SS Blagoev ex-Songa 1921 by Valeriy V - scale 1:100 - Soviet Union

[Valeriy V]

After the epoxy resin has dried, I cover the hull  with liquid automotive putty using a spray gun.

[Valeriy V]

Then I sand the hull and bring it to this look.

[Valeriy V]

It looks more interesting from the nasal angles.  

[Mirabell61]

splended work Valeriy,

its a beautiful hull, will you imitate the riveting and do plating ?

 

Nils

[shipman]

4 hours ago, Valeriy V said:

The hull of the model is covered with fiberglass with epoxy resin.

Just love your work and tutorials, Valeriy.

Thank you for sharing.

 

Question: when covering the compound curved areas with fiberglass, how do you avoid folds and wrinkles?

[Valeriy V]

3 hours ago, Mirabell61 said:

splended work Valeriy,

its a beautiful hull, will you imitate the riveting and do plating ?

 

Nils

For rivet head size calculations I show the German Lloyd chart. Circled in blue is the thickness of the cooable panel sheet that I choose. Green color is the required rivet diameter.
As a result of a simple calculation, I get the dimensions of the rivet head for my model on a scale of 1:100 - diameter 0.3 mm and height 0.15 mm.
Even if I can make such small details on the model, after covering with primer and paint they will simply visually disappear.
Therefore, it makes no sense to show rivets on this model.  

 

But the belts of the outer hull plating sheets will be shown.  

[Valeriy V]

2 hours ago, shipman said:

Just love your work and tutorials, Valeriy.

Thank you for sharing.

 

Question: when covering the compound curved areas with fiberglass, how do you avoid folds and wrinkles?

Avoiding wrinkles is not difficult:
1) I make cuts in the fiberglass fabric as shown in the photo along the green lines before applying the resin
2) after applying the resin in small portions, I smooth it along with the fiberglass with a soft rubber spatula
3) in case the resin polymerizes too quickly, I have a construction hair dryer nearby with which I can heat the desired area of the resin and fiberglass to liquefy it

[GrandpaPhil]

Very cool!

[Bob Cleek]

5 hours ago, Valeriy V said:

in case the resin polymerizes too quickly, I have a construction hair dryer nearby with which I can heat the desired area of the resin and fiberglass to liquefy it

Beautiful build so far! Not to distract you with petty questions, but I'm curious if something was "lost in the translation" of the above statement. I've done a lot of boatyard work with epoxy resin. As I am sure you know, the curing speed of epoxy resin is dependent to a great extent to the temperature of the epoxy. Reducing the temperature of the epoxy resin and hardener mixture will greatly slow the speed of the cure. With all my epoxy work, I try to mix the epoxy in a flat pan rather than a tall-sided container like a can. This expands the surface area of the resin mass to permit the greatest dissipation of the heat generated by the exothermic reaction of the curing process which otherwise can accelerate out of control dangerously.  In some large laminating jobs, I've even put the epoxy container on ice to slow things down enough to get everything assembled and clamped before the resin "kicks off." (This can reduce the temperature of the epoxy enough to cause condensation to form on it, causing it to "cloud," but this moisture seems to evaporate on its own without any ill effects to the bond and the "clouding" disappears in due course.) 

 

I gather a "construction hair dryer" is what we call a "heat gun," basically a hair dryer that gets very hot. These have generally replaced the old open-flame "painter's blowtorches." Are you saying that heat applied to epoxy that is curing too quickly can be heated to reverse the polymerization process and thus "re-liquefy" it? In my experience, heat speeds up the curing rate of epoxy resin, making it harden faster. I've never heard of heating curing epoxy to reverse the hardening (polymerization) process. (Which isn't to say I've heard everything yet!  ) In commercial work here in the United States, we use hardeners that produce a cure at varying rates of speed. I prefer using one rated for "tropical" use in hot weather which retards the cure rate substantially because I'd rather have the time to get the job done before the resin hardens and I have no reason to desire a fast cure in the work I do. (See: User Manual & Product Guide | WEST SYSTEM Epoxy translated into various languages.) 

 

I've heated cured epoxy resin with a heat gun when scraping paint that was applied over epoxy resin and found that the resin softens somewhat, but scrapes off in a dry, "crumbly," consistency and not "liquefied." If simply heating epoxy that is curing too fast with a heat gun reverses the curing process, that would sure be a good trick to know when working with epoxy.

 

Please explain if you have time from your great work. 

Edited November 4, 2023 by Bob Cleek

[Valeriy V]

41 minutes ago, Bob Cleek said:

Please explain if you have time from your great work. 

Bob, I already regretted writing this phrase.  
We live in different conditions and I don’t have such a wide selection of hardeners as you do.
And yet, with the resin that I have to work with, this is what happens. At the moment when it just begins to thicken on the hull of the model, I still have the opportunity to make it more liquid for a very short moment using a hairdryer.

This technique allows me to have time to remove all excess resin from the model body and achieve an almost ideally smooth surface of fiberglass impregnated with resin, without lumps of excess resin.

[Dr PR]

I had a problem with cured epoxy getting softer when heated.

 

I have a 6 foot long fiberglass hull with 1/2 inch thick Plexiglas frames spaced about every 6 inches. These are glued to the hull with epoxy. Between the frames are stringers at the main deck level that the deck rests on. These are also epoxied into the hull. All bonded surfaces of the Plexiglas were dimpled and these were filled with epoxy to ensure good adhesion. All of these joints were cured for several weeks and the epoxy was very hard. It was difficult to scratch and drilled/machined well.

 

I was fairing the hull with Bondo auto body filler to correct a defect in the original fiberglass hull. After applying the Bondo I left the hull outside in the hot summer sun to speed the cure (and keep the odor out of my work space). The fiberglass had white gellcoat  but the Bondo was gray and absorbed the heat (and it was also releasing heat as it cured). The whole hull heated up quite a bit.

 

If you have worked with plastic much you will know that it has a relatively large thermal coefficient of expansion - a lot greater than fiberglass! The Plexiglas frames and stringers were machined to a tight slip fit. As they heated up they expanded faster than the hull and a lot of stress built up. The heat also softened the cured epoxy so it became soft like putty. Suddenly one end of a stringer popped out of position, relieving the stresses on the whole thing. But then when it cooled the epoxy hardened again holding the piece way out of line. I had to cut it out, clean up the mess, and put another stringer back in place. And I learned to not heat the hull too much!

 

From this experience I guess that cured epoxy is like a type of plastic (long polymer molecules). Apparently the type I was using has a relatively low melting point.

Edited November 5, 2023 by Dr PR

[Valeriy V]

Stem

[Valeriy V]

Sternpost

[Valeriy V]

Making a break line in the stern.

 

[Valeriy V]

As a result, the rear part of the model looks like this

[shipman]

How did you drill the sternpost 'pintles' in-line?

[Valeriy V]

5 hours ago, shipman said:

How did you drill the sternpost 'pintles' in-line?

The holes are drilled with an extended drill bit. First, 3 “steps” were drilled from the top, and then 3 from the bottom.

[Valeriy V]

The photo shows the installation of side keels.

[Valeriy V]

Wooden slats were removed from the inside of the bulwarks and a deck was installed.

[Mirabell61]

Valeriy,

I like the surface condition of your spray putty, could this also be applied with a paint brush for acceptable results ?

It looks like your deck is from brass plates, its hard to see from the photo

 

Nils

[Valeriy V]

9 minutes ago, Mirabell61 said:

It looks like your deck is from brass plates, its hard to see from the photo

Nils!

  The deck on the model is currently made of plywood and is covered with a protective layer of varnish on top. But everything will change soon...   

[Valeriy V]

15 minutes ago, Mirabell61 said:

Valeriy,

I like the surface condition of your spray putty, could this also be applied with a paint brush for acceptable results ?

Nils!

I think yes, you can work with a brush. But we must take into account that the hardening speed of this putty is greater than that of paint and you cannot hesitate. And most importantly, after mixing the two components, the putty must be diluted with acetone until it is very liquid. And you will have approximately 20-30 minutes for the entire operation.

[Valeriy V]

It should be added that after adding acetone to the putty, it cannot be applied to metal parts. Only on wood and fiberglass with resin. This putty composition does not adhere to metal after drying.

[Mirabell61]

Many thanks for your kind advice Yaleriy,

 

Nils

[Bob Cleek]

On 11/4/2023 at 12:22 PM, Valeriy V said:

We live in different conditions and I don’t have such a wide selection of hardeners as you do.
And yet, with the resin that I have to work with, this is what happens. At the moment when it just begins to thicken on the hull of the model, I still have the opportunity to make it more liquid for a very short moment using a hairdryer.

This technique allows me to have time to remove all excess resin from the model body and achieve an almost ideally smooth surface of fiberglass impregnated with resin, without lumps of excess resin.

That's an effect I've never encountered. Perhaps what's happening is that the resin you are using is rather thick and heat will thin it out if it's heated before the polymerization is too far advanced. That said, the mixed resin and hardener shouldn't ever be "just beginning to thicken on the hull of the model" before you have the time to wet down your glass fabric. (Here, many now use a non-glass fabric called Dynel which is more like stretchy Lycra that they make ladies' stretch pants out of than woven glass cloth. It stretches to conform to curved surfaces much easier than glass cloth does and it doesn't have the nasty habit of spreading microscopic bits of broken glass that gets on your skin and makes you itch like crazy!) A hull like that is a very small area.  It sounds like you're using a very fast curing epoxy.  If you don't have a slower hardener or some type of retarder, you can try chilling the resin and hardener before mixing. The lower temperature should retard the cure rate quite a bit and give you better working time. Any way you cut it, it sure should not be as challenging a job as it is for you now. I can understand, of course, that the present isn't likely to be the time for you to be complaining about the quality of the locally available epoxy. Here's to the day when you will be able to just order some of our slow stuff from Amazon without any hassles! 

 

We don't worry about getting a perfectly smooth surface when we sheath with epoxy and fabric (glass or Dynel) in applications like we are discussing. We just want to make sure the fabric is well saturated and flat against the surface to be sheathed without any air spaces between it and the surface. Instead, what is done is to "squeegee" the mixed resin into the cloth with a piece of  flexible polyvinyl plastic card or the like just enough to soak the cloth completely. "Squeegee-ing" means spreading the mixed resin with the edge of the card like a scraper and using the flat of the card to work it in. The mixed resin is just poured, a bit at a time, as it is spread so that there isn't a lot of excess resin on the surface. When the cloth is fully soaked with resin and any excess scraped off, it is left to cure. There will be the texture of the cloth apparent, since all of the excess resin has been scraped off. You should be able to do this spreading and scraping quickly enough that there will never be any problem with globs of hardening resin kicking off while spreading the resin Glass cloth will have a bit of a texture of the weave on the surface when the resin is cured. (Dynel, on the other hand, has a bit of a "fuzz" to its surface, being very finely woven,) After the resin has at least cured sufficiently to no longer be tacky and you can work with it without getting stuck to it your self, we mix another batch of resin and hardener into which we add glass "micro-balloons" or some other "fairing compound additive." These are powders used to condition the epoxy for various purposes, in this case, to make the hardened resin and additive into an epoxy that is extremely easy to sand to a very fine, smooth surface. That batch of resin and sanding additive is then applied in the same fashion as the earlier coat of resin applied onto the cloth. It will have a thicker consistency than plain epoxy resin because of the powder additive and can be spread like soft butter or peanut butter. Spread it onto the surface no thicker than you need to fill the surface irregularities of the first resin application. When it hardened well, it can be sanded like soft auto body putty and when smooth can be sprayed with basecoat paint. 

[Valeriy V]

30 minutes ago, Bob Cleek said:

That's an effect I've never encountered................

Thanks Bob for the useful information. I already realized that my advice is unnecessary for residents of the US and EU.  

  And, as I wrote earlier, I do not have such a choice and I am forced to work with what I can buy.  

[Bob Cleek]

4 hours ago, Valeriy V said:

Thanks Bob for the useful information. I already realized that my advice is unnecessary for residents of the US and EU.  

  And, as I wrote earlier, I do not have such a choice and I am forced to work with what I can buy.  

Hah! I've yet to see anything in your great posts that I'd consider "unnecessary!" I'd say your skill and techniques are far more advanced than what most of us, here in the U.S. at least, are used to seeing regularly or capable of matching. I can't imagine what magic we will be watching you perform when you are no longer working under your present constraints. I have no idea how you can presently accomplish what you do. Please don't ever consider your advice unnecessary. I can't speak for the E.U., but from what I've seen in my country, the American amateur ship modeling hobby nowhere nearly as advanced as the Eastern European ship modeling hobbyists appear to be. While I'm sure each group has its "stars" such as yourself, here we haven't even begun to think of what we do in terms of the highly competitive "sport" that ship modeling looks like where you live. Please don't stop sharing your work with us!  

[wefalck]

How did you cut the slots for the metal inserts, free hand with a small power-drill and a saw or cutting disc?

[Valeriy V]

43 minutes ago, Bob Cleek said:

Hah! I've yet to see anything in your great posts that I'd consider "unnecessary!"....... Please don't stop sharing your work with us!  

Bob, unfortunately, Google translator distorted my thought a little, but oh well - it doesn’t matter anymore.  

I am grateful to you for your warm feedback about my efforts, thank you!

[Valeriy V]

30 minutes ago, wefalck said:

How did you cut the slots for the metal inserts, free hand with a small power-drill and a saw or cutting disc?

Using an ordinary cutter and a homemade depth stop.