My tri-hull transom replacement w/ pics

[redfury]

Re: My tri-hull transom replacement w/ pics

You can certainly feel welcome to come help me filet the corners in my boat when I get ready to tackle that job...excellent looking work...definitely looks like you put effort into it and turned out how you had hoped.

 

[drewpster]

Re: My tri-hull transom replacement w/ pics

I made a little progress this weekend. I laminated two layers of ply together. They will be used to make the transom core. I cut the ply pieces oversized and glued them together making a solid 1 3/4 board. After making a pattern I will cut the transom shape out of it.
I used PL premium adhesive to glue the two sheets together. Initially I intended to simply screw the two panels together after applying adhesive to the glue faces of each board. It occurred to me that it would be better to back the boards against a true surface to prevent the boards from warping as the glue sets. The problem I had was finding a surface flat enough.
The only surface I could find flat and true was the bed of my truck! The bed has a flat rubberized liner. Then I spotted the stack of landscaping bricks. Hmmm
I prepped each board face by sanding them with a 220 disc in my orbital sander. After lightly sanding the boards I double checked for depressions. Then I applied the glue by first running even beads across each board face. I used a 1/4 inch notched trowel to evenly spread the glue across each of the board faces. I pre-drilled holes around the perimeter of the top board so that screws could be used to prevent the boards from moving around while the glue cured. After laying the boards in the bed of my truck I stacked landscaping stones on to them with a piece of thick cardboard under the stones. I set a single screw in each corner to locate the boards and keep them flush.
Luckily we had good weather last night and today because I had to drive in to work this morning with my transom curing in the bed of my truck! After work this evening we unloaded the stones and checked our work. It worked great. My transom is flat, true and perfectly bonded. One benefit of using the stones to compress the boards is that there was no need to put a bunch of screws through the wood to get it bonded flat. Two screws were all that was needed to keep the panels from moving under the weight. Fewer holes means fewer chances of water getting in. This weekend I will use my jig saw and router to cut the boards in to the final shape of the transom core...hopefully. Come on weekend!

 

[drewpster]

Re: My tri-hull transom replacement w/ pics

BTW- redfury, send me a plane ticket and I may take you up on it. I have never been to MN!

 

[redfury]

Re: My tri-hull transom replacement w/ pics

Where do I send the tickets to?

...hope you don't mind riding the greyhound

 

[Meadfisher]

Re: My tri-hull transom replacement w/ pics

Sweet project! I have always had a soft spot for trihulls. Great work too man* LOL Im sure you could teach me quite a bit. I cannot wait to see more pics. Keep up the Awesome work!

 

[88BLiner]

Re: My tri-hull transom replacement w/ pics

Hey, I just wanted to say great job on the hull. I had a couple questions about the sanding process on my project but I think you have cleared most of it up for me. If you get a chance please come and check out my thread and tell me if you have any suggestions for me. Nice boat and great job!

 

[drewpster]

Re: My tri-hull transom replacement w/ pics

I hit a milestone today, the transom is in! Boy I hope this works. After the laminated boards had time to completely bond I went about cutting it out and fitting it in the hull. I started by clamping the boards to the outside of the transom and marking the basic shape. I then rough cut the transom using a jigsaw. I started fitting by cutting a deep bevel at the edge of the board to make it a little easier cutting the final shape. I used a grinder, a jigsaw and a circular saw to do the fitting. I took several hours of passing the heavy transom in and out of the hull. Cutting a little here and grinding a little there it finally took the profile I was after.

I used a flashlight to shine down in to the space between the wood and the transom skin to fit it in to place. I realized that I would need to add a little thickness to the upper portion of the skin to make the fit come together more easily. The skin needed a layer of CSM.

The drain holes were covered over and will need opening up from the outside.

I allowed this layer of glass to cure before moving forward. I found a total of 25 penetrations through the transom skin. Some were old and had been covered over. I opened them all up because they all had signs of water seeping into the laminate around them.

After prepping the hull I sanded and cleaned the transom. After everything was smooth and clean I coated the transom with thinned resin. This prevents the raw wood from soaking too much resin out of the fiberglass. Placing it in dry would risk dry spots and poor bonding.

 

[drewpster]

Re: My tri-hull transom replacement w/ pics

While the CSM and transom skim coat were curing I started getting everything ready to install the core. The transom skin was not flat by itself. I needed a reliable way to clamp the core in place to cure it flat and provide a good bond. I ended up using all-thread, fender washers and angle steel to clamp the wood to the skin. I wanted to limit the amount of penetrations in the core so I only used holes I knew I would need later.
I needed two batches of resin to glue the wood in place. One batch would be used to add two additional layers of CSM to the inside of the skin. The other batch was used to mix up a big glob of filler. I started by laying in the two layers of CSM and wetting the core. I mixed up a batch of filler using chopped fiber, silica and a little talc to thicken it up. I used a spreader and made large fillets in all the corners. I also liberally coated the inside face of the skin and the glue face of the wood. Then it was just a matter of setting it in place and clamping it up.

As the clamps were all tightened a good amount of filler squeezed out around the edges of the wood.

I think it took rather well judging by the amount of filler that squeezed out. I used it to form small fillets on the inside around the perimeter. I am pretty confident that I have a good bond and all the gaps are filled. I used a thin piece of wood to shove filler in every area.

Here you can see my clamp set up. I was careful not to sqeeze too tight sqeezing out the filler. I only went far enough to be sure everything was flat and I had good mush out of filler all the way around.

 

[drewpster]

Re: My tri-hull transom replacement w/ pics

I mixed the resin with just a touch less hardener then I would normally use to do this job. I knew some of the filled areas would end up rather thick. I reduced the amount of hardener to prevent too much heat building in these areas, cracking the filler.

Well, either way she is in! Hope this works, it was a hectic job to say the least.

 

[Meadfisher]

Re: My tri-hull transom replacement w/ pics

I mixed the resin with just a touch less hardener then I would normally use to do this job. I knew some of the filled areas would end up rather thick. I reduced the amount of hardener to prevent too much heat building in these areas, cracking the filler.

Well, either way she is in! Hope this works, it was a hectic job to say the least.

Nice, that looks sharp man! Great work, awesome glass insight ty.

 

[ezmobee]

Re: My tri-hull transom replacement w/ pics

First class job. That transom will outlive you.

 

[Off-Peak]

Re: My tri-hull transom replacement w/ pics

Hmmm.... Almost got me off the couch ;-)

NICE WORK!!

 

[bear_69cuda]

Re: My tri-hull transom replacement w/ pics

Great craftsmanship on the transom drewpster...

Also thanks for the Carbosil and Talc info!

 

[Truefire]

Re: My tri-hull transom replacement w/ pics

1/8" chopped fiberglass and fumed silica mixed with resin

What exactly is chopped fiberglass exactly sir, and where can one find same and "fumed" silica mix with resin. Is this the type of material that one must use in order to fillet inside corners or could you make a mixture of other sorts?

New to me, i totally understand the concept of filleting just not familiar with the products and mixtures to utilize, i am sure there lies a science in the types and grades of the various mixtures on the market.

If any of you guys could help me in this area, i would greatly appreciate it,

Chris Harrell

 

[jonesg]

Re: My tri-hull transom replacement w/ pics

You are correct, the chopped fiber strengthens resin for filets , the fumed silica ( cabosil) must be used to prevent the resin from draining out of the resin/chopped fiber paste. Cabosil makes the mix like a soft gel or putty.
Mix those together to suit yourself then add catalyst and watch out because it'll go off a LOT faster, so be ready to jump on it.
Mix a test batch, it'll surprise you how quick it goes off.

I just did my stringers, I added the fiber and cabosil then got into the boat before adding the catalyst. Do it in smaller batches, I like to limit the mix to 1 qt resin.
WHat I do is get the putty on quick then lay the glass matt into it just before it goes off and start wetting the matt out with resin, it all goes on wet and all trips off together for better adhesion, you just have to get everything ready in advance.

BTW, CABOSIL is used to thicken ketchup, its inert and passes thru the body, much like gold leaf does.

UScomposites sells most everything you need.
http://www.uscomposites.com/fillers.html

 

[drewpster]

Re: My tri-hull transom replacement w/ pics

I have had a little time so I got back in the shop and made some much needed progress. I built and bedded the stringers in place and coated them with thinned resin to prep them for glass. This boat only has three stringers. I am debating the idea of adding some bulkheads just forward of the side stringers to support a casting seat that will go on that part of the deck.

Here is a pic of the bedding under the stringers. I used PL Premium poly adhesive.

As you can see the stringers do not contact the transom. I struggled with leaving it this way. The deck sits lower in the hull here and the stringers are thin at this point. I saw no great benefit of bringing them in to the transom so I left the original design.

I added a layer of 18oz. roving over the two layers of CSM already on the transom. A final layer of CSM will finish it off for paint later.

My next move is to finish the glass work under the deck so that the deck can go down next. Hopefully I will get more time for it next weekend.

 

[redfury]

Re: My tri-hull transom replacement w/ pics

What resin are you using for your lay ups? I'm at the point where I plan to order some from US composites. I'm going to use polyester resin as that was used in my boat originally ( green in color ). Are you using Vinylester resin?

 

[drewpster]

Re: My tri-hull transom replacement w/ pics

I am using U.S. Composites 435 layup resin. It does not have wax added, so you will have to add it in the last layer for final curing. It has worked well for me. Personally, I would not go with the expense of vinylester resin unless I was doing a repair on the outside of the hull below the water line.

 

[drewpster]

Re: My tri-hull transom replacement w/ pics

I did some fillet work and glassed the center stringer with a single layer of CSM over the weekend. I would not post this portion of work, but I have had some questions about fillets. In the pic below you can see the fillets at the bottom of the stringers.

As you can see the fillets just round out the bottom corners where the stringers meet the inside of the hull. This will help the fiberglass lay in to the bottom corners of the stringers and avoid bridging of the fiberglass chopped strand mat.

I used chopped up 1/4 chopped strand fiber, fumed silica (cabasil), and talc to make up my filleting putty.

I mixed catalyzed resin before adding the components. After a good stir I added the fiber first, then silica, then talc. I added the fiber first to the kicked resin then silica because the silica tends to clump up. The fiber helps break up and mix the silica in to the resin. I kept adding silica until the mix got a little thick (about like mayo). After adding enough talc the mix will become about he consistency of peanut butter.
A good trick for applying the filler is to use a sandwich bag to squeeze a bead of filler in to the corners. Cut a small corner out of the bag. Fill it with your fillet mixture and squeeze a good bead in to the corners. A plastic spoon is also in the pic. I used the spoon to spread the bead into a curve. It worked great. It is hard to tell in the pictures, but I completed one layer of CSM down both sides of the center stringer. The cloth went in to the corner easily and I had no gaps or bridges for water to accumulate.

 

[swompfox]

Re: My tri-hull transom replacement w/ pics

Nice Job keep at it, looks good