Invested in a Hobie 18

Construction adhesive is probably much too viscous to flow into the space between the core and skin.

I think using screws to pull it together is a good idea for the large areas. You would want to use a fender washer under the head of the screw to minimize the depression caused by the screw head. You also would not want to punch all the way through the inner skin until you have injected the epoxy, otherwise it will just leak into the hull as Sabres says.

sm

Thanks! I have ordered som Loctite polyurethan construction adhesive. Gonna give it a try.

Another question is how and where to mount the spin pole. Alt 1 in the pic below is what im working on but i have some concerns about drilling in the crossbar close to the mast mount and maybe make it less strong.
Alt 2 will give additional stress to the dolphin striker.

Whoa there buckaroo! Having worked with most of the major brands and types of construction adhesive (on construction projects) and fixed my share of delaminated hulls, I agree with SRM that construction adhesive is WAY too viscous. Just because one person claim they did it (someone else filled their hull up with expanding foam) doesn't make it a sound way to repair the hull. If you want to go down that road then I wouldn't spend another dollar putting on wings, spinnaker or anything else because after you screw up the current hulls with the adhesive you are going to have to source another set of hulls

_________________
2001 H18 w/SX wings & spinnaker #16740 (purchased new)
1989 H18 w/SX wings #14565 (purchased new, sold 2000)
Would buy another if Hobie would build it.

+1000

This is what I've been trying to say the whole time. The hulls on this boat are in sad shape. They need to be repaired (if that is even possible) or replaced before dumping tons of time and money into other things like wings and a spinnaker, but the OP doesn't seem to want to believe this.

sm

christerljung, srm and Neubar are 100% correct. They are some the most knowledgeable and experienced sailors on this forum, and srm especially is definitely THE most knowledgeable on the H18, perhaps with the exception of Matt Miller or MBounds and a handful of others. These guys know so much because they've torn down and rebuilt, broken and repaired their own boats and others. If they haven't done it before, they've seen someone who has.

The boat you've bought is in VERY bad shape. Hulls delaminated to that point WILL break up and fail on the first sail in anything more than a moderate breeze. I'd be concerned about rigging the boat in my driveway, as the tension on the forestay & bridle wires will probably cause considerable flexing in the weakened bows. Most experienced cat sailors would've walked away from it then and there. Now, we understand that you put money into the boat and that H18's are probably rare in Sweeden, and we'd like to help you fix the boat or get a replacement and get you out on an H18 as much as possible, but you need to fix those hulls before even considering adding on to the boat. The reason we're so focused on that is that we aren't sure they can truly be fixed, or at least not with considerable expense and modification, and probably by a professional. The soft spots you have are much larger and in a much more important location than most others, and are likely indicative that the rest of the boat may soon delaminate. Better to find out it's irreparable now than after you've installed wings, a spinnaker, etc.

The other concern that I pointed out is experience level. Spinnaker sailing on a catamaran nearly doubles the work of the crew, and on a two man boat that you're unfamiliar with, there's already a lot to learn. You need to get comfortable sailing the boat as is before adding a significant modification such as this. The boat was never designed to have a spinnaker. It can be added, yes, but if it's not used properly or installed properly, you can easily snap your mast in half, break a crossbar, break your hulls, etc. One fellow on here (apologies, I don't remember who... John Lunn, perhaps?) has a story about someone falling off a wing after capsizing the boat under a spinnaker and fracturing a vertebra in his back. He was fortunate that his wife was a trained medical professional and able to get help quickly. Even with experience, things can go wrong. The H18 on it's own can be a handful even under the best conditions, so it is important to get a handle on that before adding on. Note too that wings also add stress to the crossbar & hulls. Later Hobie 18's had additional fiberglass & stainless steel reinforcement at the crossbar connections to handle the added stress of the wings.

You're correct that drilling into the crossbar weakens it, but the dolphin striker was never designed to carry a non-vertical load (which it will, as the spinnaker pole carries some of the driving & healing forces from the spinnaker). Personally, I've only ever seen the pole attached to the crossbar, so without taking the time to reverse-engineer the boat, I wouldn't stray too much from what others have done.

My buddy fractured vertebrae # C-3 when his H18 was hit by a gust, and he fell badly.

This was a lesson to be learned....
including what footwear to have, to always wear a PFD, to check the thickness and length of your mainsheet and its ease of operation, to travel with a phone or VHF radio, and to sail with someone who knows NOT to move you when your neck is fractured! (He lay in the water for nearly two hours before they could locate a fracture board so they could move him to shore).

He was crewing, standing on the outside of the wing, wearing Crocs (silly guy), and he had shortened his mainsheet to have less line on the tramp.
Another friend was at the helm, and even though he released the uncleated mainsheet, it was not enough as the H18 rose up quicker than expected when hit by the gust.
(These guys have been windsurfing, sailing mono-slugs and cats for years, so they are not newbies).
As the H18 lifted a hull, way up there, he lost his footing, rotated as the H18 started to capsize, and fell head first into the other wing, fracturing his neck.

He is fine today, and no longer sailing for other (medical) reasons.

Would you drive a Porsche 911 Turbo in winter while using summer tires?
Performance catamarans are fun and exciting, however, I suggest they should be sailed with respect.

_________________
2015 H16, with spin,
SOLD 1989 Hobie SX18 Sail # 1947 "In Theory..."
'Only two things are infinite, the universe, and human stupidity. But I'm not sure about the former.'

I hear you.
The hull repair will be done and when spring arrives the "Swedish Craigs-list" will fill up with some alternative used Hobie 18:s hulls, hopefully in a better shape than those i got now.

At 48 sec into this instruction they mount a pole-plate to the crossbar. Some drilling seem to be involved.
https://youtu.be/Pmckx-DuQt0?list=PLMbF ... deIe3zXW1C

That is the identical kit that I have mounted on my SX18, and yes, you have to drill.
However... without thinking it through, I should have used Stainless Screws instead of rivets.
When you mount the Tiger spin pole bracket, you can no longer remove the tramps for winter storage !
I had to come up with an alternative solution.

good luck with your repairs.

_________________
2015 H16, with spin,
SOLD 1989 Hobie SX18 Sail # 1947 "In Theory..."
'Only two things are infinite, the universe, and human stupidity. But I'm not sure about the former.'

We don't mean to lecture, just trying to make sure you know what you're up against. If you're fully intending to replace the hulls if you can't repair them, and you've got the time and money to buy the add ons, then by all means!

On the other hand, I'm jealous you've got a spinnaker setup! I'd love to try a spin on my 18, but they're pricy and hard to come by, and as one who mostly rigs off the trailer, I don't need to add more steps to my setup and teardown!

Once you do get things sorted out (frustrating and tedious though it may be), I'm sure you'll have a blast sailing the boat, I know I can never get enough of it! (Except when the wind gets light... then things get terribly frustrating and boring. Downwind in light air, you might as well swim back, lol)

Don't discount the setup on the wings either, getting those properly aligned and installed takes some finesse too!

(P.S. Thanks John, I knew I was missing some of the details! Still gives me chills thinking about what could've happened and how badly things can go wrong)

I have to machine a new 80mm pin for the mastfoot base. (the longer one). I suppose the original was made of stainless steel? 8mm aluminium would be too weak? I already got stainless steel material but it is easier to work in aluminium.

thanks
Christer

As far as your new pin goes,,,it depends on what you want to win the war.... my pin is aluminum.. you could use stainless... but the force is going to go somewhere. with a strong pin, you have only transferred the force to the much more expensive mast foot casting, and the crossbar step casting. i would rather just replace the pin. they last long enough anyways. just don't try to sail with them inserted..... i just use a stock available diameter, and cut to length, with a bend on one end (for handling, and a small hole for retaining line) "machine" this part? WAY overkill........

I didn't know that the pin should be removed? But i guess it's obvious since the mast should be allowed to rotate. Some of my students works in a training machining shop and they love to make real parts instead of fake school-things.

Guys, don't shout at me: I always forget that my pin is tied to a piece of line and is sitting quietly in the tramp pocket, waiting to be used.
So I grab an old screwdriver, push it though the hole, raise (or lower) the mast, and remove the screwdriver.
Easy-peasy.
(Yup, pin is used for raising/lowering only).

_________________
2015 H16, with spin,
SOLD 1989 Hobie SX18 Sail # 1947 "In Theory..."
'Only two things are infinite, the universe, and human stupidity. But I'm not sure about the former.'

I totally agree with this - don't use the Loctie PL construction adhesive for this . I had a spare parts boat that had really damaged hulls and I wanted to fix it as a winter project without putting a lot of money into it. (Repaired the hole on the side of the hull with balsa wood and fiber glass - that worked out fine) Then had a large soft spot in about the area 1 you were considering putting your inspection port in (it was a Hobie 16 but same concept) I too read the post about the Loctite construction adhesive and went that route incl. trying to screw the inner and outer fiberglass layers together. The Loctite construction adhesive is a good glue, but I don't think it is flexible enough for this application. So after putting weight on that area a few times it was starting to flex again...

I used Git Rot to repair a soft spot on my Hobie 18 and that has lasted all season - and it's in the spot where the skipper sits so it gets a lot of abuse - Git Rot is not cheap, but I like the way it has worked for me.

I've done the same!

The original is stainless, and costs ~$3.50 USD from a Hobie dealer. If the pin snaps while stepping the mast, it could easily come down and seriously damage your boat, your car, or result in significant injury/death if it lands on someone. Your mast step is never going to break or shear from stepping the mast, no way no how. The available surface area and cross-sectional area is much greater on the mast base than it is on the pin.

That said, I've just run some quick numbers. When stepping the mast, the pin is under ~40 lbs of force at its worst point (0 degrees and 55 degrees are local maxima, and about the same force).

With a 1/4" pin, that's 815 psi in shear stress. However, due to the gaps between the hinge and the base, there's bending stress as well, on the order of ~12-15 ksi. Yield strength of annealed 6061 aluminum is <8 ksi, while 316L SS is >25 ksi. Ultimate tensile strengths are <18 ksi and >70 ksi. 6061-T4 and T6 are considerably stronger, with T6 being half as strong as SS in UTS and actually stronger than SS in yield strength.

Personally, I'd just buy the SS pin. It's cheap, and plenty of safety margin. My pins usually end up getting a little bent as is, though I think that's mostly because I've forgotten to remove it before tensioning up the rigging on occasion.

On the note of the soft spot repair - I use West Systems 2 part epoxy (105) and slow hardener (206). 4 soft spots down, EPO rudders re-surfaced and deck/hull lip separation repaired in 3 years and still going strong!