C-25 Hull Construction

journey on · Posted: Thu Nov 20, 2008 4:22 pm Post subject: C-25 Hull Construction

Since I suffered a transom crack in Journey On, I've been interested in how a C-25 is built, and couldn't find any photos of its construction.

Well, when Journey On was under construction, and we were making progress payments, I had Laura ( the daughter in Tumwater,) go up and shoot photos, and send them down. Ah, the modern miracles of electronics. And via the age-old miracle of the human brain, I then forgot them. Finally, I rebuilt one of our PCs and whilst getting it up and running, I ran across these three pictures.

First a shot of the hull showing the balsa layup area and the transom build up. The balsa in this shot goes up to about the V-berth. Also, I believe the green structure in the transom is the rigid foam they now use, so it was present in all boats made after 5/05. Note it stops short of the outboard end of the transom. That is the fiberglass transfers the loads into the sides of the hull.

Next is a shot of the transom area showing a different angle on the transom.

Last is a picture of the deck during layup. I don't know what this shows, but it's here for completeness.

Boris

mmitchell · Posted: Thu Nov 20, 2008 5:09 pm Post subject:

Now you have me concerned that the construction is not all that? Our boat was built in 06 and did not have the luxury of checking on how it was built. We bought it from the dealer with the warranty given by c-dory.

journey on · Posted: Thu Nov 20, 2008 6:54 pm Post subject:

Not quite sure what you mean. However, (1) we had a crack in the transome. (2) The factory paid for the repair. (3) The repair has held. (4) I think, in general, that the C-Dory is very well built.

My thought was that people would be interested in the construction of the hull in case it needs repair. Don't know why ours cracked, and I wished I had remembered these pictures to show the guy who repaired it (Driscoll Boat Yard, San Diego.) And they did a good job. There has been some discussion as to how the transome is built, and now you can see.

Boris

Matt Gurnsey · Posted: Thu Nov 20, 2008 6:55 pm Post subject:

I don't think construction has changed at all in the C-Dory over the years- certainly not significantly.

The boats we've been seeing as they come in (and when we toured the factory) have been in very nice condition, ready to sell. Finish work has been top notch. A huge difference from a line we used to carry.

Pat Anderson · Posted: Thu Nov 20, 2008 7:34 pm Post subject:

The one aspect of construction of the CD25 that did change was from a plywood transom core to a green foam transom core. I actually was at the factory quite a bit while Daydream was being built but was not really tuned in to what to look for, and would not have appreciated exactly what I was seeing for better or worse.

Just a gelcoat skin inside a mold here...

journey on · Posted: Thu Nov 20, 2008 7:50 pm Post subject:

Pat, I was thinking of you when I posted the pics. Your boat and mine were built about the same thyme, and now you know what you have in there. I do think C-25 owners would like to take a peek as to how their boats are built.

And Matt, I caught myself defending the C-25. It's a great boat and doesn't need a defense.

We're going to the west side of Vancouver Isle next summer and neither Judy or I have any worries about the boat.

Boris

thataway · Posted: Thu Nov 20, 2008 8:21 pm Post subject:

Thanks Boris,
This jives with what I found out, with my "Destructive" testing of the transom of the C D 25--the difference is that my boat (2003) has a plywood core in the transom, and also stops at the edge of the well. It does not go to the sides of the hull as it should. You can tell if the core stops short, by looking at the inside of the transom. It will be thicker--a bulge--into the inner part, where the core stops. I have the impression that the newest boats take the core all of the way across the transom to the hull.

It is best if the load of the motor is taken to the sides of the hull. There are several reasons for the cracking in the older CD 25 (2002 to 2005 seem to be most affected). Apparently the designer decided that they would save wood (cost) and weight by putting in a smaller piece of core. The design was that the foreward and torque load on the transom was taken by the sides of the motor well--which are molded into the transom at the place where the core stops. That is theoretically workable. Some boats have "knees" into stringers, keelson or the boat bottom to take the load, with a shortened transom core--and this is fairly common.

The problem is that there was only one layer of mat--minimal structural strength--in the area where the transom meets the motor well sides. In our case, there was over 3/8" of filler--and very little glass. We rebuilt this area--with two layers of 12 oz triaxlial glass on the outside, after grinding out this filler, and one layer of 12 oz triaxial glass on the inside (laminated with epoxy) this gave us 36 oz of material, instead of 1.5 oz of material! Since we did this repair (and glassed over the top of the transom--which also only had one layer of mat--now solid glass) we have had no cracking--and have put about 2000 miles on the boat. We were in rough water, (seas up to 8 feet at times) with no evidence of flexing or cracking.

I agree that the boats are well built. But if there is cracking in this area, a proper repair is to replace the filler, with glass of substance. This will transfer the load to the motor well, and eliminate any flex.

I would urge any owners who have cracking in this area, to have it repaired before warantee runs out. This is not just a cosmetic repair. It is structural.

eNORMous · Posted: Thu Nov 20, 2008 10:04 pm Post subject:

I feel fortunate they gave me extra stuff when they constructed my hull and put the deck on. After opening the aft-quarter storage lazerette to gain access for mounting my ladder brackets

and looking down into the hull

I was rewarded to find these lovely items

Argh!

JimD · Posted: Fri Nov 21, 2008 12:49 am Post subject:

It is noteworthy that the Venture 26 is made with NO wood coring at all but high density foam instead.
I seem to remember that someone (maybe Dr Bob?) stated that the 26 is built at the Skagit Orca plant.

It will be interesting to follow the Venture 26 over time to see how it holds up relative to the balsa/plywood boats. Clock

Pat Anderson · Posted: Fri Nov 21, 2008 8:59 am Post subject:

I am not sure, but I think they consolidated all manufacturing operations in Auburn and shut the Monroe plant - anybody know that for sure? Balsa is good, not a problem, but plywood in the transom is apparently another story. At some point before they manufactured our boat (according to Jeff Messmer) they were no longer using any plywood in the 25 transoms. I think the future of the dual lines, C-Dory and Venture, must be questionable. There isn't enough difference to justify the price difference, and they just cannibalize each other's market.

thataway · Posted: Fri Nov 21, 2008 10:50 am Post subject:

Balsa is an excellent product--and if proberly used, is better than foams in some application. The problem with either foam, balsa or plywood, is the amount of glass put on each side of the material, and if the material is adequately sealed.

I have seen balsa sided boats which hit pilings during hurricanes, and showed no skin damage, yet a high end boato--the Camano Troll, showed depressions at each place it contacted plywood. My conclusion was that the Camano didn't have adequate glass on the exterior. The same holds true for bottom or stringer foam--there has to be adequate construction. Some balsa boats have lasted many years with zero problems.

The transoms present some different issues--but part is compression of the core material by either motion of the motor, or overtightening of the boilts. The cored transom depends on adherance of the skins to the core, and having adequate thickness of the skins--which are tied into the supporting structure (hull sides, splash well, or knees.

Alyssa Jean · Posted: Fri Nov 21, 2008 11:03 am Post subject:

HERE are pictures I took at the factory during Anna Leighs consrtuction. Like Pat on Daydream we only lived about 45 minutes from the factory and where there a lot.

thataway · Posted: Fri Nov 21, 2008 12:42 pm Post subject:

Dave, Thanks,
On the second photo, where it shows the balsa on the floor and the plywood in the transom. Is there a piece of prelaminated fiberglass clamped in the center of the tansom over the wood--and glassed in place? It is very possiable that a cut out from another molding was used to give thicker glass in the inner areas where engines might be mounted, then faired in with less glass.

eNORMous · Posted: Fri Nov 21, 2008 12:54 pm Post subject:

Dave,
I've admired the pictures of your boat & the modifications you've incorporated several times. Today, I noticed something. What is your bow stem guard constructed from? It doesn't look like brass from the picture I see of the boat on the trailer.
Norm

Matt Gurnsey · Posted: Fri Nov 21, 2008 1:00 pm Post subject:

All boats are built in Auburn at this point.

A quick note about balsa coring, As noted, when used properly, Balsa is good stuff, which is why it is still used by many manufactures. One of the keys is to use end grain balsa, which means that the bals is put in the boat with the grain vertical.

Water can wick aling the grain of a wood in a fiberglass core, but with the grains going vertiucally, it can't migrate beyond the small area that gets compromised.

This has probably been talked about all over this site, but thought it should be in this thread in case someone new to the board finds it.