Balsa Core Construction

Chuck S · Posted: Sat Jan 03, 2004 10:02 am Post subject:

There are issues with balsa cored boats. You have to be careful of any thru hull or thru deck fittings or holes. If they're not properly sealed and bedded the core can saturate and eventually delaminate. The number of deck fittings on motor boats is minimal compared to sailboats and thru hulls on boats of this size unusual.

A cored hull achieves a lot of stiffness for literally no additional weight.

-- Chuck

Da Nag · Posted: Sat Jan 03, 2004 12:31 pm Post subject:

Howdy, Calvin - welcome to the group! As many others have stated, you can't go wrong with either boat. Both have solid reputations, and many satisfied owners.

Sawdust · Posted: Sat Jan 03, 2004 1:10 pm Post subject:

Bill,

The old Duster can add a little balsa fuel to the fire. It is really good stuff -- and is a significant factor in making our little CD's true Swiss Army Knives -- easy to tow, easy to launch, economical to cruise, and the list is endless. I'm in total awe of the 4.0+ NMPG that El and Bill get with a heavily loaded 22 -- and in all kinds of weather.

Daughter and son-in-law's 35 ft. Pierson, which was built in the 50's, has edge-grained balsa core decks and cabin top -- still absolutely like new. I've had two Florida-built boats with balsa core -- both are local boats here now and at least 30 years old. Both still in great condition.

It still is wise to keep the water out by properly sealing for any possible water intrusion, but when weighing the plusses and minuses -- no contest. I guess the best indicator is the way the old CD's hold their value year after year. If balsa core construction was bad they'd be selling like Bayliners!! Also good boats, but a quick browse of Boat Trader shows the percentage of new cost a 20 year old Bayliner sellls for vs a 20 year old CD.

Gotta go play in the snow!

Dusty

Chuck S · Posted: Sat Jan 03, 2004 8:52 pm Post subject:

My J/24 had a balso cored hull and deck. On this boat we had two thru hulls below the waterline, but never had any water weep into the hull. In this case the technique was to route out balsa for a good 1/2" around the hole, fill it all with epoxy and microballons, then drill the hole again. This created a solid hull at the thru hulls.

Deck was much more of a chore, but racing sailboats have dozens of deck fittings to handle sails. Good backing plates and lots of sealant. Did I mention lots of sealant?

When I added the turn deck fitting for the anchor line on my 16 cruiser I used the same technique as a thru hull as this fitting will get wet a lot.

-- Chuck

thataway · Posted: Sun Jan 04, 2004 11:00 pm Post subject: Balsa Core

If you put a hole in a balsa core laminate, you should drill the hole, grind out the adjoining balsa (a Dremel tool or even a coat hanger L shaped in a drill will do this), fill with thickened epoxy and bed well. I was on a 55 foot cutter whose hull is balsa (3" planks, glass inside and out) when we hit a submerged shipping container. That balsa saved the boat and there was no significant water intrusion--and the glass dammage was only on the outside layer. The C Dory is well laid up and the balsa just gives a greater margin of safety--the bottom lamination is more than sufficient without the balsa or inner laminate.

Chuck S · Posted: Mon Jan 05, 2004 7:34 am Post subject:

Bob --

We used a good size Allen wrench in a drill chuck to route out the balsa at the thru hulls. Works well and these are pretty strong.

-- Chuck

DaydreamC-26 · Posted: Mon Jan 05, 2004 11:24 am Post subject: Balsa core - "holes in my boat"

For those of you who haven't drilled holes in your boat and may not quite understand what 'Chuck S' and 'Thataway' are explaining visit the West System Epoxy website at www . westsystem .com (added spaces - don't yet know how to do links) or pick up one of their free repair / product manuals at WM.

Also try This Old Boat by Don casey or The Fiberglass Boat Repair Manual by Alan Vaitses.

Those of us restoring 38 year old sailboats know all about holes in boats, decks, etc. Shocked

PS: If you really have the urge for a thru hull...Let Les install it.

Doryless in PA

Chuck S · Posted: Mon Jan 05, 2004 9:38 pm Post subject:

I was really hoping there was a solid glass section in the "blige" of these boats, but even that section is cored. Not that I wanted a thru hull, I just wanted to put a depth sounder and shoot thru the hull.

-- Chuck

C-Bill · Posted: Wed Mar 31, 2004 7:19 pm Post subject: Balsa Core Hulls

This is interesting reading.

http://www.yachtsurvey.com/cored_hull_bottoms.htm

http://www.yachtsurvey.com/core_materials.htm

http://www.yachtsurvey.com/more_on_cores.htm

http://www.yachtsurvey.com/searay_balsa_core_bottoms.htm

Sea Wolf · Posted: Wed Mar 31, 2004 10:14 pm Post subject:

C-Bill

I've read all of these before. David Pascoe is a Florida Marine Surveyor who sees a lot of balsa cored boats that have been neglected and/or had hardware installed incorrectly (without proper sealing of the core). Add to that the warm salt water environment of Florida, and the fact that many of these boats are left moored, and you have a recipe for problems.

Fortunately, most of us who have C-Dorys take very good care of them, know how to install hardware and reseal the core, and usually dry-store the boat or at least care for it while it's being moored. It's not a major issue for us, and the cored hull generates the great stiffness of the C-Dory hull without an internal stringer system or a raised inner floor, which provides much more room inside the boat as well as a lower center of gravity and a much lighter, more efficient hull to propel.

CORED CONSTRUCTION WORKS FOR C-DORYS!!! This great boat wouldn't be possible without cored construction. My $.02. Joe.

C-Bill · Posted: Wed Mar 31, 2004 10:47 pm Post subject:

Sea Wolf...

I agree with you one hundred percent. It is something to be aware of for those who consider a thru hull transducer or water pickup. To do it properly is a difficult task. Neutral

C-Dory does an excellent job of construction with this material.

Bill

Da Nag · Posted: Wed Mar 31, 2004 11:59 pm Post subject:

I've read Pascoe's observations before as well. Not to discount them, but he does tend to focus on much larger boats, where the stresses are bound to be higher than a C-Dory. Also, he's smack dab in the middle of hurricane country, and many of the vessels he's pointed out damage on were involved in weather related accidents at some point in time.

C-Bill · Posted: Thu Apr 01, 2004 12:37 pm Post subject:

I would imagine that there are C-Dory owners on this site who could benefit from being aware of the damage potential of a loose screw at the base of the fuel tank strap. Although most owners trailer their boats, the fact remains that standing water inside of the boat can also result in extensive damage.

Another vulnerable area is the wood inside the transom. This is very similar construction and the sealing of this wood from water is very important. I would like to stress knowledge of wood core construction in a none structural aspect for the average boater. After the damage has occurred, the boat owner is subject to structural problems and the devaluation of his or her investment.

I'm certain both Da Nag & Sea Wolf would look for this kind of damage before buying any used C-Dory. And yet, you question the need to post informative sites such as this?

The use of balsa core construction has existed for decades. It is an excellent structural benefit to both large & small boats. Whether the boat be large or small, in a wet or dry climate, hurricane or the wet Northwest areas, the fact is the core of your boat needs protection to remain strong.

Bill Confused

Da Nag · Posted: Thu Apr 01, 2004 1:07 pm Post subject:

Sea Wolf · Posted: Thu Apr 01, 2004 2:34 pm Post subject:

C-Bill: You're quite correct about the need to keep new boat owners informed about the need to understand the advantages, limitations, and need for care in working with cored construction. I was simply trying to put his (David Pascoe's) in perspective as compared to our experiences as C-Dory owners.

He's a very smart critic of some of the ways modern fiberglass boats are put together, and his whole set of writings consist of very strongly taken viewpoints, some of which (including those mentioned) sound quite alarmist when read at first by the newer or first time boat owner, and might just seem to indicate the whole C-Dory line up of boats are prone to premature failure throuh core decay. This is not consistent with our experiences at all. But it's a good point to remind new owners all about.

This brings up another point, which is that we recycle through many of the same issues here on this site as new owners/members come on board. Often the whole issue has been discussed two, three, or more times before, and most all that can be said now is on record and available between the the archives of this site, and the two C-Dog sites, either the current one, or the original one that has been archived.

Off the top of my head, I'm not sure how best to deal with this, but often a helpful member will look up one or more of the orignal discussions and suggest the newcomer read it while creating a convenient link in one of the responding paragraphs in their post. It's too bad we can't have a central search engine that has access to all the sources of archived material to make the search easier as well as an introductory paragraph in the membership sign up process that encourages new members to take advantage of the vast amount of knowledge that is already available before they ask a more detailed question if such remains after research.

On the other hand, re-discussing some of these topics gives all of us something fun to do, and often new points are brought up as well, so maybe what we're doing (first sentence in the previous paragraph), is the best approach, so we should just leave it all as is?!?!?

I'm looking forward to meeting you, C-Bill, in person, next October here at Shasta Lake.! Thanks for the comments and it was fun talking with all of you! Joe.