View Full Version : The "STRONG-BACK" Building platform

02-05-2012, 09:54 AM
As a kid, we built a small 8' hydroplane on a table in the garage. Now I have bigger ideas.

The builds I have seen are usually on a supported base, a strong-back I believe it's called. Some appear to be as elaborate as the boat. Looks like building something to build a 24 to 30 foot hull is a problem in itself.

Why can't you lay down some 4X6s on a hard surafce, like a driveway and just shim the timbers to level? My cat hulls would be from three to four feet high and maybe three feet wide. A mono would be up to four feet leeboard and no more than 8' in beam. Length would be say 24 to 30 feet.

Truning hulls, cats or monos, always appears like you need cases of beer for a flipping party.
How does an old guy, get it domne alone or with limited assistance?

On uneven ground, would you just sink some posts and level a ledger board say every 4 feet or so to build off of? Then how do you get it out? I guess lift it and take the ledgers out and pull it out from between the posts.

What are the tricks to getting a surface to work off of and that makes it easy at the end for a single worker?

02-05-2012, 10:06 AM
How does an old guy, get it domne alone or with limited assistance?

Leverage, several car jacks, fork lift, back hoe, ceiling winch, a rollable cradle...there's only so many ways a single person can manhandle a big heavy object and it sounds like you've thought of most of them already. Same for the strong back. It needs to be strong, stable, and true and can sit shimmed in the driveway, built on posts driven into the ground, mounted on wheels to roll in and out of a work space. Not much else to say about it.


Y Bar Ranch
02-05-2012, 10:13 AM
Why can't you lay down some 4X6s on a hard surafce, like a driveway and just shim the timbers to level?
That is essentially what I did in my unlevel garage. Build a frame on the ground, raised one corner a bit, and then used clear tubing with water in it (water level) to shim up all of the rest of the corners and internal points to match. Easy one man job.

02-05-2012, 10:27 AM
Here are a couple options:

This is a 23' dory built on a concrete slab in the back yard. Just a couple longitudinals set level and cross-braced. The frames were left long and served as the building jig, and were later cut to length. This system works well in dory construction, where the frames serve as the forms and remain part of the boat.


The photo below shows a different construction method, where the hull is planked over a set of temporary molds. This platform was 20' long and 4' wide and decked with 3/4 ply. It stood about 18" off the floor, which put the boat at a comfortable working height. I found that the decked surface allowed me to lay on my back under the hull and clean up any epoxy drips. Once turned, the boat sat just fine on the decked surface.



02-05-2012, 11:15 AM
The purpose of the strongback/work surface is to give you a solid, flat surface to mount any frames or molds to and provide a constant reference point. For instance, on the Wee Seal I am making molds for right now the design calls for the DWL to be 39" above the building surface. Lots of ways to go about getting that level reference point, I think it boils down to what works for your project and what you (and your back) consider a good working height. If you are working with a dirt floor, burying a series of posts and framing to them sounds like a great way to go.


02-05-2012, 11:15 AM
I like the system that incorporates the boat frame itself, but I can see my question really depends on the boat too.

also, I see that in my case, the first really big task is cleaning out my garage! You guys have some nice spaces there.

I have about 16 steel roof trusses about 18" with 4" flanges 24' long. Was hoping to just lay two of them on edge and put some 2X4s across, guess I'd bolt the lumber to them.

Sure would be nice just to lay a larger boat out on the floor and start assembling parts.

Guess my thing will be along the lines of Richard's Skoota or one of the Bolger sharpie types, and a slight chance of a bolger style houseboat with a garvey hull (for simplicity).

Bill Huson
02-05-2012, 12:21 PM
I have a variety of build tables. For boats with molds I use a box beam strongback, 1 x 4 with 1/2" ply both sides, and set it on sawhorse. For Stitch & Glue I have a rolling tray 8' x 3'. I can mount temp cradles on either end and tack on stretcher strips if needed. As for flipping hulls and whatnot, fire up the grill and tap the keg always seems to gather enough muscle, but usually I build small boats. Has to fit in garage and has to be single handed, or at least light enough that SWMBO won't balk at helping me move it.

02-05-2012, 06:38 PM
What are the tricks to getting a surface to work off of and that makes it easy at the end for a single worker?

I had thought this up for myself, being a bit of a single-hander when it comes to building, and then noticed that Paul Gartside uses it.
From his website "In the confined space of our building shop, turning a hull of any weight is an awkward business. "Surprise" was turned right side up using a pair of wooden hoops fitted to the hull. These sit on double planks and rollers so that she can be rolled more or less on the spot."


My plan is that once the hull is stiff enough that a pair boat rollers can be left under the wheel frames, and the boat can literally be turned on the spot and worked on at any angle.

For the initial strongback, it's hard to beat standard house framing (perhaps 2nd hand) that is well braced and screwed together, with plywood (or plywood pieces) station molds - although it's removed, don't skimp on this bit for straightness and strength by bracing - once the hull is planked and deck width braced, and the pieced up ply-wheels in place, saw off the legs, turn it on the spot and unscrew the frame.


02-05-2012, 08:27 PM
I like being able to move the setup around, change its height and even tilt it. So, I have a couple of box beams which molds get set up on. The larger one is made from 26' 2x10 I-beam joists is 16" wide and has plywood top and bottom. No matter how it's supported, it's dead-nuts stable, at least with light hulls. Two people can lift it.

When a hull is lifted off, I've erected cradles screwed to the box beam.

Peter Malcolm Jardine
02-06-2012, 09:26 PM
I find this setup extremely useful as well: ;)


02-08-2012, 02:53 PM
That's what I need, a boom truck.

I looked at Matt Layden's build of Paradox and he used the wheel frame which seemed great to roll it over.

I'll probably get some Richard Wood's cat hull plans, he has a 24 and 28 foot skoota, a motor cat. I have not seen the plans, but I believe they are flat bottom huls, not round. I think the freeboard or sides will be just under 4' and a flat deck on the hulls. Some rocker with this displacement hull...\

I doubt, but don't know, if a strong back is needed, or that when you buy plans they include such issues as how to set up a work surface or strong back.

It seems that the cabin can be built on the floor and as added to the hulls.

It seems this would only be necessary for hull construction.

There is another design, something like Bolger's shanty, the hull being a gunther bow box about 2 feet deep. Seems that could just be built on the floor???

How can you tell what set up you will need with different hull forms?

BTW, I was at the local pub last night, Sometimes I shoot pool and there were some young fellows there that I talked to. Three are on the University football team, one a nationally ranked weight lifter, so turning anything over doesn't seem to be such a problem anymore, since they said they can get more guys if necessary! Pizza and beer will be a small price to pay!

02-08-2012, 07:30 PM
Wow! 412 views, 8 replies, LOL, saying I can get help didn't mean I wanted a bunch of guys, would rather do it myself...

But the question was to building a cabin for a cat on the floor and setting it in place. Same with a shanty hull, barge like.