frames

[southport]

I'm a little confused as to the make up of the frames (ribs). Is there wood inside or are they hollow- I assume there was(is) something to give them shape while the glass was setting up. Are there drain holes at the bottom if they are hollow?

I also noticed up forward there are no limber holes in the first few frames (actually I guess the floors where the frames cross over the keel) up forward. Muskrat has had the reinforcing recomended and maybe the holes were covered/eliminated then. There is now no where for the water from the anchor rode to go.

We have serious moisture in our hull- chainplates and scuppers aand top two inches below toe rail. Inside and heated for a major drying and regrouping. I bought a moisture meter and it seems to peg itself in these areas!

Jon

 

[TomY]

Good question, I guess I don't know. I either saw or assume there may have been foam?

At any rate, I'm convinced that water runs through a channel created by the hull to deck joint on Challengers. I'm sure it's how it enters the hat frames. But I'm not sure (not onboard) it that same channel can get into the frames. I'm going onboard tomorrow to winterize and will be looking and thinking about what you mentioned.

 

[southport]

One of the plans I got from Niels is the "standard reinforcing & hull layout". It shows a cross section through the "top Hat" frame showing the base (against the hull) to be 2", depth 1' and tapering to 1" wide on inboard side. 2 layers of glass with an extra layer of roving on the inner face. It also point to a seperate inner mold(?) referenced as " AL. alloy former". It seems there was an aluminum frame or pattern used to shape the top hat. In the drawing this lays flat on the hull with the glass over it. I just don't know what 'former' means. If that was true only in previous hulls what did they use to replace it? The date of the drawing was 28-2-61.

It also details the deck to hull arrangment and it is hard to imagine how water would get into the hull there. There is a 2" flange on the hull, with a step down or rabbit that the deck lays in.this is 1" wide and about 1/4" deep. The toe rail overlaps this joint by over 1/2". Water getting in here would appear to have to run down the joint and into the interior. Where it could go is in way of the holes drilled for the toe rail bolts and run horizontally about 1" out board through the hull flange and then down into the topsides. Sorry about my description- don't really know how to describe it! What I need to do is some how scan and then post it. I have no scanner (zapped by a voltage surge) but we do have a copier and fax here in the office. I'd be glad to share/fax/ send copies if any one is interested.I got many of the plans from Alden and am tempted to get all available ones before they go to MIT, if they haven't already.

 

[TomY]

I'd be very interested to see those. I don't have a fax, but do have a scanner (that figures). We should figure out something, maybe if you sent me a copy, I could scan and post?

Here's my assumption on water getting into the hatframes. Being a first class build, they glassed the hull to deck joint after it was all bedded and sealed and bolted. If water gets through a fastener along the toe rail or the hull/deck joint area, it can migrate into the finish glass joint I mentioned above.

No matter how that glass joint is done(in my mind), the joint likely is a small piping that water could travel through. It terminates at each hat frame which was also glassed (to the deck above) from the outside after the hull/deck joint was sealed and bolted. I notice only a few of my hatframes have had water seepage from the weep holes. I would guess, some areas are channeling more deck leaks. Whether this is true of or not, I still don't see it as a problem that can't be remedied through changing backing plates, providing hatframe drainage, etc. Still, it would be nice to see the detail as drawn.

It sounds as though they may have started with a metal frame (I once read about a boat being built that way) and then discarded the idea? Of the hateframes I have cut into, no metal frame exists.

 

[southport]

email me at interport@roadrunner.com and I'd be glad to send you a copy.

 

[Whit]

I found that the hat frames on mine had an aluminum form inside. Most of the aluminum had deteriorated. If you’re going to replace your backing plates, you may want to consider doing it from the outside. I had to rip things apart to do it from inside and even then it was very involved. I thought we had a posting of the hull to deck joint somewhere in another post. The scuppers do run down the hat frames which can be damaged by freezing. Let me know if you decide to change the backing plates, I have first hand experiance and a few suggestions.

 

[southport]

Probably drilling weep holes would be a good start- I see none in our frames.

Whit if you have aluminum "hat" in 949BB I should see that in Muskrat-949N. I'll see what there is. She was completed in 1960.

Which brings up a totally unrelated topic--- Let's (start?) plan (-ning) some sort of 50th. It would be a great way to show off these boats! I'd be glad to start/help/whatever.

What do you think?

Jon Smith

 

[TomY]

Sounds like a great idea to me John. What year is the 50th for the Challenger? Let's see if we can get something going.

 

[southport]

I have the spec sheets for design # 937 dated July 17, 1958 with an addenda noting wherever 937 is mentioned to change that to 949. There are obviously more changes in the design. It looks like 937 was wood for starters.

Probably there was a year or two while Alden sought out interest before actually having Hallmatic build molds, etc. Was there a group all built at once? When was 949A delivered?

Would the classic boat weekend be a good target site?

 

[CaravelaofExe]

Re: Challenger 50th Anniversary

I've started a new topic for that here. Best to keep frames and festivities separate!

 

[Quetzalsailor]

Thus, you can see why no 'glass boat builders use frames and few sailboat builders even use stringers. Interesting using aluminum 'formers'. I'd bet the aluminum you describe is just exactly that, a former, and the 'glass is the frame. What guage metal is it? Is each aluminum former continuous? What's the crossection of the former? Clearly, a half-round shape would be harder to locate while glassing but would be better since the glass frame would be bonded to the hull nearer the 'webs' of the frame.

If you were to run the numbers on a panel made like the Challenger hull, I'd bet that the frames don't add much. Compared to a concrete double tee parking garage floor, with its post-tensioned steel strands, the amount of longitudinal fiber at the inside of the hat is pretty small; it would not move the neutral axis very far from where it would have been in a heavy unreinforced panel. Ditto the plywood deck 'beams' in a Challenger. Better than nothing, for sure, and all the more effective the thinner the panel is.

You can buy pre-shaped foam formers for stringers, and I've read that some folks dissolve the foam out with solvent (what an expensive mess!). I've used cardboard formers in a Sunfish rebuild; the originals were wood that had rotted.

LeComte finished several of the Hallimatic moulded Challenger hulls, so they would have been quite aware of the construction. I read that LeComte initially, 1962, did not build their own NE 38 hulls, but bought them from Lentch, also in Vianen. Certainly by 1970, Lecomte was still stiffening the great long aft overhang with large, 4" + radius, longitudinal hat channels which they also used for bilge ventilation ducts. I have not seen inside them to see if a 'former' was left inside. The deck drains are carried to below the waterline with Challenger-type hat channels. They're closed and ended below the waterline, and I don't see any remains of formers. LeComte used a glassed-in flat strip of foam for a bilge stringer. This is a handy place to screw conduits and casework components since the screws would only extend into the foam, rather than to the water outside.

 

[TomY]

Scans of Aldens drawings

that Jon kindly sent. One is a hatframe, the other a scupper detail.

 

[Quetzalsailor]

The frames are on, maybe 10 or 12" centers? What weight roving? Just out of curiosity, I'm gonna' try to get it calculated. Judging buy the note '5 layers where there are frames and 9 layers where there are none', the designer was counting on useful effect. Not much longitudinal fiber at the bottom of the hat, though. Imagine the difficulty cutting and placing the strip of roving reliably!

 

[Quetzalsailor]

Text of emails to my yacht designing friend follows. His answer first, my query after.

Those hats have a huge influence on both stiffness and strength. At a 12" spacing, they were probably following Nevins' Rules or other classic wood yacht scantling rules as a guidepost, and designing a laminate and framing to be equivalent. Knowing what my mentor did in this period of time, the analysis would have been carried out using the "1 inch strip" simple beam formula for the unsupported shell spans (12 inches) and the hat section would have been analysed as a composite section a la built-up steel.

Now very importantly, note that the "FORMER" inside the hat section is aluminum. It constributes a huge amount of stiffness to the system, as it is aprroximately 8 times stiffer than the surrounding fiberglass.

Finally, 5 layers of Classic Plastic isn't a thick hull shell. If you built an entire hull out of this laminate, without any hat frames, she'd be a wet noodle, and the furniture etc would pop out.




B,

An Alden Challenger is a glass hull - glass deck - wood cockpit and house - wood interior keel/centerboard boat from the antideluvian period of fiberglass boat building. It is pretty unique in that there are hollow hat frames at about 12" oc for most of the hull. Take a look at the piece of the original drawing and opine whether the hats add much.

I don't think so, but the note saying 5 layers where there are hats and 9 where there are not is suggestive that the designer thought they were useful.

D

 

[TomY]

Text of emails to my yacht designing friend follows. His answer first, my query after.

Those hats have a huge influence on both stiffness and strength. At a 12" spacing, they were probably following Nevins' Rules or other classic wood yacht scantling rules as a guidepost, and designing a laminate and framing to be equivalent. Knowing what my mentor did in this period of time, the analysis would have been carried out using the "1 inch strip" simple beam formula for the unsupported shell spans (12 inches) and the hat section would have been analysed as a composite section a la built-up steel.

Now very importantly, note that the "FORMER" inside the hat section is aluminum. It constributes a huge amount of stiffness to the system, as it is aprroximately 8 times stiffer than the surrounding fiberglass.

Finally, 5 layers of Classic Plastic isn't a thick hull shell. If you built an entire hull out of this laminate, without any hat frames, she'd be a wet noodle, and the furniture etc would pop out.


He may have the hat frames and ribs confused. The hat frames and their formers are only about a foot long. I don't think (?) Alden spec'ed the formers inside the hull frames. At any rate, it's good to think they do help in the hulls structure. In the right light angle, you can see the ribs faintly on the topsides.

I stumbled onto some old photo Dan sent my several years a go. They show one of his hat frames cut open with the plate removed, another with the new SS backing plate installed and the hat frame re glassed. He had a boat yard do this before his trans atlantic. Maybe he can chime in at some point.


As you can see, hat frames are independent of the "ribs". I replaced one backing plate this way. It was straight forward. It's important that the glass is re done correctly. Next time I replace another (most of mine are fine), I will try just cutting out an opening at the bottom of the hat frame to slide the backing plate out and install the new SS backer.

 

[southport]

While talking with a surveyor he came up with a good point- the tab to attatch the deck to hull must not have been part of the original hull mold or you would never get the finished hull out of the mold. Next time inside (today) I'll have to look and see if there's any sign of this being "added on".

 

[southport]

Turns out that was dumb of me.......... they simply bolt on another "jig" for the flange which they remove to pull the hull/plug out of the mold. I should stick to steel tugs..

Talking to another surveyor who looked at the boat the moisture reading can probably be thrown overboard thanks to the aluminum forms- conduction- and in way of the chainplates thrown out due to grounding wires to the keel- conduction- as that is all the meter reads! That is actually a good thing. I did check and the frames go all the way to the keel/floor timbers and it was suggested to drill a weep hole for water to drain on all of them. What did we do without a cordless drill?