Hard Dodgers

[Steve M]

Hi all
this I forgot to mention but its a simple way to define the central angles and heights of your projected dodger and allows a view from the side and also is a good way to transfer measurements to your boats drawings that are accurate ( use this for my measurement sheet.)
Take a line like a builders line, bright in colour  but not heavy that will sag
Tie one end of line around your mast but able to be moved ,say as a start point,about a foot up from the cabin top.
Pull it out real tight and tie the other end to your back stay(able to be moved up or down)
This, from the side can be viewed as the top of the camber of your dodger (you must be level with the line and abeam of your hatch to view it)

Now move it up or down as suits climb in and out of your hatch way and see how it fits! do you need to contort your body not to hit the line ?? etc

When you've got this line right take a small light piece if stick and with your line real tight (mark the positions on mast and back stay in case it slipsand (stick a little masking tape to prevent slipping)  

Place one end of the light stick on the hatch box or where your anticipating the fwd center base of your dodger to be and with a light cloths peg or paper clip, clip the stick to the colored line.
This will be a side view of the central front edge of your dodger (the center screen) tilt it back as required. Re test getting in and out of the hatch .

Measure the distance back from mast back edge to top of the stick at line intercept and the same from bottom,( mast back edge to stick base) measure the length of stick (deck to line intercept )
Measure also the exact vertical height of stick base to line intersect.
Once you've got some lines to work from and that can be repositioned you'll Get a better feel for what you want and be able to repeat the scenario
and better apply your thoughts to paper and with accuracy.
Steve Marshall

[CapnK]

What a great tip! Thanks, Steve!

[Tony G]

Just been to Ebb's photo gallery.  I think we're going to dig into this idea of a slider on top of the hard dodger.  One that has self-draining channels cut in that look much like the PVC channels Ebb cut into his outboard 'hutch'.  Look at photos #198, 199, 200.  If you continue the channels/drains forward and down to the cabin top where they would exit the bulwark.  They could drain off rain, spilled...soda, green water.  Given the shape they would lend more strength to the front 'pillars' and being hollow add very little weight.  The sliding hatch being of such small dimensions would not take much to make it 'step worthy'.  I mean, really, how much time do you really plan to spend walking on top a 44" wide dodger?  Barring, of course, any Parrothead activity, xmas parties, impromptu birthday parties, engagment announcements (someone elses') National and other Worldly Holidays.

Wow!  This is pretty exhilarating for people like me.  Now if only the boat wasn't wrapped in plastic in 15 below zero weather.

[CapnK]

Hmm - why make it slide? Just make it tilt, opening from the forward edge...?

In the down/closed position, it would stiffen and strengthen the structure, I'd think...

[ebb]

Hey guys...over here at the end of the bar..

Taking Kurt's idea of a  top that needs to be opened to provide more dignified egress to the galley.
His drawing shows that opening.
and Steve  is saying that cutting the panel/top will seriously weaken it. True, true.

From the forward corners of the opening put in a couple struts down along side of the sliding hatch.
Right? They won't be in the way of anything.  They'll go from the coachroof right next to the slide and up to the corners of the cutout in the dodger -  the two legs won't impede the sliding of the hatch.  

Won't impede anything going on in under there...Right?

Let's take any bendiness out of the dodger edge and the new opening by trimming it out or doubling it.
Let's play with the position of those legs by moving them back a little to take more of the load.  Might work in a couple gussets to make it near impossible to move those corners of the top.  Nah, don't like gussets.

AHHH but leave those legs still at the corners, and put in a couple more toward the opening.  The first two immobilize the top,  The second two support the wings of the top.  They probably don't have to be at the end of the cabin top but maybe half way in.... but still bracing those corners.

I think they could be legs las simple as 2x2s.  Not panels which would separate that nice space under the dodger.  I can't think what would get in the way of these support legs - except the winch handle.  Probably arrange the four struts so they are out of the way and nearly unnoticed.

If you are rich enough to have s.s tube grabbers on the dodger, they don't need to be exactly along the outer edge over the cockpit but could be inset to correspond more or less with the struts inside.  The struts are locked in to the coachroof.  Locating the exterior grabrails near the interior strut join would make for a solid feeling construction.
And the struts could be nice shiney stainless tube too.  

If tube works there, the appearance would be more like grab rails and not like structural pieces at all.  I'll bet the project would end up almost as rigid as an unbroken no hatch dodger!  These vertical grabrails might even work just that way.

Go for it Kurt!

Just throwing this out on the table....

[Steve M]

How about this opening support rail.jpg
Steve Marshall

[ebb]

Spike:  BY GEORGE, I THINK HE'S GOT IT!
The key to your cure, ducks.
The missing bloody links, it was...

Drusilla: (indicating Tarot card with an Angel)
...Right in front of us... the whole time! [Buffyverse Dialogue Database]



Steve,
  Totally Superb
Unexpected
A Quantum Leap

Don't know what engineering form Steve has here.
It's a kind of truss tube isn't it?
It definitely would fly if the tube was welded.
It's really marvelous!:D
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Can't sleep!
It's the color of the tubing..
That support rail could be made out of 6061T6!!!!!

[CapnK]

Yeppers, that looks great, like it would do the job!

(I need to learn that CAD stuff!!!)

[Tony G]

Kurt

The reason I lean toward a sliding hatch is that head knockin' boom.  A blow to the noggin', if it doesn't kill you, will keep you from doing it again.  If an accidental jibe blasts off the standing hatch, well, then you have another thing on the boat to fix.  Maybe one of those 10" spring 'kickstand' type hatch struts you see on forward hatches would buckle before a calamity happens.

But a forward lifting hatch would be easy enough to do.  Much like a cockpit locker lid with the drains is what I'm imagining.  All to often I fail to adhere to the KISS methodology.  Time to get out the paper and pencil in lieu sound CAD erudition.

[ebb]

About the hatch in the dodger.
Steve's CAD shows coamings around the opening - certainly the simplest way - if molded in, or stitch-n-glued, the rise will also provide strength and stiffening.

(Tony was refering to the lid in the rear hutch over the lazarette.  I used some pvc channel  got thru McMasterCarr to make the channel in the top.  It was only used as a form for glassing - didn't become part of the final project.  In effect the molding of the fiberglass makes that channel shape into a stiffening rib.  It was a  complicated way to get what a simpler rising coaming would  accomplish. When the lid/hatch is is place, there is nothing for big water to tear off.
When forming the male mold for this construction, the pvc forms are worked into the mold form and the hatch top is cut out later from the laminate lay-up.  It's picky but the result comes out  very fair - As fair as you make the moldform.  Could leave the lid as a plain curved panel - I chose to add a turn down, so the lid extends down into the groove around the opening.  I also stiffened the lid with 1/2" pvc foam inside and glassed it in.  1/2" pvc foam bends easy enough and can also be heat formed.  Don't think there is anything superior about this, it's just another way to do it.
It was natural to extend the grooves aft and down to mini scuppers because there had to be a way to get  water trapped in the groove out.)

I believe the UP coaming is simpler and better.
The hatch when opening it is problematic.  The above mentioned hatch on LittleGull behind the cockpit is huge and when opened is very vulnerable.  I made it big to get the OB out.  I imagine that the hatch will be seldom used.  The hatch in the dodger needn't be too large.  Do need to get the shoulders in, and there is a big measure of comfort in how much is left opened forward in that opening.  Bigger is more convenient.

An UP opening hatch will get in the way.  Probably have to open it all the time to go below, it has to be EASY to use.

I'm thinking that a hatch could be devised that would slide open...but not like the usual sliding companionway hatch.
The hatch would be in two pieces  hinged across the middle - the middle rises up as you push it forward to open it.  That way the hatch is always captured.  And if not too tall can probably be left open most of the time.  The rise would only be half the length forward of the opening.  The hinge maybe would leak a little, maybe the sides too, but could be casually waterproofed with fabric or something when closed.  The hatch would be made on top of the dodger, inside the coamings, using SAIL TRACK AND SLIDERS.  With another mini coaming just under the hatch, on the inside of the opening, channeling small water away from going below.

That tubetruss surround Steve proposes for the dodger above would work just as well on the BlueWrap style.  So I'm going for it.  I done seen da light.
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later EDIT.  Steve's coamings - shown in his cad just above here - leads to another idea:  
which is to incorporate cleats or knees INSIDE the coaming.
Consider inner cleats going fore&aft along the top (inside) and curving down to the cabintop.  The cleats would also frame the hatch opening - and also at the same time be the upright coaming in way of the opening.
Maybe this can be seen as cantilever or davit framing (using the curve of the top & front of the dodger to create a strong  structure.)  Probably take the full weight, without deflection,  of an atheletic male standing ON the corners of the dodger.   Quite possibly, no support posts at the dodger hatch corners needed.  
The hatch itself could be a laminated sunbrella (canvas affair) that could be zippered shut during water events.  When open, maybe roll it up and velcro.
 'Two Cents Worth' just became became Dime A Dozen.......
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NEED HELP ON A PROBLEM:

It's about putting  polycarbonate on the windscreen.

My windscreen section is a foam composite that is 3/4" thick.  I can't see bending and slabbing the polycarb windows to the outside, even if they are now only 1/4" sheet.  They have to be rabbeted in.  And there's the rub.  I've already cut huge openings into the windscreen and I have to figure out some way to do this rabbet stuff its rather radical form.  There are no rabbeting bits that will cut a wide enough flange.  Even 3/4", if the little 1 horse trim router will swing it, is not wide enough.  The reason is that the bolts have to go through the plastic window AND the flange.
There is set-back on those holes and holes set-back from the inner edge.  And complicated by the need for expansion of the polycarb, so the cut-out  window has to be considerable smaller than the rabbet edge.  Absolute minimum is 1/8" all round.  Holes through the sheet have to be oversize as well!  This all means the minimum flange width HAS to be 1".  And around 5/16" depth.  Better even wider, like 1 1/4"  
The PVC foamcore is structural imco. The polycarb will seat on the foam,  I don't see this as a problem, tho I may put a thin layer of glass over it, best way PITA.


Got this damn curved composite wrap.  
Anybody think of an easy way to cut that wide rabbet?  
Only a small-base trim-router can be used on the curved windscreeen.  At the moment I'll go with the widest rabbet bit - establish the depth - and figure out a way to carve the width back that's needed (Dremel tool?).  

I know, I know, make a simpler windscreen wrap.
OR slab the poly on to the outside with all the overlap needed.

[Tony G]

The one issue that leads me away from the upturned riser/coaming is the fact you can't get a nice smooth top.  Granted it is an easy answere to the issue (KISS).  But my reasoning is the slider will be closed nearly all the time anyway.  Relative to rebuilding a boat inside and out it would be easy to incorporate the slider mounting into the scupper channels.  The channels along with a couple of thoughtfully placed stringers would replace much of the strength compromised by having the cutout.  And I never have drifted away from the idea of some sturdy well placed stainless handholds...the JC bars as they're sometimes called.

Besides if it doesn't work we can 'blame' Ebb.  This slider idea came from his lazzarette hutch just like my flush cabin ports came from his chain locker.

Take one for the team, brother Ebb!!!

[Steve M]

Can you show a picture or 2 of the problem ebb ??
Steve m

[ebb]

Wish I could, Steve.
But if you would step into the front room here, you'll find a couple pix down the hall. Go out to the Pearson Ariel Forums menu page.  Click on Gallery. Scroll down to Ebb's Gallery.  Click in on page 16 and find post 231 and 232.

#232 gives an idea of what and where the present cut-outs are.  The actual cut outs now are even larger.  The cut-outs reveal why the dodger ended up too heavy imco.
The molding you  see is 3/4" thick on the stand-up face.  What the cut-outs reveal is thicker epoxy/glass-matt laminations on the inside surface, 1/2" green divinylcell as the foam core, with a thinner glass layer on the outside face.  The project was not vacuum-bagged.

The problem is that the substantial openings in the 'windscreen' are not molded and don't have molded in flanges.  There is bothersome waste of expensive materials in the cut-outs.
This is one reason why I favor the same shape as this but done as wrap with simple plycore, single layer woven fiberglass on the surfaces.  There is no need for a foam core windscreen on an Ariel.  I just got drawn into the process.  It was before you came in with your Blue Wrap Dodger CAD under yer arm!

Anyway, to how now  to cut in the rabbets is the real problem?   The curve of the screen is pretty extreme.  The router I have is that onehorse Bosch trim with the tidy interchangable bases.  The tilt base is actually a halfbase with a 3/4" wide slot that is open on the working side allowing the bit open access and visability to the work.  Also have some D-handle PorterCable regular routers.

One method is to work on the piece directly with bits that have roller bearings.

Most rabbet bits cut only 1/2".  I have a bit with a set of bearings that I think will allow a wider rabbet.  But that isn't the real problem.  Which is, according to my estimation, the need for a much wider rabbet, explained in a previous post.  
I laid out windows for the widest openings possible imco.  I'm right at the extremes of the windscreen.  And I need a flange that is at least one inch wide, but I'd be much happier with 1 1/4".

To get that wide rabbet I'd make a pass to the correct depth with a regular rabbet bit.  (Actually a three-wing slotting bit will do the job - without wasting the phenolic base for the oversized rabbet bit - attached outside the bottom of the base..)  Then 'by hand' - following a trace line - carefully cut into the fiberglass making the full new width wanted with a Dremel 542/3 carbide cutting wheel*.  Then, using the first router cut, take a utility knife and  slice over to the fiberglass cut using the flat surface in the foam as a guide.  The slice over will also, of course be through  foam.  Tedious.
Probably tedious to read too, Sorry.

The second method is to use a pattern with a bushing guide base on the P.C. and a straight bit.  The Bosch trim router does not have this option.

The way out of course is to make a female  hardboard routing pattern large enough to make the wide flange.  Screw the pattern on to the windscreen.  This is probably not possible on this windscreen because there is too little surface left to fasten the hardboard  onto along the top and bottom of the windscreen where the holes already are.  That option is no option.  !#%$&*?!  This would be my choice if possible.

I'll have to go with Tedious.
By the way, the best way to cut those wide flanges in a premolded foam composite like this windscreen...if you insist that this style and method is necessary...
is to layout all your parameters on the surface.  Then DADO in the wide flange using female hardboard patterns. Then cut the openings out.  The whole thing could be done with straight bits, including the cut-outs.  I shoulda done it that way.
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But I did ask because these days it is possible I may have missed a tool or method I'm not aware of, or forgot!

Why is it getting into trouble  so easy
and getting out so hard??
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The groove/channel in the hutch over the lazarette
that Tony mentions has photos at post 199 and 200...
It does make for a classy looking lid.

Can imagine sail-track in the bottom of the channel with a hinged two part lid on a couple sliders that will rise the lid up in the middle when pushed to open.
The lid is controlled and contained.
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*These are pricey 1"D scalloped thin circular metal plates  coated in carbide grit on the end of a 1/8" shank.  They work very well, but also get used up quick on hard work like cutting thru a couple layers of glass.  They are not the small Dremel toothed saw blades on a shank which wear out even faster. Instantly.

[Steve M]

Hi ebb
 saw the pictures 231 and 232 and understand your problem.
I don't have a ready answer nor could say "it will be easy" because even after cutting the fiberglass outer layer your moving into another problem or 2 and that is leveling the foams core and actually, successfully glassing into that little rebate.

May be heres an alternative that would ease the problem and 1/2 the time.

Consider 1. is the face surface nice and smooth or can it be made that way?
 2. do a full wrap screen using 3/16 (4.5mm) lexan polycarbonate . It bends way better than plexiglass . this would sit on the surface not into a rebate but doesn't look bad really.
A full wrap piece once cut carefully and edge finished is really quite easy to work,it would have a smooth curve across the top and need a nicely radiused corner as you step down from the hatch box.
May be you could try a door skin ply template and it will offer similar resistance to the lexan.

I would cut a piece (of door skin) to fit neat across the box then leave the rest well oversize, pull it around and flat onto the dodger surface with ratchet straps to your dodger back edge or somwhere aft
When its really flat but not all dished in mark the openings from the inside onto doorskin , remove, lay flat and mark a nice neat top sweep that allows
you a 1"1/4 bedding surface.
test your completed pattern
This in turn will allow you to very simple rake back the core (1/2" )in your window openings , back fill them  with bog , and finish with  drum sander thing in a drill.
In fact I think you will not need to use any screws to retain the lexan Ill expound on this if this surface way is of interest to you.
One point to note if theres a lot of twist as well as bend to cover the surface then it gets more difficult how ever the only areas you ever need retaining on a smooth curved surface is the very ends your existing pillars will provide a resistance to dishing and a bonding surface.

Hope this want telling you how to suck eggs and might be a help.
  I can direct you to a sight that makes and sells sealant  and bedding and on there site  has a good  run down on the correct way to use a window  bedding/glue  which is imperative to this working
Steve Marshall

[ebb]

Steve,
thanks for continuing on this subject.  Bending in or on the clear sheet is a problem that anyone doing a hard dodger can appreciate.

Your solution of bending on a single sheet of easy to bend thin stuff is a great way out of trouble.  I will consider this.

I not sure what you mean by "rake back the core".
If you are saying that the single bent poly sheet can be inset - that also is a good idea IF..
IF, by 'raking out' the inset was easy to do.
I can see doing the rake out with a router on a long stiff base with the router moving on a sub-base back and forth over the surface to lower the surface into the core so that the plastic ends up flush within the surround.

That's too hard for me.  Please understand though that the bend of the front of this windscreen is a dead FLAT curve with no twist.  The doorskin pattern material would lay flat for side to side.  And the plastic sheet would as well.


It's an esthetic problem for me to have thin sheet slabbed on top of such a THICK molding.  I would be constantly bothered by looking at the edges.  SO,
I'm going to figure something out to inset the lens separately.  Also want the center lens to open, while the big sides are structural and fixed.
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Very interested in your NO FASTENING method of slab-on mounting of the clear sheet.
Maybe you use a series of clips - whose fasteners are attached to the dodger with stepped metal pieces over the edge of the lens?  That's cool!

I would wet caulk a lens in place with a next generation silicone/polyurethane hybrid.  If you look for the stuff, "green strength" single-tube syl-polymer can be found that will not squeeze-out like regular rubber caulk.  The only hybrid caulk readily available in the USA is Life Seal.  It does not have enouigh thickening in it (aka Green Strength) to resist squeeze out.  Bostik makes a range of this hybrid and is sortof available through one marine catalog that I know about.  Bostik's main claim is using this stuff for slab-on fake and real teak decking.  It's said to be permanently flexible forever!

IF you are bending flat clear sheet onto a curved surface.

This might not be a huge problem on a dodger.
I have decided to slab-on Lexan to the Ariel cabin sides.  The cabin sides are bent slightly.  And I'm using 3/8" stuff.  I'm also aware that any polycarbonate has to be replaced at some point, especially if it is going to be cooked in the Tropics.
I've found some nice sticky 1" wide butyl tape that has a fiber core.  Using it in a non-rabbet slab-on situation is not smart I know - but I'm going to try it.  The butyl should not be totally squeezed out if I'm careful loading the through fastenings.  At least taking it apart again will be a breeze - as far as getting the goop off is concerned.

My plan for the wide rabbet in the dodger was to use the same stuff.

If you don't plan to ever remove the polycarbonate, there is another fabric tape called 'Everlast' (I think) - I have the roll down on the boat - that is nearly impossible to handle, but promises PERMANENTLY FLEXIBLE permanent bonding of dissimilar materials.  That's wut they say!

Gotta run right now...
Steve... if you interested in this diversion, post some more...ok?