Gluing planks to a filler

[Peter Y.]

I've recently completed the initial planking of my first model and proceeded to use a wood filler to smoothen the surface. The planking was quite uneven so after sanding the filler down I can see several areas that are effectively still covered with it. Sanding them down any more would leave the hull covered with nasty depressions.

 

I'm concerned that the 2nd and final layer of planking might have difficulties with sticking to these (filler-covered) areas. Am I right? Is there something I can do to address the issue?

 

The filler in question ('Super Filler' supplied by Cornwall Model Boats):

The glue ('Admiralty Water Resistant PVA Wood Glue' supplied by Cornwall Model Boats):

The wood itself is 1x4 [mm] walnut that looks quite dry (Caldercraft HM Pickle kit).

[Thistle17]

I have no experience with this filler but have used a state side product called RAGE auto body filler on a PVC skin for an RC model that needed fairing before it was planked with mahogany. Some of the filler was still present after sanding. I was timid for the same reasons as you. We finally plunged ahead and fastened the planking with CA glue and it worked. We used the 20 second variety. I might suggest that you make up a sample substrate wood/filler and try something other than PVA. PVA bonding requires penetration into both surfaces.

Joe

[Peter Y.]

Thanks for your reply Joe.

 

Yes I was thinking about using CA glue as well. I do have different varieties at hand (thin, medium and thick 'Admiralty Superglues').

 

I will most definitely do a sample, but was just wondering whether anyone had any experiences in this area. Your example sounds encouraging - sounds like I won't have to compromise the smoothness of the hull after all! That's a huge relief :-)

[Thistle17]

Peter the mahogany planking was 1/16 for the model I built with my grandson. We used medium so we could move it around as its open time was about 20 seconds. Some of the planks needed a return fill with the thin as they just didn't lay down to our satisfaction near the bow. A slight application of the thin and finger pressure holding did the trick. The model is 2 years old now and there is no sign of separation.

 

I have also used DAP Rapid Fuse All purpose Adhesive to bond wood to ABS plastic. It is an interesting product as it can be gently removed and reapplied within 30 seconds of the first application. Afterwards it is fixed and cures in about an hour. I checked with DAP and the only thing you cannot do is glue ABS to styrene for example.

Joe

Edited May 23, 2018 by Thistle17

[Jaager]

PVA - bonds by undergoing a chemical reaction as it dries - producing long and

I guess branched chains.  If the mating surfaces have pores or protrusions large enough ( I

think 220 grit or more course) and are close enough together, the bond should be 

adequate.  Most  fillers seem to have a rough surface.  As long as it is not brittle, or weak

or does not have a glass-like surface, the PVA should work.  If the surface IS glass-like, CA

would work better. If the filler itself is weak, no adhesive can mitigate that.

[Jaager]

Taking a step back and looking at this from a larger perspective,

I have what is probably an impertinent question about the core of this inquiry.

 

If there is to be a second (finish) layer of planking, why is a filler even being used?

Is the next layer so thin that it follows every dip of the subsurface?

If the planking is that thin, I would probably replace it with a more robust planking.

A filler is meant to fill holes, not do what Bondo does in auto body work?

Since it is being covered, looks do not matter.

If there is an error with a significant hollow, I would scab a piece of wood veneer there

and sand it to spec.

[No Idea]

The original poster has said that this is his first ever model and as such is obviously new to boat building.  Its very difficult to get the precision of build that more experienced builders get as this takes time, patience and many mistakes along the way.  To say that major re-working is a necessity on the first build is a bit off putting for a new builder.

 

Peter Y its ok to use filler but leave the surface rough so that your adhesive has something to bond onto.  As your building skills get better you will require very little filler indeed if any but it is needed now to get the shape that you want.  I personally would use a two pack filler in your case such as easypol - I hope this helps mate.