10 Foot Row Boat Design Information

[freeboatrsrce]

Hello All,

I used FreeShip! to design a small car top-able row boat. The estimated weight of the boat is 102 pounds. It may be outfitted with a small motor of about 2.5 to 3.5 HP (38 pounds). It was designed to carry 200 pounds (boaters and gear) on the waterline. You can view the Linesplan on my blog at : http://freeboatresources.blogspot.com.

Below are the numbers that FreeShip! calculated. I confirmed some of these numbers by hand, such as Displacement, Lcb, and the Lcg. The finer details follow:

Hydrostatics calculated using Free!Ship :
Project : 10 Foot Row Boat
Designer : wayne@freeboatresources.com

Design length : 10.000 [ft]
Length over all : 10.000 [ft]
Design beam : 4.364 [ft]
Beam over all : 4.364 [ft]
Design draft : 0.460 [ft]
Midship location : 4.846 [ft]
Water density : 62.500 [lbs/ft3]
Appendage coefficient : 1.0000
Volume properties:
Displaced volume : 6.177 [ft3]
Displacement : 0.172 [tons]
Total length of submerged body : 9.592 [ft]
Total beam of submerged body : 3.984 [ft]
Block coefficient : 0.3514
Prismatic coefficient : 0.5702
Vert. prismatic coefficient : 0.4642
Wetted surface area : 30.735 [ft2]
Longitudinal center of buoyancy : 4.680 [ft]
Longitudinal center of buoyancy : -1.731 [%]
Vertical center of buoyancy : 0.325 [ft]
Midship properties:
Midship section area : 1.129 [ft2]
Midship coefficient : 0.6162
Waterplane properties:
Length on waterline : 9.592 [ft]
Beam on waterline : 3.984 [ft]
Waterplane area : 28.924 [ft2]
Waterplane coefficient : 0.7569
Waterplane center of floatation : 4.307 [ft]
Entrance angle : 45.584 [degr.]
Transverse moment of inertia : 29.514 [ft4]
Longitudinal moment of inertia : 155.85 [ft4]
Initial stability:
Transverse metacentric height : 5.103 [ft]
Longitudinal metacentric height : 25.557 [ft]
Lateral plane:
Lateral area : 2.923 [ft2]
Longitudinal center of effort : 4.924 [ft]
Vertical center of effort : 0.277 [ft]

The boat will be used strictly in small freshwater lakes, however, weather conditions can change rapidly and the boat will need to handle choppy waters at times.

Any comments would be appreciated.

[lewisboats]

Add a tad more rocker to the chines and increase the carrying capacity. A 10 ft boat should be able to carry 300-350 lbs of people and gear. The Vee bottom will make it a bit tippier and reduce the carrying capacity a bit but you might notice a bit of improvement in ease of rowing...probably not though.

[freeboatrsrce]

Thanks for the reply. The main reason I went with the v-bottom was to reduce the amount of water slapping the bottom. I tried adding more rocker to the chines, but the Block Coefficient increased dramatically. I figured she would move through the water better by keeping the chine where it is. The chine is fully submersed when at the design waterline, so hopefully it will not be too tippy.

[messabout]

The middle of the boat is not the part that pounds or makes a lot of noise. The ends of the boat largely determines how severely it might pound. Your boat has a heap of deadrise at the mid section and not enough at the ends. Lewisboats has given you a good suggestion. Raise the chines at the ends so that there will be lots of deadrise in the extremes of the boat. The bow will be pointy and the twist in the planking (ply I presume) could be problematic. That is worthy of some experimentation. Reducing the DR in the middle will make a flatter floor and be more comfortable to use. The deep deadrise option is to install floor boards which adds weight and complexity as well as providing a hiding place for fish guts. Flatter mid section will also reduce draft for a given displacement. More severe vee at the ends will make the boat less likely to pound than what you have drawn, as well as making it easier to row.

Your transom is very wide. That presents structural problems that you will have to overcome by adding material which adds weight. This is a compromise area where you need enough bouyancy for the motor, and for you to get near enough to crank the motor. All the while keeping the transom relatively narrow. Lively sheer lines with good rise at the aft end is part of the solution. As a matter of fact, the majority of swamping incidents are caused by having too little sheer height at the aft end.

Enough of picking on your boat for now.

[freeboatrsrce]

Thanks for the comments, unfortunately, putting more rocker in the chines is causing the displacement to drop; 300 pounds displacement is really the minimum I can go. I think that I am running into these problems because the boat is only 10 feet long, and I was wanting a vee bottom. The suggestion of raising the deadrise at the ends and flattening the midsection sounds like what is needed, however, this is a plywood boat and I don't think the plywood will make the sharp turns at the ends. I have ordered marine grade plywood 1/4 inch thick at $75 per sheet. I don't want to risk wasting this plywood. Strip-plank would solve the bending problem at the ends. If I were using this boat any place other than small lakes, I would not go with this design - the boat would be way to small. I know the boat needs adjustments that only a larger boat would allow, but I am trying to keep the boat as small as possible and did not want a canoe or kayak for fishing.

[freeboatrsrce]

Correction on my last post. Adding more rocker to the chines actually gives the boat more displacement, but the boat would not move through the water as easily.

[Easy Rider]

Looks like an Ed Schock sail boat to me.
3 1/2 hp is overpowered.
What does "4 stroke" have to do w power requirement?
Why should one use a Mercury engine.
lewisboats,
Yes it will probably row easier ..but slower. I have 2 10' row boats but one was designed as a sail boat. It is much faster, has greater capacity but seriously lacks directional stability while rowing. I say that because it's fine under power. The real row boat has a small, high, wineglass transom w low PC at both ends and a straight keel. It's a delight to row but slow and that's fine as I row to row and not to get anyplace.
Pitch stability is scarce on a 10' boat and lots of rocker dosn't help.
Basically 10' is too short for a decent rowboat. 12-13 min and 14-16 ideal depending on design details.
freeboatrsrce, The best car top-able row boat I know of is a canoe w a Front Rower (rowing machine) installed: http://frontrower.com
Stability is good as you sit basically in the bottom of the canoe. Speed is outstanding and especially to windward as the oars automatically feather. See the video on their site. Canoe is 60lbs and Front Rower 25. Very easy to car-top and will carry 2 people better than 10' rowboat. I have one.

Easy Rider.

[lewisboats]

Easy Rider: A small skeg does wonders at correcting directional stability issues...much like the keel on your rowing boat. Neither boat is going to be a speedster...you just don't have the waterline length to go fast.

freeboatsrce: If done right...1/4" can handle quite a bit of twist and bend...you would be surprised. What you have right now is extremely mild...you could put a couple more inches of rocker in there without much problems. As to the ease of going through the water...getting the ends out of the water will do more to reduce wave making friction than is added by the additional displacement capacity. As soon as that transom starts dragging you will feel like you are trailing a sea anchor behind you making rowing much more difficult. If it is only you in the boat then you will get by with what you have but as soon as you add someone else...you will overload the DWL and will find it significantly more difficult to row as the ends submerge and start dragging.

[freeboatrsrce]

I agree, and was not looking at the problem that way. I originally set out to make it strictly a row boat, but since have decided to put a 2.5 hp motor on it as well. Mercury is just one of the models available, and not the motor I will necessarily purchase. The Mercury 2.5 hp weighs 38 pounds, and the lowest price looks like about $750 - $800 if I'm lucky. The boat is so small it was really designed for a single person in mind, although it could be used by a 160 lb adult and a young person of about 40 pounds for rowing; with a motor, I think just one adult. Personally, I have no children so the boat is for 1 adult as it stands. Rowing around is great for exercise, but for fishing I think a small motor is needed to get around the lake better. A conoe is a possible option, but I was concerned about stability as the winds can kick up very quickly in my area - 30 to 50 mph without any warning from the weather forcast. That's why the boat is strictly small lake, and I'm hoping not to get in trouble out there. A little over a year ago, three young men lost there lives only 2 miles from where I live in the summer. They were 4 on a small boat; one made it to shore and the other 3 didn't. I'm sure the boat was simply over loaded. Very sad situation. There is a record of men not making it in my area, mostly on the lakes. I am probably pushing the limit with a 10 footer around here, but I think it will be safe if not overloaded.

[cameron.d.mm]

I thought I'd pitch in here, as I did something very similar to your project last year. You can see it here: http://www.camerondmm.com/images/pro...boat/boat.html

I don't think I have a lot of insight to offer regarding the plans you present. I won't try to read them and tell you what to change. Listen to the folks already helping you, and I'm sure you'll be just fine.

What I can tell you is about my experience with my <10 foot home built wooden boat. First, I suspect mine is heavier than you predict yours will be. I used strip planking and internal frames. I think your plywood boat will be lighter, but I didn't glass or epoxy mine. I don't really have any complaints about rowing the boat; it seems to go very well, and easier than the 14' aluminum boat that I also row sometimes (no surprises there). However, I am able to put both myself (200+ lbs) and my wife (less) and a packed lunch in the boat without swamping it. Maybe 350-370 lbs all told. It is definetly weighted down, but still handles well. If you intend to use your boat single handedly, I think the 300 lbs displacement will be sufficient.

I have never tried using a gas outboard with my boat, but I have used a small electric trolling motor. Even a 35 lb thrust electric takes the boat to what is probably nearly hull speed, and can do it for several hours on a charge, with the throttle set to 3 out of 5. Turing it up gets almost no increase in speed. The battery at the front of the boat nicely balances me near the back. I think your boat would fly with a 2.5hp outboard.

I don't know if any of the above is useful to you, but maybe it'll help you some how. However, there are just two things to add. One: make sure you design the boat so that your transom doesn't drag at expected displacements. I messed this up because I didn't do my homework before starting (I found this site 1/2 way through the build). It makes a huge difference. Two: it sounds like you have a firm grasp of the limitations of boats this small, but try to always keep them in mind while out on the water. I keep my boat mostly in canals and very sheltered bays, but the massive wakes generated by large powerboats at speed can creep up on you. Even these 'small' waves can give you a wild ride. As previously mentioned, the danger of swamping is what you need to watch for, and over loading the boat is how it will happen.

All the best, and make sure you share the photos!

[freeboatrsrce]

As this is my first design, I have not come across the problem of "Transom Drag". Are you referring to allowing the transom to dip into the water during operation? I was also wondering how the skeg may affect the boat in turns. Will the skeg make turning the boat more difficult under power?

[Easy Rider]

Cameron and freeboatrsrce,
Nice boat. I'd like to build one similar but w less rocker and 25-27' long. I've been looking a the Atkin designs. I enjoyed seeing your pictures. If you used Red Cedar it's possible free's boat won't be lighter when he gets the plastic on. If you did'nt like the Front Rower another thing to consider is a light stich and glue boat. Could be made much lighter than reg ply and that means you could build a 12-13' boat most likely under 100lbs. It would carry more weight gracefully and being longer would go a long way toward being a really good boat. I'm sure the reason your 14' boat is such a drag to row is that w all aboard the flat transom is partly below the water line and all that boiling of water at the stern is turbulence ..drag. Rowboats need to have their transoms above the water when normally loaded.
lewisboats, I agree about the skeg for free's boat and I don't think he needs to worry about the boat being difficult to turn. Mine turns fine w a full length keel and hollow ends. They are just too short. The skeg would probably render a boat that would want to turn downwind in a cross breeze but may not present a problem.

Easy Rider

[cameron.d.mm]

Hey freeboatrsrce,

Yes, you've got the idea with the transom. Just like Easy Rider explains, it will create a lot of drag if it is below the water line. Sometimes just trimming the boat fore to aft is all it takes to get around this. Unfortunately, on my boat the problem is bad enough that this isn't really possible. (Don't think for a minute that this makes my boat unusable or less fun... I still row it for hours on end. I just might get further if I'd done my homework better)

Easy Rider: it sure looks like red ceder, but it is actually Spanish ceder (neither from Spain, nor ceder), but is quite light anyway. My problem was that I used pretty thick strips. I think they could have been quite a bit thinner, but that is why I need to make another one!

I'm not sure if I've done a good job of getting the general thrust of my argument across, so let me put it plainly: Go ahead and built a 10' row boat; you'll enjoy building and using it a lot. Don't sweat the small details, but do pay attention and savour them.

[freeboatrsrce]

Thanks again for the comments. In the boats current design, the transom just touches the water when used as a row boat. If used with a motor however, I will need to shift some weight forward, otherwise I will be dragging the transom badly. I may need to consider installing motor controls so the boat can be steered and throttled from a point closer towards the bow; something very simple regarding mechanical controls. I don't want a steering wheel on the boat.

[Easy Rider]

One of my 10' boats has a nice feature. The ex sail boat has very small benches on each side (typical of small sail boats) that I put my wood seat on. I can position it anywhere fore and aft to suit the occasion. On your boat you'll just have to figure a way to sit further fwd and use an extended tiller. With the rockered bottom you'll probably only use half throttle w a 2hp engine as the squat and bow high attitude will get out of hand fast. After we talked about these boats I put my row boat on the utility trailer and got all the other gear ready to go. I'll be on the water shortly. It's almost not raining and no wind ..perfect. I'm going to go back and look at cameron's boat again.
Free.. .. you may want to read "car topper for a woman". This thread is a good read but check out ACs boat ..the pics on page 2. Don't miss the 60lbs part.

Easy