Progress pics and questions on Aluminum Double Eagle build

Designs for inboard or outboard power

Moderator: BruceDow

North
Posts: 265
Joined: Mon Jul 15, 2013 6:29 pm
Location: Nova Scotia

Progress pics and questions on Aluminum Double Eagle build

Postby North » Sun Feb 16, 2014 5:10 pm

Hi Folks,

Hope some of the experienced members can help a novice out!

I am posting in this section, as some things are not only related to buiding in aluminum, and because the metal building section of the forum has been very slow.

I have got the frames together and mounted them on the jig (which is made out of 4 " x 4" steel - overkill, but I may make a trailer later). Most were only tacked together, so they have come off the jig now for final welding. Also cut slots for the flatbar longitudinal stringers I will be using.

I am stretching the design 10%, to about 25' and have a used Cummins 4BT (150hp) and 1:1 Velvet drive to go in.

I have the full patterns and see the lines for the stem (made of 3/8" aluminum, approx 3" wide) which goes from the tip of the bow to frame 7. However, I don't see any exact measurements, or lines for the keel /skeg (which would basically be from the stem at frame 7 all the way back to about frame 1). It looks like it has a straight edge on the bottom, and the plans say to continue the keel/skeg up into the hull, at least 2 1/2" above / past the hull plate. But, I don't see a measurement from the hull plate, or dwl at frame 1 for example, to the bottom of the keel/skeg.

If anyone could point this out to me, I would appreciate it.

I need to order the material for the stem /skeg/keel (which is all 3/8" thick) and the materials list says 16 square ft. But this in itself is not enough info, as I don't know if it is best to have a 2' x 8' piece, or if it would be less piecing/ welding together if I got 2' x 10', or even something like 8' or 10' x 2 1/2', as I don't know the exact measurements.

Then, there is the hull plate to eventually order.
I assume that once I have the frames and longitudinals in place, on the jig - I would then use something like a big roll of construction paper to make rough templates of the hull side and hull bottom plates, and see how they fit or nest togteher - so I will know if it is best to order my large sheets in 4' x 20', 5 ' x 20', 6' x 12, 5' x 12' or other somewhat common sizes, and of course how many sheets I need.

I don't remember reading anywhere in the plans or supporting material the process for what I have just mentioned. If Iam way off, or there is a better waym please let me know!
Attachments
DSCN1853.JPG
DSCN1852.JPG
DSCN1850.JPG

North
Posts: 265
Joined: Mon Jul 15, 2013 6:29 pm
Location: Nova Scotia

Re: Progress pics and questions on Aluminum Double Eagle bui

Postby North » Sun Feb 16, 2014 5:15 pm

a few more pics! By the way, the flatbar in the pics will be mounted perpendicular to the frames, at 90 degrees - not lying flat as in the pics. Just checking the lines that way.
Attachments
DSCN1858.JPG
DSCN1857.JPG
DSCN1856.JPG

User avatar
rbrandenstein
Posts: 817
Joined: Mon Mar 08, 2010 3:51 pm
Location: O'Fallon, MO

Re: Progress pics and questions on Aluminum Double Eagle bui

Postby rbrandenstein » Mon Feb 17, 2014 8:45 am

Wow, building in aluminum is a whole other dimension for most of us wood workers. Do you have to fair the aluminum frames like we do in wood or are they thin enough that you just leave it?

As for making patterns, I would suggest using roofing paper. It is cheap and comes in long rolls. I think you can get different widths, mine was 4 feet wide. It is stiff enough to hold its shape as you work with it and cuts easily with a utility knife.

I used it on my wood hull to confirm I had a fair hull and also as a pattern for my plywood. I still left a few inches on each side when I cut the wood, but it allowed me to remove a lot of plywood and weight before I mounted it.
IMG_0410.JPG
________________
Bob
Completed Malahini (launched 6/24/2012)
http://bobsboatbuild.blogspot.com/

User avatar
kens
Posts: 4388
Joined: Wed Nov 12, 2003 5:25 pm
Location: Coastal Georgia

Re: Progress pics and questions on Aluminum Double Eagle bui

Postby kens » Mon Feb 17, 2014 4:25 pm

I stretched Double Eagle in wood.
If I remember correctly, I got 2 layers of 3/4" ply (the stem) from 1 piece of 4x8' ply. I nested the lines until I got both parts on 1 piece of materiel.

My stretch was 10% and my length came out to 24'8". However, it is 27 feet each side going around the sheer.

My understanding of the stretch, is to leave the stem as is, and stretch the stations aft of frame 6. (the stem)
Also, If I had stretched anything between frame 6 & 7, then I would not have room for the stem on a 4x8 sheet.

Some of the lines fall into place on YOUR build. For example, the placement of the chines on the stem is up to you. You make the lines of your material come out fair. My wood chines were bent into the stem at the place that "felt right" without busting any wood nor terrible twisting. Thats where I "nailed 'em down"
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

North
Posts: 265
Joined: Mon Jul 15, 2013 6:29 pm
Location: Nova Scotia

Re: Progress pics and questions on Aluminum Double Eagle bui

Postby North » Wed Feb 19, 2014 4:54 am

Thanks for the replies!

RBrandenstein - I didn't fair the frames too much (it is my 1st build, so we will see whio it goes). My reasoning is that - unlike I assume in the wood construction, the hull laterial does not have to rest directly on the frames, but rather it rests and is welded to the longitudinal stringers ( I am using flatbar on it's edge). I plan on oly tacking the flatbar to the frames n a couple of spots before performing most of the hull plate (sheet) welding. Although heat will distort it some, I believe that as the hull plate is welded underneath to the stringers, the stringers will be pulled up slightly from some frames as needed, as the hull naturally takes a fair shape. If I welded the stringers to teh frams first, then the hull plate would be pulled dpown to them, and I think the hull could oil can a bit. After the hull is welded to the stringers, and hopefully the shape looks good, I will then weld all of the stringers to the frames.

I am definitely open to advice in this, and all areas.


Kens - Yes I did stretch it per your advice, only increasing the distance aft of frame 6 I believe.
re: stringer placement - I marled frames 0 (actually 1 as I don't have the transom up yet) and frame 4 per the plans, and then just held up a long piece of flatbar to aid in marking the othe rframes ,and attempting a natural curve towards the bow. I plan on letting the ends toward the bow "find their own way" as they meet the stem, as you mentioned. I will then tack then into place and see how a piece of hull maerial looks ove them. If there are any major bulges or depressions I will juts grind off the tacks, move slightly and retack to check again.

User avatar
kens
Posts: 4388
Joined: Wed Nov 12, 2003 5:25 pm
Location: Coastal Georgia

Re: Progress pics and questions on Aluminum Double Eagle bui

Postby kens » Wed Feb 19, 2014 7:51 pm

On the aluminum plans, do you weld the skins to the frames?
The wood build, you do not screw nor nail to the frames. (longitudinals only)

I used a piece of skin (plywood) big enough to cover 3 frames and adjacent longitudinals to check for fairness. Clamp it up and check for high spots. High spots simply got sanded down, not busted loose and moving of the part.
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

North
Posts: 265
Joined: Mon Jul 15, 2013 6:29 pm
Location: Nova Scotia

Re: Progress pics and questions on Aluminum Double Eagle bui

Postby North » Thu Feb 20, 2014 4:43 am

Well, I believe the plans do call for the frames to be welded to the skin. But, if you do a search on framing methods in aluminum building, I believe the double eagle plans are from the bit older school method where this was done. The newer method, of welding only the longitudinal stringers to the skin, and then welding the longitudinals to the frames, is what i plan to do.
If I have any high spots, on the frames, that interfere with the skin laying fairly on the stringers, then I will shave the frames down. But, as the stringers sit in slots in the frames, and are free to move up and down where not tacked, I am thinking that most of them will be proud of the frames, and if the hull skin looks good with them like that, I will weld them in place as such. Of course, if the skin starts pulling the stringers significantly out of their slots in the frame. I will have to tack them in in more places, and try again.

I will restate that this is my 1st build, so if anyone has shortcuts, or things they have learned, I am all ears.
There is a recent post under the metal buiklding section which was helpful, and the builder has nice pics of the boat before and after the skin is on.

North
Posts: 265
Joined: Mon Jul 15, 2013 6:29 pm
Location: Nova Scotia

Re: Progress pics and questions on Aluminum Double Eagle bui

Postby North » Mon Mar 10, 2014 7:27 am

Hi Folks,

Thought I would post a few update pics.
Also, I wanted to than KenS - as he has been great in responding to many questions via PMs. but, I thought I would try to start posting questions here, to take some of the load off of Ken, and to share with everyone.

Have most longitudinal stringers (3/16" x 1 1/2" x 20' 6061 flatbar) in place on hull bottom, and am now bending the ones on the topsides, which have more of a bend near the bow. In one pic you can see I broke one stringer ( it had been tacked/heated, then ground off, tacked again/reheated and it broke while bending a second time)
I am having some trouble deciding how much to curve the stringers upwards (really downwards as boat is upside down) as I bend them in to meet the more narrow frames 7 and 8 near bow, and finally to touch stem. The plans say (on forward stations) to try to position the stringers / side stiffeners roughly evenly spaced between chine and sheer. It seems though, that as I bend the flatbar against it's strong side- it "likes" to sweep up some near the bow. But, this would mean that near the bow the spacing would be closer to the chine and not evenly spaced between the chine and sheer. \yo ucan see in one pic that I have cut a couple of slots in the side frame, in order to try bending while changing the position a couple of inches.

I have only tacked enough stringers to keep frames level and at the proper distances from each other. The plan is that one the hull sheet is in place, I will look under and see if some stringers have high / low spots, and then I would cut the tacks and adjust appropriately. Then weld all/ most stringers to the hull sheet before welding the stringers to the frames.

As always, I would appreciate any help / advice!
Attachments
DSCN1892.JPG
DSCN1891.JPG
DSCN1890.JPG

North
Posts: 265
Joined: Mon Jul 15, 2013 6:29 pm
Location: Nova Scotia

Re: Progress pics and questions on Aluminum Double Eagle bui

Postby North » Mon Mar 10, 2014 7:28 am

one more pic.
Attachments
DSCN1894.JPG

North
Posts: 265
Joined: Mon Jul 15, 2013 6:29 pm
Location: Nova Scotia

Re: Progress pics and questions on Aluminum Double Eagle bui

Postby North » Thu Mar 13, 2014 7:17 pm

Hi guys,
I have been asking some questions on boatdesign.net, as it has a metal boat building section.
Anyway, I think I have run my stringers trending up on the jig(as upside down, this means really down) towards the bow stem. Now that I look at a pic of one of the wood builders here (below) his stringers (midway on the hull bottom) seem to trend down (on the jig) closing the distance to the chine.
Mine trend away from the chine its seems, as I thought that was where it "wanted" to go....

I would appreciate and help or recommendations if you guys think I should move the ones near the bow(or any I guess) to be in a better position to keep the hull fair, and a developable surface.
Attachments
DSCN1891.JPG
pic718a4[1].jpg
pic718a4[1].jpg (48.42 KiB) Viewed 8160 times

slug
Posts: 1438
Joined: Sat Sep 22, 2007 9:49 am
Location: Colborne ON Can

Re: Progress pics and questions on Aluminum Double Eagle bui

Postby slug » Fri Mar 14, 2014 3:45 am

I would pull the last 2 closer to the chines. Don't know what thickness of planking your'e using, but seems like a lot of battens to me...very close together. Think this will give you some grief when sheeting.
Have not built in aluminum, but did build a 34' steel sailboat that had very similar construction.
Doug

North
Posts: 265
Joined: Mon Jul 15, 2013 6:29 pm
Location: Nova Scotia

Re: Progress pics and questions on Aluminum Double Eagle bui

Postby North » Fri Mar 14, 2014 6:50 am

Slug - just to be clear - mine is the aluminum one in the top pic, and plans call for 1/8" aluminum sheet, although I am considering 3/16", at least for the bottom.

The wood one is a pic from one of our member's gallery, and it turned out very well I believe.

So, are you saying that you would pull / place my aluminum stringers (near the bow) closer to the chine, as that appears to be the case in the wood picture?

slug
Posts: 1438
Joined: Sat Sep 22, 2007 9:49 am
Location: Colborne ON Can

Re: Progress pics and questions on Aluminum Double Eagle bui

Postby slug » Fri Mar 14, 2014 6:57 am

Yes; That's my personal choice. I just think they are close enough to give you some difficulty in sheeting. With 3/16 ( my choice for the bottom ) I doubt that there is a need for so closely spaced longitudinals. Some manufactured hulls (Stanleys for instance ) are successfully sheeted with no longitudinals, depending on the compound curves to give a monocoque hull with exceptional strength.

Doug

User avatar
kens
Posts: 4388
Joined: Wed Nov 12, 2003 5:25 pm
Location: Coastal Georgia

Re: Progress pics and questions on Aluminum Double Eagle bui

Postby kens » Fri Mar 14, 2014 3:11 pm

I let the longitudinals 'flow' where they wanted to go.
I can say that on the wood plans, there is no particular location for the longitudinals to land on the stem.
So, I pushed the chines around until they made a 'natural' bend to hit the stem.

Similar with the battens. I let them go as far forward as possible without un-natural twisting.
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

North
Posts: 265
Joined: Mon Jul 15, 2013 6:29 pm
Location: Nova Scotia

Re: Progress pics and questions on Aluminum Double Eagle bui

Postby North » Fri Mar 14, 2014 4:17 pm

Ken - I have looked at your gallery pics a few times, but I don't think there are any pics specifcially of the longs. Any chance you have a pic or two tha tclearly shows where they ity the stem?

Would you agree that looking at mine and then looking at Gordon's in the pic above - his middle two longs on each bottom side look to move toward the chine, as mine move away from it?

I know this seems dumb, but I think I just missed something simple as I am building upside down and the gunwales are down near my feet, so just not in view. I dodn't notice how the gunwales and all lines should sweep up (if right side up).

Now that I think about it, if the hull were rightside up, the design of this hull, like many similar boats has the gunwales fairly low and near flat near the stern - then gently rising along the sides of the boat, then taking a more significant rise nearer the bow, to end in a quite high stem / bow roller location. It seems obvious now, that if I were building right side up, I would have expected the long stringers to sweep upwards nearing the bow in a similar fashion to the gunwales. But, as it was upside down, I just didn't view or grasp this.
I plan to lay out battens tomorrow, and see were my stringers should land nearer the bow.


Return to “Power Boats”

Who is online

Users browsing this forum: No registered users and 23 guests