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[dave parker]

Hi all

Am about to embark on my first dope and tissue covering of a hull, and have a few (probably daft) questions but before i make a mess I want to be sure.

So...

1.  Dope mixed with thinners or dope mixed with sanding sealer?? Which one and why?
2.  When covering the sections with the tissue, I know about cutting slightly over size pieces of tissue but do I fold the edges over and overlap with the next panel using the dope (with a view to sanding smooth later)   or do I just dope up to the edges of the hull and then sand/remove the unstuck areas when dry, relying on the following coats of dope to seal the edges?
3. The dope and tissue method is used for the hull, including the upstands round openings etc but is it used on all other areas above deck?
4.  If using this method, is it common practice to do anything with the inside of the hull?


Please be gentle, I appreciate these are noob questions that have no doubt been asked before, but I am looking for good advice before i have a go.
 

[Martin (Admin)]

 

 These any good?

[Martin (Admin)]

Some old posts:

https://www.modelboatmayhem.co.uk/forum/index.php/topic,3827.0.html

https://www.modelboatmayhem.co.uk/forum/index.php?topic=48716.0

https://www.modelboatmayhem.co.uk/forum/index.php/topic,51557.0.html

https://www.modelboatmayhem.co.uk/forum/index.php?topic=26912.0
 
 

 

[Martin (Admin)]

 
More:

https://www.building-model-boats.com/tissue-and-dope.html

"Cut the Dope

When you buy dope at the store it is too thick to use as is. I always dilute it about two parts lacquer thinner with one part dope. Thicker dope will build up faster, but won't penetrate into the wood very well. It also tends to go on uneven.

I buy the Minwax brand Clear Brushing Lacquer from my home improvement store. I then poor some into a washed glass jar. I like those with wide openings as they easily accommodate a 2" wide brush.

Speaking of brushes, I use disposable brushes. I can get a brush to survive a few days as I go through the steps by keeping it in a ziploc freezer bag when not in use."

[dave parker]

Thanks Martin.


I didn’t want to assume that the stuff used by aero modellers was the same as boats.


Do I want shrinking or non shrinking dope??

[andrewh]

Hi, Dave


Answering as a aeromodeller who has had their brain destroyed improved by dope from an early age
and to address your questions as you pose them:


1.  Dope mixed with thinners or dope mixed with sanding sealer?? Which one and why?


Dope mixed with thinners as one of Martin's posts suggests.  I would go about 50/50 as this will sink into balsa well and still be sticky enough to hold the tissue


Sanding Sealer IS dope mixed with talc, so mixing in dope would give you dope mixed with less talc!


2.  When covering the sections with the tissue, I know about cutting slightly over size pieces of tissue but do I fold the edges over and overlap with the next panel using the dope (with a view to sanding smooth later)   or do I just dope up to the edges of the hull and then sand/remove the unstuck areas when dry, relying on the following coats of dope to seal the edges?

All of the above as required by the shape.  overlap edges by about 1/4" (or 6mm ) sand after enough coats of dope to make the tissue sandable
Ditto at edges - remove surplus with sanding stick or new razor blade
The dope and tissue method is used for the hull, including the upstands round openings etc but is it used on all other areas above deck?
Tissue fills the grain of Balsa or other woods with pronounced grain (Obechi, Oak!) so is a good, light finish for them.  Following coats can be sanding sealer or dope mixed with talc or microbaloons (in both cases don't breathe the dust)
So if your upperworks are styrene, ply, or card there is no need to tissue-cover them for strength or to seal the grain


4.  If using this method, is it common practice to do anything with the inside of the hull?
Glyn Guest (GG on the forum) suggests leaving the inside untreated and drying out after each sail - this is better than trapping water in balsa wood!
Some of his balsa boats have survived (by my estimation) nearly 40 years

Shrinking or non-shrinking Dope?
The question suggests that you are in the US where nitrate (shrinking) and butyrate (non-shrinking) dopes are available
Ans:  it doesn't matter to boaties a hoot - use the cheapest and most available

Solvent or water-based
All my answers above relate to the smelly (   )  solvent based dope

A couple of the replies relayed by Martin relate to water based products ( EZ dope) and (maybe) Minwax brand Clear Brushing Lacquer
Water based products are relatively new, work well and don't stink the house out

I use them for stick and tissue model planes, and have discovered that EZ dope needs to be heavily diluted for use - it is too thick in the jar for anything (that I know of)

you need to pick one system or another,  both work but they don't mix well

hope some of this helps
andrew

[dave parker]

Andrewh
Many many thanks for taking the time to answer my questions.
That really helps and is fully understandable to a newbie like me.
I am uk based but found the shrinking/non shrinking on google search.
Again, many thanks 

[Subculture]

I'd use epoxy resin and light glass cloth- much better than tissue and dope, which has its advantages for covering stick balsa airframes, but no advantages that I can see for boats.

[GG]

Well, as I've been mentioned by name in this thread (even if it was misspelled) some extra comment is perhaps worthwhile.


I agree that as supplied, cellulose dope is usually too thick to use directly.  I usually thin it to something like a  50:50 mix.  I bought a gallon can of thinners from a local motor factors many years ago and have yet to empty it.


The strength of dope is that the first thinned coats of dope do penetrate into the balsa and start the sealing and strengthening process.  Light sanding removes the "surface fuzz", the dope having made the feathery surface fibers stiff and sand-able.  The subsequent coats of neat dope seem to dissolve into the previous coats and produce an excellent bond before drying, which seems much better than just drying on the surface.


The use of tissue is to both strengthen and produce a smooth surface.  I agree it doesn't make a balsa hull indestructible but it limits any accidental damage.  I bought a couple of rolls of model aircraft tissue a couple of years ago, this is much better than the stuff sold for wrapping things up.


Corners can be tackled by sanding/trimming the excess away or folding the tissue around it, a 1/4-1/2 inch (6-12 mm) width is usually OK.  I've found it is usually best to "feather" this excess by cutting it in to short lengths before doping into place.  It makes the process easier and avoids creases (a problem on curved corners).


It often impossible to cover a whole panel on a hull with a single piece of tissue (and usually bloody hard to avoid creases too!).  A modest overlap between adjacent pieces is best, any slight "step" can be removed after light sanding and a couple of coats of dope.


As for cleaning the brushes after use, I never do!  An idea seen in a magazine many years ago (Aeromodeller I think?) was to take a glass jar with metal screw-top lid and (after the contents had been used, washed out and dried of course!) pour dope into it plus any thinners if needed, and 1/2 -3/4 fill it.  Before adding the lid, a hole was made in it so that a suitable brush could be pushed up and firmly wedged into place.  The brush being positioned so that its bristles would be immersed under the dope.  The brush being held in place and the lid made airtight with a fillet of something like silicone or mastic sealer.  Now, whenever dope is needed, I reach for the jar, unscrew the cap and ready to go.  The lid has always been airtight and keeps my hands dope free should anything run down the handle.


As for leaving the inside of a wooden model unsealed, it seems to work as my three oldest models, one almost 50 years old, the other two well into their 40's, are still sound.  Give me an hour to refit some batteries/receivers and they are ready to sail.  But, if you don't seal the outer hull surfaces, have leaks, fail to check for and repair damage plus leave water inside the hull between sailing sessions, then sealing the inside might prolong the life of your model.
Glynn Guest 
[size=78%]    [/size]

[andrewh]

Profound apologies to Glynn for misspelling his name

Sackcloth and ashes for me


And I read the same Aeromodeller article and also don't clean my dope brushes after use. 
I squeeze the bristles by hand and let them harden. 
When I need to dope again the brush goes into the dope and is soft in ten seconds

[Merpanda]

Hesitate to speak up in such expert company, but the following may be of interest:


When tissue covering a balsa steam launch hull, I found ordinary pva glue cut 50/50 with tap water worked fine. In fact, I resorted to this on the back half of the hull after my aging tin of cellulose dope ran out amidships!


Finished with Humbrol enamel topcoats the boat has given years of service with no deterioration to either end of the hull finish -moreover, the join remains invisible!


As the build had already degenerated into a wild experiment, I varnished the deck and coamings with exterior grade water-based varnish, which has also held up very well.


Finally, the engine-bay was lined with turkey roasting foil, and painted with radiator enamel. Some crazing has occurred, but the finish remains basically sound.


Moral: you can get away with all sorts of combinations, but don’t try to put polyurethane based finishes on top of sanding sealer - fortunately I didn’t make that mistake on a boat!

[Andyn]

The answer to all the above is leave the dope and tissue in the 19th century where it belongs and use glassfibre cloth with epoxy resin 

[roycv]

Hi all, Balsa with a good finish can last many years.  An early build for me was a Graupner Condor motor yacht built from plans, not the kit, in 1965 / 66.  She went through a bad phase after about 10 years at the hands of my son but had run for all that time.

 I decided to refurbish her which involved replacing the aluminium prop tube which was swaged at the ends for bearings.  I did insert a small length of mahogany at the stem and she is just sitting ready to go with a charge to the batterys as I write this. This makes her 55 years old now.

If my memory serves me back then I used enamels for painting.  But for added strength also consider using ladies stockings with thinned varnish, this does give a lot of strength.  I know glass fibre and cloth is a favoured method but I suggest it is 'over engineering' for model boats. 

 I have used dope and tissue and it does work well.  But whatever method, wet and dry sanding and twice as many coats of paint than you think necessary will give you a good finish that will last.


My approach for the inside has always been to paint and seal as I have seen splits in other models which I have attributed to dampness on the inside causing the wood to expand.  But each to his own methods, what works for you is always best.
I have very recently refurbished a Billing Mary Ann fishing boat and the hardwood planking was starting to part and I noted the inside was bare wood.  What ever the reason, (t may have been drying out)? she now has repairs and a coat of thinned varnish inside and no longer leaks.

Apart from all the above advice my own two pennorth is, do not make any sealed areas or perhaps I should say volumes inside the hull.  Easy to do in the bow area, if it looks inevitable then when the glue has dried cut out the centre of the bulkhead and let the air in.
Regards
Roy

[Merpanda]

@Andyn -looking at the size of the boat you are clutching in your avatar pic I can understand why you would go the glass/epoxy route.


 On small, scale or semi scale hulls, that are generally low displacement I have found the weight of such a coating can cause problems and is mechanically speaking, overkill.


I once repaired an old 30” loa Vosper rescue launch model using this method, but found that with the lead acid batteries required by the owner for duration it was hard to trim the model without some emergency weight saving in the superstructure. In retrospect I would have used simply an epoxy varnish with a thinned first coat, with perhaps the nylon stocking option for reinforcement if it was destined for a particularly knockabout life.


The dope/tissue finish does give an amazingly hard surface for a low weight penalty. The pva version works, in my experience equally well and is a lot less smelly. Next time i have to surface a light wooden hull however, I’m thinking of trying rice paste and tissue! In another context I have found it much easier to work than pva and dries very hard. Whether it can be waterproofed effectively remains to be seen!


One ‘old school’ method I have yet to try is gummed paper tape and shellac laid up on a mould. Watched father do this many years ago and the resulting shell was light, rigid and almost as tough as the equivalent thickness of grp.

[Colin Bishop]

One ‘old school’ method I have yet to try is gummed paper tape and shellac laid up on a mould. Watched father do this many years ago and the resulting shell was light, rigid and almost as tough as the equivalent thickness of grp.

The late Don Brown used this method for his award winning working naval models back in the 1970s.

I have used gummed paper tape over a balsa hull more than once and sealed it with shellac.

On my current paddler build I will be using gummed paper tape to simulate planking on the balsa and lime hull bit will mosten it with Eze Kote and seal it with Eze Kote. I find it a nicer way of working tham with sticky epoxy finishing resin, with or without GRP cloth.

The gummed paper strip seems to shrink very slightly as it dries so gives a nice smooth finish.

Everyone has their own preferred way of working and most get perfectly acceptable results.

Colin

[GG]

Another "old fashioned" method is Paper-Mache".  I did experiment with this technique some years ago and the results were published in the May 2016 issue of the Model Boats magazine. It was also to see if some use could be made of all the junk mail which comes through the letterbox...!


Using the more porous newsprint type of paper and wallpaper adhesive, the inside of an old moulded plastic hull was coated with layers of paper that had been torn into smaller pieces and then soaked in adhesive.  Each layer was allowed to dry before the next layer was added.  A thickness of a couple of millimetres produced a surprisingly strong hull.  Some balsa strips had to be added around the edges of the hull, to add some stiffness and also give more area for the cardboard deck to be glued onto.


The outer surface of the hull was not as smooth as it ought to be and required some filler (from a tube of ready mixed Polyfiller).  The hull was sealed and waterproofed with a liberal application of some varnish left over from a domestic job and produced a surprisingly tough model.


After adding RC gear, a simple superstructure based on a small merchant vessel and a lick of paint, it was sailing around on a local water.  To be honest, it looked as good and performed as well as some models that have been made from "proper" materials.


Glynn Guest

[size=78%] [/size]

[Andyn]

@Andyn -looking at the size of the boat you are clutching in your avatar pic I can understand why you would go the glass/epoxy route.    

There's no wood in that boat anywhere, it's entirely carbon aramid and epoxy.
Done right, epoxy and glass cloth is not overengineering. Done really right, it's lighter, stronger and longer lasting than any other covering method written above

[Circlip]

All down to personal preferences, for BALSA constructions definitely tissue and whatever "Glue", only problem using nylon is that it doesn't absorb the glue, NEITHER does glass cloth/matt with resin, but would use nylon in preference to glass with resin. Not a Luddite outlook, have made my own moulds but for one offs, "Doncha luv the smell of dope in the morning?"


    Regards Ian. 


   Wonder what Vic would have renamed "Krispie" using other than cereal packets?

[warspite]

I know what building a card board vessel is like, still have not done anything on mine for years i.e. the stern, I was thinking of resurrecting it by modifying it by cutting the whole top part off, I.E. from the rear step down above the stern to the bow to reduce its free board, but I might instead go for the dremel cut out the inside to provide space - once I have completed the skin which is to finish the stern and then an outer skin applied after I take the corn flake packet wax finish off.


Note the inside was coated in cascamite glue, a white powder mixed with water, the cereal outside was attached to the grey board with impact adhesive - which seems to be a white colour now, not the toffee colour

[roycv]

Hi Circlip, I varnish the surface first and then apply the nylon again varnish for the nylon mesh.  I suppose it must form a film but it holds it in place with no problem. Very good for simulating canvas on holds etc.

The dope and making full size aircraft was a problem during WW2.  I think they provided extra milk for operative.  There were still some that found a quiet corner and sniffed it.  Did/does the milk do any good?  If not carry on with the coffee and dope!

regards
Roy

[warspite]

So as an aside question is the toffee coloured impact glue still available ? (I found it very strong - this white stuff seems to be weaker)

[Merpanda]

If, by toffee coloured impact glue you mean Bostik/Evostik I think so but: was dismantling a Billings Calypso the other day. It has an ABS hull and the original builder sometime in the 80s had stuck large parts of it together with Bostik -which in 2020 now had about the adhesive qualities of dried biscuit dough . . . In the rebuild I will be using abs pipe cement to fix abs blocks into the hull which I can then put mechanical joints into. Or failing that, use the hull to cast a mould and make a new one in gummed paper strip and shellac! 

[Colin Bishop]

I don't know what they stuck this together with but it's lasted pretty well!

Colin

[warspite]

could be a version of cascamite, they were aware of boiling animal bones to make a glue from them 

[Colin Bishop]

Cascamite is resin based, but yes, they probably did use animal glues.

Coln