MIT Tech 12'X5' dinghy rerigged to a lug rig ?

[J. Dillon]

Is it practical or doable ?


Acquired this ancient 1950 built dink . It needs a lot of work I just have the hull & rudder. My scheme is to have a rig easily stepped, struck and all spars no longer than 12 feet and about 78 Sq Feet of sail area.
Will the sail's center of effort be close enough to the original sail cat boat rig ?. Or will the boats balance be too upset, would a sprit rig be better ?


I will be putting in tankage as the boat has some at the bow and stern , probably only enough to keep it from sinking if capsized. The tankage I thinking of installing will not be any where the same as the more modern tech dinks but might be enough to permit board and bailing. If capsized. Just what is enough ? On this boat I want to be sitting in the boat not on it .

Thanks for any input.

JD

[DeniseO30]

No you would probably have to move to mast step

you going to share the pictures of this beautiful little boat???

[rbgarr]

... you going to share the pictures of this beautiful little boat???

Here's a restored one: q-DqkRSXw3TVw_moH92BnlQ3jUxPBihr_dCPjDp6aM5om1cOncfuP5AC7se4botF2EDK=s85.jpg

(Ha. Never mind! Photo's too tiny to make out!)

[Thorne]

Not being capable of doing all the complicated maths, I'll recommend building the boat and then setting up a temp mast step and partner. Take it out sailing with the intended crew (I'm assuming you'll sail it solo) and see where it balances, then make the step and partner permanent. Sailrite and Duckworks have some lug sails and kits close to that size.

[rbgarr]

As far as flotation tanks are concerned, consider side tanks with styrofoam billets fixed to double as seats inside the boat. Make sure they are designed to be removed for any future owner who wishes to restore to original. https://smallboatsmonthly.com/articl...-side-benches/

[Peerie Maa]

Is it practical or doable ?


Acquired this ancient 1950 built dink . It needs a lot of work I just have the hull & rudder. My scheme is to have a rig easily stepped, struck and all spars no longer than 12 feet and about 78 Sq Feet of sail area.
Will the sail's center of effort be close enough to the original sail cat boat rig ?. Or will the boats balance be too upset, would a sprit rig be better ?



JD

It is easy enough to find the existing rigs CoE, and then see what a different sail does. https://amateurboatbuilding.com/arti...area/area.html

[Todd Bradshaw]

Actually, if you use a lug with the right aspect ratio and proportions, it surprised me how well it would seem to work out - at least on paper. I suspect you might want to go up to maybe 12'6" on the length of the mast, depending on how far you're willing to duck when tacking, but the centers of effort for both the original sail and the lug can be matched up pretty nicely. Does this translate into the same feel and performance across the board? Maybe or maybe not, it's hard to say without trying it, but at least I wouldn't expect the boat to sail like everything is way out of balance under lug power. You can also do some serious in-flight modifications to the handling of just about any 12' sailboat by shifting your weight around a bit.

Here is a typical balanced lug at 78 sq. ft.

lug.jpg



Stepping the mast in the existing mast step, the lug rig looks like this on the tech dinghy.

Attachment 50818and-tech.jpg

[J. Dillon]

Thanks Todd. Your post answers a lot of questions for me. A bit longer mast is the way to go for me as getting wacked by a boom is not an option. Funny thing about the tech dinghy is how they evolved. Their site gives a 4' +something as the beam but my 1950 tech is just 5'.

JD

[Ben Fuller]

On these little boat rigs I like to run my boom up at angle to help it clear my head. Area lost isn't really critical.

[Matt young]

These Neil Pryde pram sails look interesting to me. I think Duckworks got a deal on them, the prices are good. They look to be good performers?? 10' mast if you go with the sprit option on the 64sqft option

https://www.duckworks.com/product-p/...m-t-parent.htm
https://www.neilprydesails.com/image...0Pram%2064.pdf


I agree with Ben, on my sailing-canoe I designed the boom to angle up and clear my head, as there is nowhere really to move to get out of the way. It has proven to be a very good idea. Not sure where these Pryde sails are on that, or if the mast would need to be a bit taller?

NeilPrydeRig.jpg

[johngsandusky]

These Neil Pryde pram sails look interesting to me. I think Duckworks got a deal on them, the prices are good. They look to be good performers?? 10' mast if you go with the sprit option on the 64sqft option.

I bought two of these, the 50' and 64' for use in eight and ten foot prams. I set the 64 up in the back yard yesterday using spare spars, I like it.

[Todd Bradshaw]

Of course, the easiest way to deal with tacking and jibing low booms on boats that small is simply to head up, wait until the sail luffs and the boom starts inward and simply grab it and pass it over your head under control when tacking. For jibing, you trim the sheet in with the boom, grab the boom, pass it over and ease the sheet out as it goes out the other side. It's a cleaner, more efficient, more controlled process than just letting it wander over on its own.

[Ben Fuller]

I built my ducker sails pretty much the way they used to do it, with boom jaws and the tack right down at the deck. You still needed to kick the boom up over your head tacking or jibing but at least you could see to leeward.

[J. Dillon]

I've been thinking ahead on my rebuild of Tech dinghy and even though it is a small boat a paired topping lift sounds appealing as kind of directing the yard when lowering. Also a pitch pole for a cover to keep out the rain etc. But gulls might like it too so maybe a lazy jack might be discouraging.

I also figuring I might add about 5 cu. ft to the tankage about 2.5 per side

JD

[rbgarr]

Gartside's 10' RIFF has an 80 sq ft sail that mimics the shape, etc. of the Tech dinghy's pretty well. WB has a RIFF in their fleet that you could get to sailon for an idea of how it wold suit: https://store.gartsideboats.com/coll...iff-design-136

[Nicholas Scheuer]

Raced MIT Tech Dinghies in College back in the late 1950's. Simple, tough little boats. Yours should have better aesthetic value.

[J. Dillon]

Thanks rbgarr for the link I found it interesting I would like to enlarge the details of the halyard and mast attachment of the yard but the more one hits the+ sign things get blurry A neat little boat for sure.

Nick This boat I'm refurbishing is a rescue boat probably bound for the dump. A lot of broken stuff and patches on it as well. A mixed bag of blocks still clutched on hoping to turn in earnest some day You might have sailed it as the most recent owner said it's linage dates back to the 50"s. Did they have a name plate on them?
I'm thinking of naming it" SAVED" in latin or Norse or in Celtic .

JD

[J. Dillon]

Anyone here ever tried pitched seating ? By that I mean the seats are "pitched " or slanted so that the outer edge is lower than the inside edge allowing the windward side level or close to it. In restoring my MIT 12' tech dinghy I'm constructing the tops of the tanked to be so inclined. Still looking for a lug sail.

JD

[Matt young]

Here is LFH example, and I swear Dunbar did it on his Little Dipper too, but can’t find my picture of that right now.

959FCD31-DF0D-4D04-815E-304CA0A8FC34.jpg

[rbgarr]

Here is LFH example....

959FCD31-DF0D-4D04-815E-304CA0A8FC34.jpg

Interesting that you chose LFH's SOLITAIRE to show as an example. One of them is here in Maine, sitting on the hard for a few years well covered and cared for. IIRC, she has full length planks.

[J. Dillon]

I hope LFH shows a drain for the back side of his seats I did.

JD

[Matt young]

I hope LFH shows a drain for the back side of his seats I did.

JD

Thats why you have to rotate it ever now and then, like the second picture. Ha!

[xkdrolt]

LFH didn't design the Tech Dinghy -- but George Owen did. I think he also redesigned it for fiberglas in the early 1950s.

https://collections.mitmuseum.org/vessel/60877/?sr=tech+dinghy&fwp_paged=3

https://collections.mitmuseum.org/ve...hy&fwp_paged=2

If I find sail plan options, I will edit & post those too. HTH

[Ben Fuller]

With the MIT plan this becomes easier. Both the cat and the sloop have 60 plus sq ft so that looks like a lug in that area would be fine. You can down load the sail plans and figure out where the center of the sail areas are on the existing boats. Then draw in what you are thinking about as a lug and compare. I'd have a look at an off the shelf lug rig for starters.
Having raced them in college, they always had cat rigs. Seemed to be enough sail area to move the boat around and sporty when the wind blew.

[J. Dillon]

Apparently a few here have sailed this design. My project boat has an unusual CB arrangement . That is a lever on the stb side with no provision for partial settings like half down etc. I plan to change that with a tackle with leads back to the helmsman as with all lines, sheet, halyard and tack down haul

A question for former sailors of tech dinghy What is your opinion of the sailing qualities of this design ?

Thanks

[Ben Fuller]

Apparently a few here have sailed this design. My project boat has an unusual CB arrangement . That is a lever on the stb side with no provision for partial settings like half down etc. I plan to change that with a tackle with leads back to the helmsman as with all lines, sheet, halyard and tack down haul

A question for former sailors of tech dinghy What is your opinion of the sailing qualities of this design ?

Thanks

That lever works pretty well. Seen on many boats of that era. I never found partial up-down a problem as the water pressure in the trunk plus the system friction pretty much keeps it in place.

As far as sailing, they are relatively heavy dinghies. I don't recall ever getting one to plane. They are agile which they needed to be to sail on the Charles. When the breeze was up I recall the skipper planted on the rail with the crew in and out balancing the boat. If you do a lug rig. stick in a set of points.

[xkdrolt]

I never sailed on the wooden ones, just the glass versions. Otherwise I agree with Ben's comments above.

[J. Dillon]

Thanks Ben for your info about the boat.I still think the CB might need some sort of control as to how high or deep it's set. I don't intend to race the boat but water pressure and friction some how doesn't seem precise. However your hands on experience is valuable input.

Can any former MIT sailors remember the diameter of the mast, yard and boom. That's soon on my agenda. Figuring how to get it out of the basement without damage is in the works as well.

BTW two guy's muscled it in sideways but scraped it a bit. There was nothing in the boat then just one thwart across the CB case. I 'm making a "wagon" with two wheels castors and two straight so that when the boat emerges it's edge ways. The door opening is out the 70"" high. The boat on edge on the "wagon" will have 1" clearance. I have about 60 t0 70 lbs of more wood in the boat with the 5 opening locker/seats and 2 sealed

JD

[xkdrolt]

http://www.herreshoff.info/Menu/inde...ech_Dinghy.htm

then go to the tab for Plans, then look for the spars dwg, then zoom in. The HCR (Herreshoff Catalog Raisonne) is linked to the HMCo documents at the MIT Museum, so you get linked to just what you need. HTH.

edit: I should have added, Herreshoff in Bristol RI built the original wooden Tech dinghies for MIT. Another firm built the fiberglass versions (Cape Cod?), and yet another builds the new carbon fiber hull boats. The CF boats are apparently much lighter. I would like to get down there and test one out. FYI.

[J. Dillon]

Shaula 3 repairs as seen at inspectio 1.jpgThShaula repairs painted with kick up rudder.jpg

First photo boat as acquired 2nd image boat now with 7 Water tight compartments with 5 of them opening lockers for gear.

Thanks again for the replies. But I still have a question for those who have the sailed this boat before. Can former sailors of the MIT Tech dinghy answer this one? Does the boat throw up some spray over the bow to warrant a spray rail before the mast ? BTW I did make a tiller from a nicely curved blow down maple. The boat is FG but I now have about 75 lbs of wood in her.I cannot proceed with the mast and yard as I have the self quarantine in effect I did managed to get a boom together by scarfing together two spars left over from my last build.

Thanks all

JD

[rbgarr]

I don't remember that the MIT Tech dinghy was any more likely to be wet than any other similar boat. But i only sailed them on the moderately calm Charles River. Conditions will dictate.

[xkdrolt]

Later ones all used a V-spray rail: http://sailing.mit.edu/info/history.php and do a Google search on "Tech Dinghy" Many examples of old and new.

edit: great job btw!

[xkdrolt]

http://sailing.mit.edu/info/beaver_eng.jpg

[UCanoe_2]

My father-in-law learned to sail as an MIT student in the early 1940s. At that time there was a chocolate factory on one side of the river and a soap factory on the other (one of them was still extant when we were in Boston in 2013, I disremember which). He told us the MIT team had a home court advantage in regattas, because they could tell the wind direction by scent.

[Monkey Butler]

My father-in-law learned to sail as an MIT student in the early 1940s. At that time there was a chocolate factory on one side of the river and a soap factory on the other (one of them was still extant when we were in Boston in 2013, I disremember which). He told us the MIT team had a home court advantage in regattas, because they could tell the wind direction by scent.

Likely referring to Lever Brothers, makers of Lifebuoy soap later to become Unilever, and Derans, later New England Confectionery Company, makers of NECCO wafers. Both were located in Cambridge thus on the same side of the river but at opposite ends of the length of the Charles River sailed by MIT. Lever Brothers closed in the late 50's. Necco was still around in 2013 but not at the Cambridge Street location that manufactured chocolate.

https://cambridgehistory.org/industr...rbrothers.html

https://thecambridgeroom.wordpress.c...an-exhibition/