Pilothouse on a 1972 20' Thompson

[Twoweeks]

Let me start by thanking everyone that has posted on this forum and will be helping me get through my project. I have been reading the postings on this forum for about 4 months now and I believe I am ready to get started.

I have a 1972 20' Thompson runabout. I am planning to build a pilot house on it to extend my boating season her in western Washington. My plan is to use 1/4 inch plywood and 1x material (for rigidity and strength) to mock up the pilot house on my boat then remove it and take it into my garage and glass it inside and out. I want to replicate the Sea Sport boat line. I like the look of the windows in the front that angle out at the top.

Anyway I have read up on how to go about covering plywood with fiberglass and the need to coat the wood first then put the glass then apply more resin. Any other things I might want to know when getting started??

I am getting ready to go to the BIG Seattle boat Show in a couple of weeks is there anything I might want to see while there that may help me with my project?? I will be talking to different venders of FG and resins and that kind of thing but if anyone has some suggestions on what I may want to think about before starting that would be great!!!

If anyone has any suggestion on any reading material or threads that I may want to read up on before I start, please let me know.

Again thank you in advance for all of the help and constructive criticism. I plan to start gathering up the materials and things in about two weeks so any reading material will help.

 

[jcsercsa]

Re: Pilothouse on a 1972 20' Thompson

welcome there Twoweeks,

your in the right place we will help all we can !!

Frist how is your deck and stringer and transom ? I would hate to see you do all this work and have to tare it apart next year !! John

 

[Twoweeks]

Re: Pilothouse on a 1972 20' Thompson

Yes that is a good point. I got the boat and it was gutted on the inside the previous owner had taken up the floor and redone the stringers and laid down a new floor and epoxied it in. It is nice and solid. I have to check on the transom, I read on one of the threads that I can drill small holes and check the wood shavings that come out for wetness and discoloration. I have not done this as of yet but will within the next two weeks....

 

[DJ]

Re: Pilothouse on a 1972 20' Thompson

Be thinking about-TOP weight. You do not want this boat to turn into a "wallowing pig". The more weight topside, the more it will roll.

If you do not have hard chines, the top weight will significantly effect "roll" in "abeam" seas. Not to mention the "sail" factor in winds.

 

[Twoweeks]

Re: Pilothouse on a 1972 20' Thompson

I do have some concerns about TOP weight and will be trying to keep it as light as possible. The floor to the top of the gunwale measures? 3 feet so I will be adding another 3 feet to get a 6? head room on the inside. I only plan to make it 7? front to back and 7?3? side to side. Hopefully it will not add too much weight top-side.

I would post some pictures but am having a bit of trouble if anyone could point me in the right direction on how to post pics or what the easiest way would be I will get some pics up asap. There are hard chines on this boat.

 

[Twoweeks]

Re: Pilothouse on a 1972 20' Thompson

This is a test to see if I can post a stinking picture to this.

 

[Twoweeks]

Re: Pilothouse on a 1972 20' Thompson

Ok that was EZ I will post more pics soon.

 

[jonesg]

Re: Pilothouse on a 1972 20' Thompson

Look at how Mark42 built a hardtop from extruded foam, then glassed it.

http://www.shareaproject.com/pages/projectTut,p,386,00.html

You might opt for formica with 1/2 inch foam backing epoxied together.
It could be designed low, sit down only with a pop-open roof hatch if you gotta stand up.

 

[Twoweeks]

Re: Pilothouse on a 1972 20' Thompson

I have read this posting about 2 weeks ago. I would like to see it when he gets it done. It looks great so far.
Here are my questions. Would it be less expensive to do it in foam or wood? How much lighter would it be with the use of foam? Streighth?? Dose anyone else know of anyone useing foam that I may get more info??
This looks like a great way to build.

 

[Twoweeks]

Re: Pilothouse on a 1972 20' Thompson

If you do not have hard chines, the top weight will significantly effect "roll" in "abeam" seas. Not to mention the "sail" factor in winds.

Here is a picture of the stern of the boat. Would this be considered "hard chines"?

 

[jcsercsa]

Re: Pilothouse on a 1972 20' Thompson

Hay , the chines are on the bottom of the boat !! John

 

[Twoweeks]

Re: Pilothouse on a 1972 20' Thompson

Then would I need to crawl under the boat and take a pic looking up??

 

[Twoweeks]

Re: Pilothouse on a 1972 20' Thompson

Look at how Mark42 built a hardtop from extruded foam, then glassed it.

http://www.shareaproject.com/pages/projectTut,p,386,00.html

You might opt for formica with 1/2 inch foam backing epoxied together.
It could be designed low, sit down only with a pop-open roof hatch if you gotta stand up.

I have decided to go with the hard foam. I will have a little bit different look when done but same idea as Mark42 has built his. Hopefully Mark will read this and comment on it I am sure I will have a bunch of questions. I will be getting the supplies this weekend. More pics to come.

 

[Twoweeks]

Re: Pilothouse on a 1972 20' Thompson

Dose anyone know where you can buy new or used windows for boats and maybe local dealers in the Pacific NW.

Thanks.

 

[Mark42]

Re: Pilothouse on a 1972 20' Thompson

Hey twoweeks!

Nice boat, and a pilot house would look neat on it.

The pilot house will affect the boat in two ways; 1) more surface area will allow the wind to push it easier, and may affect top speed due to increased wind resistance. 2) weight - Try to make it as light as possible, and remember to weigh everything you remove from the boat, like windshield and seating, etc so you can accurately calculate the final adjusted weight increase to the boat.

One trick I'm using to get a few inches of additional head room ( and reduce the overall height) is to drop the floor into the bilge between stringers. In my boat, there is a whopping 23" between the stringers. So the floor can be lowered there about 5 inches, leaving about 2" of bilge below. The boat never takes on water, so for me this is not an issue. I'm 5' 8" in shoes, and even as it is, I can stand up behind the helm and not hit the roof. But taller people (like my brother) will appreciate the dropped floor.

I like the suggestion from jonesg about using formica. My experience with formica outdoors is the actual plastic laminate always held up, its just the plywood or press board that came apart. Think of using the 1-1/2" panels, but glue 1-1/2" inch wood strips to the perimeter of each panel, then glue the formica on both sides. The wood strip will give something to screw pieces together with and the basic pilot house can be built as a combo of stick framing and pre-formed panels. Use marine grade caulk and sealers on the seams and I bet it would last for years. And yes, I would use pressure treated lumber (1x or ply) for all the wood work. I think it would be much cheaper than using epoxy and glass, would give a pre-finished surface that would really speed up the project, and in plain white, it would be maintenance free!!! (just stay away from those 1970's colors and patterns )