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Vagabond 20 questions for Jacques

Posted: Mon Dec 14, 2020 9:15 am
by Jeff
This question arrived via email over the weekend: "Greetings, I am planning to build a weekend cruiser boat in the 18-20 feet range and Vagabond 20 caught my eye, looks good in the study plans. It's cabin seems wider, (although may also be shorter) and it's a heavier boat then my other alternative. However, one of my concerns is the complexity of the keel system as seen in project just right. I guess there is a deeper steel keel option as well, but I wonder whether a simpler lifting keel option was available to keep it trailable and simpler to build." Jeff

Re: Vagabond 20 questions for Jacques

Posted: Mon Dec 14, 2020 11:17 am
by jacquesmm
Somewhere, in my design archives, I have drawings for a fixed, deeper keel but are you willing to cast a lead keel shoe?

Re: Vagabond 20 questions for Jacques

Posted: Mon Dec 14, 2020 5:39 pm
by Sarp
Thank you for the prompt response Jacques. I'm new to amateur boat building and Vagabond 20 will be my first project, it is probably the finest looking sailboat I have seen over the past weeks of searching trough multiple boat designs around this size. I will go over the plans and tutorials in the following few weeks and hopefully start building within a month or two.

Re: Vagabond 20 questions for Jacques

Posted: Mon Dec 14, 2020 7:21 pm
by new to sail
Sarp
Welcome to the Board. Looking forward to seeing another Vagabond 20 build.

Rick

Re: Vagabond 20 questions for Jacques

Posted: Mon Dec 14, 2020 9:21 pm
by Sarp
Thanks Rick, hopefully I will be able to start within a month or two.

2 questions came to mind, please forgive my inexperience if the questions seem illogical.

I'm going over the keel plans and the fixed keel looks good. Am I correct to assume that the boat will have better stability as opposed to the drop keel with plywood frame version, since it's cg is significantly deeper (By rough estimates, it has around 80-85L of inner volume, which 21-22L of it filled with lead seems enough to end up with a 250kg keel). However, the shallower lifting keel option also sounds good for easier trail-ability. I was wondering if I could have a shallower fixed keel, like chopping off the bottom part by say 15-20cm (somewhere around cg of lead from bottom). Would adding an additional 20-40kg of lead to this new shallower fixed keel give me comparable stability?

My second question is regarding headroom inside the cabin. I was hoping that the cabin headroom would be around 110-120cm and was a little worried to see that it's 99-107cm. I read in the FAQ that although not recommended, the size of the plans can be stretched up to 10% without major changes to dynamics. I was thinking whether stretching the plans on side panels to give a little more headroom, is feasible or not (5-10% accounts to roughly 4-8cm increase in headroom and 1-2cm wider hull overall)? It may affect the looks and plywood optimization, will it also have an impact on stability? Finally, shall a first time amateur builder stick to the plans 100%?

Re: Vagabond 20 questions for Jacques

Posted: Tue Dec 15, 2020 11:50 am
by jacquesmm
Keel first:
The plans show two keel versions: a CB keel and fixed deeper keel.
You choose which one you want. You listed the pros and cons: trailer ability or a little more righting moment but not much.
If it was possible to design a simple fixed keel with lees draft and same LCG, I would have done so.
It is possible to draw some type of bulb keel but that keel would be very difficult to build by an amateur.
BTW, I hope you realize that the deep keel is a welded keel.

Re: Vagabond 20 questions for Jacques

Posted: Tue Dec 15, 2020 11:54 am
by jacquesmm
Scaling and headroom:
this is a small boat and I can't give you more headroom without major distortion.
You could scale but why not, instead of scaling, pick plans for a larger boat like the VG23?
I can supply the fixed keel plans for the VG20 with that set of plans and you would have to scale the keel only.

Re: Vagabond 20 questions for Jacques

Posted: Tue Dec 15, 2020 2:56 pm
by Sarp
Unfortunately, I only have access to a building site where the outside frame doors are 2.40m, so a VG23 would not work, besides I already got the plans.

Is it possible that I can get a little more headroom with some tweaks like lowering the front triangle bed floor by 5-7cm and possibly enlarging the space around the sliding cabin cover?

Re: Vagabond 20 questions for Jacques

Posted: Sat Dec 19, 2020 7:07 am
by Sarp
Dear Jacques,

I studied the plans and noticed that I have about 6% margin within the plywood dimension limitations (125*250cm metric) and a 6% increase in overall height, can increase my headroom over the side bunks from 82 to roughly 89cm (Bulkhead E). My car's rear seat headroom is 90cm, I believe I would feel crowded if it was 7-8cm lower, so I believe this upgrade can be worth it. I can also increase the width by 6% to keep the proportions. All bottom and hull sideplate width dimensions are increased by 6%, so as the corresponding outer bulkhead faces. My question is do I have to increase overall lenght by 6% as well or, keeping the boat at 6m original lenght would not compromise it's stability or handling at this level.

Thank you for your help.

Re: Vagabond 20 questions for Jacques

Posted: Mon Dec 21, 2020 11:24 am
by jacquesmm
Scaling 6% is reasonable. You may have to add a little ballast but that would make the boat more stable.

Re: Vagabond 20 questions for Jacques

Posted: Tue Dec 22, 2020 6:05 am
by Sarp
Thanks for the info Jacques,

I created some cad drawings scaling the boat by 7% overall (6.5m limit) and decided to use the fixed keel. I have a few questions regarding some options;

Okoume is the original plywood, would it be ok if I switch to baltic birch? It is around 25% heavier but also a more stiff plywood. I also could not find 9mm marine grade, but there is 10mm instead. So, the bulkheads and lower chine will be 10mm instead of 9, do you think this substitution will be sufficient to support the additional weight? Do I have to scale any other panels (6 to 8mm and 12 to 15mm swap seems a bit too much)?

Can I still use 280g/m2 biaxial fiberglass or shall I swap to a heavier cloth?

Are there any other hull reinforcement I should take into account (seams, mast support pillar)?

Do I have to scale the sail area, rudder length, mast length and keel weight by 7% as well or keep them the same as in the original plans?

Sincerely,
Sarp

Re: Vagabond 20 questions for Jacques

Posted: Tue Dec 22, 2020 11:34 am
by jacquesmm
If you scale, you must scale everything including keel, rudder and the complete rig.
For the glass, use a minimum of 400 gr/m2. That means your 280 gr biaxial plus a thin layer of woven for a total of 400gr.
Same for the seams and all fiberglass specs.

No birch please. We did some testing: birch rots easily and is weaker. Meranti or Sapele are good substitute.

Re: Vagabond 20 questions for Jacques

Posted: Sat Dec 26, 2020 1:29 pm
by Sarp
Dear Jacques,

I plan to place 2 small water tanks (50L each, regulations mandate the use of a grey water tank) one between bulkhead B/C the other between C/D on mid/starboard position. Unfortunately the C/D tank is in the way of the vertical panel coming from the cabin bunkbed lower vertical faces. Instead of having the C/D vertical plates at 34cm off-center, is it possible I install them at 51cm and use a high middle beam (10mm plywood, from bottom of hull to deck attached to the kitchen cupboard (lined 25mm to starboard side from center)?

Merry Christmas

Re: Vagabond 20 questions for Jacques

Posted: Wed Jan 06, 2021 12:36 pm
by Sarp
I found a good deal on an 8.0m mast at 74x110mm profile, 2.14kg/m. Since my hull is scaled by 7%, I was thinking about scaling the jib (both height and length) and scaling the main's length by 7%, height by 1.4% (100mm, 7.9m vs 8.0m mast). Overall sail area will be scaled by a square of 5.5% with 21.8m^2 total area. The draft of the keel will be increased by 5.5% and weight by cube of 5.5%. Is this setup suitable for my boat?

Also any insight regarding the vertical panels at bottom side kitchen cabinets?

Best Regards,
Sarp

Re: Vagabond 20 questions for Jacques

Posted: Wed Jan 06, 2021 1:27 pm
by Jaysen
Keep in mind that scaling "unevenly" will change the CoE on the sail area. This will potentially result in the CB/keel being "in the wrong spot" which will lead to some unwanted behavior. You are further complicating by changing the sail ratios as well. that changes the CoE in even more dimensions. This means that you need to rerun all the CoE calcs and ensure that you get the CB/keel AND mast in the right location now. It will be dang hard to move them once the boat is built.

If you are scaling the hull by 7% then you really really should scale EVERY DIMENSION by 7%.

Re: Vagabond 20 questions for Jacques

Posted: Wed Jan 06, 2021 1:33 pm
by jacquesmm
Keep it simple and scale everything by the same factor, for example 7%. There are sufficient safety margins built in the design when it comes to plywood thickness and fiberglass layers but it will not hurt to add a layer here and there using common sense: bottom panel, keel, mast step.

For the mast, that profile should work. The plans show the moments but the spar supplier does not. Ask him for the moments and compare. Going by what I see: size, wall thickness and weight, it looks fine, maybe a little over weight. A splice at the spreaders level is fine.

About the galley and seat, again use common sense. Scaling up by 7% will be beneficial from an ergonomic point of view. You will sit better with that 7% higher and wider bunk.

PS: thanks Jaysen. I was posting at the same time and your remarks are correct.

Re: Vagabond 20 questions for Jacques

Posted: Wed Jan 06, 2021 1:51 pm
by jacquesmm
More about the mast: I did some quick calculations and that profile looks heavy. Please stick to the moments I show on the plans, increase them a little bit if you want. I show 28 and 45 cm4, stay close to that. Most of my spar manufacturers tables show a weight of about 1.5 kg/m, 70 by 90 section with a 2 mm thickness. Your supplier (Ottomast) does not show thickness or moment of inertia . Their profile 3409 looks better.
My old Proctor mast table shows something closer to the heavy profile 3419. You choose.
If you plan to sail hard, go for the 3419, for most sailors, profile 3409 will be sufficient.

Re: Vagabond 20 questions for Jacques

Posted: Wed Jan 06, 2021 3:54 pm
by Sarp
I tried to find comparable dimensions for the mast as stated in the plans (80x120mm), shall I aim to match weight instead (1.8kg/m)?

In case I cannot add a reliable splice and the mast is at 8.0m, (1.4% increase in main height), shall I scale both the luff and foot by 1.4% or increasing luff by 1.4% and foot by 7% for both sails is fine (their area's will be scaled at the same level)?

Re: Vagabond 20 questions for Jacques

Posted: Wed Jan 06, 2021 6:43 pm
by Jaysen
The problem is that the Center of Effort (CoE) is based on the geometry of the sail. So if you only scale by 1.7% you won’t have the CoE on the sails aligned with the expected CoE the keel is resisting. The CoE will be forward on hull. This will tend to push the bow leeward.

This is why scaling really needs to adhered too.

You should be able to splice the mast. You need an interior sleeve that you peg into one section. Then you secure the sleeve in the other section once assembled.

To Jacques point, if you make the splice align with the spreaders you can leverage the spreaders mounting to secure and provide some external reinforcement.

Re: Vagabond 20 questions for Jacques

Posted: Thu Jan 07, 2021 3:25 am
by Sarp
This is very valuable input for me, thank you. I knew that scaling was not recommended since it would complicate calculations, but I had to either pick this boat and scale it or another 20 feet one with a slightly higher headroom. I liked this Vagabond 20's overall design and the construction method. All in all, I need to be extra carefull so that there are no issues in terms of structure, balance & handling of the boat.

I may have to find a workshop to fabricate a mathcing sleeve to the inside of the mast. Assuming 110mm profile lenght, will a 440-500mm lenght sleeve suffice? Shall it be epoxy glued to the 2 mast parts, fastened with screws/sleeves, or welded? The spreaders are installed at 3000mm, (3210mm with 7% scale). Shall I cut the splice at slightly above this point, say 3250mm?

I still worry about the durability of a splice vs a one piece mast, but I guess CoE is more critical. The original luff and foot are 7200 / 2500 for the main and 6350 / 3300 for the jib. As an alternative to spliced mast and 7% overall scaling, If I increase the foot of both sails by 7% and their luff's by 1.4%, I think the CoE will still be at the same point on the longitudunal axis. It will be at a lower place on vertical axis compared to a full 7% scale. Would this increase the stability of the boat compard to a 7% full scale? The boat will have a lower sail performance on weak winds, but will it be noticable by an ameteur like me? (I know its a boat, but rough rule of thumb for a car's noticable performance is around 5%, anything less is usually placebo effect) Would such a setup cause any other issues to stability and handling?

Besides sails, I would like to ask about structure as well. I have scaled the entire hull by 7% in all three dimensions. The bulkheads are incresed to 10mm as it was an option in the original plans. I found 450g 45x45 biaxial fabric instead of 400 and thought it would suit well for the increased size and weight. It will be used for all structural seams as well as covering the bottom + chines from bottom side. Here is an area that wasn't clear for me in the plans. The topsides&decksides have an option of using 6mm plywood with biaxial fabric on both saides, but from the drawings I can only see a bottom covering for the 12mm bottom and 8mm chine plates. Shall I use the 450g fabric to cover both sides of these bottom and chine frames or just the bottom side? (Is the inside of the cabin just seams on edges and epoxy on the rest of the surfaces?) I will use the 300g biaxial to cover 6mm decksides, 6mm topsides and 8mm deck from again both sides? Do I need to increase the fabric to 350g/m2?

I'm planning to enlarge the mast support pillar from 50x25 to 60x30 while the deck support stringers will be 28x30 and 20x80 middle (I could not find 25x30 or 15x75). All of the seating surfaces and vertical panels both inside and outside are also 10mm (8mm marine okoume was not available at the larger size to cover the seating surfaces for cabin/cockpit with minimal plywood waste and I used the inside of the bulkhead frames as well) Do you see any issues with the hull structure?

Thank you for your help

Re: Vagabond 20 questions for Jacques

Posted: Thu Jan 07, 2021 10:16 am
by jacquesmm
The profile manufacturer should supply the splice. The inside part will be made from the same extrusion but with a small slice cut out. I am surprised that he can't supply a full length.

As for the scale, it is simple if you stay with a uniform scale. Problems appear when you want to use different scales for different parts.

Re: Vagabond 20 questions for Jacques

Posted: Sat Jan 09, 2021 8:01 am
by Sarp
I found another mast supplier and he suggested that the splice could be added as a taper piece at the top with 30-40cm overlap, adding 40cm to overall height(so one 7.5m piece + a 1.3m splice piece with 0.4m overlap). He also suggested that the splice could be done at the bottom as well close to boom with a 0.9m+7.5m 2 piece mast + a 3rd splice piece inside. Can these methods be an alternative to a splice at spreaders level + 2 piece mast (btw is it roughly around 3.4m from deck assuming 7% scaling above the boom level)?

Re: Vagabond 20 questions for Jacques

Posted: Sat Jan 09, 2021 8:54 am
by Jaysen
What’s the objection to a one piece mast?

Re: Vagabond 20 questions for Jacques

Posted: Sat Jan 09, 2021 11:48 am
by Sarp
I talked with a few mast suppliers, some do not have anything smaller than a mast for a 9m size boat. The ones that make suitable profiles only have 7.5 or 8m length in stock. One said they could supply a 8.5 but then it would not be anodized. So, either it will be a splice at bottom (near boom), spreaders or top, or it will be an 8.0m instead of the scaled 8.4m. It is relatively easy to have a small piece splice (bottom or top), but a splice in the middle costs me double for the mast profile.

One supplier said they could have a short extension at bottom (around boom) and they can weld the alu splice profile to the bottom part with enough extension for the main mast. The main would slide over this welded bottom splice. If this approach does not compramise integrity I could go for it, but if the only proper way is a splice at spreaders level, I will have to get 2 mast profiles cut to certain length + the splice piece assmbled as one unit.

What would be the issue with a small splice piece right at the top? I know the loads there are high, but it will not be 2 profile pieces attached with a splice inside, but the inside splice will be the only piece added (like a tapered profile at the last 70-80cm)

Re: Vagabond 20 questions for Jacques

Posted: Sat Jan 09, 2021 1:46 pm
by Jaysen
The mast is under high load every point on its length. I would think cutting a longer, stock mast down to size would be cheaper and less prone to failure.

That said all the mast slices I’ve seen are at the midpoint or at the spreaders (mounts adding reinforcement to the junction). Given the options you listed I would go for the upper insert using the spreader bolts to anchor the insert.

Not sure how that will work for the sail cars. It will be interesting to see.

Re: Vagabond 20 questions for Jacques

Posted: Sat Jan 09, 2021 3:27 pm
by Sarp
What about I use a heightened hinged mast step, say 180mm instead of 30mm. All I need is 0.5m above boom for an exact 7% scale. I will get 0.1m from mast and 0.15 from this heightened hinged, step that covers half of it. Does 0.25m (10 inch) length has such an impact on boat handling that it would require a splice and a 2 piece mast?

https://www.dwyermast.com/itemdetails.asp?itemID=448

Re: Vagabond 20 questions for Jacques

Posted: Fri Feb 05, 2021 3:55 pm
by Sarp
I started assembly of the hull. Lower and chine panels are glued with spliced joints and settled on the basket mold. I stitched the panels at some places dry to see how it shapes up around the bulkheads. There is a significant tension at the bow where I try to mate the panels at bulkhead 0. It seems the chine panels are resisting to twisting from semi-lateral to vertical after bulkhead E. At bulkhead A, tension is around 15lb on each side when I press on the gap between the panels and bulkhead, At bulkhead 0, it is around 25lb. Are these loads normal in a stich and glue boat of this size? The chine panels edge touches the bottom panel's sides. Is there a special type of orientation regarding stitching?

Another question comes to mind with stiches, most methods I see use fast epoxy to tab the panels, then remove the stitches and epoxy glue the entire joint and radius fillet. Unfortunately the weather is cold and ı do not have a suitable fast cure epoxy. Is it ok if I epoxy glue in between the stiches and once its dry, remove the stiches, then do the radius fillet and seam joint at the same time?