building a model into a kitting master help needed

[raser13]

hello ladies and gents. i need the expertise of those of you that are in the kitting industry part of our world. i've been working on scratch building a model of the probert ambassador class ship.

http://www.starshipmodeler.net/talk/vie ... 89#1497389

and there has been some strong interest in there being a kit of this model produced. this prompted me to contact Mr. Probert to see what his feelings on this were. he has given consent to me kitting this model up.(see link above for quote) right now i have the ship still in pieces and she's not quite done yet.

what i was needing was some advice from you kitters out there was what i needed to do to build this up so that it would make a better master that could be kitted if i wanted to pursue that avenue latter. here is the link to the photobucket album so you can see where it's at so you can advise where it needs to be.

thank you in advance for your time and advise. if you don't feel comfortable posting here in the open please pm me.

[Ziz]

First, make sure your pieces are SOLID. Not just well constructed but totally through and through solid. My first attempt at molding the Coventry saucer, the master was hollow and collapsed under vacuum. Had to totally rebuild it and fill it with resin. Since then, all my masters have been either resin filled or built up from sheet/rod to be completely solid by design.

Second, figure out where the "break" lines are - where can parts be separated in such a way that they can be glued back together as a kit without a lot of cleanup/putty work on the builder's end? You don't want to break a kit down into too many parts but, at the same time, a complex shape will be harder to mold and cast for production.

Third, which is sort of corollary to the previous point, figure out where the pour stub/sprue is going to be for casting. I try to put them at the joints or in spots that will be otherwise covered up on the finished build. Ideally, you want those points to be as inobtrusive as possible to the overall design.

Finally, try to figure out how you're going to get the part out of the mold once it's cast. Again, a complex shape will have to be done as a two-part mold, but even at that, depending on the shape and depth of undercuts (holes/recesses in the part), it could make removing the part difficult. Rubber is flexible but it has its limits.

Generally, you need to learn to think in terms of "negative space" when designing a part to be molded. What is the mold going to look like when you remove the part? If there's a lot of "J" and "L" shapes that require resin to go over, under and around to get into, you're going to have problems. You want to keep things as "free flowing" as possible.

[Ramsayman]

Good advice! Just working on a possible master now myself. Glad I read this!

[raser13]

thanks for the tid bit on filling it. i would never had thought of that. would have sucked to have done all of this hard work and invested all this time just to have the thing implode.

ziz, since you're pretty much the master of nacelles would you do the nacelle as one piece or two?? two being the bussard collector and the rest of the nacelle. i would have to have the main engineering and the saucer of the kit done solid as i've already mostly sealed them in.

any other tips from you kitters??

here's one question i have.(i haven't bought many resin models) but how do you make it so the model builder knows where to place and align the attachment points?? do you scribe a outline detail?? alignment pins? counter sink part A into part B so you have a peg hole set up??

also how much detail do you put on the model and how much do you leave up to decals? the reason i ask is there is a lot of VERY small details on this model that i believe are above my ability to model in at this scale. plus if you scale it out these details would be only microns thick. would you just leave them up to decals?

[Ziz]

For that design, yeah, do the bussard collector and nacelle body separately. That allows you to put the sprue/pour stub on the mating surfaces rather than the outer surface of the part AND it allows you to cast the bussard collector in clear resin while doing the body in standard resin.

Attachment/alignment points - better to work them as longer slots/tabs where possible. Thin pegs/rods are hard to cast if they're smaller than 1/8" or so because the resin is too thick to flow into small holes properly (remember "negative space"? A peg on the model is a hole in the mold) so you end up with a lot of short castings on tiny areas like that. Also, make the proportions of your slots/tabs different for left/right parts so the builder can't accidentally reverse them.

As far as sculpted/textured detail vs decals, that depends on the scale of the kit relative to the detail in question and how good you are at modeling said detail. Judgment call.

[raser13]

thanks for the info ziz.