1970 Larson Shark-trihull Restore

[Captain Smitty]

Hello, I'm new to this life of boats, but I decided I wanted a boat so I searched up and down endless craigslist ads and came across a 1970 Larson trihull. Before buying it I familarized myself with the "what to look for's". Boat has a working johnson 85hp with shifter and cable in working order as well. There were board covering the floor covered I'm dried up brittle resin but I thought no biggie I'm pretty fair at carpentry so I hauled her home. I flip the boards back to see what's underneath and found two long planks one on each side and a bulk of foam underneath. No stringers not even bulk heads. Does anyone know if this is normal or has this boat been frankinsteined? Thanks for any input.

 

[Woodonglass]

Re: 1970 Larson Shark-trihull Restore

I think pics are in order so we can see what you see. Open a free photobucket account, upload your pics, then use the IMG Code to copy and paste your pic into iBoats. Once we can see what you're talking about, I'm sure you'll get a lot of advice on how to proceed!!!:joyous:

 

[Captain Smitty]

Re: 1970 Larson Shark-trihull Restore

Thanks for the advice here's a few pic. 1st is after clear the deck.

 

[Captain Smitty]

Re: 1970 Larson Shark-trihull Restore

My foot is right above the wooden planks I found underneath the decking and just beyond my foot is approximately 16 inches of foam. My question would be are there any stringers below the foam or is the hull's structure supported by the foam? Any and all info would be great. Thanks

 

[Woodonglass]

Re: 1970 Larson Shark-trihull Restore

You are standing on a stringer...

I may be a foam filled engineered stringer but it is a stringer. It appears to me your boats hull is designed to be a structurally dependent upon the foam. You will need to restore it back the same way. If the two stringers are indeed foam cored and they are not water saturated you are in luck. You won't need to do anything to them. Have you confirmed the foam is waterlogged?

 

[Captain Smitty]

Re: 1970 Larson Shark-trihull Restore

I've pulled back the glass there and don't see any signs of the foam being waterlogged.Zero moisture. Should I dig deeper? Or just replace the planks that were there and begin constructing my deck. Thanks for your quick reponse.

 

[Woodonglass]

Re: 1970 Larson Shark-trihull Restore

Have you drilled into the stringers to see what's inside? I'd make a foam core sampler out of 1 1/2" pvc pipe. Cut some teeth in one end of a 2' section of pipe and twist drill it down into the foam until you hit the hull. pull it out and see what the foam looks like If its dry, then Yeah, you're a lucky fellow. I'd say put her back the way you found her. You've got yourself a Deck job and that's bout it.

 

[Captain Smitty]

Re: 1970 Larson Shark-trihull Restore

I used the technique you gave me and I have piece of mind now. Thanks. I also began to tear away most of the old deck and carpet. There is a piece on the bow that's glassed in doesn't seem to be original. You can tell better than I. Thanks.

 

[Woodonglass]

Re: 1970 Larson Shark-trihull Restore

I'm not quite sure I'm seeing what you mean. Clean her up a bit an point out specifically what it is.

 

[Captain Smitty]

Re: 1970 Larson Shark-trihull Restore

Ok will do.

 

[GT1000000]

Re: 1970 Larson Shark-trihull Restore

Hi and welcome, Capt.Smitty...

Do you mean this area?


Regards,
GT1M

 

[Captain Smitty]

Re: 1970 Larson Shark-trihull Restore

Thanks for the welcome. You beat me to it. Yes that's it.

I was thinking maybe reinforce it with a stringer or two then lay my deck. Let me know what you all think.

 

[GT1000000]

Re: 1970 Larson Shark-trihull Restore

Yeah, you can remove the bad and go back with the good...you can use a circular saw set to a shallow depth, a reciprocating saw, a jig saw, an oscillating tool or a grinder with some cut off wheels...
Just be sure to have on some PPE...fiberglass dust is very UN-forgiving to your eyeballs, skin, and lungs...
Woodonglass made up a really good PDF that shows some of the PPE...if I can find it I'll post it, if not, woody will be along soon with a copy...

 

[Woodonglass]

Re: 1970 Larson Shark-trihull Restore

Yeah cut all that out and start from scratch. Here's the pdf file..View attachment MaterialsList.pdf.

 

[Captain Smitty]

Re: 1970 Larson Shark-trihull Restore

You guys are aweSome. Thanks a lot for getting me this far. I'll wait for the pdf before I dig in any further.

 

[Captain Smitty]

Re: 1970 Larson Shark-trihull Restore

Thanks again.

 

[Captain Smitty]

Re: 1970 Larson Shark-trihull Restore

I'm glad I have almost all of the tools or this could get pricey. Alls I need is the mask and suit and I can get to work.