Wobbly round the bend

[fragged8]

hiya all

it will come as no surprise to you guys , i'm having problems
again heheh

I went to fit the front cover on the boat i've been doing for ages
and although I can live with it the front pocket as it goes around the bend
is becoming slack as you can see in the picture.



Would this be because i'm marking the Bow in the wrong position
as i go around the bend ?

Rich

[Mike8560]

It's jars to say from the pic but you may be rite.
I mark mine at the point the 2planes intersect.
Picture a straight edge laying on the tops two front bows   Then a straight edge from the sindowcto the front bow   The point where the 2 intersect is were I mark.   

[Mike8560]

I forgot then sewing your pocket I leave enough slack for the tube to fit inside.   Ieen if the top is 6' long and the pockets wee sewed down flat and tight then inserting the bows would expand the sleve and shorten the distance   See what I meen?

[fragged8]

I did mark the intersect, I carry a long rule to lay along the line the fabric would take
and mark right between where the 2 planes touch the bow.

It's always going around the bend that things get funky though :-)

Easing the pocket is something i still struggle with, i still don't think i fully
understand pockets. some people ease them, some people don't.
Some people ease the pocket by the way they lay the pocket and rain flap
while sewing, and so it goes on.

I do know if the bow doesn't have enough room the cover sucks down
just behind the bow and if the pocket is eased too much the seam rides
around the frame causing more problems.

What i don't really know is how much easing is too much and how little is not enough,
a lot of our boats here have 3/4 " frames too so i guess I ease less on a smaller frame.

[MinUph]

And I wanted to learn how to make boat canvas. After reading all these issues that you guys run into I think I'll stick to furniture.  :o

[sofadoc]

And I wanted to learn how to make boat canvas. After reading all these issues that you guys run into I think I'll stick to furniture.  :o

I'm one step ahead of you, Paul.
I NEVER wanted to do canvas!!! If a sofa cover doesn't fit quite right, you can usually stuff it out a little, or staple it down a little tighter. If a boat cover doesn't fit (or "wobbles 'round the bend"), it's "Do the whole blankety-blank thing over!!"
You auto/marine guys have both my respect, and my sympathy.

[JuneC]

I mark like Mike for the two pieces to intersect, but like you say, getting the amount of "ease" can be tricky.  It's pretty easy in the center of the top.  I ease the 1/2" seam allowance - just roll the fabric as you mark and sew the pocket to the top.  I think what happens as you approach the corners, though, is that the plane changes and you have to ease more.  Here's how I see it.

The tension is fore/aft, right?  In the center this tension is correctly placed with your marking and placement of the pocket.  But, as you make the bend, the bows start to travel toward the midships point.  Now, if the bow was completely vertical, your consistent easing would make the corners perfect - just like the center.  But it's not vertical.  It not only bends down, it bends towards you as you stand in the center of the top. 

So... as the pocket makes the turn down and towards midships, it needs to be pulled further in.  Follow me? Not much, but a bit - maybe 1/4" to 1/2" more.  What I typically do , rather than pull it in more is to  simply taper the pocket and make it slightly narrower on the corners to the edge.  The geometry gets complicated but that's the best way I know to explain it after a few glasses of white wine  :-\

So, if your pocket is 5" wide all the way across the front, as you go into the bend, you gradually go to a 4-1/2" or even a 4" pocket, depending on how far back the curve goes.  This is heavily dependent on how far down the bows you go with your top.   

June

[Peppy]

This was a huge revelation for me when I figured it out. I made the 'push gauge' to figure it out. I got so excited I made this thread-

http://get-up-and-go.com/upholstery-forum/index.php?topic=8530.0

But..

The geometry gets complicated but that's the best way I know to explain it after a few glasses of white wine  :-\

Beer in my case...here goes...

If you sew a flap flat to the top- no easement- The seam will be at the mid point of the tube- parallel to the forward bar. A 1" tube = the seam will be 1/2" down from the top of the bar. A 7/8" tube = the seam will be a half of 7/8" down from the top of the bar. Easing the pocket lets the seam 'crawl' around the bar in circumference to lay at the top of the bar.

The gauge lets you position the line on the pattern to the correct amount of easement when the pocket gets sewn down.

But, thats why I put tabs on the bends. Cause it gets all complicated around a radius. It's much simpler *for me* to monkey a pop rivet into the bar than to get all elegant with the fitting.

[Mike8560]

Your tabs ya peep I was just thinking rich doese what he calls s ulpted pockets   This is snaps at the radius right ? Then if somwht are there ripples wobbles? Can't you just pull it out to not have them and snap it ?
Me peepy I dont mark where the pocket will
be this push tool
is to mark where tour pocket lays right ?   I just sew my top pocket and flat together then fold ot all o er and topstitch the seam with the pocket under and flap up. Rhe turn the top over upsidedown and sew the back of my pocket  I used to pull it back tight at first   But the. Saw my error and then just allowed it by feel experience    But as June says I think I have more alllowance in the center of the pocket where thee is lees strength of the bow and have less at the corner where the bow can resist the preasure of the window  pull  and of course if the window are off you still have a support legs or straps pulling
but in the center of the bow it couldn't resist this pull

[fragged8]

hiya

I am struggling with this because I feel i really don't understand long pockets well
enough, short pockets no problem, I mark a line on the pattern in front of the mid bow from underneath, this line is self adjusting for the bow diameter and if you transfer it to the pattern it gives you a line to roll the mid pocket to for the pocket allowance, that works really well.

with long pockets I have messed myself up really, I have 2 methods in my head and they can't be mixed together.

1. marking the bow is done 90 deg to the top of the bow, when laying out i lay the pocket down flat on the upside down top and mark the forward edge and make reference marks.
Sewing the forward edge down I line up the forward edge with the reference marks and the forward edge mark I drew while the pocket was laid flat.  this works because the marking of the bow is at 90 deg to the bow top and not at about 2 oclock.

2, is marking the bow at 2 oclock or where the planes intersect , lay teh pocket flat on the top and make some reference marks, sewing the pocket down i fold the rain flap forward so it lays flat against the pocket.. 
Pocket flat rain flap flat then sew down the pocket front edge like that.

I am trying to get to grips with making perfect pockets , perhaps it's unobtainable  and it doesn't help that i only make these types of top occasionally,  when i do get to make them I end up back to the same old problems.

[Mike8560]

Couple  thoughts you mentioned the dip behod the bow fron the pocket.
I don't think it can be eliminated.  It a loop goese around a now and pulls won't the connection point of the loop always be in the center of the bow picture a rope with a loop at each end   Each loop is around a pole. And the 2 poles are pulled apart tight  won't the center of the loops be at the center of the poles?  So no matter where the sea
is on your top you will get this dip when pulled tight   Rich your snapped pocket would eliminate this.  I once saw a top that the pockets snaped the entire length  just a flap wirh. Snaps onto the bow.
When I do a sime Bimini patterned witht he can as I'll do it you #1 way. I'll clamp
the fabric on the  frame mark the fron ond rear bows at the 90•   Te center bow in front of the bow then cut it all out. 

[Peppy]

I'm with you Mike, I doubt you can ever get rid of that dip. The better I've been getting the tops to fit seems to make it less major.

I like your rope analogy Mike, and your clock one Rich. Here goes...

If there was a seam in the rope, like in a pocket, at the mid point of the loop that goes around the bar- that would be a 'flat' flap/pocket.  Say we're looking at 2 bars, front bar on the left main bar on the right. The seam would be at 3:00. (Where 9:00 is pointing to the center of the front bar) pushing the flap/pocket (where it sews to the main top) back towards the main bar lets the seam rotate around the bar. Pushing it a 1/4" lets the seam lay at 2:00. 1/2" lets it lay at 1:00. 3/4" = 12:00.

You could push that seam 3" around the bar as long as you mark it there on your pattern. And thats what that gauge thingy does. Finds a point on the circumference of the bar that can be replicated in the tarp.   

On little boats i'll often snap directly to the bar. On aluminum anyway. And only if there's one bar.

[Mike8560]

This was like a 40' sea Ray all stainless and all snapped.  Big beam also I had that was done that way

[JuneC]

Hmmmmm, Mike.  You got me thinking - dangerous after only half a cup of coffee.  :-\  Just wondering if anyone's explored alternatives to our traditional pockets.  Maybe replacing the zip with grommets and lacing the pocket closed instead of zipping it.  I'm thinking a narrow flap on the underside of the top and slightly wider flap on the edge, small grommets every 3 or 4 inches.  Think of the possibilities ! Maybe a misting system along the bows to keep you cool!  Maybe LED strip lights!  All that would be feasible if the pocket were open.  And, your lacing would certainly even out the tension along the pocket where there might be differences like on the curve. 

June

[regalman190]

Hi Rich....I think the curve of the pocket around the tube is not bad. I think the issue may be more with the outer edge of your pocket. Since you made your pocket with the zipper sewn between two pieces of the flap, you're introducing another curve to deal with. Instead of the tube curve and the outer flap edge curve, you now have the tube curve, two zipper edge curves and then the outer edge of the flap.
The way I was taught was to make your flap, sew one edge of the zipper to the flap and the other edge of the zipper to the top. Now you only have the one zipper edge to contend with. I then sew everything flat until the last 3 or 4 inches of the end of the flap. At this point I roll the flap back, or towards the tube about 1/2". This helps eliminate the pulls in the corners. I'm not saying this is the better way, I just think it's more controllable. Here's a picture. Hope it helps.

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