1949 Chris-Craft 19' Racing Runabout by gjdale - FINISHED -Dumas - 1:8 Scale - RADIO

[gjdale]

Thanks so much Ken, Rusty, Sam and Mike, and all the "likes".

 

Sam, to answer your questions:

 

Yes, fibreglass will go over the hull.

 

Cloth weight is 2 ounces (very light)

 

Epoxy will be West Systems and using their 207 Hardener, which is specifically designed for clear finishes (as I understand it anyway).

 

No to the vacuum bagging.

 

Please bear in mind that I have never fibre glassed ANYTHING before, so I'll be learning as I go!

 

What could possibly go wrong?

[wefalck]

I always had a weak spot for those mahagony run-abouts since I was a small boy and went down to the boat-yard at Lake Constance (Germany), where my grandfather kept his wooden dinghy with a small outboard engine - and where a couple of them were moored under a wooden roof for protection. I loved the sound of the heavy engine, when they were taken out occasionally by their (rich) owners.

 

Missed this building log until today. Nice job !

[src]

Grant,

I have a long way to go to be able to all myself a fiberglass expert, but, I have been doing a lot of hand layups with our FRP department. If you haven't already, make a template and use one of those pizza cutter style fabric cutters instead of scissors to cut your glass, you will get fewer stray strands of glass:

http://www.joann.com/fiskars-45mm-titanium-rotary-cutter/10805208.html?gclid=CPix-Pr-nc8CFZSJaQodePQBXA

 

Pot life is based on a 100 gram mix, for small to medium size parts we try to stay at or below that amount and mix more as we go.

 

We double mix the epoxy; after mixing in the ferst cup, pour it in a new clean cup and mix again.

 

There are special stippling brushes sold for hand wetout, we use cheap chip brushes and cut them down to about 3/4"- 20mm. Just make absolutely certain you get all the loose hairs out.

 

You are going to do a test layup or two on scrap I assume? It might be worth checking to see what overlap will do to your transparency.

 

Use a respirator especially when sanding, but you didnt need me to tell you that.

 

Have fun, I will be watching - and learning - as you do this.

Sam

[John Allen]

Grant,

 

It just flows, very smooth & clean.

[mtdoramike]

I can't wait to see the fiber glassing phase

 

 

mike

[CDW]

If you don't mind me saying so, 2 oz fiberglass cloth is not what I would call "light". 1/2 oz or 3/4 oz cloth is light.

In my humble opinion, 2 oz cloth may be too heavy for a model like this. To be on the safe side, try a piece on some scrap, first. Just to get a feel for how it lays down and what it looks like after it's down.

I am basing this on my own personal experience with laying fiberglass. The lighter the glass, the more transparent it will be in the end (a good thing) and the easier it will be to prevent any wrinkles and/or bubbles. 

[src]

They make 1/2 & 3/4 oz cloth?? Never seen it, but then we are always building things that have to take abuse.

 

Grant, maybe I missed it as I was catching up, why glass anyway? Why not just the resin?

 

Sam

[CDW]

They make 1/2 & 3/4 oz cloth?? Never seen it, but then we are always building things that have to take abuse.

 

Grant, maybe I missed it as I was catching up, why glass anyway? Why not just the resin?

 

Sam

Sam

 

I buy 3/4 oz cloth here: http://www.sigmfg.com/cgi-bin/dpsmart.exe/IndexMiscellaneousF.html?E+Sig

They also sell a .56 oz cloth that I call 1/2 oz (close enough for me).

 

I primarily use it when I build balsa cowls for my R/C aircraft models. I use the light cloth to fiberglass the outside of my cowlings. tt makes them much stronger, dent resistant, and fuel proof. Or, in the case of a model boat, water proof. 

But as you mentioned, just finishing resin without any glass at all would probably work just fine. The glass will give an added level of protection and resistance to cracks of dents if the model is to be powered and used in the water. For a shelf display, it probably doesn't matter.

[wefalck]

I gather the fibre glass matts are there to take up the strain from the wood in changing humidity and prevent the surface from cracking. Resin alone would not be able to take up these strains.

 

Still I was wondering, whether some good marine varnish wouldn't be sufficient because the planking is on some composite board that should take up the strain.

[gjdale]

Wow,

 

Thanks so much for all the input guys - really appreciated!

 

Sam - some great tips, especially the safety reminders! And yes, some test pieces are called for.

 

Daddyrabbit - you're quite right that lighter glass is available, and used extensively by the aircraft folks where weight is a real consideration. I'm basing mine on advice from guys who've built a number of these boats before, over on the RC Groups forum.

 

Sam - Wefalck is spot on the money. The fibreglass not only adds strength and waterproofing, it also prevents the wood from shifting and cracking open seams later on - a problem I've certainly read about.

 

Mike - me too!

[mtdoramike]

To me, Varnish would not be enough, initially it might not leak, but if you hit something or just the strain and stress from the motor(s) could cause issues. I too have never glassed anything either and is why I'm curious to see how yours turns out. I intend to build an R/C boat as a gift for my son in law and my grandson, so I will be glassing what ever I choose to model.

 

 

mike

[Keith_W]

gjdale, if you get around to fibreglassing your boat, I think most of us would appreciate detailed pictures on how you do it. I have never seen a model fibreglassed before, and I would love to know how. 

 

Keep up the great work, she looks magnificent. 

[captainbob]

One of my first RC boats (17 years ago) was finished with resin only.  It now has cracks between the planks.  You need to use light weight glass or nylon stockings for strength.

 

Bob

[mtdoramike]

Well that IS a new use for old Stockings. Then when your boat gets on plane you can say your boat is getting a little "leggie".  

 

 

MIke

[wefalck]

Slightly off-topic, but there various uses for ladies' stockings. For instance, the purse-net on this 1:90 scale botter model was made from a (new!) ladies stocking:

 

 

I also know that some people make shells for small boats from stocking-reinforced resin over a positive form.

[mtdoramike]

That is really neat, I would have thought to use it myself.

 

 

mike

[mtdoramike]

OK, on with the fiberglassing.

[mtdoramike]

I just bought a 1954 Dumas Chris Craft Commander Express 36" kit that I will be starting on one I finish the Montanes. It will be my first RC boat. What a classy looking boat. Man they sure knew how to make them back then. The Commander reminds me of the SS Minnow that sank on the Gilligan's Island show.

 

http://www.dumasproducts.com/product_info.php?products_id=186

 

mike

Edited September 26, 2016 by mtdoramike

[gjdale]

Congratulations Mike - I'm sure you will enjoy this adventure. I look forward to following your build log in due course.

[VACorsair]

I just bought a 1954 Dumas Chris Craft Commander Express 36" kit that I will be starting on one I finish the Montanes. It will be my first RC boat. What a classy looking boat. Man they sure knew how to make them back then. The Commander reminds me of the SS Minnow that sank on the Gilligan's Island show.

 

http://www.dumasproducts.com/product_info.php?products_id=186

 

mike

I believe the S.S. Minnow was a 40' Wheeler. 

[Captain Slog]

Wow!

 

Apologies Grant I only stumbled across your log today. Beautiful work.  I will need to spend a bit of time going through it all!

 

Cheers

Slog

[mtdoramike]

I believe the S.S. Minnow was a 40' Wheeler. 

I didn't say it was VA, I said It looked like it. But thanks for the observation.

 

mike

[VACorsair]

Mike -  Wasn't trying to correct you.  Was thinking out loud.   During research of Hemingway's boat Pilar (which is also a Wheeler) I had found that tidbit and it came to mind when I read your post.   I will be very interested in your build of the Chris Craft Commander.  If you are looking for info and pics you can go to the Chris Craft Commander Club sight. 

 

Stan

Edited September 26, 2016 by VACorsair

[mtdoramike]

Thanks for the club info Stan, look like some valuable information.

 

mike

[VACorsair]

Mike,

 

Found another site that looks promising for anyone building a Chris Craft model. -----> http://www.chriscraftmodels.com/#  

[mtdoramike]

Ooooooo, thanks Stan, those are some real beauties and brings back some fond memories of some of the best boats ever made.

 

 

mike

[gjdale]

The Fibreglass Trials

 

As I have never attempted fibreglassing of anything, ever before, I decided it would be prudent to do some trials before “going live”. I read a number of “how-to” guides, and found that the one by Pat Tritle on RC Groups Forum was probably the simplest to follow. For anyone that has never done this before, my advice up front is “trust the process!” It is really quite a simple process, but if you don’t know what to expect along the way, it is easy to think that something has gone wrong. It hasn’t (probably…..)

 

Materials used for the test were exactly what is planned for the actual job, and comprise some 2oz. fibreglass cloth, West Systems Epoxy Resin (No 105), West Systems Hardener (No. 207, which is supposedly designed for use with a clear finish), Feast Watson Spar Marine Varnish, and Krylon Premium “Copper Brilliance” (rattle can spray paint – for the below the waterline colour).

 

I made up two test pieces of roughly three inches by four inches Sintra (the plastic sheeting that also forms the sub-planking). One of these was planked with Mahogany strips just the same as the sides of the hull, and the other was left ‘au-naturale’, the same as the bottom of the boat.

 

The first step was to cut some cloth a little over-size and drape over the test pieces. The Epoxy was mixed according to the West Systems directions (a three to one ratio by volume in this case). A lot of folk say to thin this mix by adding up to about 20% denatured alcohol (methylated spirits here in Australia). The reason given for this is that it supposedly helps the epoxy penetrate the timber substrate and also reduces the chance of bubbles in the mix. The West Systems website advises against thinning and states that strength is significantly reduced by thinning. I decided to stick with the West Systems advice and did not thin. I applied the epoxy by pouring a small amount onto the centre of the test piece and then using a hotel room keycard (same size and shape as a credit card) as a squeegee to spread the epoxy and press it into the weave of the cloth. The important part of the process here is to ensure that the epoxy gets into the weave all over, and right up to the edges (though excessive over spill along the edges is to be avoided).

 

 

Here’s what the test pieces looked like after this step:

 

 

 

Once the epoxy had cured, the excess cloth was roughly trimmed back with a single edge razor blade, and then block sanded with 80-grit sandpaper to the edge of the test piece. The surface was then lightly sanded with 120 grit to remove any high spots. Care needs to be taken here not to sand through the glass itself.

 

 

Note that the weave of the cloth is still visible here. Don’t panic!  Here’s another couple of shots to show clearly how much of the weave is still visible.

 

 

 

A second coat of epoxy was then applied, this time with a stiff brush. The aim of this coat is to fill the weave of the cloth. This is what makes the cloth seem to totally disappear. Once that coat had cured, it was again lightly sanded and a third coat applied. The aim here is to get a smooth surface with the weave of the cloth completely filled. If it isn’t to your satisfaction you can keep adding more layers until it is, but I stopped at three coats for the purpose of this trial.

 

Here is what it looked like after the third coat and wet-sanding with 240 grit. Not sure if the variation in “shiny-ness” is due to light reflections (which is what I think it is), or whether that section was still wet from sanding. Again, the aim here is a flat smooth surface – don’t worry about “shine” at this stage (remember, trust the process!).

 

 

At this stage, it is time to start adding the clear coat (or colour in the case of the bottom)

 

I brushed on one coat of Spar Marine Varnish on the planked test piece, and then lightly wet-sanded with 1200 grit. On the unplanked piece, I sprayed one coat of Copper from the can, followed again by lightly wet-sanding with 1200 grit. My observation at this point is that the Copper paint probably needs at least two coats, and probably no sanding on the final coat.

 

For the remaining clear coats, I wanted to spray the varnish. I thought that a standard airbrush with a 0.35mm needle might not be the best approach, so after seeking some advice from the Airbrush Megastore (based in Adelaide), settled on this as my weapon of choice:

 

 

The directions for the Spar Marine Varnish say to thin by 10% with Mineral Turpentine for spraying, so that is exactly what I did.  Oh boy, what a piece of kit! Took no time at all to lay down a good coat of varnish and I can see that when I’m painting the whole boat, I will be praising my good sense in purchasing this! As the varnish is thinned just that little bit, it also levels very well.

 

Here is a picture of both test pieces having had one coat of varnish sprayed on. It's really difficult to capture the gloss shine on these pieces in a photograph. You'll just have to trust me on this. The copper painted piece shows both some variation introduced by sanding, and also a blemish where the initial epoxy coats did not quite level. Lessons for the “real thing”.

 

 

And finally, here is a shot of the planked test piece next to the un-treated hatch cover. Notice how the grain is much more apparent after glassing and varnishing, as well as being a slightly richer colour. 

 

 

At this stage, a few extra coats of varnish would be followed by further shine imparted by very fine sanding and polishing. I'm not going to bother with that on the test pieces as the purpose of the test was purely to get comfortable the fibreglassing process. Okay, on that basis I think I’m ready to declare a win and proceed with glassing the whole boat. I’ll be back once that is well and truly underway.

 

[Captain Slog]

Hi Grant,

 

Thanks for the detail in fibre glassing.  I like your purchase of a spray gun.  I am thinking along this lines for painting hulls as advised by Paul Budziks videos as my 0.3 Iwata airbrush struggled a bit for a full hull.

 

Cheers

Slog

[cog]

Grant,

 

I'm enjoying the ride of your log. Very informative too! Thus, a question arises: How much varnish did you make to use in the spray gun? Not a lot of waist when using a 44 magnum on a square inch wooden target?

 

I'm pondering for some time to buy such a gun for larger area's, as it takes a long time, even with an airbrush with a .4 needle, to cover a hull of some size.

 

Cheers

[gjdale]

Thanks Slog and Carl.

 

Slog - it was watching the Paul Budzik videos that sent me down this path in the first place. I can thoroughly recommend the Airbrush Megastore - check out their website. Great friendly service, reasonable prices, prompt delivery, and good advice. Go on, you know you want to.............

 

Carl - that gun has a 1.0mm needle as standard but also comes with a 1.2mm in the package. With the recommended spraying pressure of 40psi, you can cover a large area very quickly indeed. To answer your question, I made up a batch of about 50ml and used only a fraction of it. I was able to decant the leftover back into a glass container afterwards. Not sure how well it will keep, but we'll see.