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SUBJECT: # 26012: How Much Epoxy in Transom Repair?
Submitted by tbaker (66.138.79.113) from TEXAS on 9/29/03 4:32:00 PM
So I pulled the motor and found the transom to be completely rotted, end to end. I am going to go back and replace the whole thing from the outside skin...in. Basically, I have left the outer shell, and will rebuild the transom.
Now, a question for the experienced folks on the board. How much epoxy should I plan for?? I'm looking at a 2'x6' maximum on the transom, and planning to build it about 2-3 inches thick.
I like the plan that I have read about here about layering the thin sheets of luan wood with the woven roving, and that seems to be a good fix. Although I can be persuaded to cut down on some work and use a different thicker type of plywood.
How much epoxy should I plan to use in the transom repair only?? I will have to put new stringers in the boat as well, but should have a better idea of the quantities necessary after doing the transom. I have used polyester resin previously, and have become pretty good at building with it, but have never used epoxy.
Also...how do I tell the naysayers that what I am doing is actually better than buying a new boat?? I don't know how many times I have heard..."what the @#$% are you thinking"???
Thanks in advance for the help.
tb
- 9/30/03 6:53:00 AM
Submitted by
shoes from MAINE says epoxy
t, I'd start with a 3 gal kit from RAKA...two gallons of resin and 1/2 gal each of fast and slow hardener. $129.00 plus shipping (compared to West System at almost $100/gal over the counter at the nearest boat yard). You'll also want to get some fillers: fumed colliodal silica for structural fillets, phenolic microshperes for fairing work, and maybe some wood flour for thickening the resin you put between sheets of ply. You'll alos need some glass cloth for the final outer application. Call Larry at RAka and tell him what you're doing. He'll set you up right.RAKA 561-279-8929 www.raka.com
shoes
- 9/30/03 8:42:00 AM
Submitted by
Thom (198.99.246.254) from WEST VIRGINIA says You're Doing The Right Thing
Don't listen to them, you are doing the right thing.A couple of things come to mind. First I think Shoes has it about right on the epoxy, 3 gallons might be a little bit much but in this case you want to get started on the job and not have to take any breaks while doing it. Once you begin putting the new transom in place you should keep layering until you have it done. Do not try to do half one day and half the next, or the second half next week or next month. You want to be putting each new layer right up against a layer that is still at least a little bit tacky. Do that and combine it with a good soaking of the luan (quarter inch - TAKE NO SHORTCUTS) and what you end up with is basically a sold transom with no cold joints. By that I mean that if you don't let the layers set up completely you get a chemical bond from one layer to the next, and that is as strong as it can be. Otherwise you will have to either scrub or sand between layers and you don't want to have to do that.
Luan, nothing else (once expecption) and no thicker than 1/4". Here is the exception - make the first layer of plywood, the one that will be closest to the skin, out of half inch. You will want to set up some sort of table and use a roller to apply epoxy for a good soak before you put each piece up there.
When you buy your resin and hardner from Raka ask if you can substitute slow set hardner for fast for all but one quart of the fast. Do the whole job in slow set hardner or only use some fast with the mix if it is a cold day and do your layup in a shaded place if one is available. This has two advantages to using just fast or a mixture of fast and slow set hardners, one is that it gives you working time and the second is that is forces you to not use to much resin, a common mistake.
This is vital - do not forget it: One of the major differences between epoxy and polyester resin is that you control the set time of polyester by adjusting the amount of hardner for the most part. Epoxy is much different. With epoxy you have to use exactly the right amount of hardner or else you get some strange properties in the final mix, but you adjust the set time by changing the type of hardner you use. RAKA will sell you kits of mix that have resin and both fast and slow set hardner. As you mix batches you will use their hand pumps (buy a set when you order the resin) to measure both resin and hardner. So for a batch you might give it 5 pumps of resin and so will need to mix with that 5 pumps of hardner (the pumps measure out the stuff in the correct ratio so the hardner's pumps are actually quite a bit smaller than the one for the resin) which can be 1 pump of fast and 4 of slow, or anything else that meets your needs. It is also desirable to mix your resin/hardner in a wide shallow container. You do not want that resin to be deep in a pot. Its exothermic stuff and the heat that is generated when it sets up will cause it to set up faster and generate more heat. Shallow mixing containers really help slow this down. Also, through mixing is essential and slow set hardner give you more time.
Start looking around now at places like Wal Mart and such for very very cheap rollers and those big bags of rubber gloves. You're gonna need them. Buy a couple of gallons of Acetone for cleaning everything. Buy a couple of bundles of rags. Buy a cheap set of large sissors, maybe 2.
I would suggest that you not use wood flour myself, using cabisol instead. Actually this is one place where I defer to West System. I tend to use their fillers, particularly their 404 high density filler, with the RAKA epoxies myself. At any rate my preference is to keep it all plastic and not use the fine sawdust as a filler.
Oh, here is a tool you need if you don't already have it. Get yourself a 4 1/2" angle grinder. Get a good one. Go to E-Bay for it. Also get a hard rubber pad for it and a box of 36 grit sanding disks. Both Sears, Lowes, and Home Depot sell both the pads and the sanding disks. These disks are not like the hook and loop or adhesive backed things for conventional sanders. These will take off serious material in a heartbeat. This will be the very most valuable tool you buy.
Get yourslelf a half dozen or more dirt cheap paint brushes, ones with about a 3" or 4" width are good. You will use these to apply resin and to wet out spots of matt or clot in the boat. You will be amazed how well they work.
Now, to get down to the job. The very first thing you need to do is get every single bit of the old wood out of there. Every single bit. Every single bit. Every single bit. Then clean it, wire brush and that grinder will do wonders. Don't cut through the skin though, and that can be easy to do with the grinder. Be careful. The first layer of plywood is the hardest because you don't have a truly flat smooth surface to bond it to. Mix up filler and epoxy to a consistancy close to mayonaise and basically plaster the inside of the transome with it, then place your first layer of plywood into it. Put it against the transom at the bottom and then push it up into place from an angle so that you have complete and continous contact between the plywood and the skin with the filler inbetween to make sure there are no air spaces.
Now this: When you were getting ready for this job there were all sorts of holes in the existing transom. There were motor mount holes, there were holes where bow-eyes were mounted, there may have been holes for transducers and cable hold downs, maybe trim tabs too. All of that stuff has to have been removed and those holes are going to be life savers for you. First useing duct tape cover each hole. Then cut out a small blocks of plywood out of scrap, make the blocks a couple of inches square. Put a sheet metal screw that's about an inch long through the middle of each block. Now, when you put the first layer of plywood in place (and it has been on your table soaking up at all the resin it can hold before you brought it into the boat) have someone on the outside of the boat start taking those blocks and putting them in place. They will put the screw through the existing screw holes and then into your plywood on the inside of the boat. As they tighten the screws the blocks of scrap plywood will come up flush against the outside of the transom and they will pull the new plywood inside the hull up tight against the skin, or at least they will pull it into the filler. This is layer one. If you wanted to cheat on this one layer and use half inch it would not be the end of the world, and in fact would give you a flatter base for succeeding layers of plywood,
Ok, layer 1 in in place. Now take your template and cut out a layer of matt then put it up against your first layer of plywood. The plywood is already wet with resin so its tack will hold the matt in place. Make sure it is adequately wetted out, adding more resin if needed with either one of your brushes or with a roller. On goes the next sheet of plywood, presoaked with resin as it is, and then it gets screwed to the first to pull it tight, then the next, with its screws to old it tight, and so on.
Finally you will get up to the stringers. They will have to be glassed up to the final layer of plywood with no spaces. Use filler as necessary to take care of smaller spaces and buy yourself some glass tape to make the connectorion of stringer to transom. Next to last cover the final inside sheet of plywood with matt and use the roller or paint brushes to wet it out.
Hints: When you cut each section of plywood make it just a bit smaller than the skin cutout. Maybe a quarter inch all around. Fill the space with thickened (404 filler or cabosil) epoxy. Using either cut sections of matt that are about4"x6" you need to lap glass between the transom and the hull sides and bottom. I find that 6" wide glass tape works very well for this (glass tape in various weights and widths is worth its weight in gold - trust me, you'll see).
And that's all that comes immediately to mind. Oh, I sould have said something about glass weights. Figure most of what you are going to be using will be somewhere around 7 oz or so. Don't be to concerned about the weights of glass but don't get the very fine stuff that is down there around 2 oz and don't go up to the very heavy stuff of 10~12 oz or so.
What else? Oh, get a large thing of waterless hand cleaner. You will be using it a lot. Get some old clothes of course. Now the encouragement. This is not as hard a job as you might immagine. The real hard part is in the preparation, not in the acutal layup. What you will find is that getting the old stuff out first is the hardest part, cleanup is next, and actual replacement of the transom is actually the easiest part. By the time you get to tieing in the stringers you will be much more experienced than you are now and that is good because you will want to do a bang up job on this part. The key through all of this is to avoid voids in the material. Air spaces are simply not going to be allowed and you will have to figure out how to avoid them. Every boat is different and everyone has different stuff to work with and on and on.
Anyway, that help any?
Thom
- 9/30/03 6:16:00 PM
Submitted by
tbaker (66.138.79.113) from TEXAS says Wow...
I'm always amazed at the amount of good stuff on this board.....thanks guys for the tips, and especially Thom for the very much appreciated "how to" guide.I do have a question about the screws though.....are they just turned by hand to pull the wood together or do they go through the wood?? Any difficulties with the matting and the screws??
Also, is there any rule of thumb for stringer length that is attached to the transom?? I'm not sure I'll be ready to do the full length stringers at the time of the transom fix, but if I need to fit them and glass them in at that time, I can plan for it.
Thanks again for the help....
tb
- 9/30/03 11:09:00 PM
Submitted by
RingLeader (68.114.97.243) from LOUISIANA says Epoxy
I went through 5 gallons of Epoxy resin on my transom job alone. I rebuilt with 3 pieces of Marine plywood. I imagine that the luan soak method with a layer of 18oz roven between each sheet may require 5 to 6 gallons... Maybe more
- 10/1/03 9:00:00 AM
Submitted by
Thom (198.99.246.254) from WEST VIRGINIA says Screws Pull Wood
The screws are going to be used to pull the plywood tight against the skin of the transom. Realistically that usually means that you will change the screws a couple of times and it also means that at least for the first layer of wood you might find that you want to let the glass set up for a bit (enough to easily hold the wood in place) before moving to the second and subsequent layers. Its also likely that you are going to improvise all sorts of temporary clamping and forcing stuff to press your wood back into the transom. Of course screws are good for this (make sure they are countersunk if you are going to put them in from the inside of the boat to pull succeeding layers of wood tight to those already in place). A real part of keeping the resin use down is to avoid causing the wood to be uneven, with dips and mounds in it. The flatter that initial layer of wood lays the less resin you will use on succeeding layers. So while you strive for that keep this in mind, with epoxy it is not necessary, nor is it desirable, to clamp the pieces that are to be bonded as you would if you are gluing wood togheter. When you glue two pieces of wood together you want to have strong clamping pressure. That is not necessairly true with glass. With glass what you want is constant coverage and no voids but tight clamping is not desirable because it can force resin out leaving a starved joing but if the layers are flat it actually takes suprisingly little resin to wet it all out. Along the same lines when you wet out the wood you don't have to dip it into a pool of resin and let it soak in. All you have to do is take the roller and give it a coat on both sides (dont forget the edges too) just like you would if you were putting on a single coat of paint. Also, keep moving.By keep moving I mean this. The first thing you are going to do is make up a template for cutting your plywood and cutting the sandwiched layers of glass. Take some time on making the template just right. Cut out all of your wood first and have it ready to use. So you'll mix up one batch of resin and you'll paint your first layer of wood, with will be the 1/2" stuff. Then you'll set it aside and mix filler with the remaining resin from the first batch (remember that slow set hardner? Its giving you time) and get in there and plaster it up agains the inside of the transom skin. Then you're going to be putting the wood in place and you and a helper are going to be screwind and wedgeing, and clamping, and everything else you can think of to hold it in place. That was batch one.
You're second batch of resin will be an ongoing batch. By that I mean that once you start the actual layup of succeeding layers of wood and glass it will be one continous process. You aren't going to stop now until you are done but in fact you're going to be supprised how fast this is going to go.
Now the big if. If you find that you are going to run out of resin do it so that you are putting up a layer of plywood but do not wet out the side of it that faces the front of the boat. Leave essentially dry plywood facing the inside. If you do that you can come back a week later and start again and all you'll have to get the amine off of first will be the edges where the transom has been bonded to the bottom and sides of the hull. By the way, don't forget that part. With every layer of glass that lays between the sheets of plywood you need to overlap onto the sides and bottom to make that tie. You can do this with glass tape or you can simply make the sandwiched layers of glass wider than the wood and cut slots into it every couple of inches to ease its application
On the stringers they should have been glassed into the existing transom. With any luck they will be sound right at their current ends so its really mostly a matter of building the transom until they almost touch and then just bridging the gap. The narrower the gap the stronger the boat will be.
I really want you to understand something here. There never have been two glass jobs that were the same. You are going to have to improvise right and left, up and down, in and out. The wood you are gettng ready to use, the Luan, will soak up resin like a sponge if you let it but its not necessary that it be totally saturated. It is necessary, however, that the matt you put inbetween the layers be fully wetted out. This is where folks will often use more resin than is necessary and while most folks don't realize it the excess resin will weaken the job. Of course glass starved of resin won't have full strength either so its gotta be fully wetted. One pretty easy way to make sure you don't waste resin is to buy (cheap) one of those semi-hard squeegees that are sometime used to apply plastic body filler (bondo). You can use it to effectively remove excess resin from glass before you put it in place. Remember, the roller will almost always put on more than you need or want.
Also, while all expoy is not created equal there is nothing that is going to stop you from running over to your local boating store and picking up a quart of West System's (available pretty much everywhere) resin and hardner if you find yourself a bit low (I don't think you will because your transom job is not extremely large at 2'x6'.
At that side what you are realistically going to run into is this. You'll buy a sheet of half inch luan and that is going to give you two layers of the transom, each a half inch thick for one inch of the thickness. Half of that sheet will be used right up against the skin and the other half of it will be the last sheet you put up. You are going to need either 2 or 3 sheets of 1/4" luan too. If you use two sheets you're going to end up with a total transom thickness of about 2 1/2" total. From rear to front the layers will work out like this:
1. Skin
2. Thickened (with chopped glass filler) epoxy filler used to fill any irregularities.
3. 1/2" plywood
4. Glass (7.5 oz will work just fine here though you could go higher but its not necessary)
5. 1/4" plywood
6. Glass
7. 1/4; plywood
8. Glass
9. 1/4" plywood
10. Glass
11. 1/4" plywood
12. Glass
13. 1/2" plywood (second half of sheet 1)
14. Fiberglass cloth to layer
15. Bond in stringers
I think I'm just rambeling now. I should quit.
Thom
- 10/1/03 9:38:00 AM
Submitted by
Gene from GEORGIA says copy/paste, thank you very much. lol...
great stuff Thom, wish you were my neighbor.
- 10/1/03 1:17:00 PM
Submitted by
Dunk75 (68.46.147.52) from NEW JERSEY says Well I was....
But Thom has it about covered and a 1/2. Raka's slow set epoxy will give you 4-6hrs working time if the temp is below 80 degrees. If you've got everything cut to fit, plywood and cloth, someone mixing resin, coating the luan with resin and laying the cloth out wetting it. You should be able to put the lay the whole mess in 2-3hrs. No matter what you do you are going to wind up with puddles of resin at the base of the transom. While it's still liquid it's easy to scoop out with flat bladed squeege and reuse it. Even if the epoxy has been mixed for hours if you add it back to the working resin tub your helper's using to coat and wet out cloth with. It won't activate until the fresh stuff does.One thing I use instead of regular cloth is 18oz woven roven. It's lots heavier than cloth and it's tougher to squeeze the resin out of. As far as clamping the transom. You really don't need to do that until the resin just starts to kick. I would recommend using bolts all the way through the transom once it's in place and the resin "just" starts to stiffen some. This will eliminate squeezing too much of it out. I like the heavier WR because you've got gravity letting the resin drain down and the WR will hold more resin till you clamp it down.
http://www.jamestowndistributors.com/cgi-local/SoftCart.exe/index.htm?E+scstore
Jamestown has the best prices on cloth, tape and woven roven.
http://www.shopmaninc.com/epoxy.html
As much as I like and have used Raka's epoxies their prices have gotten nuts. These guy's above have better prices. I also like the fact they have thin and thick epoxy. I'd order a 3 gal kit of the 635 thin stuff(2 to 1) for coating wetting out. Then a 3 gal kit of the 150 thick in 2 to 1... 10qts of cabosil.. Nothing worse than running out of materials in the middle of the job. Believe me once you see how easy epoxy is to work with you'll be looking for places to use it.. It's not like it goes bad...
- 10/1/03 3:07:00 PM
Submitted by
Hawkeye (129.86.240.203) from VIRGINIA says Just to add
Those puddles that you will get, you can mix a little cabasol right where they puddle to thicken it enough from running and scoup it up and put it in a seam somewhere. If you wait those puddles will thicken on there own but get real guey. Wait too long and they will be part of the boat. When you start messing with that guey stuff, you will realize why epoxy is so much better then polyester resin for repair work. Stuff sticks like white on rice.Hawkeye
- 10/2/03 2:55:00 PM
Submitted by
Chinewalker (24.97.102.12) from NEW YORK says Great stuff!!
Thanks for the step-by-step Thom! You've probably saved my 9-year old helper from a heap of colorful language. We're looking at a 1975 Starcraft 15-footer in need of stringers, transom, etc. It looks sharp, it's priced right and the winters are long up here... - Scott
- 1/2/04 7:56:00 PM
Submitted by
daryl marse (68.11.102.187) from LOUISIANA says transom repari
I went into my transom, 20 ft V-20 Wellcraft from the outside. Don't ask why, long story.How do you build a transom from outside in?
I've got all of the wood out and part of the cap off to allow access from top, also 6 inches of the original outer skin remains in the transom area.
I was thinking about making a one piece transom alternating plywood and mat, slip it into via the top and reglass the outside.
Big question, to rebuild the outer hull skin, what would I use a far as cloth, mat, etc?
