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Greetings fellow builders!

I'm new here. I've built electric guitars for roughly 8 years, but just bought a stewmac OM martin kit to learn more about building acoustic guitars. Eventually I want to build from scratch, but that'll be a little while.

I'm having an issue I hoped for your input on.

The stewmac kits have designs for a "waistclamp" to be used with the provided cardboard form. My issue is the sides have sprung out making the waist clamp not fit. Stewmac support advised to trim the cardboard form. Good news is that the waist clamp now fits, but as you hopefully can see in the included picture the shape does not line up perfectly with the plans.

Now for my question. Would it be advisable to build an actual mold and force the shape? Or do you think contuing with the build being slight "off" from the plans is ok?

Im leaning towards building as is, being slightly off of the plans shape. Can anyone think of any issues this could cause? The top and back are oversized, so I dont anticipate any issues there

I've alway built with an outside form and since this is not going to be the only acoustic you'll build, you might as well make one. I've got 5 different shapes hanging on my shop wall. Of course many guitars have been built with no form for 100+ years. If the side outline you show in the photo is your concern, I wouldn't worry about it. Even with a form, unless you have the ability to touch up the bend on a hot pipe sometimes you will have those small deviations. Keep going! That won't effect the sound.

Carl

Carld05 - thank you for weighing in!

The SM kits are designed for the builder w/o a full luthier shop.I built mt first 4 or 5 kits using the cardboard pattern and plywood waist gauge. I’d guess not one of them matched the drawing exactly. As said above, it won’t affect the sound.
If you plan to build more, consider investing in a a mold for your next build. It will help get you to started on the road to getting the rim square and plum. An important first step.
But, be aware.Buying a mold is just the first stop down a really wide and deep acoustic guitar builder’s rabbit hole! One equipment/shop improvement demands another.
Speaking from experience,, if you intend to build a lot more and can afford it, go for it. It’s the most enjoyable hobby I’ve ever had.lf you’re just planning a few builds, you may want to approach the rabbit hole cautiously. John Hall at Blues Creek Guitars is a great source for advice.
Good luck and enjoy.

Blindbo, I was considering making a mold by tracing the provided body pattern on several pieces of 3/4" plywood. Do you think this would be effective, or is buying a mold better for the first-timer?

I’m sure many people here make their own molds. That said, there are some tricks to the trade that a beginner might miss.If you have the funds, I’d buy one from John. His are spot on and should be very price competitive. Building a good guitar is an accumulation of many small steps (someone told me over 270). Each one needs to be done right for good results. The rim is a very important building block.
Good luck on your journey.

Make your mold. Strace the outline of one half of the pattern and make a template on some 1/8 or 1/4 MDF or plywood. Use that to make your pieces for the mold. If you have a router table you can make pretty quick and accurate work of it.
You make one piece and make it as perfect as you can to the shape. cut the other pieces a tiny bit outside the line (oversize)
Attach your perfect piece to the others and use a flush cut bearing router bit to make them all the same. if no router then you have more hand work to do but it can be done.
you won't be sorry making and using a mold. if you purchase a mold it may not match your bent sides anyway. Not all OM shapes are the same.
there are different ways to make the 2 halves of the mold fit together, as it needs to be able to separate.

I just made this Jumbo mold from scraps of particle board and pine planks. I have other molds I've made from plywood and mdf.
They all work.
Make yours 3 or 4 layers tall. either will work.
Go for it you can do it you will be much happier with the result than trying to use that inside cardboard form . I know I tried it on my first build, a kit and promptly made an outside form!!!

This is the OM Mold I made 12 years ago.

Outrageous, your screen name is long, is it ok to call you OM?😉
Kevin is exactly right if you have the equipment and inclination. Many do.
Below is a photo, one of my molds.Guess I should mention that I’m 85-90% blind, so ease of use is very important to me.
One other helper is a indexing dowel on each end to assist in getting the mold clamped in the same orientation each time.
I highly recommend these options for your build.
Take care.
Bo