of a nest out of the orginal. After about the 5th sail I started to notice water inside. After reading all your post, I am ready to dry her out and do the leak test.

My question is should I remove the aluminum trim before preforming the leak test?

Thanks in advance.


Member Emeritus
Preforming the leak test?

. . . should I remove the aluminum trim before preforming the leak test?
The leak test is so simple and removing & reinstalling the trim can be time consuming at the very least, I recommend you do the test and see if the deck-to-hull seam is even suspect. The points below the waterline like the corners of the daggerboard slot or the bailer seal are much more likely candidates
Pick a day with no wind or waves, let the hull float in the water for a hour or so. If it leaks you know it's Dagger Board Trunk or Bailer. Does not exclude hull seam but will give you a place to start.