Making a mold build thread (How to)

[Thin water]

The first step in making your own mold is to build your plug (and not
just use a boat someone else built). See picture. It must be fair and
true or your mold will make bad boats of no value. Spent the time to
get the plug right.
[image:
http://www.modelpowerboat.com/gallery/files/6/5/9/72inchinsun.jpg]


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[Thin water]

Another view of primered plug.
[image:
http://www.modelpowerboat.com/gallery/files/6/5/9/plugprimer2.jpg]


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[John]

Good start Jim. I'm looking forward to seeing the whole process.


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[Thin water]

Nothing worth taking pictures of right now. I just sanded down the
second coat of primer and sprayed on a third. I smeared a very thin
layer of Bondo in the seams on the outside to fill any grain and the
joints. A (Very small) small amount of grain texture can be sanded out
of the finished mold but you strive to have no flaws in the plug. You
will still have flaws but if you can't find them in the plug they
should be small enough to sand out with 220 then 400, 600 and 800 grit
wet sandpaper once the mold is done.

When the hull is smooth enough we will make the flange. This makes it
3x easier to remove a layup from a mold without damage to the mold or
the part.

After the flange is made we will prime the entire thing once more, sand
it down then paint it with several coats of paint.

After that the plug will be waxed about seven times, buffed between
each coat then the layup of the mold will begin (no PVA will be used
since it will bond to paint). The method for laying up a mold is
similar to making the part with some small differences that I will
show.

After the mold is done I will sand it through 1200 grit wet paper then
polish it and lay up a hull in it.

After the hull is done I will use it's final size to measure out the
deck plug and make it to fit the boat then repeat the mold making
process for it.

I will make a deck in the deck mold then join it to the hull.

JIM


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[Thin water]

Here is the flange being glued onto the plug. This allows you to put
wedge between the part (the boat you are making) and the mold to pop it
out. It is not really needed since a V hull comes out of a mold with
very little effort. It also adds a lot of rigidity to the sides of the
mold so they don't flex and the hull shape remains true to the plug.

[image:
http://www.modelpowerboat.com/gallery/files/6/5/9/72inchflange.jpg]


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[Thin water]

The primer was not enough to fill all of the grain in the wood so I have
smeared a very thin layer of spot putty also known as glazing putty into
the grain. It is hard to sand so it is best used in very small amounts
at a time then more added to any grain still seen. This must dry well
before sanding or it will just clog the paper. Final sanding will be
done over the weekend then it will be time to paint the plug.


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[John]

Do you have spray putty that is used by Auto painters over there? I've
used it before and it is great to fill in the small scratches and
stuff.


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[BCRandy]

Drywall compound or spackling paste also works well. It is
about as soft as balsa for sanding, but a coat of shellac or
clear polyurethane soaks in and hardens it.


"John" <John.2q3sbb@no-mx.forums.yourdomain.com.au> wrote in
message news:John.2q3sbb@no-mx.forums.yourdomain.com.au...
>
> Do you have spray putty that is used by Auto painters over
> there? I've
> used it before and it is great to fill in the small
> scratches and
> stuff.
>
>
> --
> John
> ------------------------------------------------------------------------
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> View this thread:
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>

[The Evil Tessmacher]

Thin water writes...

>
> The first step in making your own mold is to build your plug (and not
> just use a boat someone else built). See picture. It must be fair and
> true or your mold will make bad boats of no value. Spent the time to
> get the plug right.
> [image:
> http://www.modelpowerboat.com/gallery/files/6/5/9/72inchinsun.jpg]
>

Excellent thread!

This is the solution to a problem that has been facing me for a while
now. I had no idea how I was going to make a hull for my next model,
and this appears to be the ticket!

Thank you! I can't wait to see the rest of the photos.

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Coming Soon to a Kiosk near you!

[Thin water]

I have not seen the spray putty, I wish I had some. The spot putty is
working great. More pictures will be posted on Monday after it is all
sanded smooth. It is getting very close to being ready to paint.

I just laid up a mold of a hatch for one of my production boats today,
it is good to keep in practice.

JIM


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[wizardrincewind]

the best thing to use when making a mould is car body filler, when you
have got it smooth give it a coat of black gloss spray paint and any
inperfections will show up. before you take a mould give it two good
coats of black and polish it to a mirror finish. dont use matt PVA
(poly vinyl alcohol) only the gloss. it saves alot of polishing of the
mould later. spray it on dont brush it to keep the surfice smooth.
dont use a polish with silicone in it WILL kill you mould

[Thin water]

Here it is in the first coat of paint. a couple more coats and it will
be time to make a mold! Is is sitting on some consoles I used to make
for small boats.

[image: http://www.modelpowerboat.com/gallery/files/6/5/9/DSC00063.JPG]


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[Thin water]

I was just thinking, I could make four of these hulls and attach them
but to but, call them a pontoon and make a pedal boat. At 12' long I
think it would work.

Just a few more spots to touch up then final paint and mold lay up.

JIM


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[yeeharacing]

Jim, Thanks for this tutorial, you are helping me out alot.

Im still in the drawing stage but hope to be building my plug in the
next few weeks. 70+ inch cat.

Thanks again,
Rick


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[Thin water]

I hope to apply the gel coat within two days. I ran out building a
couple of deep V' s and will pick up another 5 gallon pail tomorow. I
will wax the plug about five to seven times, letting it dry then
buffing between coats. I won't use PVA because it can and usually does
bond to paint and I hope to extract the plug in one peice. A boat shaped
plug is not to hard to get out. I made a radio/electronics box plug a
few months ago (28" wide for offshore boats VHF radios and stereo
systems) and since it is nearly square with minimal draft I had to
break it up to get it out of the mold. Polyester resin can shrink from
1.5 to 2%. On a big plug this can be a lot and really squeeze itself
around the plug. The resin shrinking actially helps when you lay up a
boat in a mold since it makes it easier to get out of the mold. I made
a little hatch scoop mold today and had to cure it in my oven on very
low heat since it started raining. The plug popped out of it with only
finger pressure. I love it when everything works.

I tried to upload new pictures to this site but it kept saying
"Internal server error".

JIM


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[Thin water]

The pictures worked now. Here is the radio box I made in the mold I made
for it. I made the plug out of 1" thick pine and about 1 qt of bondo. It
was finished in white enamal and PVA coated. I had to chip it out of the
mold very carefully so I did not hurt the mold. It took me a month to
get it out, a little each day. It was soaked in water, let dry heated
in sun, put in deep freeze etc... until it was all free. The PVA bonded
to the paint. This box was made as a gift for a friend of mine. It now
has stainless steel acorn nuts holding the smoked plexiglass on a
stainless hinge and looks great.
[image: http://www.modelpowerboat.com/gallery/files/6/5/9/DSC00616.JPG]


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[Thin water]

I have purchased all of my supplies needed to finish the mold. I am
still filling all little scratches that I find and sanding it smooth.
Final paint will be on today or tomorrow then I will post pictures of
the gel coat and lay up process.


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[Thin water]

Here is the plug done. As always it could be better but I always get
over it before it is perfect then I am mad at myself as I wet sand out
the mold. I am letting it flash off solvents in the house overnight
since it is about 80% humidity here in FL and it gets really damp at
night. I will wax it in the morning then begin the gel coat. It will
get at least six coats of wax before I gel coat it. This I won't skimp
on. It must be allowed to dry between each coat of wax then buff off
the wax and apply the next coat. This will take about 5 hours including
the drying time.

You can really see how big it is against the full size stove.

JIM

[image:
http://www.modelpowerboat.com/gallery/files/6/5/9/72inchplugready.jpg]


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[Joe Petro]

Looks great, Jim!

Keep it going...


Joe Petro
'Zippkits.com' (http://www.zippkits.com)


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[Thin water]

I got the plug gel coated yesterday so it would not be worth taking
pictures of. The lay up will be delayed until Monday or Tuesday due to
the tropical storm due to hit us tonight.

TIP: Don't use aluminum color metal paint. The mold release wax did not
like it. It all came off down to the white paint that I painted over the
yellow paint. It had to be waxed seven times to get off the silver. Wax
on Wax off grasshopper. I don't remember my Kung Fu classes being like
this.

It's to bad this size boat would be next to impossible to sell due to
the new and improved shipping rates at most of the major shipping
companies.

UPS wanted $130 to ship a 54" v hull last week. The post office went
from $20.80 for a 54" V to over $56.00 this month. I guess I will have
to make smaller boats :(

JIM

JIM


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[Thin water]

The lay up has started! First I cut a sheet of fiberglass "veil" mat
about 36" wide x 54" long into strips 3" wide then cut it into 3 x 3"
squares. This stuff looks like tissue. It will wet out and conform to
corners without getting bubbles. I painted over the gel coated plug
with resin then laid the veil along all corners. I wetted it out by
using a stabbing motion with a 2" chip brush to keep out bubbles.

First important note:

DO NOT brush the fiberglass. It will bunch up and get bubbles under it.
Where there is a bubble there will be a hole in your mold. It will be
worthless. Mat is always laid with a stabbing motion, if you brush on
it you will mess it up.

After I coated the entire thing in a layer of veil I gave it a second
layer of the veil squares and dabbed on as much resin as it would take
without it running off. This assures a full contact first layer and
gives the mold a smooth finish on the inside. You do not want to lay up
your hull in the mold in this manner because It will be brittle and
heavy.

The second layer has been started. I split 1.5 oz mat by peeling it
apart. This makes a nice thin layer with ample space between the
strands for air to escape. Tear the mat into 3 x 3" odd shaped peices,
don't cut it or it will leave ridge lines in your mold. Apply it the
same as the veil, with as much resin as it will take and make sure
there are no bubbles under it. If you get a bubble dab at it until it
goes away. If it comes back PEEL THE PEICE OF GLASS OFF and put down
another smaller piece.

Don't let any glass you apply bend in more than one dirrection. It can
go around a corner but the rear of the transom at the chine needs
peices going from the transom to the bottom then other peices going
from the side to the transom. If it trys to go all three dirrections it
will lift and leave a bubble. It can be cut at these type locations at
the corners of the plug to get it to lay down.

The next layer can be full thickness mat. Do not use woven or it will
"PRINT THROUGH" and give your hull a woven impression. This is because
as the resin shrinks and the glass does not the weave puts stresses on
the layup transferring it's pattern all the way through the mold. Since
mat has no such pattern it will remain smooth inside.

Pictures to be posted later tonight.

Questions so far?

JIM


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[dwr9]

Very interesting so far. Can't wait to see the pics. Doug


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[Thin water]

Here is the veil mat used for the first layer. It is like tissue but it
has to be cut, not torn. If it is torn like regular mat the edges will
lift up sometimes. A hydro plug is in the background.

[image:
http://www.modelpowerboat.com/gallery/files/6/5/9/veilsquares.jpg]


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[Thin water]

Here is the plug after it's first full thickness layer of mat. This
should be hand torn, not cut. Let the ragged adges overlap the chines
and the edges of the transom. it will conform to the shape without
lifting or getting bubbles. I sanded it with 60 grit after the first
layer had dried. This knocks down any little fibers that may be
sticking up and would leave an air bubble trapped under the next layer
of glass. This is not needed if you don't let it dry between layers of
glass.

I had to stop today and let it harden so I can wipe off all the love
bugs that landed on it as it got dark. These things are nasty and smell
bad when they splat on your car.

Two more layers of the heavy mat then I will apply some core mat to
stiffin it up then some more glass. You get the idea.

JIM

[image:
http://www.modelpowerboat.com/gallery/files/6/5/9/firstlayer.jpg]


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[Thin water]

No glass work tonight, it is raining hard and the resin would not kick.
At least there are no bugs.

If this thread is sucessfull a person who has no clue about how to make
a mold will read it and almost feel like they always knew how to do it.


Is this the case or are there still voids in the process?

JIM


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[dwr9]

Hi Jim. Any more progress? Doug


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[dwr9]

The hull came out of the mold looking real nice! I hope it performs as
good as it looks. What is the size of that last boat you made? Doug


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[Thin water]

The above boat is a 54". I don't know if I will make any more because of
several flaws in it requiring body work (I hate having to do body work
on a part that should be right, right out of the mold). I have a very
nice all original 47" deep V mold set that is perfect. I just made the
plug for a hatch for it. I will make that one and Plumkrazyrcboats will
sell them. It is the perfect length for most motors. It is in my photos
sectionj. Here is the bottom of the first one.
[image:
http://www.modelpowerboat.com/gallery/files/6/5/9/47invbottom.jpg]


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[Lushy]

Hi all how hard would it be to make a paddle steam hull concidering it is
relatively flat bottomed???
Lushy
Down Under
Thin water wrote:
> The above boat is a 54". I don't know if I will make any more because
> of several flaws in it requiring body work (I hate having to do body
> work on a part that should be right, right out of the mold). I have a
> very nice all original 47" deep V mold set that is perfect. I just
> made the plug for a hatch for it. I will make that one and
> Plumkrazyrcboats will sell them. It is the perfect length for most
> motors. It is in my photos sectionj. Here is the bottom of the first
> one. [image:
> http://www.modelpowerboat.com/gallery/files/6/5/9/47invbottom.jpg]

[dwr9]

Jim, any more news on how this boat is going?


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[Thin water]

No progress due to a lack of funds. I am making a couple of kayaks to
sell on ebay to raise a little cash.

JIM


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[rc john]

Worth a read:
http://www.cfsnet.co.uk/Web_FibreglassGuide.pdf
(If the link is not active then cut and paste.)


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[dwr9]

Jim, Didn't you say you didn't think you were gonna make any more of
that 54" boat? It's now listed as coming soon on PlumKrazy and he's
calling it the Daggeroo. Doug


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[Thin water]

It has been up on that site since I started the project. It is undecided
what I am going to do with it now. They look very nice but have some
hook. I don't know if it is to much or not as none have been run unless
Carl at Plumkrazy ran his yet. It was to be called a Dagger but another
RC boat already uses that name. I have another set of molds for a 47" V
that is a little wider by an inch or two that has no hook at all. I need
to finish the mold for a hatch for it. It is an all original design and
nearly perfect. I may offer thase as an epoxy/fiberglass/kevlar and or
carbon high end boat of the best quality. Still low on money so no
progress has been made on much lately.

Any feed back, ideas?

JIM

thinwaterboats@yahoo.com


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[KalNomaD]

Great thread, I love the how to stuff, and as a note spray putty is also
known as high build primer.


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[Heynow999]

I have been reading the thread with interest. It looks good and is very
informative. I am actually trying to build a fiberglass tank right now
so this is very helpfull. It will be about 5 gallons and a funny shape
to fit under the hood of a car. It is for a vegetable oil conversion I
am working on.

I will try to post a picture. I am still working on the plug.

Peter


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[Thin water]

Vegetable oil and deisel are safe to use in a fiberglass tank but any
alcohol in the new gas as well as alcohols blended in veg oil to burn
it in a diesel will eat up and soften the resin. Epoxy may be more
resistant to this but I am not sure. Read about the serious damage to
boat fuel tanks being caused by the new gas mixes.

A one off mold can be made with MDF and waxed several times then
layered with PVA, allowing it to dry between coats. ABout 5 thin coats
are what many have had good luck with.

JIM


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[dwr9]

Hi Jim. Anything new happening with the 72" boat? Doug


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