Transom rot

Jmusick

Petty Officer 3rd Class
Joined
Sep 23, 2021
Messages
79
Whats the best way to fix my rotten transom? Its a 18 ft fiberglass trihull. Ive heard many different options, just wondering what the best way to fix it would be. Its not falling apart, but its seen a bit of water and if getting soft. Keep in mind im very new to boat repair and fiberglass work. Thanks
 

havoc_squad

Senior Chief Petty Officer
Joined
Mar 5, 2011
Messages
738
Whats the best way to fix my rotten transom? Its a 18 ft fiberglass trihull. Ive heard many different options, just wondering what the best way to fix it would be. Its not falling apart, but its seen a bit of water and if getting soft. Keep in mind im very new to boat repair and fiberglass work. Thanks

Given the rising cost of prices for materials and labor recently that has made it even more costly to do a major fiberglass job (even if this is DIY job), one is better off to sell a trihull off as a project or for parts.

Tri-hulls have terrible resale values and you'll never recover or pay off the money you put into it.

If you live in an area where boats are accessible, you're better off getting someone experienced to help you look for a different one that likely does not have structural rot (boat cancer).

If I had a tri-hull now found with structural rot, I'd legally file it as destroyed, cut it up into disposable pieces, and sell the engine & drive and trailer as parts. Then walk away quickly.
 

racerone

Supreme Mariner
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Dec 28, 2013
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37,818
Is it just the transom rotted ?-----Looked under the floor and condition of stringers ?-----Some boats can be done from the outside.-----I am still busy on an ---Action Marine 17-----Did transom from inside with composite material and epoxy.
 

Jmusick

Petty Officer 3rd Class
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Sep 23, 2021
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79
Well... This is more of a learning experiment for me. Ive workes on cars and bike in a hobby way for my whole life. Its not about being to hard or tring to save money on a cheep boat and do the work myself. Im attempting to learn something new, and taking something that most would consider "dead" and giving it life again. I have no intention of profiting off this restoration. I just more or less want to say "i saved that boat".
 

Jmusick

Petty Officer 3rd Class
Joined
Sep 23, 2021
Messages
79
Is it just the transom rotted ?-----Looked under the floor and condition of stringers ?-----Some boats can be done from the outside.-----I am still busy on an ---Action Marine 17-----Did transom from inside with composite material and epoxy.
No, im doing the stringers as well. There not completely rotted but enough where id feel better about replacing them as well. I was thinking of hollowing out the transom from the top, and dropping in a couple boards of 2x8 for structure and then a poured liquid transom to fill everything in? Or is there beter option?
 

racerone

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Dec 28, 2013
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So what make of boat ?----Any so called " floatation foam " under the floor.-----Many boats have that stuff that has become water logged and the stringers rotted as well.
 

Jmusick

Petty Officer 3rd Class
Joined
Sep 23, 2021
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79
So what make of boat ?----Any so called " floatation foam " under the floor.-----Many boats have that stuff that has become water logged and the stringers rotted as well.
Its a 1969 crestliner not sure model. The is no foam in the hull at this moment. The rot is mostly limited to the rear of the boat. It had been sitting for at least 4 years uncovered. And was sitting pretty level so i dont think it was draining properly
 

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Scott Danforth

Grumpy Vintage Moderator still playing with boats
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49,548
Whats the best way to fix my rotten transom? Its a 18 ft fiberglass trihull. Ive heard many different options, just wondering what the best way to fix it would be. Its not falling apart, but its seen a bit of water and if getting soft. Keep in mind im very new to boat repair and fiberglass work. Thanks
the best way....

go here https://forums.iboats.com/threads/how-tos-and-other-great-information.283508/

read links 14, 15, 18, 2, 3, 4a, and 4b in their entirety to understand what you are getting into

then realize that you will be spending about $3k in materials and incidentals to just restore the hull, along with an entire year of your weekends if you do the work yourself

if your boat needs interior work, etc., you will spend much more.

if this boat has sentimental value and you have the time, go ahead and restore it.

if this is a cheap boat that you just bought, I would part it out, sell the bits you can, and landfill the hull to maximize your money back
 

racerone

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Dec 28, 2013
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There are many factors.------I am doing an ----Action Marine 17-----Not a common boat in my area.-------And yes.------Sometimes it can be scary if you keep track of the money and time involved in fixing up a boat.----Example ----1 can of epoxy, along with 1 can of hardener and some filler to make glue with epoxy.-----Total was near $300 in Canadian funds.
 
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88 Capri (2022 SOTY)

Master Chief Petty Officer
Joined
Aug 25, 2019
Messages
819
Well... This is more of a learning experiment for me. Ive workes on cars and bike in a hobby way for my whole life. Its not about being to hard or tring to save money on a cheep boat and do the work myself. Im attempting to learn something new, and taking something that most would consider "dead" and giving it life again. I have no intention of profiting off this restoration. I just more or less want to say "i saved that boat".
Hi Jmusick,
I had the same frame of mind for my project. My boat is pretty common in my area but none are water worthy but mine is. This was my first and a huge learning experience that I am glad I went through and if I decided to do it again there were many lessons learned that will make the second time around easier.
From the way it sounds this will be your first also and with that being said take your time and don't make a date that you want to finish because it makes it less of an enjoyable experience šŸ˜Š.
Also before you remove anything document the entire boat with pictures and measurements because it will save alot of aggravation later oh and lastly there are many experienced people here that will help you if needed.
 

Pierce89

Seaman
Joined
Jun 21, 2019
Messages
50
If you can share pictures of the stern/transom area we can help better. I had the same exact mindset when I restored a '76 Invader, I wanted to learn something new even if I didn't get the money back, and it was worth it. I redid the transom, stringers, bulkheads, and deck and it was about $1500 in materials, and I likely overdid it. Boat is like a rock now.

Don't do it from the outside on that boat if it's a 2 part hull. Separate the hull cap from the hull where the green and white colors change, get some buddies to help you lift it off and put it on some stands. It took 4 people to lift the cap on my 16fter.

If you're actually going to begin I can walk you through it with pictures from mine. The bones of both boats will be similar.
 

gazza2007au

Chief Petty Officer
Joined
Mar 9, 2007
Messages
429
I done my 19ft transom in less than 50 hours, what took the most time was the epoxy resin "curing" which is not calculated in the rebuild time, each epoxy laminate takes 48 hours to cure for sanding

You can cut the outside transom skin 3-4 inches in around the outside than chip out all the plywood, sand the inside skin free of plywood, bevel your 3-4inch radius right around, vaccum the whole lot, wipe the whole lot down with acetone

Cut your plywood and test fit however many layers you would like to use cut various shapes for maximum strength and make sure no two cuts align between the layers of plywood thickness

Remove the plywood, fillet the radius both sides and the bottom you want enough glue to fill the voids once the plywood is pushed into place also smear glue all over your internal transom skin, now place the first layer of plywood up against the front transom skin than use clamps, screws, bolts and tightly press the front transom skin against the plywood

Next smear glue all over the back of the plywood you just installed, prepare your second layer of plywood to go in and push it in now screw or clamp this second layer of plywood to the first layer (you can use screws from the outside on this layer of plywood) let it cure, remove screws

Grab the transom skin u cut out at the beginning you'll notice the inside of the skin will have remnance of plywood sand all of this off, next smear glue all over the the second layer of plywood or the rear facing piece of transom plywood, grab your transom skin and clamp or screw it to the rear transom plywood, let it cure

Remove the clamps or screws

Bevel the radius of the transom skin 3-4 inches, wipe with acetone, clean any glue that has squeezed out you can just sand it off with a grinder, now cut your fibreglass cloth/mat in strips going from thin and progress to wider, start glassing the joint where u originally cut out the transom untill u build up enough thickness u can sand the whole transom flat and level ready for paint or flowcoat

You are done
 

Jmusick

Petty Officer 3rd Class
Joined
Sep 23, 2021
Messages
79
Finally got to opening up the back of my boat good thing i did found more water damage than i had thought. Now starts the chipping and chiseling. Ill keep updating on my progress
 

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racerone

Supreme Mariner
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Dec 28, 2013
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They harvest logs that have been submerged in cold water for over a 100 years.----Wood is good they say.----I have sailed ( recently ) on a wooden sailboat built in 1972 or so.----A Vic Carpenter boat !!----No permanent bilge pump installed.----Buddy owns another example by Vic.------Or use some HUON PINE in your transom.-----The wood in most of our boats is junk.-----And in a moist environment , oxygen and heat from the sun it just rots !!
 

Jmusick

Petty Officer 3rd Class
Joined
Sep 23, 2021
Messages
79
I think the biggest flaw is the top of the transom is open with just a metal cap to keep out water. Myself would have wrapped the fiberglass over the transom from both sides that way it would have been water tight from the start
 

racerone

Supreme Mariner
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Dec 28, 2013
Messages
37,818
Simple----Don't use wood !-----Wood is used because it is cheap / easy to work with.------I helped rebuild a 25' sailboat that was assembled with cheap materials at the factory 40 years ago.------Was a leaker due to porous fiberglass.----Now I believe it is the strongest hull out there and has not leaked or shown signs of stress in the last 10 years.---No wood went back in under the floor.--Sails just wonderful in 5' to 6' waves.
 

SavinRaven

Petty Officer 1st Class
Joined
Sep 16, 2021
Messages
228
Gazza is on the right track. When it comes to these things there is not just one correct way to do it.. I think I spent approx.: 30-40 hours in mine all though it was an I/O same process exists get rid of bad wood replace with good wood/ try to improve upon factory install in the process. I think last year cost me around 6-700$ by no means did I use the highest end materials but I also understand this solution wont last forever. Maybe 10-20 years or so. I just wanted to keep the boat around a little longer and as you mentioned and learn from it. You can check out my thread on my "restoration" it goes through in detail what steps I took.

An air chisel saved me a lot of time getting rid of it all.
 
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