Airex Core

Discussion in 'Downeast Projects and Boat Building' started by Ripcat, Aug 22, 2018.

  1. Ripcat

    Ripcat Senior Member

    Joined:
    Sep 7, 2012
    Posts:
    306
    Likes Received:
    76
    Location:
    Hampton Falls, NH
    On the search for a DE. Interested in one that is Airex cored. I was under the impression that Airex would not absorb water but read a post on here that contradicts that.

    Airex absorbs water. True or false?
     
  2. CapeCodNorton

    CapeCodNorton Senior Member

    Joined:
    Sep 6, 2015
    Posts:
    108
    Likes Received:
    64
    Occupation:
    Firefighter/Paramedic Hyannis Fire Department
    Location:
    Yarmouth Port, MA
    Boat Make:
    23 Crowley Beal
    I rebuilt my 19 Norton with it and out of curiosity left some scrap soaking in a bucket for several days. Pulled it out and cracked it in half and there was no water absorption passed the open cells on the surface. I would say once it is saturated with resin and glass it is impermeable to water and even it it wasnt it wouldn’t migrate very far or rot the core material. This is my only experience with it and I was impressed but others may have other things to say about it.
     
    Liberty1, PBianculli and Ripcat like this.
  3. Genius

    Genius Captain

    Joined:
    Feb 11, 2016
    Posts:
    1,794
    Likes Received:
    695
    Location:
    Rhode Island
    Maybe with a freeze / thaw cycle it could cause some damage that would appear like absorption.
     
    Ripcat likes this.
  4. LadyMaureen

    LadyMaureen Captain

    Joined:
    Apr 27, 2012
    Posts:
    681
    Likes Received:
    827
    Location:
    South Shore Long Island
    Boat Make:
    Wesmac
    I have a 42 Wesmac that is aired cored. I swore I would never buy a cored hull but after doing research I learned how different airex was from other coring materials. Needless to say I got over my fears and bought the boat. I have no regrets. I had a 38 Duffy (solid) , a 42 Wesmac (solid) and now an aired cored 42 Wesmac. There is no comparison in my opinion. My current boat is so much stiffer and better in a head sea than my previous two solid hulls.

    Just my opinion. Good luck whatever you decide.
     
    PBianculli likes this.
  5. Ripcat

    Ripcat Senior Member

    Joined:
    Sep 7, 2012
    Posts:
    306
    Likes Received:
    76
    Location:
    Hampton Falls, NH
    I really appreciate the feedback. I had the same fear, also did research and here I am with an airex cored hull as my top choice. I've been following your work on the new rig...very very nice.
     
    LadyMaureen likes this.
  6. fortier256

    fortier256 Captain

    Joined:
    Feb 10, 2013
    Posts:
    505
    Likes Received:
    161
    Location:
    Narragansett Bay
    Boat Make:
    Fortier 26
    Fortiers are airex cored. No water intrusion anywhere in core. Have had the usual leaks around port lights etc but never any moisture readings in the surrounding core. As stated above a good core makes for a very stiff hull.
     
    ckinneavy, PBianculli and Ripcat like this.
  7. skyeboat

    skyeboat Senior Member

    Joined:
    Dec 2, 2014
    Posts:
    149
    Likes Received:
    45
    Location:
    Rhode Island
    Boat Make:
    Coastal 27
    Airex is a good core and does not absorb water. Divinycell, Corecell and other modern cores also do not absorb water.

    The key point in this conversation is to have laminates which are well bonded to either side of the core, and is "thick enough" , whatever that means to you. Coring gives superior sound deadening , much improved thermal properties and 3 times the stiffness of a single skin laminate. Improperly installed core of any type will be a problem, but is almost always fixable.
     
    Keelboater and Ripcat like this.
  8. EZ1

    EZ1 Member

    Joined:
    Aug 16, 2018
    Posts:
    85
    Likes Received:
    36
    Occupation:
    boat builder
    Location:
    Marina del Rey
    Boat Make:
    Freya
    The problem with cored construction is usually not the core absorbing water--that's easy to choose the right core material to mitigate this potential problem.

    I was installing a bilge pump float switch on a Mapleleaf 50 while it was in drydock. Drilling into the inner skin produced a geyser of water a couple feet high! Thru-hull fittings had been installed without creating hard spots. Being as there was only foam core around the thru-hulls, inadequate sealing allowed water to enter. Unfilled core seams allowed water to disperse throughout the hull, presumably up to the waterline, judging from the amount of water which drained.

    If you buy a cored hull, make certain it is not cored below the waterline.
     
    EZ1,
  9. tailhook

    tailhook Captain

    Joined:
    Oct 15, 2011
    Posts:
    989
    Likes Received:
    311
    Location:
    buzzards bay
    Boat Make:
    31 JC
    Mapleleaf 50 is cored with what?
     
  10. EZ1

    EZ1 Member

    Joined:
    Aug 16, 2018
    Posts:
    85
    Likes Received:
    36
    Occupation:
    boat builder
    Location:
    Marina del Rey
    Boat Make:
    Freya
    Airex.
     
    EZ1,
  11. fortier256

    fortier256 Captain

    Joined:
    Feb 10, 2013
    Posts:
    505
    Likes Received:
    161
    Location:
    Narragansett Bay
    Boat Make:
    Fortier 26
    Sounds to me like poor build quality? The fiberglass must have delaminates from the coring to allow water to enter?
    You are a boat builder and I am not so you would know better than I but it sounds strange.
     
    tailhook likes this.
  12. EZ1

    EZ1 Member

    Joined:
    Aug 16, 2018
    Posts:
    85
    Likes Received:
    36
    Occupation:
    boat builder
    Location:
    Marina del Rey
    Boat Make:
    Freya
    Sorry if I was not clear. Because the thru-hull fittings were only tightened against a foam core, rather than a hard spot, they allowed water to pass, under pressure. The scoring between the separate blocks of foam had not been thoroughly sealed, and so allowed water to travel throughout the hull.
     
    EZ1,
  13. CapeCodNorton

    CapeCodNorton Senior Member

    Joined:
    Sep 6, 2015
    Posts:
    108
    Likes Received:
    64
    Occupation:
    Firefighter/Paramedic Hyannis Fire Department
    Location:
    Yarmouth Port, MA
    Boat Make:
    23 Crowley Beal
    So the issue you witnessed isn’t as much an issue with the material as it is with the manufacturing. A balsa core would have done the same thing but you would add rot to the equation and the hull would be shot but if this one is allowed to dry out and then the throughhulls decored and filled with resin to form a solid structure between the hull skins it’s no harm no fowl lesson learned. My CB23 has rotted balsa coring in cabin around the portlights where water migrated and this fall I’ll pull them, dry out and decore the rot then fill back in with Epoxy and airex and likely never worry about it again.
     
  14. EZ1

    EZ1 Member

    Joined:
    Aug 16, 2018
    Posts:
    85
    Likes Received:
    36
    Occupation:
    boat builder
    Location:
    Marina del Rey
    Boat Make:
    Freya
    Before we jump to this conclusion (that it is a simple fix to restore 100% integrity) let me relate the story of a large custom sportfisherman which had been built with an Airex cored hull and integral waste tank. By the panting of the hull when under way, when a (hidden) failure occurred in the laminate, raw sewage was pumped throughout a significant portion of the cored hull. I was not involved with this project, but learned of it through a professional publication.

    The reason I bring this up is to point out the risk of hidden damage to the cored structure due to hydraulic pressure from the hull's panting, as water is not compressible and the possibility exists for delamination. The Mapleleaf 50 I worked on shed 10's of gallons of water; it was just allowed to run out onto the ground; I made no attempt to measure the quantity. No telling how much water remained that couldn't find its way out.

    I would avoid any hull with coring below the waterline.
     
    EZ1,
  15. Downrigga

    Downrigga Captain

    Joined:
    Mar 25, 2016
    Posts:
    967
    Likes Received:
    489
    Location:
    Harwichport MA
    Boat Make:
    36' NB
    I know your really concerned about the cored hulls. Find out who finished it. See if they finish a lot of boats and do a good job. If the holes that were drilled in the hull were properly back cut and properly filled you have nothing to worry about. Pull out a thru hull and check it out. The only way your going to have an issue with a cored hull is if something was not done right. I would be less inclined to buy a hull that was not cored. A properly built hull with a core adds value to the boat in my opinion. If it didn't no one would be doing it. I believe Airex is a very good core but kind of a pain in the ass to use when laying up the hull. I also believe all the cores will absorb water but is only if you don't follow the proper protocol. My boat is a 2005 cored hull and I have had zero issues. Someone telling you to avoid a cored hull should take a ride up to Maine and learn how boats are built.
     
    Last edited: Aug 24, 2018
    Ripcat likes this.
  16. EZ1

    EZ1 Member

    Joined:
    Aug 16, 2018
    Posts:
    85
    Likes Received:
    36
    Occupation:
    boat builder
    Location:
    Marina del Rey
    Boat Make:
    Freya
    No need for insults.

    For over 40 years I've been a boat builder specializing in customizing yachts, have made passages aboard yachts from Florida to Panama and Washington to the tip of Baja, and have hands-on experience with repairing failures due to cores of honeycomb, foam, plywood and balsa. Also have visited boat yards from Maine to Florida, and from Washington to Cost Rica. A common thread among blue water boat builders and knowledgeable yachtsmen is this:
    Avoid coring below the waterline.

    There may be compelling reasons to sometimes do otherwise, say to break some speed record, etc. Otherwise one is well served to heed it.
     
    EZ1,
  17. Downrigga

    Downrigga Captain

    Joined:
    Mar 25, 2016
    Posts:
    967
    Likes Received:
    489
    Location:
    Harwichport MA
    Boat Make:
    36' NB
    Not insulting you one bit. Nothing wrong with a hull cored below the water line if the boat is built properly. You think otherwise and that is ok. We can agree to disagree. What boats yards did you visit in Maine? The water up this way is mostly green and many DE boats are not built for speed but they are very often cored.
     
    Last edited: Aug 24, 2018
  18. leaky

    leaky Captain

    Joined:
    Sep 9, 2014
    Posts:
    1,804
    Likes Received:
    556
    Location:
    NH
    Talking an older boat cored with "Airex" and a new boat cored with Airex core XXXX are two different things. There is Airex & "Airex" and different types of those materials have been in use since the 80's or something.

    Look up Airex and note the various products today, also be aware the term "Airex" is used to describe basically all structural foams casually, many of such foams not actually made by the brand Airex, similarly CoreCell which is a product by Gurit is used to describe all sorts of such foams that may not be CoreCell/Gurit (and might be Airex even :) )..

    My understanding, some of the older cores are not closed cell foam or did not work as well as closed cell foam today, and can soak up water. Not sure if Airex was around then or not, or if Airex products were really closed cell then or not, but even if some were - "Airex" often just means foam, and not all foams prevent water absorption very well, many of them it's more of a matter of time & pressure.

    If you are researching a foam cored hull I'd be asking/verifying what type of foam, specifically the exact product it was built with, and researching that, - which again, if you are talking brand name Airex today that might be one of 10 different options just with that brand, what they made 10, 20, 30+ years ago - beats me, but was different.

    Have heard of older "Airex" hulls being soaked, needing to be vacuumed out to remove the water (some method of putting a suction on the hull and pulling water out).. Similarly have had a boat builder describe issues with earlier types of "Airex" foam cores not being closed cell to me.

    Jon
     
  19. Frank Grimes

    Frank Grimes Captain

    Joined:
    Dec 20, 2011
    Posts:
    1,255
    Likes Received:
    356
    Location:
    N41°41'46.91" W070°15'35.13"
    The implications here are either all hull bottoms cannot be cored because all core material cannot handle the pressure of supporting a boat being driven at high speeds through various sea states, OR all boatbuilders cannot be trusted to build competently with core materials.

    All I can say there is that if either is true, Viking Yachts (among many others) appear to have some big-time class action lawsuits heading their way in the not-too-distant future.
     
    Downrigga likes this.
  20. Keelboater

    Keelboater Captain

    Joined:
    Oct 3, 2013
    Posts:
    4,240
    Likes Received:
    2,113
    Location:
    Clinton Harbor
    Boat Make:
    35' Bruno & Stillman
    Modern composites offer many advantages over solid glass - providing the craftsmen who use them adhere to the correct procedures. Find a rock solid builder - you found a rock solid hull for life. But fast forward to the third owner who went crazy with a drill while installing all sorts of useless crap in the worst possible locations and then the fourth owner is guaranteed to find all sorts of headaches because the third owner used silicone.....or nothing at all. I don't think it's the cored hull as much as it is the owners down the road and nobody has control over that. For that reason, solid glass will always continue to be sought after. However, from an engineering perspective you can't beat a properly cored hull that is dry.
     

Share This Page