I built my first US1 meter this past spring from the SCEPTER plans. Had a great time !! I am designing my next boat and was wondering if I should go with a narrow hull or a beamy hull. Hoping that sailors with more experience than I can chime in with the pros and cons of each.[:-pirate]
Go narrow! Beamy hulls don’t work too well in models based on looking at a lot of the top boats and my own experience. First, though, take a look at the best boats in the class and see where they are. The problem with some narrow boats can be an increased tendency to pitch pole which can be dealt with by increasing the freeboard forward and slightly fuller sections forward.On the F100 One Meter Graham Bantock chose a hull shape with a sweeping sheer line and lot of freeboard forward including a slight flare to the hull to reduce the potential of nosediving downwind- but it carries 50% more sail than a US One Meter.
Also ,I’m not positive but a t-foil may be legal in the US One Meter class and it could help downwind and not hurt too much upwind IF the foil had a controllable angle of incidence–but the increase of freeboard forward is probably the best solution to prevent or reduce nose diving in this class.
Pay very close attention to your foils! Try to keep them in the range of 6-7% thickness/chord ratio; put a small “fillet” at the intersection of the leading edge of the fin and hull: a sort of knee that extends about 9/16" forward and the same down.Keep in mind that the area of the foils is best determined by designing for the anticipated speed and load; rough estimates for a narrow lite hull would be 4-5% of SA for the fin and 2-2.5% for the rudder.Note that the sail area that you have to design for is NOT 600sq.inches which is the measured area; the actual area includes the roach area and can add more than 200 sq. inches to the sail plan over the measured 600(at least in a 36/600; I think the unmeasured roach is less in the US One Meter).
Make sure the boat doesn’t pitch down as it rolls; that can have a negative effect on pointing…And good luck; keep us informed of the choices you make and the results you come up with…
Doug Lord
microsail.com
monofoiler.com
High Technology Sailing/Racing
Thanks Info Doug.
So if I go with a narrow beam (6?+/-) should I go with a shorter Mainsail to stop the tendency to pitch pole (48?+/-)?
Great info, when is the book coming out?[:-graduate]
http://www.rcsailing.net/uploads/~tb/rev1c.jpg
Posted this in the homebuilding thread. One of my newer designs, shes only 4" wide at the widest points on deck, and 3.75 wide at the widest point along the waterline (when verticle). I have learned ALOT from sailing this narrow of a boat that goes contrary to what alot of people told me. if you cant tell from the pictures, she is very verticaly slab sided all the way up to the bow. No flair like the bantock design reccomends in dougs post above. I elected to take the pitcpoling concept in a different direction then most. by adding flair to the bow, you increase the area on your foredeck. As soon as it goes bow down, this much area serves as a HUGE break and stops the boat dead in the water and increases pitchpoling. by keeping a very slender bow and narrow deck, the “rev 1” manages to pierce through the water going down wind. Long story short, she is a VERY fast submarine. sure,the bow goes all the way under now and again, but she dont slow down when she does it. My reccomendation would be to go with NO flair what-so-ever. Increase the freeboard in the bow more than I have, move some volume forward at or below he waterline and keep a very fine entry on the bow.
There are some other lessons learned in rocker stern profile, bow profile (or general underwater profile) as well as displcement for narrow boats, but dont want to clog up this forum. Feel free to contact me “offline” via PM or e-mail about this. and KEEP DESIGNING!
~tb
PS: Oh yeah, if anyone wants shadows for the “rev 1” I will gladly furnish them to anyone for FREE (or whatever it costs to get them to you . . . self addressed stamped envelope if by mail, nothing if by e-mail). All I ask is credit where credit is due if you start winning with the design. I will be building a new “rev 3” this winter and hope to race it next summer.
I think tb’s idea on a sort of “wave piercing” hull design is worth looking at…
TB, you’re not going to clog the forum; if you feel like it why don’t you share some of your other ideas?
Doug Lord
microsail.com
monofoiler.com
High Technology Sailing/Racing
I started writing an e-mail to someone about this. . . and then realized that I should really get my thoughts gathered on the subject. I think I am going to see if I can get the rev1 lines at 2" stations loaded up into a .jpg in my photo album. all you will have to do is figure out how to scale it appropriately to print and trace the sections.
Then I started thinking. . . how much of my learings do I want to share prior to having a “winning” design. Then I realized that I really dont care. All for promoting the sport. I hope to make available eventually a half way decent moulded hull pretty much at cost of materials (ok, I aint going to lie. . .plus aa couple bucks for me to buy the beer I will be drinking while working). This winter I should be making the mold, once I get off the water!
Once I get my thoughts together on narrow boats, I will post here and e-mail to a couple people. But remember, I am not claiming to be any form of expert, just someone who designs and sails his own designs. Take anything you hear from me at face value.
~tb[8]
Hull and appendage design is very hard and usually success is found in the middle. Currently, the dominant boat in the US1M class is the Sterne Venom and while it is on the “narrow” side of the spectrum, it is not extreme. The foils are pretty much in the middle also (not radically thin) and don’t incorporate either the filets or tfoils suggested below. Usually, the more you push a design toward own side of the equation or the other the more likely you are to have a condition specific boat (typically, thin boats go better in lighter air, wide boats in heavier air). However, it’s not just the waterline beam that can effect hull performance, the shape choices you make can have just as much influence as the beam. One thought, before you built your design; you might try to show the plans to some of the successful designers out there for their critique. Very few designers with a winning track record in model yachting post on the internet, but they can be reached on the phone or even via e-mail. In the US1M class look to Bob Sterne, Bob Debow, Swede Johnson, Steve Andre. In the IOM class try Jon Elmaleh, Martin Firebrace, Brad Gibson, Martin Roberts or even Graham Bantock. Ask nice and you never know what kind of response you might get.
I am actually quite interested in your thought about rocker design for narrow boats. Even know I?m not a huge fan of skinny boats, my home build USOM is quite narrow too, - 5 inches 51/2. My design I was inspired by the ORCO. Unfortunately she doesn?t perform as well as the ORCO or yours; well my sailing might have some major responsibility in that regard too. But, I have noticed a similar behavior during my down winds runs with the pitch poling, she seems to sail right trough it, or at least she doesn?t seem to be affected as other boats do, I have seen more than one Venom stopping dead in the water after submerging half boat, and thinking back your thought are making sense. I hope your going to post the rest of your thought soon, as well as the lines of your ?skinny?. I?m not an ?expert? either but I like to build and sail my own boats too. I was starting to give up on that design, but if I could improve it would be nice, it?s actually a nice looking boat too. I will try to post some pictures if your or someone else is interested.
Gio
Roy, why is your advice not to use the fillets or LERX(leading edge root extensions)?
Doug Lord
microsail.com
monofoiler.com
High Technology Sailing/Racing
He didn’t Doug. He just commented that the Venom doesn’t employ them. That stuff is great and Graham seems to be the only one in production with them. It’s neat but won’t be the difference between 1st and 2nd on the race course.
Rob
Are you really sure about that Rob? Anything that reduces drag between two otherwise identical boats could make the difference between first and second…
Doug Lord
microsail.com
monofoiler.com
High Technology Sailing/Racing
I built a really narrow 1m boat years ago. I think it was about 4.5-5" beam. One thing I found very important to overcome the submarine issue was the rear underbody. Too flat or not enough rocker promotes planing, but also forces the bow down. More racker tends to keep the bow up. As the water “sticks” to the hull it seems to pull the stern down. It would be interesting to build two 1m slab boats but vary the placement of rocker.
Kristopher
Very funny story about “anything that reduces drag between two boats”…About ten years ago John Amen and I went to a 36/600 US Nationals in Florida. At the time we were both using a “friction reducing” spray on our hulls to try to get a little bit more speed in light air. One of the locals came up and asked John if he thought that the spray would be worthwhile on his boat. John looked the boat over and noticed that the keel bulb was attached with a pair of angle brackets. He then noticied that a nut and bolt were sticking out of the bottom of the hull about two inches down as part of a claimed “drain system”. As much as John believed in the “Go Coat” spray we were using, he told the local fellow it wouldn’t make a lick of difference.
<blockquote id=“quote”><font size=“1” face=“Verdana, Arial, Helvetica” id=“quote”>quote:<hr height=“1” noshade id=“quote”>Originally posted by lorsail
Are you really sure about that Rob? Anything that reduces drag between two otherwise identical boats could make the difference between first and second…
<hr height=“1” noshade id=“quote”></blockquote id=“quote”></font id=“quote”>
Even if they are identical it’s my contention that missing a shift, rig tune etc. will play a much larger role than having Lerx’s everywhere possible.
Rob
Kristopher was right on with some of his comments on the rocker. I have seen the same thing in a couple boats of narrow design. IT would take some carefully shot video to demonstrate, but I might be able to accomplish that this weekend. The thing that puzzels me though, is if you are counting on the water to “stick” to the rocker as speed increases, then is that same “sticking” effect actually increasing drag and reducing speed? Dont really know for sure. Still working on that one on a couple pieces of paper.
~tb
If you look at the design of any boat from the side you’ll notice that IF you were to try to use “rocker suction” to prevent pitchpole AND you were effective you would be slowing the boat down; a vector taken off almost any boat would provide an aft component to the suction or negative lift being developed: not a good idea in my opinion.
What has been found in the full size I14 Class is the use of a properly positioned adjustable angle of incidence
T-foil will reduce drag upwind and downwind. A rudder T-foil with an adjustable angle of incidence deserves a very close look by anyone interested in improving upwind and downwind performance. It is known that such effects DO scale down; the negative is that on I14’s they can keep the boat level making the foil work better. However, the designer himself(Paul Bieker) is experimenting with the foil on full size keel boats.Look under “Rudder T-foils” for the post by “Skiffy” showing a picture of the foil used on a 14.
I believe that a very low wetted surface design with a fine entry utilizing a controllable angle of incidence foil could be quite fast.
Doug Lord
microsail.com
monofoiler.com
High Technology Sailing/Racing
I see ppl have built plenty of boats narrow. i also have a lot of hull siting around around (I like to design my own boats.} my narrow beamed boat is 6 " and found it to be wanted in many areas. in heavy wind it goes like a rocket but in fair wind and lite , a fairwind can overtake. so most of my designs have been around the 7-9 inch range. this all has to do with the IOM calss of boat. I look at the ts2 and THAT boat is very wide at almost 15" and it is always in the top 10
Doug; Do T foils work on boats like this, I know the moth and Int14 classes use them but when slower, heavier development classes such as the merlin rocket have tried them them they havent had much sucsess. Surely a heavy keelboat like a US 1m is not quick enough for a t foil to work effectively on all points of sail.
If its not blowing it sucks!
From my own observations and experiences with my own designs the heavier the boat the less sensitive it is to wider beam; Light displacement boats REQUIRE narrow beam to perform well in most conditions , in my opinion.
T- foils will work well for sure on boats that can be kept upright-that has been shown clearly in full size boats and would translate to models directly.But boats that heel throw in a new wrinkle because then you have potential cross coupling between the rudder and foil. You absolutely would need an all moving foil to make it work and that would take lots of experimentation to get it right. Bieker has worked on the idea for heeled boats but I haven’t read any results yet.
The potential is there to allow a hull form more optimized for upwind yet not susceptable to pitchpole downwind.
Doug Lord
microsail.com
monofoiler.com
High Technology Sailing/Racing
~tb
I saw you boat. and wow it looks great, did you design it. because it look like a copy of lite ice. down from australia. you did a great job and would like to here more about it. I am surrounded by sailor that buy there boats. there is nothing wrong with that, but I find there is more sastifaction in design a boat that sails well and goes fairly fast. i have 3 hulls one at 6 inch beam and 7 and 7.5. i was just wondering if you had the same problem i had . going narrow meen having more hull in the water and a larger rocker panel?
Lloyd