Repairs and upgrades for Hammerhead

thataway · Posted: Tue Apr 13, 2021 5:01 pm Post subject:

Yes, to both. I don't have time / health issues or I would do a layup to see. I do have the 1708 and 6 oz, but no balsa. As understand you are using 2 layers of 3/4"--and this may be thicker than the single layer of 1 1/2???

I always used grinders 8" 1 1/2 hp Craftsman was my go to machine, when we were boat building or doing restorations. I can no longer handle that bruit. The professionals I know here use almost exclusively air tools-they are lighter and easier to use. I do have a couple of air grinders/sanders (both straight and orbital), but you need a really good air source of high pressure and volume.

clayhubler · Posted: Sat Apr 17, 2021 2:37 am Post subject:

Made a test panel. I think it went well. I took one layer of 3/4 balsa and rolled a thin layer of epoxy onto the top. Let is soak about 30-45 min. Very few bubbles formed in the epoxy. Then, wet out a layer of 1708 and put a thin layer of lightly thickened epoxy on top of the balsa with a notched spreader, and then rolled the 1708 onto the balsa. Looks like it is going together as it should. I decided to only apply one layer of 1708 at a time, I feel the 1708 is hard to get the air out.

There are micro bubbles in the layup, but nothing large, and no epoxy starved areas. I don't know what to do about the micro bubbles. They look so small that I don't think they are going to weaken the laminate or be a problem in any way.

I'm going to bed before this cures, so hopefully it will continue to cure without any surprises.

Pictures in the album:
http://www.c-brats.com/modules.php?set_albumName=Core-rot-repair&id=20210416_211839&op=modload&name=gallery&file=index&include=view_photo.php

thataway · Posted: Sun Apr 18, 2021 3:38 pm Post subject:

I do not see any issue with these micro bubbles. Yes, any roving is difficult to get epoxy into. We used to use 24oz roving--and that was very difficult. The 1708 is much better. But if you come closer to "level" with the 6 oz cloth on top, that would be fine also. I probably would feather in the edges in any cases and the cloth would be easier for that. (Grind a bevel on the "good" laminate, and then cover that with the cloth or 1708 and then grind that fair.)

Of course waiting between layers does complicate the issue, by having to prep before the next layer (layers).

Great documentation.

clayhubler · Posted: Mon Apr 19, 2021 2:25 am Post subject:

The test panel turned out fine, no issues arose during the cure.

clayhubler · Posted: Mon Apr 19, 2021 2:41 am Post subject:

clayhubler · Posted: Mon Apr 19, 2021 3:07 am Post subject:

Okay, really got some stuff done today: All glasswork inside the cabin is done!

There is one layer of 6oz glass cloth over the entire sole. But, I cut my two pieces for the floor a foot too wide each, so the area where the aisle is there is two layers overlapping. Also, added reinforcement to both bulkheads by putting a fillet and glass on the bulkhead to floor joint. 2" 6oz tape over the fillet, and then 4" 6oz tape over that. I felt this would help tie the floor into the bulkheads, and give it a little more strength. I also put 2" tape followed by 4" tape along each side where the floor and hull meet, just because I could. I also added a lot of glass tape to the sump area.

I feel that this may have been overkill, but I want a rock solid hull that I can depend on. The aft bulkhead in particular was showing stress cracks at the bottom where is was bonded to the hull.

This took pretty much all day. Some final fairing this morning, then a lot of prep work, cutting glass, make scaffold, get everything ready. I had the wife mixing epoxy for me, which was a huge help, and this took 4 hours from the time we mixed the first batch till it was pretty much done. The scaffold was absolutely necessary. It's been about two hours now and I am going to go roll another coat of epoxy over it before it blushes. I am super pleased with how this turned out, it went way better than expected and I am super happy to have this part done. Next up will be the cockpit and transom. I feel that I gained some good experience here, but the cockpit is going to be a lot of work...

Lots more pics in the album:
http://www.c-brats.com/modules.php?set_albumName=Core-rot-repair&id=20210418_163802&op=modload&name=gallery&file=index&include=view_photo.php

thataway · Posted: Mon Apr 19, 2021 12:27 pm Post subject:

Nicely done. Yes, there is always a learning curve with this type of work.

Robert H. Wilkinson · Posted: Tue Apr 20, 2021 8:58 am Post subject:

clayhubler · Posted: Tue Apr 20, 2021 2:07 pm Post subject:

Thank you, Rob. I really hope that I do not wear out any of these tools, because that would mean I did a lot more grinding than I want to think about!

clayhubler · Posted: Tue Apr 20, 2021 2:24 pm Post subject:

I want to try my hand a making a mold and then making a part with a compound curve, so I was hoping for some info about chopped strand mat and epoxy.

I know that polyester resin dissolves the binder in csm and allows it to conform, but I thought there are csms that are compatible with epoxy, too. My understanding is they are only compatible, and that the binder is not really dissolved, and the layup may be more difficult and not wet out fully. If anybody could advise on this it would be appreciated.

I also think I read somewhere about being able to epoxy over polyester, but you should not try to apply polyester over epoxy???

And I believe there are laminating resins and finishing resins??? Laminating resins will not fully cure by themselves.

If I could use the epoxy I already have (west system) it would simplify this, I think. I know the polyester is a lot less expensive. I think the factory uses polyester.

If anybody has any info to add or if anything I said is incorrect I would love to hear about it!

Thanks all

thataway · Posted: Tue Apr 20, 2021 10:37 pm Post subject:

Here is the definitive information on epoxy and mat. This is from West Systems "Epoxy works":

clayhubler · Posted: Wed Apr 21, 2021 5:42 pm Post subject:

thataway · Posted: Wed Apr 21, 2021 6:22 pm Post subject:

Yes you can use an occlusive agent to allow the laminating resin to fully cure. You can work CSM into corners, but I probably would use cloth if you go with epoxy. You might use PVC pipe for the mold--if the size is close. That could be waxed and then be one surface. If not you can bend a formica type of laminate, or masonite (finished surface) is used to make mold parts. I suspect that you could use acrylics or the HDPE if heated and pre-molded into the shape.

The current technique for making large molds (and small, if you have the tool) is to use a computerized router and made the mold out of foam and using a 5 axis computer driven router. Put the coating over the foam, PVA and then make the mold directly.

clayhubler · Posted: Mon May 03, 2021 1:48 am Post subject:

Yesterday I made solid glass panel out of 1708 and today I epoxied it to the lower part of the transom instead of balsa. There are so many holes that get drilled in this part of the transom that I will just feel better knowing that there is no wood there. So the screws for the transducer, trim tabs, and the drain plug will all be into solid glass. In case you are wondering, yes, this did use a lot of glass and epoxy. Much more that I thought.

But, I'm happy with it. I am going to be working on the boat hot and heavy for a while, so hope to splash this thing sometime in june. I have some of the thick panel left over and when I do the balsa I am going cut in 4 pieces of the solid glass where the lower bolt mounting holes for the engines go so there will be no potential for water intrusion there either. Anything that is going to be below the water line and have a penetration is going to be solid.

Here is pic of the piece bonded into the boat. More pics are in the album with captions:
http://www.c-brats.com/modules.php?set_albumName=Core-rot-repair&id=20210501_124903&op=modload&name=gallery&file=index&include=view_photo.php

thataway · Posted: Mon May 03, 2021 9:26 pm Post subject:

You will have the strongest and best Buil C Dory. Probably last over 100 years! Thanks again for the updates.