Transom replacement full vs partial
 

Currently rebuilding a 93 Mirage trovare and need some opinions on repairing some slight water intrusion on the lower transom. All of the other surrounding wood is dry and rot free. This is what I have thus far. Appreciate the responses. I'm most concerned with strength as I'm installing a 600hp BBC. Thx

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The worst part which was at the very lowest stud

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Rest of the wood is rot free and dry
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time wise youll have about the same in either way. The prep needed to properly do a partial replacement is about the same as just doing the whole thing and you will have a far far better transom at the end. Shelfing in just the center section requires a stepped joint and it a pain to do and in an afternoon you could just have the entire old transom out ready for grinding (looks like your half way there already :D) . Been there dont that and there are very few circumstances that i would do a partial.

Thanks Dave! Would it be best to just cut the stringers that tie into the old transom back a few inches to get all of of it out, then patch those back in once new transom is tabbed in? You can see from the photos how my transom is partially hidden by the laminated floor on the sides. Also, planning to place an order with US Composites today. How much vinyl ester, 1708, chop strand and cabosil should i order? Thanks for your time dave!

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I have to say; Beau, Dave is going to be the expert going forward to your transom replacement. From what; I'am seeing the lay-up looks pretty dry, especially between the 2 sections of plywood. Better get going on the de-rigging of the rest of the engine compartment.

for those corner sections because its boxed in you can get away with a butt joint there (as long as the wood left is dry). One quick question before moving forward with the how-to, what are you using to cut the old transom out with? Circular saw or??? i have some tips in that area that will help

Thus far I've been using a RotoZip circular saw, chisel and breaker bars only on top layer. Really appreciate your help Dave!

just go at the whole thing and replace it. the work to detail in the little section its easier just to rip the whole thing out and do a whole repair... who knows you might find some more rot in those hidden areas!

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u can see the 4 layers of resin/glass in the slug from the drive cutout.

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i dug all mine out with a oscilating saw... it cuts through glass easily and doesnt throw dust around like a typical rotating saw. to get the pieces that are stuck to the outside glass put a flat scraping bit on it... its amazing how well it chips that stuff off so you can get back down to bare glass. Harbor freight has a cheapo that'll get you through the job.

http://www.toolsnob.com/pictures/ski...ating_tool.jpg

I have a twin engine 35" Cigarette Cafe Racer and have done only partial transom replacement. agree with your to do complete as your engine is out. Mine only had leakage from stbd side exhaust and it came out ok.

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Partially my stringers were also replaced, did you check yours?

Great work there guys! To answer the stringer question, yes I drilled them and they seem very solid and dry. I have a feeling the rest of the transom isn't going to be fun coming off as it appears solid and dry except for the very lower portion. Could be worse, so I'm pretty pleased. Thanks for all of the suggestions on this, it's very much appreciated! Hope you all have a great thanksgiving.

hey if you have a blains farm and fleet they have a porter cable osolating cutter for black friday for 59.00 top of page..

http://www.farmandfleet.com/promotio...4#.UpbUVNK9vTo

As the the first picture depicts; A MESS! As work proceeds, a quality of workmanship and time WELL spent. When you get the fillets glassed in, post the steps of progress.

We have done some transom and stringer replacements on a 35 flat deck years in the past. I have a Fountain 10 meter # 12 built, we stripped every piece of wood out of it all the stringers, bulkheads, transom, cut the dash out. Used Okumie plywood, 3/4 deckalite panels, hat sections between bulkheads and hull for hard spots used all epoxy glass. Cloth and bidirectional cloth came from Composites One.
Built it off of Fountains layup schedule for the race hulls. 5 forward bulkheads, ballast tank, hat sections glassed in at 45 degree angles, installed new tanks. Floor is raised for a sit down version, like the poker run dash. Cored the engine room bottom with foam coring, installed thru hull water pick-ups from Stainless Marine. We cored the hull in the engine room to eliminate all those intermediate small stringers. Now it sits, waiting to be completed. We also gel coated the hull, all of this was a great expense. We did in a separate section of the business, I had a full time fiberglass at that time, that did all the work under my direction through out the project. I hated the mess made in the area for the project.
I will have to get some pictures posted, I only have the completed pictures now. This was done back in early 2004.

If it's not too late I'd like to suggest that you don't take the wood all the way down to the drain plug. Stop about 2"-3" above the drain plug. cut a nice angle on the bottom of the board for the glass. The drain plug is where all this water "Wicked" Up from. If there no wood around the drain plug hole it can't wick up water :) No loss of structural integrity since there's so many glass overlaps at the keel/transom anyway. Try it, you'll like it... (now I'm like the fiberglass pusher guy :) )

Just wanted to update this with what I decided direction wise on the transom repair:

I haven't been able to do much of anything on the boat lately, so I woke up at 5:45am this morning and started removing the rest of the transom. All of this work has been done with zero help from anyone(besides you guys giving me much needed advice!). Dad bought me a porter cable ocilating saw for christmas(thing is awesome!) and I am also using a circular ZIPSAW. Worked until 10am today, and almost have the entire transom done. Signing on a new home today, so finishing this up later this evening. Stringers are next.....

5:45am
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10:00am
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Also spoke too soon on stringers. After doing some exploratory cutting with the ZIPSAW, it's obvious the stringers got the majority of the water that leaked in as the lower rails are pretty rotted. The transom was only moist at the bottom, so that makes sense the water would get sucked up by the rear stringers. The layup on your stringers is about 3/8+ thickness which was good to see. Plan to duplicate this after cutting it all out next week.

Glassdave- should I cut out the plywood caps where the batteries sit, just forward of the transom, or just butt up the new transom as is?

Just ordered a 7 inch Daredevil blade to use on my rotozip when removing the engine stringers. The rotozip blades are pretty weak and expensive. I love the saw, hate the blades. Same thing with the oscilating saw. I also ordered some Japanese blades for that, so hopefully these work better as the stringers will be more intense vs the transom removal. As always, more pics to follow.

I tell ya what, i have purchased blades for my Sonicrafter from just about everywhere (brand name stuff from big box stores, specialty saw and blade shops, etc) and by far the longest lasting are the semi round ones from Harbor Freight). I typically get three or four transoms out of a single blade, make sure you are always using bimetal blades. I have a rotozip as well but never had any luck with that thing. Got it years ago and blades seemed to be toast after just a few minutes so i gave up on it. Are there different blades for it that I'm not aware of? o be honest though i can get through stripping a transom and stringers pretty quick with just the sonicrafter, I can typically have everything out and ground in a day or so.


What is the Daredevil blade?

I'm guessing its a moot point with the discovery of the bad stringers. Just for reference its generally not a great idea to butt joint but it can be done if you absolutely had to and the remaining wood and stringers was absolutely bone dry. If you butt joint like that it has to be right where the stringer or box meets the transom to give some other support to the joint. Again, its not ideal, but can be done on smaller boats where the loads are not as great.

Bosch actually make the daredevil blades. They are 7 1/4 inch blades (the ones I bought) and really last a long time. Only negative is you can use a guard and have to be careful, but the typical rotozip kickback is practically non existant because of the blade design and they stay sharp for a LONG time! Other downside is the larger blades limit the space you can operate the saw in. I purchased some Japanese blades for the porter cable saw, so we will see, but I like the idea of using the larger harbor freight cheap ones. Hey if it works I'm good with it. The roto zip and porter cable blades are an absolute joke! Honestly I should have consulted you first before deciding on these, although the oscilating saw seemed like a requirement.

As for the transom, I decided that cutting out the side floor sections is the proper and only way to do it (as you suggested prior) so why do a half assed replacement at this point in the game. When I cut out the old stringers can I leave about a half inch or so of existing glass to relocate and bond the new wood to, and in order to have a point of reference?

Also, is it ok to remove all of the engine stringers with the boat sitting on a bunk trailer?

I'll hafta check 'em out all i ever had for the rotozip was these small 1/8th inch or so two inch long drill lookin things that lasted all of five seconds before they turned blue and started to glow lol. I did get a tile bit that seemed to work but when i got the oscillating Sonicrafer i havnt used much else, maybe a sawzall from time to time but i got pretty surgically quick with the Sonicrafter. I actually have a Rockwell Sonicrafer and a Porter Cable Multi with the quick release blade (great tool but the quick release thing is crap). I just keep a plunge blade on one and a half round on the other so i dont hafta change anything out, being in the biz it makes sense.






(note) Ahh i see, i looked up the Daredevil blades on Amazon and see there for a standard sawzall. I was thinking rotozip drill cutter type thingy (they suck)

Yeah the daredevil fit the rotozip rotary saws without the guard. Personally I think the guards on these just get in the way. I'm hoping the new made in Japan bi-metal blades I ordered from eBay work longer than what came with my porter cable oscilating saw. Things wore out and started smoking so quick it was SAD! Kinda useless having an awesome saw with S%#T blades offered by the OEM. I'm glad there are alternatives. Might just get the adapter and try the harbor freight blades. How far down should I cut off the stringers to the hull? Thanks

thats weird. im still on my first blade with my craftsman saw. i had better results with the half moon type blade as it didnt deflect as much as the long flat one and start cutting crooked. cut em down close and then grind em all the way down smooth and then wire wheel the whole area to get it nice and clean and ready for bedding in the new stringers.

I've noticed blades run either great or they suck. the majority of the blades I got from HF lasted a long time but it seemed the brand named stuff wore out in no time. Anymore I just buy HF bimetal blades and to date I have broke more then I've worn out, well I didn't break them but a greenhorn shop helper did. I've yet to break any and have no idea how he did but he cracked three of 'em :picard1:

I also have one of those dual blade cutters. the one with like 2 five inch circular running in opposite directions. thats another habdy tool right there :D

Are these the ones? http://i1140.photobucket.com/albums/...pst7iszxhl.jpg

Also, found out the daredevil blades DO NOT, fit the rotozip saw! Advertisement on the site I bought them from stated they would, but they need a 5/8 arbor for daredevil blades. Rotozip is smaller. Now I know why everyone just sells these rotozips on CL, frickin expensive blades that can't even last halfway through a wood/fiberglass job!

yep those are the ones, I like the offset ones to. I seem to get a lot of life out of those from HF, they last me months and I use them regularly. I also picked up one of those circular saw thingies that has two blades that spin in opposite directions, that thing is a beast but blades only last through one transom job. It has its place but doesn't see a lot of use, it works good for cutting remaining transom wood into little blocks to be pried out. The good part about that tool is limited depth like the rotozip so you have a bit of a safe margin away from the surface fiberglass.

Just to update, purchased 2 3/4 sheets of mahogany faced marine grade A plywood. Was $100 per sheet from woodworkers source here in Phoenix. Let the fun commence!

Clamped the two pieces so they wouldn't warp
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Stuff is literally flawless..
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Better than the original 7 ply outdoor stuff by just a little lol
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Now if I could only find a place to buy some transom core bonding material!

Looks good Borgie. When I got my wood I almost went with Shop Birch which had i think 9 plys. Did some quick resarch on phone and saw mixed reviews so ended up with two sheet of 7 ply marine wood for transom and two sheets of 7 ply CDX for stringers.

Hey thanks! Just got the fiberglass supplies today that I will need excluding 3M Corebond. Stuff is impossible to find and I'm not paying $300 for something that's not worth that. Think I'm just gonna go traditional as far as layup schedule on this. Will need to assure the surface is good and true. What method are you employing on yours?

I'll be using the normal 1.5oz mat laminating the new transom would to inner skin. First I have to layer up some mat on my stb side. There is about 1ft by 8in area in the upper corner where it either delaminated or was never there. That's my only trouble spot. I just cut one piece of transom wood tonight, hope to test fit tomorrow.

Just a few pics to update those of you that might not have seen my build thread. Just decided to stay the course and do it the right way, even though most of the surrounding wood besides engine stringers were quite solid.

Stringer jig
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Big thanks to Glassdave for all of his help thus far! I'm learning a lot.

Looking good. How much more grinding you going to do?

Just need to do a final faring in on transom surface and hand sand the inner stringer areas where I plan to bond to the floor. This grinding crap is for the birds!

Just to update:

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Corebond:
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looking good bud

Thanks!

Everything looks precise and on the money!................very professional!

I really appreciate the kind words! Glassdave has been a huge help along the way and I've learned a lot here on OSO. Looking forward to this thing floating again! Lol

So you use the 3M Corebond to adhere the outside gel to the inside of the new transom plywood? And, you also use 3M Corebond to make the fillets where the inner hull meets the new transom? The you just glass the over the new transom connecting it to the inner hull?

Looks Great!

Yes, the crucial part of this process is mixing up a hot batch of VE to the surfaces to be bonded with the corebond, wait until its tacky (30-40 mins roughly) then apply the corebond that's been mixed thoroughly with 1.5% by volume tinted MEKP. This part is absolutely necessary. The nice thing about corebond is using it in a situation like this where the transom surface will never be completely flat and true. Stuff has an absolute and tenacious bond.

Thanks for the props. Glassdave should be given some serious credit here as he was the one who steered me toward Corebond and has given me quite a bit of advice. Couldn't be happier with the results. If anyone here needs a good source for relatively inexpensive Corebond, feel free to PM me.

So you are saying: VE on bare transom wood, tacky VE on transom wood add Corbond 1.5%, bolt to existing gel transom on boat.

Thanks