Replacing transom and ribs

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Replacing transom and ribs

Postby Ron Zito » Mon Aug 17, 2009 11:59 am

To my new Thompson Boat Club associates. My name is Ron and I live in Pittsburgh PA. I’m a 72 year old retired engineer. I’m probably not the oldest rookie in the Thompson restoration community but I maybe the one having owned the same Thompson boat the longest.
I bought my Cortland NY Seacoaster, new, in 1960. It is 49+ years old. The Thompson transom # is 56349. The original outboard motor was a 1960 40hp Evinrude Lark. It was a bit under powered so I replaced it in 1963 with a 75hp Evinrude Starflight. That outboard still powers the boat. The trailer is a 1960 TeeNee which I modified years ago adding an axle cradle system with 13” wheels and support bunks eliminating the “rollers”. Yes, the boat has a hog, about 3/4” or so.
I stumbled on this club web site about 3 or 4 years ago and have learned some interesting information. Some things I applied correctly others I did not dig deep enough to do things right. One that stands out right now is the use of RED OAK for sister rib ends. They looked almost as bad in 3 years as the white oak looked in 49 years.
So much for me and my Seacoaster biography.
There are several projects that I have identified that I will and have started to undertake.
Please correct me if I improperly name a boat component.
New transom
New scarfed in ribs, about 5 or 6, not to be scarfed in line
Additional sister ribs, possibly
New scarfed in inner keel, maybe, the oak appears borderline
New scarfed in center longitudinal floor support, not sure of proper
New scarfed in side longitudinal floor supports, at least on one side
New scarfed in top mahogany ¼” lapstreaks, about 60” per side
Etc. etc. etc.
I will have tons of questions, many of which I have read opinions on in this web site postings. Some leave me with needing to ask more questions about the subjects. I have taken about 65 photos so far and hope to attach a link for this posting, if I figure out how.
I have posted an album on HP Snapfish photo gallery. Snapfish is a free to join website and I have added the following link. ... /otsi=SALB not sure if that will work.
Lots of pictures!
Things I have learned of from postings on the site. I know of the products but not enough to talk in any detail.
West System epoxy products
White oak heart wood
Silicon bronze fasteners
Cutting boat shorter to fasten new transom, I’d rather not, lots of screw holes???

Looking for, critique, opinion, questions and anything to help me thru this.

My spesific questions will follow.

I'm not sure if I have started this clubsite entry correctly, but please advise if I've done it wrong.
Respectfully; Ron Zito
Ron Zito
Posts: 15
Joined: Sun Aug 16, 2009 9:37 am
Location: Pittsburgh, PA

Postby LancerBoy » Mon Aug 17, 2009 4:17 pm

Welcome aboard Ron!

Nice boat and quite the project! Best of luck.

We all look forward to hearing from you as you progress.

As I am sure you know, your boat was shipped from Cortland on 17 February 1960 to Carlings Sport Center in Pittsburgh. She appears in the shipping ledger archived at the Mariners' Museum in Newport News, VA.

I recently obtained a 1961 Sea Coaster made at Cortland. She's in rough shape.

Keep in touch!

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Location: Minneapolis

Postby Ron Zito » Mon Aug 17, 2009 5:16 pm

Andreas, thanks for the welcome!

To any and all out there!
My first question, is there a need to interlock the mahogany planks on the main face of the new transom. For those viewing my photo's, the original transom plank are interlocked with an unusual double finger bead & groove. I've read postings mentioning that interlocking is not required. I've read that the consenses is to use 3M5200 and I am hearing that it is available in brown at West Marine. That seems to be prefered over West System epoxy. My basic question, is it best to take my planks to a shop and machine an interlock into them? A bit of a dilemma is that if I machine the plank edges I will loose enough assembly dimension to require small pieces at the top ears of the assembly, doable. If I dont interlock the smaller pieces go away.

My second question concerns all the holes in the lapstreak planks. The ends of all the plank are very sound. I prefer not to shorten the boat. Is that a bad idea? I guess I believe that a combination of a two part wood epoxy to treat any frayed areas and the use of 3M5200 as a bedding sealant when re-attaching the transom is acceptable.

My third question, is scarfing the inner keel and center and side longitudinal floor support beams a good plan? If so what is a good offset dimension to space the scarf joints? My gut says about 3 ribs, 12" plus.

My timing is as follows:
I'm picking up my 3/4" 7 ply marine plywood this thursday at the lumber yard. I'm also hoping they have the proper white oak in stock. I plan to start shaping some of the mahogany parts this weekend.
Ron in Pittsburgh
Ron Zito
Posts: 15
Joined: Sun Aug 16, 2009 9:37 am
Location: Pittsburgh, PA

Postby LancerBoy » Tue Aug 18, 2009 3:31 am


1. the tongue-and-groove on the transom boards is not necessary. On the boats built at Peshtigo they never did this. The boards just butt up to one another. Same goes for boats built by Cruisers, Inc. It must have been something unique to Cortland built boats. 3M5200 is a better choice than hard epoxy, in my opinion

2. this is an area where a epoxy such as West System is appropriate to fill the holes.

3. scarfing is a tried and true method of joining wood lengthwise. Keep the angel about 8:1. At least a 12 inch offset.

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Postby LancerBoy » Tue Aug 18, 2009 3:42 am

OK Ron, I have some questions for you! As I mentioned, I recently obtained a Cortland Sea Coaster. It was all torn apart when I got her. The deck and gunwale covering boards are long gone.

1. is the inner layer of your transom plywood or solid wood boards? I can see solid wood boards at teh outer edges, but are the pieces inside of them plywood or solid wood?

2. is your outer keel original? is she the original shape?

3. can you get a close up photo of the block that is under the bow light? Mine is missing and I need to know what shape and size it is. How think?


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Location: Minneapolis

Postby LancerBoy » Tue Aug 18, 2009 3:45 am

Here's a picture of the '61 Cortland Sea Coaster.

Another question, did your boat have a stylized "T" on the hull planking near the bow on either side? If yes, what was it made of?


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Postby Ron Zito » Tue Aug 18, 2009 6:04 pm


1. Yes the inner layer core on my Cortland Seacoaster is plywood. It is 7/8" 9ply. It is the original transom. It is the same design that I see in your Cortland Seacoaster. I've seen a handfull of this vintage Cortland Thompsons and they were all built this way. There is also an additional piece of 3/4" plywood from memory about 13" x 16" scabbed on below the horizontal stiffiner piece that spans the inside of the transom. The inside perimeter around the larger plywood is mahogany and better facillitates end lapstrake fastning. There is a third 3/4" bottom mahogany plank outside the outer mahogany transom boards to increase the amount of bottom plank fastning. Yes the bottom plank from splash rail to splash are 3/4" longer then side lapstreaks.

2. Yes the outer keel is original, only the"HOG" has been added.

3. The bow light base is in it's 3rd generation. The original was made of 3/4" plywood. I think it was mahogany not positive. I made a 2nd generation a few years down the road from an exterior grade (not marine) cabinet grade Luan, did not hold up well. About 6 years ago I made the present one from 3/4" thick Poplar and so far it looks good. Because the Poplar plank that was available was not wide enough I slightly modified the shape. I looked around the garage for several hours looking for the original piece to give you a template, but I hav'nt found it yet. I did find the two "T" pieces you asked about and also the original bow light that I changed out when I fabed the the Poplar piece. Notice in the photos I'm sending that at the base of the Poplar piece I curfed 4 saw cuts to bend it to follow the deck curve. I also simulated in one photo the original shape by adding a paper cutout.

4. The "T" pieces are original, the original color is and was gold. and they are made of plastic. If you need templates of any of these let me know.


Photos: ... =snapfish/
Ron Zito
Posts: 15
Joined: Sun Aug 16, 2009 9:37 am
Location: Pittsburgh, PA

Postby LancerBoy » Wed Aug 19, 2009 1:17 am

Thanks Ron. This is exactly what I need! The pictures and your description are very helpful.

I stopped at Cortland, NY on my way home From Albany with the Sea Coaster. I invited Ted Thompson to come take a look. He was amazed that I would tackle such a project! He didn't think the plywood inner layer in the transom was original, but he wasn't certain. So I assume now that it is original and that he just didn't recall that detail.

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Postby HalcyonDays » Wed Aug 19, 2009 2:20 pm

Wish I read this last post before I painted my "T" on my 1960 Sea Lancer red. It may have originally been gold as well. When I got the boat the "T's" were off and painted red; there were a few chips that showed that gold was under the red. The boat had no other red on it and as you said they were made out of a plastic material I figured red was original. Oh well... here is where I am so far with the redo

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Joined: Tue Jan 22, 2008 6:09 am

Postby Ron Zito » Fri Aug 21, 2009 3:26 pm


If you have any red paint left, the splash rails on my 1960 Seacoaster were originally painted red from the factory. I left mine red for years, but when I decided to put blue automotive vinyl on the decking, I changed the splash rails to blue and then to gray.

Ron Zito
Posts: 15
Joined: Sun Aug 16, 2009 9:37 am
Location: Pittsburgh, PA

Postby john » Fri Aug 21, 2009 4:47 pm

Ron, I'm an engineer also, I reworkedmy 1960 Cruiser's Inc, 6 years ago. You can see pictures at

Call me, if you like 832 473 8928, would enjoy visiting with you.

John Platou
Posts: 261
Joined: Tue Dec 27, 2005 7:33 pm
Location: Crosby (Houston) Texas

Postby gts » Wed Aug 26, 2009 3:13 pm

Hi Ron! Welcome aboard! You beat me. I've been driving my Thompson since '68 so I'm just a young pup. My father bought it new in '66, one of the last of the wood boats from Peshtigo - a 20' cuddy cabin.

Small world - I'm IEEE also.

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Joined: Wed Sep 19, 2007 4:13 pm
Location: NJ

Project Update

Postby Ron Zito » Fri Nov 06, 2009 2:14 pm

After several months of pain & agony over the project and way too many distractions the new transom and most rib repairs are installed. The weather did catch up with me so the project will now come to a stop.

The fabrication of the transom was a real learning experience. Fabricating the multi-pieces each having multi- facets with compound angles was challenging. In particular the like pieces on the opposite side were not mirror images. I guess back in 1960 you just hacked away until things fit. So I found myself grinding & sanding away until things fit, but I think I might have been a little more precise in making things more symmetrical.
The assembly looks quite good and the fit was much better than I expected. I used CPES on all parts, Interlux Schooner 96, diluted for the first two coats and sealed all appropriate parts with mahogany colored 3M 5200. Where I made a few small cutting errors I repaired them with West System 105 epoxy. All fasteners are new silicon bronze. I tried hard to stick with the expert advice from all you experienced guys on the forum.

The planking which indeed looked ragged and certainly full of screw holes was really still very strong. I did process it with CPES and filled the splintered areas with West 105. The planking (lapstrakes) re-attached to the transom very soundly.

The ribs fall into another category. Just for the experience I tried multiple ways to bend a rib. Failure, failure, and more failure. Got to get the hot moisture all the way thru. Did enough reading to know you can not really do it proficiently without steam. Again my feeble attempts were just for the experience. One silly idea just for laughs, I rapped the rib in soaked towels and put it in the gas grill @ 400 degrees, got about a 30 degree bend out of it. Yes it snapped.
I looked at the scarfing approach and tried one. The 8:1 or 10:1 ratio seemed impractical to me on a rib end that is in place. A rib 1/2" thick would be feathered thru 4" to 5". That hurt my eyes. I've attempted something a little different. The photos in my Snapfish web page "#4 Thompson Project Album" will show the effort. Fasteners will be added thru the side wood cleats and thru the old and new rib ends. If this rib splice technique does not work, (cracks) I'll replace the ribs entirely.
I have now stopped the project until Spring. A lot yet to do. I am including two photo albums for your scrutiny, critique is accepted and appreciated. Ron Zito ... =snapfish/
Ron Zito
Posts: 15
Joined: Sun Aug 16, 2009 9:37 am
Location: Pittsburgh, PA

Postby JoeCB » Fri Nov 06, 2009 8:49 pm

Ron, It sounds like you have made real progress and based on your descriptions the work is "first class". As for the insitu rib scarfing, I appreciate your pain. When confronted with the prospect of cutting a dozen or so scarfs at even 4:1 my head hurt too. There had to be a better way ... I came up with a set up using a 4 inch angle grinder mounted with a side cutting mill cutter (machine shop cutter) and made a sheet metal guide shoe. The rib to be scarfed is straddled with a ramp like guide made of wood. The cutter is (carefully) guided down the ramp guide cutting a beautiful scarf. Being a metal cutting mill cutter, interference with imbedded brass screws was not a problem, cut them off cleanly. I could do a rib scarf in less than a minute.
I'll try and post a couple of pics of the setup that show a mock-up of a rib with the guide ramp thingee attached.
Also ,note that this procedure is likly not OSHA approved... use care!
Joe B
Posts: 241
Joined: Fri Dec 30, 2005 5:17 pm
Location: Farmington Hills , MI

Postby thegammas » Sat Nov 07, 2009 5:27 am

Greetings all you Cortland guys - if you think detail pics from 62 sea lancer can help with your efforts, please let me know - been away for a while so please forgive if you asked previously and I did not respond.
Peter Stransky
1962 Cortland Custom Sea Lancer
Wilmington, Delaware
Posts: 563
Joined: Sat Nov 25, 2006 2:10 pm
Location: Wilmington, Delaware. - put wooden boat in the subject


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