CS17 #339 Questions on Fairing Hull Seams

[acreew]

I have flipped the boat and would appreciate any help with several questions:

1) What is the best way to radius the plywood edges along the chine to ensure consistent lines?

2) How much does it need to be rounded....how much material needs to be removed?

3) There are several places where the side and bottom panels do not meet perfectly. How do I address this where the side panel is proud. Do I sand the side panel ...apply fairing compound/goo to the bottom panel? (Tried to download pictures but could not ...will attempt again later)

4) I will glass the hull with 6oz glass. Do I also need to put 2 layers of 10oz tape on all seams?

 

Thank you,

 

Will

[LennieG]

Will-

I will leave these answers to the experts mostly, but will say this....I am six weeks ahead of you (#370), I have now put on 4 coats of primer, and one of three or four finish coats. While my boat is coming out nice, if I could do it over again I would fair the seams more, and add an extra coat of epoxy to fill the weave. The pre painting prep was a little inadequate. I suggest you search on this forum for

" longboard" and then read PAR explanation of fairing on one of the threads, and do it.

See my seams, attached:

[mattp]

Here is what I did (not necessarily the best way):

 

1.) I put a 45 degree bevel with a plane, then nicked the two resulting corners then hand sanded round. 

2.) I think I ended up with 3/4" to 1" radius

3.) My side panels butted into the bottom panels and I had a bit of bottom panel to plane flush before rounding.

4.) I did one layer of tape and 6 oz. cloth over that. I wish I had of went ahead with two layers of tape for more abrasion resistance but that's just an afterthought, it may be ok.

[Dnjost]

Lennie has it right.  Longboard sanding will show where the filler is needed and where it needs to come down.  I am on my third weekend (limited to Saturday mornings) of filling and sanding.  I did discover a pretty good dip in the stern bottom panels where they meet at the center about 2' long.  Deciding whether to live with it or to apply perhaps a layer of 1/4" ply and fair it into the hull.  Will decide after a good night's sleep.  It just means another weekend of filling and fairing.  

 

David

[LennieG]

Will-

As far as shaping the Chines I too had a lot of extra wood to take down. What I suggest is a good quality low angle block plane, sharp, to slim down the ply overlaps at that joint. The low angle plane is easy on end grain plywood and is low risk as it won't tear the material. After you take off the edges, hand sanding brings you down to the radius you want, approx 3/4 to 1 " as Matt says, and in fairly short order.I used one layer of tape, and 10oz glass and feel it is adequate and on the conservative side of the plans.

Good luck and please post pics....the deal is we show you ours if you show us yours.

[acreew]

Here are some pictures... The first two are of the area where the side panel is not aligned with the bottom panel. Others = before the flip

[acreew]

Lennie,

Thanks for the picture... The finish looks great to me... I hope I can get there.

[LennieG]

It looks great from 12', without my glasses.

[PAR]

I use a belt sander with an over size belt and wooden shoe, so it has a U shaped gap in the middle. This allows me to push the floppy belt down on the corner as it wraps around, making a radius. You don't need this modification to the belt sander, as it's a good tool for bulk material removal and shaping, though some practice is in order. I use the belt sand (regular belt) to rough it in, making a first longitudinal pass, bisecting the corner angle. Then I split the difference of this angle 50% on both sides (45 first, then 22 and again 22 on the opposite side). This roughly leaves several "flats" along the chine seam that are easily rounded over with my floppy thingie or one of several other tools. The longitudinal flats help keep the radius uniform, but again this does take some practice, so start on the chine aft of midship, where it's under the LWL and out of sight (mostly).

 

I know a few that use tape to define the edges of their radius, rounding the chine over, until they reach the tape. This does leave a uniform line on the hull sides/bottom, but the radius can still change in diameter. I also know a few that rough it in with a big round over bit (3/4") and a router or laminate trimmer (little router). I find this is difficult with rolling bevels, like that on the sides/bottom of a boat.

 

I all boils down to the eyeball method really. It's very easy to get carried away with material removal and make inconsistent radius chines seams. This is why I like to make the longitudinal passes first, which help define the radius width, using some care to bisect the angle (eyeball thingie). You can get quite close this way and fairing will fix the odd dip or bump later. The tape definition thing I mentioned is better in the fairing process, instead of shaping IMO.

[Howard]

The best solution for rounding corners has always been a roundover bit on a router, but since the chines generally come together at an obtuse angle, not 90 degrees, the roundover bit will only hit the tip of the edge at best (depends on the degree of angle and amount of roundover wanted).  Generally, you only want enough radius to allow the glass tape to stay with the edge and not pucker up. A good rule of thumb might be to radius it to about the same radius as the thickness of the plywood, since the heavier the plywood, the bigger the boat and heavier the glass you will be using. Keep in mind, the radius will increase with each additional layer of glass, so it is the first one you have to worry about. This would be the most important on the transom edge, with as little rounding wanted as possible (sharp edge allows water to break free vs. sucking around, creating drag). I believe Graham has even suggested rounding over, glassing, and then if the a roundover is still present, put a sharp edge back on with thickened epoxy outside (on top of) the tape. This would be more important on the transom than the chine (water running 90 degrees to the edge).

 

Anyway, since the roundover bit doesn't work, the old school tool for this (before shapers and routers) was a hollow ground molding plane. You can still find these in antique stores, but they are expensive and you likely won't find one of the diameter/radius you want. So my plan is to make something similar by drilling a hole (say 3/4" diameter) lengthwise through the end of a 2 x 4 (about 8 inches long), then rip a saw cut through the middle of that, creating what is essentially a hollow molding plane. But instead of a plane blade, use sand paper. Essentially, creating a hollow ground roundover sanding block.

 

Ease the edge of the chine or transom to about what you want with a hand plane, then dress it down with the block. If you offset the cut in your sanding block (cut beyond the middle of the hole), you will only have a small segment of a circle left. That will easily fit over a really obtuse angled chine, but still have a consistent radius and thus a uniform roundover.

[PAR]

I find it easier to get the radius uniform during the fairing process than the 'glassing. You just need any old radius for the 'glass to lay down, but making them look good is a different issue.

[acreew]

Thank you all for the suggestions on the seams.....was not as difficult as I was making it in my head. Now I have a new head scratcher...

 

There appears to be a dip maybe 20 inches in length...approximately 1/2 inch at its greatest on the centerline just before the transom. Attached are some pictures. Any idea what caused this? Do I need to fix it and if so, How?

 

Couldnt get pictures to load....will try again tomorrow.

 

Thank you for any help!

 

Will

[LennieG]

Look forward to the pictures. Some of that dip may be built in the design and someone else recently expressed concerns about the dip. So, may not necessarily be a problem....I can't say with available info.  I had a kit but as you can see from attached picture it appears to me anyway there is a slight dip.

 

[LennieG]

If it helps when I go to my boat tomorrow I will get under boat with a metal straight edge and measure the dip, unless the cradle support prevents that, which it may.

[acreew]

Thanks Lennie,

I cant get the pictures to load....dont know how I did it before.....will keep trying.

[LennieG]

And I am unable to measure a dip, if there is one, under my boat due to cradle support.

[Dnjost]

I had the dip.  1/2" 20" long and not on the plans.  I used some Okoume to fill and added Microballoons.  It is now almost fair after several round of fill and sand.  The cause of the dip was my poor job of scarfing the bottom panels, combined with not bringing the panels fully in at the centerline near the transom.  This set me behind about a month.  I hope to be glassing next week. 

[LennieG]

David-

i know what you are saying about re-do's . They cost time and it means you have to adjust the launch date

I just spent the better part of two days re doing small projects where I made a slight error. I had to cut a apart the hatch seat covers frames, flip over one piece, and re glue, a three day three stage project. Also had to cut the joined mast sections, eliminate a bad joint, build new " collars" blah blah blah.....

Hey, I wanted a challenge

[acreew]

Another try with pictures. Hey David ....appears to be the same issue you had.... Not sure i have your tenacity.... Any thoughts on leaving this as is?

[PAR]

This hollow section will delay the transition to plane and generate some drag. The boat isn't going to sink with it as is, but if interested in the best performance potential, you'll want to straighten this out.