Hard Top Plans

[fg1]

The last hard top we made was 2 layers of 17.08 on top, laminated off-axis, and 1 layer of 17.08 on the bottom. No csm, too heavy, requires too much resin. That top was for a 65 foot sporty and was more than adequate. No matter what core you use, you're going to have to make compression sleeves for every bolt and penetration.

[Entourage]

I wish i could be of help here about the layers used, but mine was built in a mold with a chop gun and sprayed in resin. So im not sure about thickness. I can take some photos of the flange.

[Entourage]

Here is a photo of the base and the thickness of one of the window cutouts. Hope this helps

[BigLew]

Originally Posted by Islandtrader
This is wear I tend to differ with Gilly...I do agree it is a class and they are teaching techniques. However when I got my 21 the deck was shot...the balsa core was soaked and rotten. Everyone says it will work as good as...blah blah blah. As long as it is sealed. What everyone forgets is that once some one drills that first hole and does not over drill and epoxy, you start down a long slippery path.

Plascore is not that much more than balsa. Do once and do it right.

Sorry Gilly"

Originally Posted by pelican

can't agree more...especially on a hard top - holes are gonna be drilled - balsa quickly turns to sawdust,when it gets wet...

"Reminds of the old Fram Filter commercial, "Pay me now or Pay me more later!"

So many things in this life are this way.

[McGillicuddy]

Champ, it's your decision and coring foams are the current trend. Your grade will reflect your effort. All three options are viable. Here's a thought - use a section of each material and get back to us in 15 years.

Terry, you're right - composites may prove better long term. Certainly no apology necessary. But at this time I haven't seen any 40 year old foam coring other than in a couple of very heavy Boston Whalers. Strick mentioned Corecell and indeed that's the coring shizzle as it's even being used as hull coring. Plascore seems to be an exciting product but I don't know much about it. I know honeycombs (hex-cells) have worked for bees for aeons. My contrarian point of view was more aimed at preserving end grain balsa as a very acceptable coring.

I think fg1's point is important. Even the greatest composite advocates will insist on sleeving virtually all modern coring materials, especially foams. This effectively "seals" the deal, even with end grain balsa. Now we can't keep every knucklehead from drilling random holes in their boat, but ...

My 40 year old Seafari balsa is in great shape. My 47 year old 21 balsa has a couple of broad soft spots on the fore deck where the horns were mounted. Island Trader's 21 and mine both came from the frozen tundra of the Great Lakes region so you know freezing expansion of wet wood exacerbated the problem of laminate separation, as did fresh water to the rotting process. The former will likely happen with polyester and many coring foams too. Less likely with epoxy.

In Champ's case its a one-off hardtop with a camber that sheds water and is in the sun and wind all day. He's working for a top grade so you can bet he'll do a top notch job.

Pelican, I get where your coming from but, I think your point is more relevant to a cored hull than a hard top. I know you advocate sleeving for composites, and I'm sure the instructor does, too.

Weight of 12 mm balsa compared to similar thickness foam will be nominal and some foam composites may actually add weight due to greater absorption of resins. I ain't smart enough to do the math.

Anyway, Champ, good luck with the cool project. I look forward to seeing the results.

[strick]

Originally Posted by fg1

The last hard top we made was 2 layers of 17.08 on top, laminated off-axis, and 1 layer of 17.08 on the bottom. No matter what core you use, you're going to have to make compression sleeves for every bolt and penetration.

With only 1 layer of glass then sleeving would be a must. The top I pictured earlier weigh's less then 120# The bases of the piping are 3.5 inches diameter and there are 3/4 " diameter washers on the top. No dimples anywhere in the glass. If one decided to use balsa then I probably would agree that sleeving to prevent water intrusion would be a good idea. I dont think Balsa is a good idea on a roof especially when there are so many other good products out there....just saying...

strick

[Caymanboy]

Here's a little tip for you:
When mounting ant's, mast, rigger bases, etc. Drill and tap through the top, core and all, tighten down the bolts, then put your washer and backing nut on. Properly bedded of course! Get much better holding power that way, never seen one pull out or compress.
Strick is God! :-)

[Entourage]

Sorry i thought this was going to be a pilothouse, sounds like its going fiberglass top with the aluminum pipes supporting.

[pelican]

Originally Posted by McGillicuddy

Pelican, I get where your coming from but, I think your point is more relevant to a cored hull than a hard top. I know you advocate sleeving for composites, and I'm sure the instructor does, too.

balsa coring is balsa coring - it's a hard top - antennas are gonna be mounted,along with anchor lights and the actual bolts securing the hard top to the frame - that's alot of holes...great lakes region too - freshwater rots wood,seawater tends to preserve it...

a good example of this process was a 21 parker i worked on - 1yr old hull - the owner had a complaint of "cracking around hand rails on cabin top" - end result was the entire top was soaked,and rotting balsa coring - due to the lack of proper sealing techniques - parker replaced the top,under warranty...

technology changes,with this being a class,you would think the instructor would be teaching the latest techniques,using composites - what's mostly used in the repair/fabrication process,versus basically a "stone age" product such as baltek...most people "in the biz",myself included,use composites versus wood.composites have proven themselves,in many applications - light weight,high strength,and the fact they will not rot...

if technology/techniques never changed,we'd still have wooden hull'd boats...

you've got one chance to make a product - why not use the best coring materials available ?

[pelican]

Originally Posted by Caymanboy

Here's a little tip for you:
When mounting ant's, mast, rigger bases, etc. Drill and tap through the top, core and all, tighten down the bolts, then put your washer and backing nut on. Properly bedded of course! Get much better holding power that way, never seen one pull out or compress.
Strick is God! :-)

that's an "old school" technique - drill a 3/16 hole,and run a 1/4 - 20 machine screw in - no need to "tap" - again,old school technique - ocean yacht used this alot...