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Redline Hull Reinforcement
http://www.hobie.com/forums/viewtopic.php?f=13&t=49780		 Page 2 of 3
Author:  Tropical guy [ Thu Jan 30, 2014 10:55 am ]
Post subject:  Re: Redline Hull Reinforcement
Very nice work for such a tough place to access. I just wanted to add a suggestion for those doing internal hull repairs regarding material choices. I have experimented over the years with layups for molded RC racing planes to creat "hulls" with stiff areas blended to impact resistant zones yet preventing twist and stress failures. While carbon fiber is great for areas you want to be as stiff as steel, it can create stress points at its edges and increase the chance of failure. Blends of S glass carbon and kevlar are available and give you options that are great for hulls. Kevlar is hard to cut but manageable. It provides a highly flexable patch yet with extremely high impact resistant. It is very light as well. Glass is great for bonding and resin up take. For the sides of hulls a blend of the three would likely be superiour to a hard spar. http://shop.fiberglasshawaii.com/ This is just one source of many outlets for fabric mixtures. Your repair above was great for a section that no flex can occur at and your tapering of the carbon thickness is the right idea to avoid focusing stress. If you do use a solid spar I would add a bit of kevlar under it to spread the stress to the hull.
Cheers, Steve
Author:  srm [ Thu Jan 30, 2014 11:07 am ]
Post subject:  Re: Redline Hull Reinforcement
Thanks for the positive feedback. This repair/reinforcement is a bit of uncharted territory for me. Minimizing edge stress concentrations was definitely a concern and the reason for generously overlapped patches. If I go with the reinforcing stringers/spars I will likewise use a tapered design where the thickness reduces at the ends in order to minimize stress concentrations.

sm
Author:  areisenweb [ Sun Jun 15, 2014 1:00 am ]
Post subject:  Re: Redline Hull Reinforcement
Srm

Thanks for sharing your hull reinforcement work.

I'm considering doing the same for my 1983 hulls. I'm seeing some hairline cracks in the gelcoat forward of the front cross beams. They are not redline hulls.

Last year, I added the extra chainplates, and repaired a large deck delamination in the port hull aft of the board trunk. Delamination repair looks ugly, but the deck is stiff again. I was also thinking about adding deck ports here, but reinforcing the rim with carbon fiber.

How many yards of carbon tape and fabric did you end up using?

RR
Author:  srm [ Mon Jun 16, 2014 12:36 pm ]
Post subject:  Re: Redline Hull Reinforcement
I think I ended up using about 1 yard of 50" wide fabric, 2.5 yards of 6" wide tape, and 16 oz of resin.

sm
Author:  Matt15 [ Fri Dec 04, 2015 7:34 pm ]
Post subject:  Re: Redline Hull Reinforcement
sm i'm about to undertake a similar repair to an Australian BB coded H18 estimated to be about a 96??? model.

Taking on water on my last sail and not being satisfied with a visual inspection I used the air mattress pump and soap spray to find these cracks which became easier to see with the air pressure pushing out on them. I've removed the channel and bolts here:
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And the other side:
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The inside layup area looks to be re-enforced with a thin layer of glass and a white glue (instead of red) used by glue gun without even applying pressure to bond it into the corner area. On one of my photos you can see a small opening where the crack is. I've only sailed this H18 twice and i'm sure glad i used a front cross bar as the possibility exists for huge failure.
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So i'm keen to get working on a similar repair that you've done sm. Do you feel the anchor plate kit is a must and worthwhile addition here?
I have the anchor plates on the side stay areas but not at the cross bar ends.
Author:  srm [ Sat Dec 05, 2015 5:55 am ]
Post subject:  Re: Redline Hull Reinforcement
I would definitely add the anchor plate kit, especially since you're seeing cracking. It looks like adding the fiberglass/carbon patch to the inside of the hull shouldn't be too bad. Just grind away the white glue, fillet the area if needed, and then laminate in the patches. It's best to take the hulls apart for this project.

sm
Author:  Matt15 [ Mon Dec 07, 2015 3:35 am ]
Post subject:  Re: Redline Hull Reinforcement
Cheers sm, i've ordered them today. Still unsure I want to take it all apart - i do have an area i can safely turn my H18 on its side which would help alot.
Thanks again for your advice and of course these detailed pictures of your repair!
Author:  srm [ Mon Dec 07, 2015 10:23 am ]
Post subject:  Re: Redline Hull Reinforcement
It is much easier if you can take the boat apart - let gravity be your friend. When you pour the resin into the hull/deck joint to create a fillet, you want that to be the low point. Also, when you laminate the glass/carbon, it needs to wrap around the hull/deck joint area, so again, you want that area to be down so the cloth doesn't fall off while you're trying to adhere it to the hull. With the boat apart, you can flip the hulls into whatever orientation works best.

sm
Author:  Matt15 [ Mon Dec 07, 2015 11:11 pm ]
Post subject:  Re: Redline Hull Reinforcement
Yeah i think your right and the extra effort will be worth it long term. Today I bought some double bias cloth @ 400gsm and also some Qcell for filling. I'll post back when its done.
Author:  rickmatos [ Tue Apr 04, 2017 12:23 pm ]
Post subject:  Re: Redline Hull Reinforcement
hi,

Did you ever get to install the stringers? How have the hull reinforcements worked out to date?

Thanks,
Rick
Author:  srm [ Tue Apr 04, 2017 3:20 pm ]
Post subject:  Re: Redline Hull Reinforcement
The stringers have been installed, yes, but the hull's have not been closed back up from the project. It has turned out to be a very long project. I ended up using "Prisma Composite Preforms" stringers rather than trying to make my own. They are sold in four foot sections and I ended up splicing two together to make eight foot long stringers that started at about the front of the daggerboard trunk and went forward to about the bow tang. The hull sidewalls are very solid now.

Two access holes were cut in each deck in addition to the access port already there.

Image

Then the inside of the hulls were sanded and the stringers glassed in. A pretty time consuming process. The hull was placed on its side and each stringer was individually installed and weights were placed on top to hold it in place while it cured. I had quite a few pictures of the stringers installed, but haven't been able to find them.

Image


The holes in the deck are in the process of being glassed back in place. Again, a time consuming process. Reinforcement flanges are laminated and cut to size. Then epoxied in. Then the section of deck is epoxied back in place, and large fender washers are used to make it planar with the existing deck. Then the seam is glassed over, sanded, filled with putty, re-sanded, and gelcoated. Next will be trying to replicate the non-skid.

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Still more work to do, but it's getting there.

sm
Author:  jim-doty [ Wed Apr 05, 2017 2:57 am ]
Post subject:  Re: Redline Hull Reinforcement
Wow!
Author:  SabresfortheCup [ Wed Apr 05, 2017 2:48 pm ]
Post subject:  Re: Redline Hull Reinforcement
Wow indeed, that's some serious dedication!!! I have to say, I'd probably have just gone looking for another/newer boat at that point, but I suppose that would only be delaying the inevitable. Sooner or later, reinforcement like that would probably be necessary even on a 90's or 2000's hull, I suppose. And if you're not taking your only H18 out of commision to do the work, it's much easier to pour yourself into a big project like that, or get it taken care of as time allows. I'm always in a hurry to get back on the water! :lol:

Out of curiosity, why didn't you just buy one of the hull sets Hobie offered a few years ago? Are the redline hulls really that much lighter than even the latest production run of H18 hulls? (Not to offend or diminish the work you've put into it, as this project is clearly something that you've thoroughly thought out in advance! And it's something that's probably doubled the lifespan of your hulls!)
Author:  srm [ Wed Apr 05, 2017 4:00 pm ]
Post subject:  Re: Redline Hull Reinforcement
Well, the replacement hulls were several grand a piece each. Not really in the budget. This was more of a "let me see if I can do it" project. Either fix it or ditch it. As you mentioned, I have another 18, so taking this one out of commission for a while really hasn't been a big deal, so why not try to save a set of hulls? It's been a fun project and a good learning experience so far.

We'll see how it works out.

sm
Author:  Matt15 [ Fri Apr 14, 2017 10:01 pm ]
Post subject:  Re: Redline Hull Reinforcement
That sure is dedication srm. I'm sure those stringers will give this H18 afew more decades yet, great work.
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