# Transom Rot Repair



## BVBFly (Jan 23, 2012)

I recently decided to start another project (adding flotation foam below rear deck on my gheenoe) which has been derailed after noticing delamination in the top of transom area. 

After peeling it back, my heart sank upon seeing rotted wood. It appears he previous owner used 5200 or something similar to fill small holes in top of transom...perhaps from hardware installed there (see photos below).

I have some previous fiberglass experience, albeit a several years ago when I rebuilt front/rear decks and the false floor.

How much of the transom should I starting cutting into to determine whether or not it's isolated to this one area or larger problem? 
I suspect I'll have to at least remove the entire top of rear deck? 
Any suggestions/guidance would be most appreciated.


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## DuckNut (Apr 3, 2009)

Its all rotten. Cut the whole thing out and rebuild. Cut it out from the inside and don't cut the outside skin.

The metal plate is teltale the transom is rotten.


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## BVBFly (Jan 23, 2012)

I removed the motor, jack plate, aluminum plate, and used a wood chisel to remove fiberglass skin down to the bare wood. It is most definitely rotted on the port side and bottom portions nearest the thru-hull drain. Middle section seems ok. 

I think i already know the answer to this question, but should i replace the whole thing?


























i just purchased a sheet of 3/8" marine fir ply that I was planning to use for making a bulkhead in the aft deck to add some flotation foam. Could I cut 3 pieces of this 3/8" ply (total of 1.125" + 0.25" outside skin = 1.375") and just bond them together? 

This would bring it close to the current thickness of the transom (see below). I run a 15hp 2-cycle Johnson so the beefier, the better I'm thinking. 

The current transom thickness is 1.5" ==> outside skin 1/4" + wood 1-1/4" 


















I've done a little research here on the site on how to bond a new core to the transom skin, but it seems there approaches employed vary. Should I:


use a layer of fiberglass mat between the outer skin and the wood core or just thickened epoxy between the two?
use glass between the 3 pieces of ply or just bonded together with thickened epoxy? 

type of cloth for glassing wood core to hull sides and hull's bottom? 
Lastly, any recommendations on best methods for making templates to cut the replacement wood core? For previous builds I've just cut pieces of cardboard and taped together. It's quite time consuming and I'm sure there are more precise ways of doing it. 

Thanks in advance for your suggestions/feedback.


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## yobata (Jul 14, 2015)

BVBFly said:


> I removed the motor, jack plate, aluminum plate, and used a wood chisel to remove fiberglass skin down to the bare wood. It is most definitely rotted on the port side and bottom portions nearest the thru-hull drain. Middle section seems ok.
> 
> I think i already know the answer to this question, but should i replace the whole thing?
> 
> ...


Where are you located? I have about a 48" x ~30" of 3/4" marine fir ply left over. I'm in Melbourne FL and could drop it off to you. Might be enough for your needs??

Use the old rotten plywood for your template... or make new cardboard templates. Yes they take a while but are worth it when considering the price of marine plywood....


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## DuckNut (Apr 3, 2009)

No need to use glass between ply's but you can if you wish. If not alternate the wood direction for one of the layers.

The standard is 1708 covered with a 6 or 9 oz cloth.

Use epoxy for everything.

You will never get that out in one piece so you will end up using cardboard as a template.


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## BVBFly (Jan 23, 2012)

Yobata, thanks for the offer but I'm a ways from Florida. Live in Houston. 

Ducknut, good suggestion on alternating wood direction for different ply sheets. 

I'll be ripping up old wood tomorrow and will post pics as things progress.


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## BVBFly (Jan 23, 2012)

Was able to work on this new project a last night and made a little progress.
I removed a portion of the aft deck for easier access to the transom. I was then able to cut out and remove one of the two rotted plywood core pieces.




























Found one the potential sources that lead lead to the rot. As you can see in the picture below, the transom core was not properly tabbed into the sides of the hull. It stopped just short. Water or moisture over time likely penetrated from the deck sitting above it, leaving nowhere for the moisture to go but into the wood core.



















The [Before] picture showing a piece of plywood that was glassed against the transom core and into hull sides. The only thing plugging that hole you see in picture below was thickened epoxy.









I suspect the transom was built/modified this way by original owner as a work-around due to the rub rail height being higher than the actual transom height (i.e. instead of removing rub rail and actually extending the core and then tabbing to the hulls' sides). I think i'm just going to drill out that rivet you see and cut off a portion of the rub rail so that I can properly glass the new core to the hulls' sides.









The bigger challenge, as I see it, will be getting the remaining plywood sheet removed that's currently laminated to the outside skin. I could probably just chip it away if the whole thing were rotted. But for the most part, it's still pretty solid (aside from the rotted portions circled in red below).










The sheet is only a 1/4" thick and my concern is cutting it out without damaging the outside skin. I can't just wedge a chisel and crow bar in there...any force applied will crack the outside skin...and I'm hesitant to take an angle grinder to it. 

Will be brainstorming more over the next couple of days. In the meantime, if there are any suggestions from you experts out there...please shoot..


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## DuckNut (Apr 3, 2009)

Set your circular saw at a shade light of total thickness and cut relief lines- make a 100 if you have too. Then you can chisel off the wood and then eventually get behind it to chisel off the skin.

After you get it fixed, take the time to lower the rubrail to the right height.


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## BVBFly (Jan 23, 2012)

Finally got the old plywood core out tonight. Carefully made 50 or so punch cuts to a depth of 0.25" using my oscillating multi-tool, then chipped away piece by piece using a wood chisel, careful not to damage or puncture the outside transom skin.




























You can see the inside transom skin is uneven in spots. This is definitely new territory for me...not entirely sure what prep is required to this inside skin before bonding my new plywood core to it? 










A few of gouges/small holes that were exposed after grinding. I'll fill these with a thickened epoxy mixture and sand it back smooth. 

















I found this "carbide grit finger rasp" on my oscillating tool to be effective at grinding down where the old bonds met the hull, especially in those tight corner areas. Hopefully I'm not oversanding/grinding the hull itself. 









Any suggestions on best way to remove the thru-transom drain without damaging the outside skin??









While i wait on my fiberglass cloth to arrive I'll be prepping and laminating pieces of new plywood core. I plan on applying two to three layers of 7725 Bi-directional E-Glass (8.5oz) and tabbing into hull sides with 1208 biaxial tape.


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## DuckNut (Apr 3, 2009)

The uneven skin is nothing to worry about nor are the small pin holes. When you slobber up the new pieces for the transom you will squeeze the thickened epoxy into them sealing them off. Just let them squirt out through and deal with afterwards.

Just remove the drain tube. Put a piece of wax paper on a piece of duct tape and cover the hole from the outside. Let it get filled as well - you will install a new one later.

Also, recheck the thickness of your 3/8" ply - it is not .375 so you may need 4 not 3, or do an extra layer of glass.


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## BVBFly (Jan 23, 2012)

Ducknut, thanks for the feedback. This is helpful. 

I actually returned my 3/8" ply, exchanging it for a 1/2" sheet. It was only an extra $10. Figure I'll save that plus some using less epoxy laminating 2 sheets instead of 3 or 4.


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## Backwater (Dec 14, 2014)

Gheenoe??

Make sure your grind out the gelcoat before you glass anything back in. I'd glass back to the bulkhead where you cut the deck out from.

Definitely grinding that old glass some, on the inside of the transom skin before you glass it back in. If you are sticking with the 1/2" plywood, I'd go 2 layers of 1708 on the transom skin and out along the inside of the sides and floor up to that bulkhead. Then add your 1st 1/2" plywood layer, then another layer of 1708 and then add the 2nd layer of 1/2" plywood in while it's still wet. Then brace the clean side of the plywood from the bulkhead with 2x4 braces and wedges, to keep pressure on the whole mess (thereby removing bubbles and avoiding delamination) until it kicks. Make sure you are rolling the resin into the glass good and getting all bubbles out before it kicks. Finally, do 2 layers of 1708 on the outside, over the floor to the bulkhead and tab in the sides with 5" 1708 strips and another tab at the floor. I'd also install transom knees.


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## DuckNut (Apr 3, 2009)

great write up on the schedule- he needs to add some thickened epoxy onto the skin to make up for the uneven surface as 1708 wont compress enough to fill all those voids


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## BVBFly (Jan 23, 2012)

Backwater said:


> Gheenoe??
> 
> Make sure your grind out the gelcoat before you glass anything back in. I'd glass back to the bulkhead where you cut the deck out from.
> 
> Definitely grinding that old glass some, on the inside of the transom skin before you glass it back in. If you are sticking with the 1/2" plywood, I'd go 2 layers of 1708 on the transom skin and out along the inside of the sides and floor up to that bulkhead. Then add your 1st 1/2" plywood layer, then another layer of 1708 and then add the 2nd layer of 1/2" plywood in while it's still wet. Then brace the clean side of the plywood from the bulkhead with 2x4 braces and wedges, to keep pressure on the whole mess (thereby removing bubbles and avoiding delamination) until it kicks. Make sure you are rolling the resin into the glass good and getting all bubbles out before it kicks. Finally, do 2 layers of 1708 on the outside, over the floor to the bulkhead and tab in the sides with 5" 1708 strips and another tab at the floor. I'd also install transom knees.


Certainly is a great write up, thanks! Definitely have more grinding to do. Tough to get to many of the uneven areas with a grinder flap disk wheel. Did some more grinding tonight. Gouge/Crack from the other day got a little bigger. Just trying to determine if it's big enough now that i need to grind/sound a 12-1? bevel before filling with thickened epoxy and laying glass. 









Couple questions about adding 2 layers of 1708 to inside of the transom skin:


Sketched out where edges of the cloth should lay, if i understood your suggestions correctly. Question is how I get the cloth to lay up properly from the transition at bottom of the transom to sides of floor? I'm concerned about the slant of the sides of the hull, getting cloth to lay flat and rolling epoxy resin on good enough.








Could I cut a slit in the cloth to produce a smooth corner at this transition without air bubbles? Something like in the pic below...










Lastly, would either of these fiberglass cloths work? Not entirely sure if the first link is the same is as 1708 biaxial cloth. 

http://www.fibreglast.com/product/Bi_directional_E_Glass_1094/Fiberglass_Fabric

https://www.jamestowndistributors.c...&familyName=Fiberglass+Cloth+-+17+oz+Biaxial+


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## Backwater (Dec 14, 2014)

Yes! Scissors are a wonderful tool! 

E-glass can be expensive. You don't need boat builder's grade (grade A glass) You can use 2nd's to save some money and be just as effective on small home projects and repairs like you have there. Call the guys at Fiberglass coatings in St Petersberg, FL and ask if they have a few yards of the 2nd's in the 1708 (strands run at a 45 degree angle). You can also buy their boat builder's grade of epoxy resin, instead of the more expensive "West Systems". They ship all over. Also buy the 5-6" 1708 tape to tab with and they had the glass rollers and whatever else you need.

Go buy a couple of disposable tyvek type suits to cover up with, when you are grinding.

Buy a small amount of Cavicel to make putty with (using your 2 part epoxy) to fill in voids and level a few pockets, like what Ducknut said.

Make sure you completely grind out ALL the gelcoat before you glass. That little grinding wedge will allow you to get into the tight corners. You may also want to consider glass up that bulkhead in that front bilge area, to add strength back there.

When your glass job is completed, I'd recommend painting it with 2 part white epoxy paint. You can buy that from Fiberglass Coatings as well. I'd recommend painting one coat with a brush and sponge roller (it will self-level too), let it kick, mix up another batch and then do a 2nd coat and you will be done. That finish will be bullet proof and you'll never have to fool with it again! Worth every dime!


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## BVBFly (Jan 23, 2012)

Thanks backwater, your feedback is most appreciated. I'll keep everyone posted as I progress.


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## DuckNut (Apr 3, 2009)

Backwater said:


> Cavicel


Actually it is Cabosil also known as fumed silica. Look at the FGCI.com website and you will see it. You could use any that you wish - except for the cotton one.

Also, get the glass that is compatible with epoxy - not all of it is compatible.

Person preference for the heavy weight glass like 1708 - for me I like 0/90 rather than 45/45. The reason being is the thread that is used to stitch it together shows more with the 45/45. Just my preference.


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## Backwater (Dec 14, 2014)

DuckNut said:


> Actually it is Cabosil also known as fumed silica.


Yeah ok, it was late and tired and couldn't think straight. My wife has to correct me from time to time too, but I'm sure she is better lookin than you tho! Ha! 

BVBFly, get the powery shizzit that you add to resin to make putty!


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## DuckNut (Apr 3, 2009)

Backwater said:


> Yeah ok, it was late and tired and couldn't think straight. My wife has to correct me from time to time too, but I'm sure she is better lookin than you tho! Ha!
> 
> BVBFly, get the powery shizzit that you add to resin to make putty!


LOL - Ijust didn't want him looking all over with that spelling as he might end up on a porn site and his wife beats him into oblivion and he won't be able to finish his project.


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## yobata (Jul 14, 2015)

You'd change your mind on not looking for it if you ever saw two cavicel, one cup!


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## BVBFly (Jan 23, 2012)

Haha, I'm covered on the "fumed silica." I had some left over from a previous build. 

Ordered glass from FGCI as Backwater suggested. Went with the 1708 45/45...placed my order before seeing Ducknut's suggestion on 0/90 but should be fine. 

While waiting on glass to arrive in the mail, i got after the inside prep. Started with a 40 grit flap disc wheel on my angle grinder which i found it to be a bit too aggressive --> See photos below...old hull color was blue which you can actually see showing through in a number of spots. I'll probably go 3 layers of 1708 instead of 2 on the transom skin and out along the inside of the sides and floor up to that bulkhead to build it back up.

I switched to a 60 grit disc which seemed more controllable. The only bit I wasn't able to get out was in those corners where sides of the hull meets the chine flat. Will give it one more shot with my multi tool & triangular-shaped sanding pad in just those corners where i'll be tabbing the transom to hull sides and chine flat. 

















Figure the white area in corner where transom meets the hull side will be covered with a fillet, so will just remove the paint & gelcoat in corner of chine flat and hull side where i'll apply tape to tab it in. 









Close up of area where blue hull is exposed.









I used one of those disposable tyvek full suits I bought from Lowes this time when grinding and am sure glad i did. Messy job.

That's it for now. Hope to have more updates soon once my glass arrives.


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## BVBFly (Jan 23, 2012)

It's been almost a week since I've been able to work on this project, but got my first ply core cut out tonight. I had to shave off more than I wanted to on the starboard side of the ply core to get it back in there, leaving quite a sizable gap between the transom and hull sides (~3/8"). There's also a 0.4-0.5" gap between the ply core and bottom of hull.

Starting to second guess myself before I start the whole glassing process. 

Are these gaps acceptable? 
Can i just fill the voids with thickened epoxy (peanut butter consistency), then making a fillet to tab in core to the hull sides/bottom?


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## yobata (Jul 14, 2015)

Yes, make sure you use overlapping layers of 6" biax tape to tab in the transom to the sides and the bottom of the hull. By over-lapping I mean first layer of 6" tape is 4" on transom and 2" on hull side, next layer of tape is 2" on transom and 4" on hull side.. also use at least 2 layers of biax to then cover the entire transom and the hull sides and bottom (I extended this parts past my alternating layers of 6" tape just to be sure...)


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## yobata (Jul 14, 2015)

Also when you bed the transom use a nice thick bead of thickened epoxy and let it squeeze out as you set the transom in place. I would also work wet on wet meaning I would bed, fillet, tab, and lay the inside layers of glass all in one session/day... otherwise there is lots of sanding in between steps.


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## yobata (Jul 14, 2015)

http://www.microskiff.com/threads/build-thread-1967-johnsen-starfisher-14.36427/#post-295149

Link to my build of the interior of the transom. In some spots there were 1/4"-3/8" gaps...


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## BVBFly (Jan 23, 2012)

Thanks for the feedback yobata and sharing the link to your rebuild. This is helpful. Impressive work by the way! May have to take a few of your ideas, particularly on the rear hatch. 

I wanted to start laying glass tonight but rain put a stop to those plans. 

My goal is to work wet on wet and glass everything in one go. This may be a dumb question but if I bed the first ply, can I fillet and tab it in...then bed second ply, fillet, tab and lay outside layer of glass. Or is it better to just laminate the two ply sheets together then bed, fillet, and tab to hull? 

Lastly, should I be concerned at all with this uneven surface on outside transom skin? Seems solid but not really sure why/what caused this..


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## yobata (Jul 14, 2015)

If you bed one ply in first and tab and fillet it, the second ply will need quite a bit more thickened epoxy to fill the gap between the two sheets (created by the thickness of the tabs and possibly the fillet). I chose to glue the two pieces together first before bedding them in.

Most people leave the outside skin on because the fairing is already done for you. It will be easier to sand, fill and fair that vertical channel than to redo the entire outside skin... You will end up drilling some holes on that outside skin in order to pull your new transom ply sufficiently to the skin (with screws) when bedding. After it cures you remove the screws and fill in with thickened epoxy. There are some examples of this on other re-build threads...


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## DuckNut (Apr 3, 2009)

yobata said:


> If you bed one ply in first and tab and fillet it, the second ply will need quite a bit more thickened epoxy to fill the gap between the two sheets (created by the thickness of the tabs and possibly the fillet). I chose to glue the two pieces together first before bedding them in.
> 
> Most people leave the outside skin on because the fairing is already done for you. It will be easier to sand, fill and fair that vertical channel than to redo the entire outside skin... You will end up drilling some holes on that outside skin in order to pull your new transom ply sufficiently to the skin (with screws) when bedding. After it cures you remove the screws and fill in with thickened epoxy. There are some examples of this on other re-build threads...


This and the skin is left on for structural integrity of the boat. Cut it out and all kinds of crazy things can happen to the hull. In addition the skin is an integral part of the boat that would be difficult to achieve if removed and then added in.


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## BVBFly (Jan 23, 2012)

Got my two 1/2" marine ply pieces cut out and applied a coat of epoxy resin on each side before. It's been rainy and cold (relatively speaking for Texas this time of year at least, ~50deg) the last few days so will have to wait on glueing them together, bedding into transom and glassing. 

I covered my saw horses with 3mil plastic sheeting and left pieces sitting on top of them while the epoxy cured. Thought the cured epoxy would just peel right off. Kind of hard to tell from picture but a thin layer of plastic adhered to the surface when I pulled it off. Rookie mistake perhaps. I'll give us a good sanding to make sure it all come soon out.


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## yobata (Jul 14, 2015)

BVBFly said:


> Got my two 1/2" marine ply pieces cut out and applied a coat of epoxy resin on each side before. It's been rainy and cold (relatively speaking for Texas this time of year at least, ~50deg) the last few days so will have to wait on glueing them together, bedding into transom and glassing.
> 
> I covered my saw horses with 3mil plastic sheeting and left pieces sitting on top of them while the epoxy cured. Thought the cured epoxy would just peel right off. Kind of hard to tell from picture but a thin layer of plastic adhered to the surface when I pulled it off. Rookie mistake perhaps. I'll give us a good sanding to make sure it all come soon out.


I don't think that is plastic, I think the epoxy just squeezed out there. It is a good idea to lightly sand the whole thing anyway before gluing the two pieces together...


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## DuckNut (Apr 3, 2009)

Yep, that sure looks like resin that ran down the board and under the board.

Remember, it is not imperative to sand before full set of epoxy. But after 24 hours sanding is a must as it has cures.

Wet on wet is a chemical bond. Wet on cured is mechanical bond. Chemical is the best if it can be achieved.


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## BVBFly (Jan 23, 2012)

An update on the progress of my repair is officially long overdue, but I finally finished this transom mod. Thanks again to all those who commented here and helped me along the way, your input was much appreciated.

My initial plan was to work wet on wet to finish in one working session, but life’s just been a little crazy lately with two little ones at home, only getting 1 or 2 hour windows of time here and there to work on the boat. Hence, required more sanding in between than I would have liked but overall I'm happy with out it turned out.


Went with 1 layer of 1708 on the transom skin and out along the inside of the sides and floor up halfway to the bulkhead (initially had planned to glass 2 layers but was surprised by how much resin it took to wet it out so just went w/ the 1 layer)
Did 1 layer of 1708 sandwiched between the two pieces of ½” ply
Then bedded, filleted and tabbed in new ply core using two overlapping layers of 6” 1708 biax tape
Finally, used 1 later of 1708 to cover the entire transom and the hull sides and bottom










Tabbing w/ 6" biax tape:


















As a quick aside, one of the best decisions I made during this whole process was investing in some quality fabric cutters. Really made cutting fiberglass cloth so much easier. Picked up these scissors from JoAnn Fabrics one weekend. Sell for ~$50, but lucked out they were having a big 40% sale on all fiskars.










1-1/4" Thru-hole transom drain cut out. I drilled it out using a slightly larger hole saw (1-3/8"), sealed the inner surface with thickened epoxy, then came back in after it cured and drilled out with a 1-/4" hole saw. Then used a Moeller drain tube tools to flange end to transom

















Sectioned off two areas below aft deck to add flotation foam (eventually added more foam than is actually shown here in the picture). Tabbed them into bulkhead and transom so will also serve as "knees" and additional support for the deck on top:









Added deck - 1708 biax top and bottom sides....bedded, filleted and tabbed in with 6" biax tape. After it cured and some sanding, I then applied the Interlux Interdek non-skid paint with krylon webbing to match rest of my interior.









As you can see in the photo below, the surface is a bit uneven where I joined the new deck piece to old section. Probably could have used a bit of fairing there but the yeti that i use for a poling platform will cover most of this area.









Took her out on Saturday for the first time in months. No fish, but she ran great. 

I also repainted the aluminum rubrails as you can see in photo below. Had previously applied a truck bedliner product but didn't last long before it started flaking off. After removing old bedliner paint, I prepared the surface by etching the aluminum surface with a vinegar solution (50:50 ratio of water/vinegar), working until surface became dull and darker, then washed with warm, soapy water before patting it dry. 

After allowing it to air-dry, I then applied that black flex-seal product (https://www.getflexseal.com). I was a bit skeptical about whether or not this would work, but thought it was worth a shot considering everything else I've slapped on there before hasn't stayed adhered. It's still probably too early to tell, but definitely held up nicely after my first time out on the water this past weekend.


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## DuckNut (Apr 3, 2009)

Great job man!

Now go catch some fish would you.


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