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Volume of air in the Hulls http://www.hobie.com/au/en/forums/viewtopic.php?f=20&t=4331	Page 1 of 1

Author:	GAhobie [ Wed Jul 26, 2006 7:15 pm ]
Post subject:	Volume of air in the Hulls
I just bought a hobie 16 that has major delam issues. I am repairing them with the drill and fill method but I also wish to fill the hulls completly with expanding foam for structural reasons. I understand the foam will add weight and cause the cat to ride a little lower in the water but should give an added level of structrual stablitly to a set of hulls that were in really bad shape. Can some one tell me how many cu.ft. of air the hulls contain?

Author:	mmiller [ Thu Jul 27, 2006 5:27 pm ]
Post subject:	Volume?
Sorry, don't know. Never seen it posted. You are looking at a heavy boat if your fill it up. At 2 lb per sq foot, I have to think the hulls are going to be 30-40 lbs more each? Just a wild guess.

Author:	Hammond [ Fri Jul 28, 2006 12:28 am ]
Post subject:
You can not do this, even if you were able to place a filling tube to the bow and pull it back as you filled the hull, the expanding pressure will explode the hulls, additionally, the foam expands due to release of gas. Sealed hull means no release for the gas. As several sailboard manufactures found, this foam has a tendancy to look fully cured until it heats up and then the boat once again explodes. Hi-Tech a top manufacture had boards made by Water dogs and these boards blew up like baloons. Also consider, there are styrene foam blocks in bags in each hull. Maybe it is time to consider a new/newer boat. One other issue, even "sealed" foam will take on some water, and once saturated, it ususally will not release it making the already heavy boat really heavy.

Author:	mmiller [ Fri Jul 28, 2006 10:34 am ]
Post subject:	Foam
HAMMOND is right on... Not a good idea.

Author:	Windschief [ Tue Aug 01, 2006 1:14 pm ]
Post subject:
Hi all, first time I'm here, just got into Hobie-cating with a H16 and I love it - BUT I have the same problem here with the delam issue, now I thought the foaming was really a good idea - should add major stabilty and in case it still breaks somewhere outthere it would stay afloat ok it expands, thats why it would be good to know the volume, as I understand it would explode - but only if you put to much foam in there. I take the wild guess of 20lbs foam per hull (so about 10cufeet) as pretty close. the weight issue I would accept having only 2 skinny persons sailing it anyway. I certainly don't want to lose that baby by blowing it up, what about drilling one or more small "breathing holes" or even injection holes which can be patched afterwards? What about not filling the entire hull but only the weak part? well greetings and I guess u'll see me here more often from now on

Author:	ALEXSAILS [ Tue Aug 01, 2006 1:53 pm ]
Post subject:
If I were u guys, I would just pour foam around the pylons to add rigidity and lock them in place....lets say 2cubit feet per pylon section. they sell 2 to 16 lb per square foot foam density, I would just use the 2lb stuff. Before foaming making sure pylons are well bonded inside the hull (deck and keel) As per the delam I would treat with a traditional method of drill and bond by injecting epoxy or resin.... No need to foam the entire hull. Install deck plates to deal with the foam near pylons.

Author:	Windschief [ Wed Aug 02, 2006 11:12 am ]
Post subject:
sounds good too, now another idea, since getting that resin injections down here is quite a task while some fiberglas wouldn't be too big of a problem: if i would cut the top layer in a 3-4'' wide stripe from from lets say about 6'' from the front pylon towards the bow, open the layer, apply a layer of fiberglas and close it up again (and maybe try and inject some resin on the sides between the layers still), would that be possible and usefull? I guess it depends how far the layers are already seperated...

Author:	GAhobie [ Wed Aug 02, 2006 4:19 pm ]
Post subject:
The way it sounds is the the main issue with the hulls blowing up is not having enough air to cure the foam. So what if I were to make a lot of smaller pours maybe like 1/2 cu/ft at a time. Leave enough time for the foam to cure and then pour the next layer. Would this take care of the late expansion problem. Anyway is there any way for a Hobie engineer to tell me what the buoyancy of a 1977 H16 is in lbs cause I can get real close too the air volume from there?

Author:	ALEXSAILS [ Wed Aug 02, 2006 4:33 pm ]
Post subject:
I dont feel there is need to pour the entire hulls full of foam,,weight weight weight and then if u need to make a repair its gonna be nearly imposible with all that foam inside. just my opinion!

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