Malahini... Step 1.

Designs for inboard or outboard power

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gap998
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Joined: Wed May 20, 2015 5:40 pm
Location: Wales, UK

Re: Zip or malahini, or ... ?

Postby gap998 » Wed Jul 27, 2016 5:30 pm

I have a rough Malahini Hull "skin" solid model in Autodesk Inventor if you want it - I was originally thinking of tweaking a Malahini into an overnighter so I modelled it using the line drawings on the website - Obviously it's not accurate enough for a build but will help you to play around with cockpit designs etc. I know Inventor can read, but can't remember if he reverse is true - I could convert it to STEP format else.
Gary

Planning a whole fleet, but starting with a Zip...I think.

"Just when you think you've made something idiot-proof, someone builds a better idiot!"

Brandlin
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Location: Nr Chester UK / N Wales Coast

Re: Zip or malahini, or ... ?

Postby Brandlin » Thu Jul 28, 2016 2:07 am

Hi gap.

Sure send the file over to brandlin@btinternet.com, can't hurt. The model I showed earlier is simply the plan view from this website traced and then extruded with a draft angle to get a very crude volume roughly the boat shape. Took about 5 mins.

Rbrandenstein kindly sent me his sketch up file of the 'skeleton' without skin. I'm attempting to convert to solid works so I can skin it. Having to do that through .dxf export which is giving some issues in scale and orientation, but I'm getting point and line segments which I'll have to replace with splines. I'll take the frames, transom and stem from this file and model my own chines and sheer. I should then be able to 3D loft the skins and use the intersects to 'fair' the frames, chines, sheers, battens and transom.

Then it's just a case of finding a big enough 3D printer right?

(Isn't that the YouTube view these days? You can make anything better by 3D printing it?)

Brandlin
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Location: Nr Chester UK / N Wales Coast

Re: Zip or malahini, or ... ?

Postby Brandlin » Wed Aug 03, 2016 3:46 am

Ok,

First milestone reached...

My gorgeous and utterly wonderful wife has said "yes!"

(Well technically she didn't say no, and I'm claiming that. I just have to be charming and convincing)

So, it's my birthday in three weeks and I've asked for a set of plans. Normally my birthday 'list' has things like ' a new bandsaw', 'an original 1965 AC Cobra' and 'a weekend with Kate beckinsale in a leather factory'. So I'm hopeful that 'plans' will be considered a suitable present.

I'm recovering from a difficult wisdom tooth extraction... Urgh. So haven't spent anytime in front of a CAD station. But I have been trying to price lumber and ply. I love my country, but I think the bottom line is I need to stop converting dollars to Stirling when you guys quote costs, and simply assume that $=£. :-( everything is expensive!

In a vaguely boat-related first step on the way to a build, I'm putting a coat of paint on the workshop floor tonight. Long overdue and a first step to helping keep dust unnder control. I'm declaring this officially makes me "a boat builder!"

:D :shock: 8)
Last edited by Brandlin on Wed Aug 03, 2016 6:08 am, edited 1 time in total.

Ranny
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Location: Lake Monticello, VA

Re: Malahini... Step 1.

Postby Ranny » Wed Aug 03, 2016 5:19 am

Good idea about painting the floor. I am also taking Bill's advice and painting the floor, right before the gathering. That should ałlow plenty of time to set. I am also taking advice and adding lots of lights before building.
Ranny

Brandlin
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Joined: Thu Jul 21, 2016 6:22 am
Location: Nr Chester UK / N Wales Coast

Frames ... Lots of questions...

Postby Brandlin » Wed Aug 03, 2016 7:11 am

Lighting I have plenty of... Boat knowledge on the other hand is more scarce than a sober Irishman on st Patrick's day in Boston.

So, I have a pretty simple philosophy when making things

1. Nothing is hard, other people have done it before and I'm 'a people'. I just have to ask the right questions.
2. PLAN. Everything is better and easier with a 'couple of coats of looking at'.
3. Do it once, right, is better than doing it once wrong and three more times to fix it.
4. Pre-build. Do as much on the workbench as possible. It's more accurate and will help save my back.
5. Pre finish as much as possible.
6. Work in METRIC!
7. Use my woodworking knowledge where sensible to simplify/improve construction. (There are a few areas in the plans that I've seen that already say to me they have been done that way to allow people with less wood working experience or fewer tools to be able to construct. The plywood gussets on frames is a case in point.)

So, my plan for the frame construction is... (unless any of you shout up from your own experiences) ...

A. All frame component templates cut from cheap ply/hardboard.

B. Frame components will be rough sawn close to line and then templates used to bring to the line with router table and pattern bit. Including notches for sheer, chine, battered and limbers. Also dash layout and potentially any relief cuts or holes for cable routing etc. Also any half blind rebates or dovetails for motor well, Carlings and deck supports. Round over bit used to ease non mating edges.

C. All frame joints will be half lapped with material removed by router. This removes the need for hideous plywood gussets and mechanical fastenings. (I'd prefer bridle joints but I don't believe the frame needs that extra strength as it is predominantly in compression and not subjected to sheer in the plane of the joint. Also as the frames have curved profiles and are quite wide, trenching the centre of the bridle gets trickier. Likewise mortise and tenon joints.)

D. Joints reinforced by dowel pins. No mechanical fasteners. Potential for contrast wood or matching grain for decorative effect in visible areas (which I think is just the dashboard frame?)

E. Internal gussets of same material as frame used on visible frame members, reinforced with biscuits/dowels or dominos/loose tenons. (Gdcarpenter has done this on his dash frame for decorative effect). Note I mean internal gussets, not external laminated plywood gussets as per the design.

So. This approach leads to many questions.

Foremost in my mind are...

Q1. Frame material thickness? I'm assuming the frames are nominal 4/4 (25.4mm) stock resulting in near 3/4 (19.5mm) finished size and therefore 20mm planed stock would be OK?

Q2. lumber choice African Mahogany or Sapele or ...? I'm thinking that colour wise I want dark mahogany cover boards, teak coloured deck planks and either a dark paint sides or bright finished mahogany sides depending on how well I can scarf the plywood sides. Note I'm in the UK and timber options differ to the USA and tend to be more expensive.

Q3. Are the plans going to be accurate enough for me to notch and rebate for chines, sheer battens etc before offering up the curved members? I'm guessing I can cut the notches square but will have to fair an angle on them when assembling?

Q4. Is it possible to construct the transom with frame, plywood sheath and the motor well as a sub assembly BEFORE installing into the build strong back? If I was looking at this as a woodworking exercise I'd assemble it with sliding dovetails and rebates as a single sub assembly.

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rbrandenstein
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Re: Malahini... Step 1.

Postby rbrandenstein » Thu Aug 04, 2016 10:18 am

Q1. Yes, your thickness should be fine.. anything 3/4" or larger is OK. My 4/4 lumber was planed to 13/16 (20.6mm)
Q2. I used white oak for frames, African mahogany for decking, dash, and Meranti plywood.
Q3. Once you know the thickness of your chines, keel, etc. you could do preliminary square notching. As you mention, they get tweaked to match the curve. The book recommends notching for the bottom battens after the frames are faired.
Q4. I framed the motor well into the bottom battens and frame #1. I think it would be very difficult to align this all ahead of time.
IMG_0653.JPG
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Bob
Completed Malahini (launched 6/24/2012)
http://bobsboatbuild.blogspot.com/

gdcarpenter
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Re: Malahini... Step 1.

Postby gdcarpenter » Thu Aug 04, 2016 5:42 pm

Hi, call me the odd man out, but I built my entire transom/motor well as separate assembly and mounted it as a complete unit onto the building form. I used blind sliding dovetail joints to connect the sides of the motor well to the transom, adding significant extra strength.
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This is my first, last and only boat build.

http://www.gdzipbuild.blogspot.com

Brandlin
Posts: 29
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Location: Nr Chester UK / N Wales Coast

Re: Malahini... Step 1.

Postby Brandlin » Fri Aug 05, 2016 2:45 am

Thanks rbrandenstein, I'm still a little unsure about lumber, there are many differences between USA and UK naming and of course suppliers but also so many opinions.

Gdcarpenter - that's exactly what I was thinking! Where there are nice straight edges to be machined and assembled, and the possibility to use joinery techniques for far greater strength and durability it makes sense to me to do these things in the bench as a sub assembly. I clicked on the link in your signature and read through your rTher impressive and well photographed build. Just the inspiration I was looking for that I wasn't barking up the wrong tree!

Food for thought though. I hadn't considered the number of places in which the transom and motor well are pierced for cable routing etc. I won't have a motor and associated equipment for quite some time into the build so regrettably I don't think I can pre plan and pre drill in the way you have. But assembling with sliding half-bling dovetails is EXACTLY the way to go when building what is essentially just a strong box shape. I think I may make it somewhat easier on myself by having verticle sides and front to the well rather than the draft angle you have. That way, only the transom itself and the floor of the well are angled.

Classically, a box like the motor well would have a loose base to avoid cross-grain gluing. Are you concerned that this may cause movement issues even when you have the whole thing encapsulated? I was initially thinking that some members of the motor well should be ply to prevent this? Sliding dovetails in ply is not conventional and will lose some strength but in quality marine ply should be ok.

Brandlin
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Joined: Thu Jul 21, 2016 6:22 am
Location: Nr Chester UK / N Wales Coast

Re: Malahini... Step 1.

Postby Brandlin » Sun Aug 07, 2016 9:37 am

Was a little bored this afternoon and so have been converting the sketchup file of frames to Solid Works where i can construct the skins.

I have a little problem with the transom which doesn't export without corrupting, but the rest of the frames have allowed me to loft a first skin

Image

I dunno what all the fuss is about, this boat building thing is simple! :-)

briand
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Location: Auburn, Al

Re: Malahini... Step 1.

Postby briand » Mon Aug 08, 2016 9:20 am

Are you using the "Lofted Surface" tool? Haven't had a chance to use that one yet, and always trying to improve my skills in SW.

Brandlin
Posts: 29
Joined: Thu Jul 21, 2016 6:22 am
Location: Nr Chester UK / N Wales Coast

Re: Malahini... Step 1.

Postby Brandlin » Mon Aug 08, 2016 10:24 am

Yes Briand.

Using a spline to draw in upper edge of sheer and lower edge of chine, then lofting between them using the stem centre line and rearmost frame profile as guide curves for the edges.

I tried lofting between each of the frames but this gives quite a 'wave' in the surface. I'm not sure how accurate the frames are as I didn't draw them from a set of plans.

It's entirely possible that the original plans are a little out anyway but nothing that plywood, wouldn't 'take up', and fairing wouldn't fix.

I'm actually learning quite a bit about the construction sequence and fit of the boat from modelling it. To do this the same way as the boat is made I should loft and project the chine and sheer along the frame edges, then loft the skin surface and use that to intersect all the members it cuts into. That would simulate the fairing process. Then thicken the skins and extend them until they intersect.

Then I could 3D print it!

Like all the cool kids do.


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