Bimini (crappy corners)

[RandyOnR3]

  over the years, I've built hundreds of bimini s  and inclosures and most all have come out looking great,
  but every now and then one slips throu that looks like crap in the outside corners..
  and the bad part, I dont know what I did to make it come out like that..

common sence would tell you that its to tight at the end of the zipper but when I unzip it, the issue moves further up the top...
  If I knew what the problem was, Id know how to fix it but I cant figure out where the problem lies.....
  please help with my crappy corners.. ??? ??? ??? ???
   

[Mike]

Do youkneen the zippered pocket or the enclosure zipper?

[RandyOnR3]

Do youkneen the zippered pocket or the enclosure zipper?

its the zipper pocket of the bimini.. I dont sew in a pocket without a zipper.. I find it easer to install instead of feeding all the tubes through the pockets..
the nasties are being created from where the zipper pulls from the outside fabric

[Peppy]

I had something like that happening to me a while ago. It was because I was drawing the line for the seam on the wrong place on the pattern.



Here you can see the flap with the zipper leaving the top from 12 o'clock, here labeled B

The clock shows the cross section of the tube

I was drawing my line on the B plane but not allowing  anything in my flap going around the bar. That forced the seam to lay on the A plane, tightening up everything along the flap but not at the corners, making big divets where the flap ended.

The distance from A to B around the circumference of the bar is 3/4". If you don't allow for it it can screw you up.

[regalman190]

Had this problem in the beginning as well. I spoke with the folks at Marine Canvas Training in Florida and they told me to try this. Typically on an enclosure top, you would lay the sleeve flat and the flap flat and then mark where the zipper edge gets sewn flat to the top. On a bimini top you do the same, but at the ends (about 3 to 4 inches before the end of the zipper), start moving the zipper towards the flap about a 1/2". This effectively gives a little more room at the ends of the pockets at the curve of the frame. Worked for me. Much better now.

[JuneC]

I've found my inconsistent results have more to do with the frame than my methods.  The more vertical the frame ends are, the easier it is to get a good fit.  If the bow ends "flatten" out and go more horizontal, getting the zips in and having the corners fit is a real chore.  I'd love the opportunity to experiment with a frame and different methods of pocket installation.  Unfortunately it takes time and fabric. 

As I see it, when the bow is more vertical, the seam doesn't have to move around the bow much.  It can be pretty much at 9 o'clock all the way, moving to 11 as you approach the end.  Not much stretching and easing of the zip tape is necessary to accommodate the curve.  As the bow gets more horizontal, the seam needs to move from 9 o'clock to 11 with LOTS of stretching and easing of the zip.  The curve becomes severe, almost a flat plane.  Sometimes I wonder if a tuck on the zip that attaches to the body of the bimini would work best.  Actually, Peppy's and Richard's (?) method of not pocketing the ends, but instead putting a short flap with snaps at the ends, would end the guesstimation altogether.

June

[CreativeCanvas]

Reckon it all boils down to how you come around the corner. I start my line in the middle of the bow @ about 10 oclock. As I round the radius I gently nudge her to 11:30 or so. Then add seam allowance.

Contrary to ole Don Wedge @ MCTI. I prefer to sew zippers in before stitching the pocket into the top. Leave em a lil long'n trim afterward. I fold my fwd & aft pockets flat but add a lil frame allowance on mid pockets.

'Course if you're working off somebody's mutilated frame ya never know. This one was purty beat up when we recieved it but tweaked it the best we could. Customer wanted it to match his hideous seat covers. (I did not make those.) Right down to the black binding. Yuk!

Sorry ain't the best pic:

http://s918.photobucket.com/albums/ad24/71V153/?action=view&current=4bowss.jpg

[Peppy]

I've found my inconsistent results have more to do with the frame than my methods.

Not to be rude June, but if your methods don't work for every boat I don't think you can blame the boat. Using tabs helps but also creates new problems. You need some coordination between the pattern and the cloth. I built a 'push gauge' letting me mark my line on the pattern exactly where it will fall after being eased/pushed.

I've tried explaining this several times, alas I'm bad at typing complex ideas. It wouldn't even take two beers if we could meet in person.... Anyway, see if this helps anybody, from a thread called 'Pushing' zipper flaps.

The Push Gauge-




The ruler touches the top of the leading bar and the hook hooks on the bar needing the flap.



I have it marked in 1/8" but only ever mark 1/4". I use it to make ticks then join the ticks with the ruler. Here I'm marking 1/2" push.



It seems to me that the optimum place to mark the seam is the last point that the ruler lays flat on the pattern without going over the edge. Seems the rain flap lays better when marked like this. What do you guys/gals think/do?

I then mark the push on the pattern, in this case 1/2". The sewer then lays the flap flat, then subtracts 1/2" and sews it down. (actually she now measures from the seam but same difference.)

This is only for marking seams with a flap. I almost never lay a flap flat anymore. My tops fit nicer than they ever did before in front and behind the bar. I felt like a real dummy making tops for so long without giving flaps a second thought. Oh well, hope it'll help someone else if your not doing something like this already. If anybody's interested I'll detail how I made it.



This is what I was making. A flybridge bimini, enclosure pattern to follow. If it ever stops raining. (I kinda hope it doesn't. I hate flybridges. Pinstripes don't make good scaffolding.)

*sorry the pictures didn't copy*

[JuneC]

Not to be rude June, but if your methods don't work for every boat I don't think you can blame the boat.

Not to worry, Peppy - I have VERY thick skin  ;D  And I totally agree.  I have to change methods for different boats and I wish I didn't.  There's always going to be variability in frames.  If there weren't, we could all have exactly one pattern and use it for everything.  But, if your pattern method is consistent for ALL frames, I'd bet your sewers have gotten really good at installing the zips and sewing the pockets to the bimini with exactly the right amount of "roll".  Or do they sew them absolutely flat against the top? 

Personally, I don't like the rain flap to creep up the pole as it rounds the corner.  I like it attached at no more than 10 o'clock so that when the enclosure is attached and snapped down, it doesn't pull the top and make the pocket baggy.  I find that if the seam is too far onto the top side, that's exactly what happens.

Speaking of bad tops, there a boat at the yard I just HAVE to get some pics of today to post.  The canvas was apparently done by (I hope, anyway) the owner or a friend, not a canvas shop.  Never saw anything quite that bad.

Contrary to ole Don Wedge @ MCTI. I prefer to sew zippers in before stitching the pocket into the top. Leave em a lil long'n trim afterward. I fold my fwd & aft pockets flat but add a lil frame allowance on mid pockets.

Same here.  Why handle all that canvas when installing zips.  On everything I make, I try to create small subassemblies before joining them all together. 

June

[Peppy]

I'd bet your sewers have gotten really good at installing the zips and sewing the pockets to the bimini with exactly the right amount of "roll".  Or do they sew them absolutely flat against the top? 

Yes. I work with the best sewers on earth. You can either lay them flat and mark, then subtract your 'push'. Or measure from the seam if you have the flap width and push allowance all figured out. Then you follow that line while sewing.

Regalman's problem (and anyone who runs the flap around the corner) is do to the fact that the cross-section of the tube in relation to the top is oval and therefore has a larger circumference around the corner. This is due to geometry and not a squished tube. And why June has problems with steep pitches.

Here's how to make the push stick-

I'm not sure anybody wants to know, but here it is anyway. How to make the gauge-

This is a scrap of 1/8" HDPE high density poly-ethylene it's what they make yougurt containers out of, it takes a staple awesome and is easy to cut. We also have 1/16" that I make all my permanent patterns out of.
(sorry it's so faint you should be able to see when it blows up?)


So- I use a fostner bit the same size as the tubing and cut half way into the plastic making 2 holes. I join the 2 centers with a line. This line is 0" push, or laid flat.


Then I take a cloth tape and wrap it around the tube and hold it in the half drilled hole. Keeping the inch mark on the ruler lined up to the 0" push line. Then I mark 1/4" increments. I guess you could mark 1/8" or for that matter 1/64" but a 1/4" seems enough.


then join the tops of the 2 circles with a line and cut it out like shown. The lower part of the plastic is scrap or can be used to make a second gauge. I mounted mine on a ruler so I don't lose it. And I cut the lines out with a hacksaw so I can see the push lines on both sides of the gauge.

Ta-da! There is a push gauge! I encourage you guys to give it a go on a future boat top. The fit noticeably improves. And there's nothing to lose. You've pushed the flap into the bar 1/4" or a 1/2" if it doesn't work or you don't like it you can trim that 1/4" or 1/2" off at the zipper (so long as you do zipper flaps/pole pockets that is)

Regalman's problem (and anyone who runs the flap around the corner) is do to the fact that the cross-section of the tube in relation to the top is oval and therefore has a larger circumference around the corner. (This is due to geometry and not a squished tube). And why June has problems with steep pitches.

[JuneC]

Regalman's problem (and anyone who runs the flap around the corner) is do to the fact that the cross-section of the tube in relation to the top is oval and therefore has a larger circumference around the corner. (This is due to geometry and not a squished tube). And why June has problems with steep pitches.

Exactly!  So when you get to the corner of the bimini, and the bow angles sharply back towards the center pivot-point, how do you use your tool to mark the pattern?  You continue to use the same line?  Your last pic has a fairly upright frame.  I seem to get lots of windshield mounted frames that are a lot more horizontal than that one.  Take that frame and lower it by about 1.5 feet and that's what I have to deal with.

And, how far from the edge of the bimini do you stop your pockets?  I generally leave 2-2.5 inches for the bimini to overlap the enclosure.  Carrying the pocket too close to the edge makes it tough to get a watertight fit.  It can also wreak havoc with the fit of the top itself.  Not carrying the bimini down far enough on the sides makes it easier to get a good fit, but not very good for the shelter you're trying to achieve. 

June

[Mike]

I like it attached at no more than 10 o'clock so that when the enclosure is attached and snapped down, it doesn't pull the top and make the pocket baggy.  I find that if the seam is too far onto the top side, that's exactly what happens.

I know what you meen getting baggy pockets. but i find it the tops tight( not easy wiyh an aluminum frame ) having roll in the pocket so the seam in not at 90º i find a tigh top will not roll and have baggy pocket once the window is snaped on anp pull tight
I also put my zips on the pocket first dong then nice i sew then in the center of the p[ocket  a fast cheap top somtime ill sew then on the tail edge of the pocket once side of the zipper to the top
I placw my seam here as if you layed a straight edge from the widow to the first bow and a 2nd from that bow to the next thew point were the 2 strait edged intersect is my seam location
i think part of the problem at the cornewr occors because there is flex in the frame in the center of the frame but at the corner it more rigid  located at the top of the leg plus you either have a support strut or a strap pulling tight also but the cventer of the fram had give no what i meen'/?

[JuneC]

Ok, so here's an extreme example of what I'm describing.  Look at the first photo (larger photo gives best view) - note the forward top frame.

http://boats.iboats.com/2006-chaparral-boats-310-signature/337767.html

Peppy, how would you use your tool when approaching the corner of that?

June

[Peppy]

And, how far from the edge of the bimini do you stop your pockets?  I generally leave 2-2.5 inches for the bimini to overlap the enclosure.  Carrying the pocket too close to the edge makes it tough to get a watertight fit.  It can also wreak havoc with the fit of the top itself.  Not carrying the bimini down far enough on the sides makes it easier to get a good fit, but not very good for the shelter you're trying to achieve. 

June

We stop the flaps at the bend marks. Before the curve. Then tabs are used on the curve approx 2" apart. I don't have good pictures.



Here you can barely see what I mean,



And here the tabs aren't installed yet. It is a pain to drill the tabs but I'm over it. The (relative) ease of drilling holes offsets the headache of trying to figure out the curve pocket, and adds a huge amount of leeway fitting the top.

I'm sure you could make a push stick to do the corners but it would take some figuring. I have run a flap to the edge a few times but haven't a science for it yet, just eyeballed it with my push stick guessing. Since it's an oval and the oval would change depending on the angle you might need a few different profiles.. But Regal's suggestion of adding extra push is the right answer, I haven't found the right question yet I guess.

Marking a flap I would want my seam to lie where Mike says. I lay my stick on the bars-



this looks like a 1/2" push. I make ticks on the bar every 6" or so along the width of the bow, then join the ticks. Now when I push my flap 1/2" on the canvas my sewing is coordinated to my pattern which has been pushed 1/2" by the stick .

[Peppy]

I forgot to say, I only use the stick for flaps, when the flap ends I just go by eye and try to get to lay in the same place with the tabs. On that June, instead of tabs I might go with a solid doubled piece with snaps in it spaced nice. Or something.