scale models?

Life long boater, first time builder. No doubt I could find the boat I need (and afford it, if its old enough). But instead of buying a project boat, after much research I decided to build instead. Just because. And now I want to design my boat, same reason.

Nothing fancy, 18ft freshwater outboard fishing boat. Center console. Trailered. I'd love to work with some space-age foam but sadly I'm on a plywood budget.

I'm wondering, do you guys ever put together a small scale model for a design, like 1/12? What do you like for cheap materials? I'm talking throw-away type model.

I'm also kicking around the notion of maybe about a 5/8 scale prototype -- I have some small outboards laying around -- using cheap plywood and whatever materials come to hand. If nothing else it might be a good project for my nephews (their parents aren't teaching them any boating skills).

I don't really know how to scale horsepower though.

 

A couple of thoughts. One; a model 18" long is easier to build than a small one so your size is fine. I recommend doing a lift type half model for this purpose. Two; it is difficult to learn much from a model less than 48" long. Aircraft plywood from Aircraft and Spruce Co. in 1/16" and 1/32" thickness is very good to work with for the small model and 1/8" will work for many 48" models if there is not too much forward twist in the bottom. In that case, the 1/16" material can be used for the forward bottom part. For a running model that you hope to learn much from, you really have to watch the weight to keep it under the appropriate scale amount.

 

I am building an 18' long, outboard plywood boat currently. I made several models prior to starting the real thing. I agree with Tom, especially on what I consider a few key points. 1/8" ply is readily available and at a 1:5 scale (I use decimal dimensions) will give you a model almost 4 feet long with a scaled 5/8" hull thickness. This size is large enough to really see the details yet small enough to handle easily. For me, insuring that the plywood sheathing would take the significant curve needed in the hull forefoot was important. 1/8" ply showed me that, and I was also able to cut scale boards for all other parts of the framing. Then I could float the model in a bathtub, also weigh it, and check the projected weight of the full size boat and, using 1/125 scaled weights, check the flotation and trim.

Not sure you can reliably do that on a much smaller model. All the wood I used was from a big box store, so the price was very reasonable. All bonding was done with Titebond; no mixing and easy to use.

 

this is good stuff, thanks. just the sort of thing I'm looking for.

Have you ever tried to evaluate planing characteristics by towing a model? Is that even possible? I wonder, where would you put the tow point?

 

Wayne's comments are spot on relative to checking floation lines and fore and aft trim.

As for where to attach the tow lines, look at the photos on my website (use IE browser): http://bluejacketboats.com/boats/bluejacket-24/

You will find some more info on other pages of the site that may be of interest in looking at planing characteristics and model testing. Don't expect to be able to accurately scale performance figures though. That is for the experts, expensive test facilities and sophisticated computer programs. You will be able to observe other characteristics such as attitude and handling. If there is any weird behavior observed, I would be reluctant to scale that up without more study.

Even with these limitations, there is lots of value in model building and testing.

 

excellent work, Tom, impressive. well documented, too. I appreciate that.

 

Why would you have to use IE? The gallery works fine in Firefox and if it works in FF it should be good in Webkit (Safari/Chrome) and Opera as well.

Any site that requires IE to view a gallery is a badly coded site.

 

No doubt.

Some of the pages don't work well in Mozilla and I have not gotten Front Page savvy enough to fix it. I'm better with boats than computers.