Molded vs Moldless Fiberglass Construction

[CaptainKickback]

I?ve been watching a ton of videos lately about creating FG parts. While most of the videos show you how to make plugs and molds, some show modeless construction. Here are my thoughts?

When you use molded construction, you make a plug (exact replica of the part, or the part to be copied). Then from the plug, you make the mold, which becomes a negative image of the part. Finally, from the mold, you cast your new part. This is the basic process, however EXTREMELY simplified. There are so many steps in laying up FG, fairing it, sanding, fairing, sanding? Not to mention many, many, many coats of wax, each drying for an hour in between coats. Then, you put on several layers of PVA. Now you have a plug. Then for the mold, you do layers and layers of FG, followed by fixing imperfections in the mold surface, all that waxing again, and more PVA. Now you?re ready to FG your part. Layers and layers of FG, and then probably some fix up on the part?s surface. While most videos show putting on gel coat first when making a part, you have a problem if you have to fix any imperfections or if you have to FG the part into a bigger structure.

Man! I?m exhausted.

Some videos show doing modeless construction. The drawback is that some or all of your form materials are left in the part. I see several benefits however. The biggest benefit is time, and that?s worth a lot to me. Also, some of the form materials may be desirable for strength or rigidity. Since (in molded construction) in making the plug itself, the surface must exactly match the desired part. The surface of the final part will not be any better than the quality of the plug?s surface. So, if you think about it, the amount of work to get the plug surface exact is about the same as if you properly surfaced your form,, without a hundred more steps to do.

So, I?m thinking, for my project, moldless construction is the way to go. What are your thoughts?

 

[chriscraft254]

Re: Molded vs Moldless Fiberglass Construction

I would not put any mold in your project, it is bad for your health. Couldn't resist!:facepalm:

 

[CaptainKickback]

Re: Molded vs Moldless Fiberglass Construction

I would not put any mold in your project, it is bad for your health. Couldn't resist!:facepalm:

I can't believe I didn't think of that. Good one!!!

 

[ondarvr]

Re: Molded vs Moldless Fiberglass Construction

There is no hard and fast rule, every part is different so you need to look at each one independently to see which method will be better. Some molds can be very easy to make, others are very complicated. The only time building a mold is clearly better is when you need to make more than one part.

 

[CaptainKickback]

Re: Molded vs Moldless Fiberglass Construction

There is no hard and fast rule, ever part is different so you need to look at each one independently to see which method will be better. Some molds can be very easy to make, others are very complicated. The only time building a mold is clearly better is when you need to make more than one part.

ondarvr, I did think about the multiple part benefit. My helm, staircase, etc, will be one off parts. I guess I could sell copies of the staircase though (lol).

Thanks for the input.

 

[Yacht Dr.]

Re: Molded vs Moldless Fiberglass Construction

There is no hard and fast rule, every part is different so you need to look at each one independently to see which method will be better. Some molds can be very easy to make, others are very complicated. The only time building a mold is clearly better is when you need to make more than one part.

A mold is a negative .. a Plug is a positive..

You can build a Plug first..then a mold..or build a Mold first and pop off duplicated from it. Need be you can pull off multiple parts from your Mold. Plugs are not sometimes used..just the Mold..

ondarvr, I did think about the multiple part benefit. My helm, staircase, etc, will be one off parts. I guess I could sell copies of the staircase though (lol).

Thanks for the input.

You have 2 choices here.. you can build your Plug ( your finished product ) .. then make a Mold off of it..then reproduce off of the Mold.

Or you can produce a Mold first ( without a plug..kinda inversed plug ) and start popping them off if you like..

Or you can just build what you build and install it. .. but once you build your finished part..you have a Plug. In which case you have to make a mold..

I have built a 'Mold' without making a Plug .. so the final outcome is the Part..

Yes it was a One off part .. Now that is considered the Plug if I wanted to reproduce it ( I would have to Mold the part .. which I was completely aware of angles to have my build be able to reproduce ) ..

Is this what your suggesting ?

YD.

 

[j_k_bisson]

Re: Molded vs Moldless Fiberglass Construction

Yatch Dr, I have to say, once again I am left a little lost with that response and not fully understanding where I was at (plug or mold). But it all makes sense and is correct the second time I read it! And hell I make Injection molds for a living!

Dame, for a man that spends as much time in these fiberglass chemicals as you do, I am constantly surprised on the clairity of your thinking... lol

Keep up the good work!

 

[oops!]

Re: Molded vs Moldless Fiberglass Construction

as ondarvr mentioned.....you kinda lave to look at each project by it self.

however, in multi part production, a mold is the way to go

the trick to doing what you were mentioning in the above post.....is to make the plug with out imperfection.

however, in your case with the stairs , where they will be premanantly attached to the boat,

i would just puild the part....glass it.....fait it....and gell and fair. right on the boat.

this is due to the fact that you will have to fair the new part in any how. so you can get the base plug (plug if you will, but i guess structure is the best word). as good as you can out side the boat......but in any case, you will still have to attach it to the boat.

fairing in the joint is tideious.

i want to re build my dash again...that means a new part. and joining the new part to the boat. that means alot of fairing.
why do it twice?

especially when the edge of the part pulled form the plug will have gellcoat over spray, and the edge will be the same size as the base it is attached to....so fairing is a real pita.

 

[CaptainKickback]

Re: Molded vs Moldless Fiberglass Construction

A mold is a negative .. a Plug is a positive..

You can build a Plug first..then a mold..or build a Mold first and pop off duplicated from it. Need be you can pull off multiple parts from your Mold. Plugs are not sometimes used..just the Mold..



You have 2 choices here.. you can build your Plug ( your finished product ) .. then make a Mold off of it..then reproduce off of the Mold.

Or you can produce a Mold first ( without a plug..kinda inversed plug ) and start popping them off if you like..

Or you can just build what you build and install it. .. but once you build your finished part..you have a Plug. In which case you have to make a mold..

I have built a 'Mold' without making a Plug .. so the final outcome is the Part..

Yes it was a One off part .. Now that is considered the Plug if I wanted to reproduce it ( I would have to Mold the part .. which I was completely aware of angles to have my build be able to reproduce ) ..

Is this what your suggesting ?

YD.

I re-read your post as well, so I get what you are saying. I guess my confusion came in the use of the term "plug" for the finished (moldless) part. Reading your post with that in mind was clearer.

As for intent for the thread, it seems there is always emphasis on making molds and I just can't justify the work. So, I guess I was partly looking for vindication here on iboats,

Thanks for the input. I'm sure this will eventually read by a lot of people and it will help them decide which way they want to go.

 

[CaptainKickback]

Re: Molded vs Moldless Fiberglass Construction

as ondarvr mentioned.....you kinda lave to look at each project by it self.

however, in multi part production, a mold is the way to go

the trick to doing what you were mentioning in the above post.....is to make the plug with out imperfection.

however, in your case with the stairs , where they will be premanantly attached to the boat,

i would just puild the part....glass it.....fait it....and gell and fair. right on the boat.

this is due to the fact that you will have to fair the new part in any how. so you can get the base plug (plug if you will, but i guess structure is the best word). as good as you can out side the boat......but in any case, you will still have to attach it to the boat.

fairing in the joint is tideious.

i want to re build my dash again...that means a new part. and joining the new part to the boat. that means alot of fairing.
why do it twice?

especially when the edge of the part pulled form the plug will have gellcoat over spray, and the edge will be the same size as the base it is attached to....so fairing is a real pita.

Yea, the stairs and the helm will be one offs. Do you think there's a market for a stair mold? lol

However, even with the moldless construction, you're scaring me, man, with the fairing talk!!!

 

[logan944t]

Re: Molded vs Moldless Fiberglass Construction

I used to be a patternmaker in another life. We made parts from wood and fiberglass/epoxy--then sent it to a foundry so they could cast it in whatever metal the part called for.

For me, I would have to have a good reason for making a mold and going to all the trouble that entails. If I needed exact copies--or maybe 5 of something I would find it worth it. Otherwise the investment in time and material wouldnt make sense.

I much prefer making the part or structure in place and in real time.

 

[Yacht Dr.]

Re: Molded vs Moldless Fiberglass Construction

Yea, the stairs and the helm will be one offs. Do you think there's a market for a stair mold? lol

However, even with the moldless construction, you're scaring me, man, with the fairing talk!!!

So basically you want to Make the Part.. not a mold..or a Plug.. just go right to the Part itself ( finished installable Part ).

Remember the Golden Rules of Custom Part Making..

1. Measure...
2. Measure again..
3. Measure again and again..
4. Work from the Install side Out to the finish side. ( If your Part is a finished side mating with another finished side..then your good to go with the glassing as you see fit. If your Blind side is mating to a finished side..then you have to account for the build up of glass of that part or it will not fit ).

Plugs,Molds and Parts have inherently different characteristics in the build process..

Each one has Values that one must be aware of before choosing.

YD.