hull repair discovery

I am sure that I am not the first to discover this method of fixing soft spots on the tops of your hulls but it was new to me and made it super easy.
I have done the traditional method before of drilling holes every 2 inches and filling void with epoxy in syringe. I have had pretty good results but its time consuming and messy. not to mention creates lots of small hole to re gel coat or fill in with bondo. I feel like it does a pretty good job of reattaching the delamination but isn't perfect.

So I recently acquired some spare hulls with some pretty serious soft spots- 8" x 20" long. I was going to do the traditional method when I spotted an"expand -a -foam" can in the garage. It was such a large spot that I thought maybe I can put this stuff in first and then when its set up , I can do the epoxy. Well, I drilled one hole in the center and then a hole at either end of the soft spot. I put about 1/4 of the can in till it started expanding out of the holes on the edges. I put electrical tape of the holes to stop the expanding foam from escaping. The tape held for a bit but the foam eventually won and I ended up having to temporally stop up holes with drywall screw. (keep some acetone on hand to help clean up foam before it drys and wear latex gloves as the stuff is super sticky and hard to remove) So 1 hour later, the hull was rock solid and I didn't need to come back with epoxy. I was amazed at how well it worked. I would say it has firmed up the soft spot better than any of my epoxy jobs. seems to have filled the void and resealed the delamination very solidly.
Time will tell how it holds up but for now I am very pleased. Less drilled holes, 3 compared to 20 with epoxy method, to touch up and better end product. The foam I used was the lesser expanding foam for cracks less than 1". Cost about $3 a can.

Curious to see if other have tried this method and if it has held up over time.

I'd really like to see what the inside of the hulls look like where you did this.

The inner fiberglass layer is not nearly as stiff as the outer. I'd wager that what you've done is separated the inner skin from the foam core and created a huge blister on the inside. Only time will tell whether your repair will hold up.

Urethane foam has great adhesive properties (Gorilla Glue has a similar formulation), but controlling the expansion is difficult if not impossible (as you found out).

I would think that foam would cause more delamination when it expands, making for a larger area effected.

_________________
JKK
83 yellow/ white decks Hobie 14 Corando turbo
82 yellow hulls Hobie 16 Cat Fever
84 yellow hulls hobie 16 Yellow Nationals
plus a few extras that I'm restoring

and... the stuff is typically not closed cell foam and can become saturated.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

There are some great pictures of the inside of a hull on this forum, just need to search for them. Matt Bounds had some great ones posted on here.

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Steve
2017 Hobie 16 "Cayman" sails 114795
1985 & 1973? Hobie 14 "Sea & Ski"

Yeah, I'm not sure what it looks like on the bottom either. A fair amount of the foam escaped out of the holes at the end and I tried not to inject too much foam. All I know that for now it feels like one of the most solid repairs I have ever seen. I do know the stuff is very very sticky and nearly impossible to get off once dried. I think the trick would be to just inject the smallest amount possible and wait a bit and then a bit more until the foam just started to come out the other holes. I am glad I used the foam with less expansion (small cracks < 1" ). Anyhow, thanks for everyones imput. Winter has set in and sailing is done for the season but I will update the post in the spring to report on how repair is holding up.

Picture of hull cross-section:






The YouTube video "Anatomy of a Hobie 16" by Surf City Racing shows a H16 hull cut up into sections (WARNING: a Hobie hull was destroyed while making this video).

https://www.youtube.com/watch?v=nEZJd-LpUws

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Tim
84 H16
82 H16
87 H14T
Tortola Sails: 115222
Blue Prism Sails: 88863
Clearwater, FL