C-25 Hull Construction

J

journey on

New member
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.

Hull_side_5_5jpg.sized.jpg

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

Hull_mold_5_5jpg.sized.jpg

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

Deck_Mold_5_5jpg.sized.jpg

Boris
 
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.
 
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
 
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.
 
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.

Daydream_25_in_the_Mold.sized.jpg

Just a gelcoat skin inside a mold here...
Matt Gurnsey":2d1r5rbo said:
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.
Click to expand...
 
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
 
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.
 
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

CIMG0547.jpg


and looking down into the hull

CIMG0551.jpg


I was rewarded to find these lovely items

CIMG0543.jpg


Argh!
 
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

:mrgreen:
 
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.

JimD":24e85nd0 said:
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

:mrgreen:
Click to expand...
 
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.
 
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.
 
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
 
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.
 
Pat, I don't know about what anybody else thinks or has experienced but the difference in the ride and handling of a 22 Cruiser with max hp and a 23 Venture with a 150 is nothing short of ASTOUNDING!!! The Venture is quieter and simply eclipses the 22 Cruiser for comfort in a short interval confused chop. I'm not sure about the difference between the 25 and 26 because we haven't powered our first stock 26 yet but I'd be willing to bet the difference is comparable. For a fact NOBODY that has taken test rides in both boats has said that they couldn't justify the difference in price. A Cadillac Escalade and a Chevy Tahoe are pretty much the same truck but the difference is in the niceties and how much better the Cadallic feels to drive...and pretty much justifies the price difference.

This probably isn't the right thread for these thoughts but I felt I had to get my 2 penny's worth in! Anybody considering a purchase owes it to themselves to test ride BOTH!!!

Charlie
 
A comment about balsa cores. I doubt if you will find any use of balsa in production boats in anything other than end grain balsa--such as "Baltec" or "Baltaire" which comes in various depths, and with scrims which are compatable with polyester, vinlyester and epoxy resins. Often the end grain balsa is cut in small blocks set in the scrim so that it will fit contours of the hull mold.

However, longitudinal balsa planking--with good structural overlay of glass (and various resins) is also an outstanding structural material--in in some ways better than end grain. End grain balsa is good in that balsa is a "hard wood" by defination, because of the short cells. The resins not only permiate the scrim, but into the cells, which give a better adherence. As noted, does not migrate any great distance, both because of the end grain--but also importantly because of the short cells.

The method of construction, where stations are put up, and planks of balsa--typically 2 x 2" x 15 feet long (often coved as many monique constructions are) are laid up with aluminum nails and epoxy resins (best to put a layer of cloth between every 6" of planking to tie the inner and outer layers of glass together). After the hull is laid up, it is easily faired with a power plane--and then glassed over with any one of several glass and resin combinations. The inner and outer glass are about the same thickness as the end grain boats laminateions--but the beauty of this longitudinal construction is the ease of building a custom boat. I have been involved in the construction of about half a dozen of this type of boat and followed them for over 30 years--they are all as solid as the day they were built--including one 55 footer I was aboard when we hit a shipping container at sea--going 8 knots in 15 foot seas. A typical fiberglass hull (probably including a balsa cored one) would have ruptured. This boat only impacted the 2" planking about about 1.5", tore off the outer glass, and delaminated the inner glass, but sailed several hundred miles to safety--could have crossed the ocean if necessary. The forgiving nature of the balsa along with the short cell structure, allowed the miminal damage.

So don't discount other uses of balsa.
 
I would guess that the transom is a pre-molded piece of structural foam sandwiched in fibreglass, delivered to C-Dory and glassed into place on the hull.

My source is a post somewhere in the C-Brats, or a conversation with a C-Dory dealer. It has some validity, but not much. Anybody know more?

End grain balsa is better than most foams/plastics used to separate layers of fiberglass. In terms of structural rigidity or strength, neither can claim an advantage due to the core material, it's all in the construction.

Boris
 
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