electric jigsaw question

Hi all,
I am new to woodworking and loving it.
However:
I messed up with the jigsaw. I had a 5cm thick slab of fijian mahogany, i draw in thin texter the shape of what i wanted to cut. I got i got out the jigsaw and started cutting away. After I had done that, I held up the block and i thought 'what a beautiful job I have done!' then i turned it over to inspect the other side, a and it was horrible, sometimes i cut too much and sometimes i didn't cut enough. Is this cause the blade was somehow bending, ot i was somehow making it go on an angle? what have I done? Any tips for next time?
Any help would be greatly appreciated.

There is a variety of problems here.

The thickness of your timber, this dictates the speed at which you can move the blade through it. Then there is how you're cutting the grain, with it or across it (or more likely at various angles). The size and tooth pitch of the blade you used, the power and quality of your jigsaw and if it's got it the pendulum action.

If your ability to follow the line you set was good enough for your stated comment then it's not you that's at fault.

Basically jigsaws are not very good at fancy cutting on thicker timber, the blade will flex around corners, more as the grain gets harder going from a rip to a cross-cut mode. And if you were cutting an intricate shape I'll lay odd on you having used the thinnest blade you could find, exacerbating the problem.

Take things slower, let the blade catch up with the saw bodies position (keep the blade going but don't move the body) on a regular basis as with all things Practice makes perfect (and a lot of scraps on the way).

You might try a Fretsaw for smaller items but again go slow, or a Bandsaw for larger ones. If you don't have either ask for someone nearby who has to give you a lesson and learn from them.

Welcome to the wonderful world of wood - the good news is it does grow on trees.

dr4g0nfly,
thanks for your advise. i noticed with the side that i hurried that it was worse than the other.
my router:
I am not sure what model it is but it is just an entry level ryobi. but i believe it does have pendulum action. the cutter i was using was just the one that it came with. I think i had it on the slowest speed (i think there is 3 speed settings). One thins i noticed was that the blade was not always in the center of the hole of the steel plate around it, is this normal. once again thanks.

If the blade wasn't tracking in the centre of the hole, you were applying too much sideways force on the jigsaw.

You can't force the blade to go where you want; you've got to direct it, but let it come around to that direction at it's own pace...otherwise the blade bends (or even snaps) and you get the result you've seen.

Tight cuts in thick material may need to be done in a number of goes, from a number of directions. The easiest way is to make a few roughing cuts, and then slowly work down to the finished shape so that you're not trying to cut too tight a curve.

I have got around this problem using a variety of methods including the advice above plus:

Cutting from both sides. draw your shape on both sides of the timber. This must be done accurately but by having some form of indexing you can easily do it. cut a bit wide of the line and when you notice the bottom is wandering, turn the timber upside down and cut from the other side. Keep alternating and correcting. Use a rasp etc to get it right down to the line.

Make a series of easing cuts so that each section starts again before it wanders too far.

Since owning bandsaws I no longer have this problem but it can be done with a jigsaw, a bit of thinking and some patience.