Buying Filler Blocks

[mikiek]

To this point in my career I have never made filler blocks to fit between frames. OK - well maybe back at the transom but as far as side or bow blocks, never. The builds have come out OK so far. I don't think fillers would have made any difference.

 

After some hiatus, I am building Cazador mostly just to get my skills back again. I thought I would have a go at making filler blocks at some of the hull positions and see how that works, if there is really any benefit. The Cazador frames have a fairly large space between them - but typical to most kits I have built so far.

 

The kit offers nothing in the way of filler material. I see a lot of basswood blocks of various sizes for sale online. From 1x1x3 to 2x2x6 to 3x3x10 pieces or some combination. I'm just wondering what makes the most sense. I imagine the smaller pieces would not be useful. But I am stuck between buying some big hunk and cutting pieces to size (probably with a lot of waste) or the medium size pieces. I'm just hoping to be as efficient as possible.

 

There's probably a simple answer to this. Any help would be appreciated...

[Dr PR]

Balsa would be easier to cut and shape. The filler blocks do not need to be strong. They just provide a shaped surface between bulkheads to glue the planks to.

 

You don't need to fill the entire space between bulkheads. All you need is something out at the hull surface. Some people just use pieces of wood dowel, with multiple pieces cut to fit horizontally between bulkheads along the outer edges.

 

Whatever you use should extend out beyond the bulkhead edges a bit so you can sand them down to fair a curved surface between the bulkheads.

[wefalck]

... and the wood should not be much softer than the bulkheads, otherwise there is a tendency to sand hollows into the fillers, which defeats the object. On the other hand, one can always build up the surface again or apply wood-filler putty.

[brunnels]

9 hours ago, mikiek said:

see a lot of basswood blocks of various sizes for sale online. From 1x1x3 to 2x2x6 to 3x3x10 pieces or some combination.

I don't know if you all have Hobby Lobby's down there in SE Texas, but I was in my local Hobby Lobby and they had a pretty good assortment of basswood blocks that I thought would be perfect sizes for filler blocks.

[Pete Jaquith]

Mikiek,

I have used pine or basswood for filler blocks.  Easy to work with but firm enough to provide excellent planking support.  Attached are pictures from my Fair American build.

[manning16]

Hobby lobby balsa blocks..I used them between all frames on my Confederacy..no problem and easier to shape than basswood.  Use them  now for bow/stern scratchbuilds

[mikiek]

Thanks for all the replies. I guess what I am wondering is if it is more efficient to buy a couple of big blocks and cut smaller filler pieces or buy smaller pieces. I'm kinda thinking a big block would be better but there might be more waste.

[mtaylor]

On 3/20/2025 at 8:34 PM, mikiek said:

Thanks for all the replies. I guess what I am wondering is if it is more efficient to buy a couple of big blocks and cut smaller filler pieces or buy smaller pieces. I'm kinda thinking a big block would be better but there might be more waste.

I think there's trade-offs with either method.  You might buy a small sampling of the larger block and test to see how everything goes for you. It's probably a bit more time consuming than the smaller blocks but overall, less money. 

[Snug Harbor Johnny]

  I used both bass and balsa on a hull as an experiment, and found that balsa is a bit soft (but after shaping it can be 'hardened' by applying titebond and rubbing it in a little - then allowed to dry before sanding).  Now some balsa may be denser, but dense balsa if hard to find these days (not so 50 years ago for RC planes).  You need to mind the grain direction of bass as filler - amidships to app reaching bow and stern, the grain should run fore-and-aft for easier shaping/shaving.  Where the curve plunges at the bow, cutting a piece to fit with the grain at a 45 degree angle will limit carving across end

grain.

[Pete Jaquith]

I used 1/8", 1/4" 1/2" and 3/4" basswood sheet laminated for the bulkhead spacing for filler blocks.  If basswood is not available, I would use pine or popular.  Shaping was done with #80 grit paper wrapped around 1" and 1.5" dowels.  They turned out to be very effective fairing tools rapidly removing unneeded material.  This was followed by #120 and #150 grit paper using the same large dowels.

 

After initial shaping with gouges and chisels, I use the same large dowels for fairing laminated solid hulls.