Custom Extended Swim Platform

[tpenfield]

The extended swim platform is getting some good use over the 4th of July weekend. Having 2 boarding ladders works well for the dog ramp and the people boarding is quite easy with the extra handle on ends of the platform width.

Here are a few pics . . .

 

[gonzo]

There are extension blocks for risers, which are cheaper.

 

[tpenfield]

There are extension blocks for risers, which are cheaper.

Yes, I think I can get them for about $165/ set. Then I’ll need some 4” dia exhaust tube for the ‘down’ side to reach the y-pipe.

I may have some time in a few weeks to install them. For now I’ll just make sure to keep the stern load low.

 

[tpenfield]

We had the chance to do some 'load testing' of the platform with 4-5 people sitting on the edge. . . maybe 700-750 lbs. No worries structurally. The stern is down about 4" with that amount of load, so I will definitely want to add the riser blocks.

 

[tpenfield]

Now that my custom DIY designed and built extended swim platform is in use, I thought I would just summarize this journey . . .

I've had an extended swim platform on my boat 'bucket list' for quite a few years and finally decided to do it.

It started in August 2018 with an idea and some basic measurements . . .

I started with a rough foam board structure of the platform, which would become the 'plug' for making a mold.

As I worked the foam structure, I enhanced the design a bit . . .

I got lots of input along the way. One of the key points was when I contacted Formula (boat manufacturer) about how they do their extended platforms, and got some great insight, encouragement, and pictures. This helped me refine and greatly simplify the attachment design.

I tried infusion molding for the first time, which proved to have a fairly steep learning curve; more so than other boat building and restoration projects that I have done in the past.

I finished the 'plug', then made the mold from the plug. Then I made the actual swim platform from the mold.

10 months after starting (August 2018 -> June 2019), working 1-2 weekends a month, this was the final outcome.

.

Overall, I'm quite satisfied with the results, having achieved my objectives.

My main reason for doing the 3-steps of plug-mold-part was to get a nice, factory-like non-skid surface in the gelcoat. My rationale for doing infusion molding was to achieve good strength to weight. I think my final weight of the platform with all of the hardware and struts ended up being about 135 lbs. If I had to do it again, I might opt for a fiberglass over foam approach. . . but maybe infusion would be easier the second time around. . . not sure.

Anyway, I hope this thread will be useful to others who may be contemplating a similar project on their boat.

 

[tpenfield]

Here is a video summary of the significant steps in building and installing the swim platform.

 

[MassimilianoPorta]

Thanks a lot for sharing your experience and for the many pictures/video.
I'm going to build the swim platforms for my rhib this winter, your thread will be inspirational!

 

[tpenfield]

Here are a few learning's, tips, tricks, and general opinions that I want to share with anyone considering a project like this, be it a swim platform or a similar project involving a plug/mold/part approach and possibly resin infusion . . .

For the Plug & Mold

• Make sure you have adequate flange area . . . I would say at least 6" of flange around the plug and the mold perimeters. This will give adequate room for resin feed and air flow tubing and associated materials around the perimeter. . . I had a 2-3" flange in many areas and that was not enough.
  
• Make sure to reinforce the flange area as it will be used to pry the pieces (mold/plug & part/mold) apart. Some of the flange areas on my plug & mold were not useful in prying the pieces apart.
  
• Be sure to have adequate tapers on all 'vertical surfaces' . . . I had a few areas ( ladder hatch openings) that were not tapered enough and they seemed to have a death grip when trying to separate the mold from the plug, and the part from the mold.

Resin / Gelcoat / Catalyst

• Make sure to use the proper resin for infusion or hand layup . . . I had bought my resin ahead of time and it was too thick to do infusion properly. I accommodated that issue by doing fewer layers of glass in each infusion, and also did more hand layup than I had originally planned. I also used plastic drop cloth sheeting to cover hand layup areas to keep them 'tight' while curing.
  
• MCP Catalyst will give you an hour of working time and little exotherm. I highly recommend it. TBC inhibitor also will extend the working time, but will give you a fair amount of exotherm (heat) once the MEKP 'kicks in'.
• Use MEKP for gelcoat . . . I made a mistake on the tooling gelcoat and used MCP hardner. Later, I found that MCP is not recommended for gelcoat, as it will not harden properly, which explains the problems I had early on with the tooling gelcoat.
• Experiment with the time interval between a first layer of gelcoat and subsequent layers. . . I could never seem to get that right and applying the second layer ended up causing some wrinkles in the first layer, even after a day of curing.
• The Duratec high-gloss gelcoat additive is a great thing. Really brings out the shine.

Infusion Supplies & Process

• Some of the infusion supplies are a bit pricey, but many are well worth having, if you are going to do infusion.
• Vacuum pump . . . a $100-$150 pump should be able to do the job. Make sure you can pull about 26 in.-Hg. with the pump. Get a stethoscope to listen for air leaks . . . you will have them.
• Perimeter sealing tape . . . gives the best seal and accommodates unevenness and gaps well.
• Resin tube & air fittings . . . probably worth getting the good ones. I used various fittings, and sometimes that led to air leaks during the infusion.
• Strechelon bagging film for less wrinkles . . . there are two types . . . one for epoxy resins and another for Poly/VE resins. I found it really only likes to stretch about 2X vs. the 3-4X that is advertised. Plan accordingly.
  
• Peel Ply & Flow Media . . . might be a combination of art & science to figure out when/where to use these materials. For complicated shapes, I would cover more of the area with flow media. Where you use flow media, you will want peel ply in order to remove the flow media after the resin has cured.
• Infusing the resin . . . Practice makes perfect, which is hard for a one-off project. I found that if you have a lot of area to cover, then you will want to get a good amount of resin flow into the mold. Also, it may help to reduce the vacuum slightly during the infusion, then increase it after the resin supply pot has emptied to really 'squeeze' the mold and force the resin throughout the part.
• Individual resin feed lines (tubes) from the resin pot can give you a better means of controlling the resin flow into various parts of the the mold. I used a single feed with multiple branch lines and that seemed to have less control. The resin never seems to flow in a balanced manner among the several branch lines.

Wax vs. PVA

• I found that PVA tends to work better in getting the part/mold to separate after curing. PVA can result in unevenness in the resulting part surface though. It is great for molding non-skid surfaces.
• Wax on the smooth surfaces and PVA on the textured surfaces may be the way to go.

Design & Structure

• I am a big believer in using foam cores when making things out of fiberglass. If you can add some amount of corrugation/weave to the core, then even better. I used only 1/2" of core and the resulting part was very rigid, very strong, and quite light. The use of wood as a core tends to result in heavy structures that may absorb water prematurely. Balsa wood, although light, can absorb water as well.
  
• Geometry is your friend . . . design and make strong shapes. Triangles are strong . . . cored lamination's are strong. It is difficult to make a weak shape strong, so start with shapes that have inherent strength. Use lightweight, water resistant core materials. Designing strong shapes means less material and less weight.
• Understand your sheer forces and bending moments. Then you will have an idea of the forces involved with the planned load on a platform or a deck, for example. Look up some reference material if need be.
• Design & re-design . . . typically you will find design improvements as you go . . . I certainly did.

Anyway, I hope that these tips are helpful to anyone considering taking on such a project.

Not sure what sort of project I may take on next . . . @ondarvr thinks I should build a boat. Actually I do have a 19 foot sailboat (1976 O'Day Mariner) that I have disassembled, having taken the 'cap' off of the hull in the process of restoring it. I still have to finish that project, which was interrupted by my swim platform inspiration

 

[MassimilianoPorta]

Eager to follow your next build thread!!

 

[tpenfield]

Circling back on a question that @fallguy had asked about the non-skid surface. . .

I had the opportunity while out on the boat the other day to take some close-up pics of the OEM non-skid that is on the boat and the DIY non-skid that I molded into the swim platform surfaces.

Here is the boat's non-skid . . . . it is about 8 'dimples' per inch.

Here is the pattern that I molded into the swim platform . . . it is about 6 'dimples' per inch.

I would have preferred to go with the OEM pattern, but the cost of the material was cost prohibitive for a one-off mold.

 

[fallguy]

What material did you use?

I'd like to check it out.

Can it be applied to a 'finished' part?

 

[tpenfield]

What material did you use?

I'd like to check it out.

Can it be applied to a 'finished' part?

I used a rubber floor runner material for the non-skid as part of the plug. You can see the material applied to the plug in some of the pictures at the early pages of this thread. The material is a 1/8" thick pyramid pattern floor runner (black). The floor runner pattern of the plug was then transferred to the mold.

I suppose it could be applied to a finished part (with epoxy or other adhesive) as long as the color matched what you wanted. The standard floor runner material came in black, and that is what you see in the pictures of the plug earlier in this thread.

https://www.americanfloormats.com/pyramid-runner-mats/

Once I secured the floor runner material to the plug, I sanded the 'tops' of the pyramid pattern down a bit, so the resulting pattern would not be rough on bare feet.

 

[fallguy]

I used a rubber floor runner material for the non-skid as part of the plug. You can see the material applied to the plug in some of the pictures at the early pages of this thread. The material is a 1/8" thick pyramid pattern floor runner (black). The floor runner pattern of the plug was then transferred to the mold.

I suppose it could be applied to a finished part (with epoxy or other adhesive) as long as the color matched what you wanted. The standard floor runner material came in black, and that is what you see in the pictures of the plug earlier in this thread.

https://www.americanfloormats.com/pyramid-runner-mats/

Once I secured the floor runner material to the plug, I sanded the 'tops' of the pyramid pattern down a bit, so the resulting pattern would not be rough on bare feet.

Might be hard to use outside the mould. I suppose one could try to fill the mat with thixo and a piece of glass and then bond it to the floor/deck.

What did you fill the mat with? Just cabosil and epoxy? Or pigment, too?

 

[tpenfield]

Might be hard to use outside the mould. I suppose one could try to fill the mat with thixo and a piece of glass and then bond it to the floor/deck.

What did you fill the mat with? Just cabosil and epoxy? Or pigment, too?

The rubber mat is a solid material . . . you don't (you can't) fill it with anything. What I did was coat the underside of the mat with epoxy and then coat the surface of the plug with more epoxy (thin layer of epoxy). Then apply the mat to the plug's surface . . . get it properly oriented/aligned . . . then I vacuum bagged the area of the mat while the epoxy cured.

For a visual on the floor mat material, you can look at the first page of this thread, post #4.

 

[tpenfield]

I thought I would post a couple of 'as built' diagrams of the swim platform mounting, given the amount of discussion earlier in this thread.

Here is the top view diagram, similar to what is posted on Page 1, Post #10.

Here is the corresponding side view/section . . .

Fairly simple vs. where things started out. 4 stainless steel U-channel struts and 2 stainless steel straps on the sides. That was it.

The platform is quite solid and I have not noticed any flex or sag in the mounting. I did add a third bolt to the struts on the transom side of the mounting, as I made the struts 18" in length instead of the original plan of 12-15".

This approach of embedding the hardware and doing away of the 'support struts' from the lower part of the transom to the edge of the platform simplified the mounting considerably.