i550class.org

Well, I've started out on the i550 mission. I now have plans (#519). A garage that is probably too small (6.3 m x 3.2 m). And also I have just taken ownership of an International 14 to act as a donor boat. What could possibly go wrong?

The International 14 looks like a pretty good donor boat - 18.6 sqm (200 sq ft) of sail set on around about a 7.6 m mast. I now have two mains (one dacron, one mylar), 5(!) jibs, and two hooge asymmetric masthead kites. They are a bit tired though. The boat has carbon mast (of a chunky stature - 75 mm OD - 40 mm OD at the top), carbon boom and carbon prod. Also lots of nice Harken fittings and foil set. I just have to convince myself I want to strip down a perfectly good boat, get rid of the hull (see also small garage) and start something new entirely. As they are a development class, they can be picked up pretty cheap for a rather less than cutting edge boat with lots of fancy stuff on them.

Now I just need some plywood, and also to work out if I can recycle the I14 foils somehow onto the i550.

Ben / Analog

...welcome to i550 world Ben!

...be careful about your mast from a much lighter boat!....from past experience ,it's well advised to use a mast that's engineered fro a similar-weight boat,,,including crew-weight!
....by the time you're 3-up on an 800lb boat,,yer possibly will be exceeding the design limits of an i-14 mast

...I've long used old 49er chutes on bigger boats,and have one as a spare on my i550,,but it's pretty clear by the # of clew-grommets blown,that high performance dinghies are engineered for the loads they'll see rather than where they sometimes end-up!

regarding the small workspace, I started my build in a similar shaped area. I used a tripod build jig, and put casters on it so it could roll side to side. Throughout the hull building, I could shift it so I could work on whatever side I needed, and having three wheels means that it doesn't matter if the floor is uneven, as far as imparting different torques into the build frame.

The RM's for the two boats aren't too different- an I14 has two guys hiking with their CG maybe 6' from the boat's CL, and the i550 gets three guys hiking with their CG about 5' from CL, so within 20%. Better staying angles on the i550 mean less rig tension needed, so ~maybe~ it'll be alright?

Chad wrote:regarding the small workspace, I started my build in a similar shaped area. I used a tripod build jig, and put casters on it so it could roll side to side. Throughout the hull building, I could shift it so I could work on whatever side I needed, and having three wheels means that it doesn't matter if the floor is uneven, as far as imparting different torques into the build frame.

The RM's for the two boats aren't too different- an I14 has two guys hiking with their CG maybe 6' from the boat's CL, and the i550 gets three guys hiking with their CG about 5' from CL, so within 20%. Better staying angles on the i550 mean less rig tension needed, so ~maybe~ it'll be alright?

...methinks the leverage #'s are already a stretch,,but the overall weight would be the killer....prove me wrong!!

......didn't 'Tokyo' or someone origionally try a 49er rig or something?.....how did -that- work out!??!

It was this boat, seen here in build and (I think) after the 49er rig experiment, and subsequent conversion to on-deck articulator.

Thanks for the replies everybody! Yeah - I'd noticed a lot of folk had attached wheels to their jigs for ease of working. That should work out well, and will have the extra advantage of letting me work outside on sunny days as well.

I've been reading quite a bit about getting the basic form of the boat right. It seems the way to avoid endless fairing is getting the basic shape fair at stiching together time. Here's my take on things - please correct me if I'm miles off!

1. Build a full 20 station bottom panel jig (a la PDX and plans) and then force the bottom panels to conform to the jig profile prior to stich up/installation of frames. This makes sure the bottom is pretty fair.
2. Trim or pack out the left and right hand sides of the frames to match the curvature of the side panels to avoid weird corrugations in the side panels.

Are there any other 'keeping the basic shape fair' tricks that are helpful to know? I presume any epoxy sealing work of internal (and external?) surfaces is better done before assembly?

With regards to the rig, yeah, it's a bit of an unknown. I know that 49er/16' skiff rigs haven't worked well in the past, but they are designed to be pretty whip like I think. This mast is straight, and quite substantial looking to the untrained eye. I guess where I'm getting confused is that the section diameters and wall thickness of my (carbon) mast seem comparable to the (aluminium) sections of the Dwyer DM4 mast which seems to recommended pretty frequently. My hope (!) is that by designing the stays, spreaders and ram (?) for the mast properly I should be able to get the whole thing to stay in one piece. But if anybody can point me in the direction of some calculations that can at least tell me if I'm in the ballpark, that would be great - obviously it would be pretty grumpy making to commit a bunch of effort to getting a mast up and going to have it fail and require major surgery or replacement!

Once again, thanks heaps for the replies to my questions!

The new plans show material added to the frame sides to let the hull sides lay fair. I'm a fan of full length sheer clamps and at least one mid-panel stringer placed before the hull sides are glued to the frames, to keep things fair fore and aft.

Pre-epoxy sealing is a matter of preference I suppose. Some do it (and thoroughly wash/de-blush and abrade the surface), and some just coat as progress allows. What matters is getting everything with enough mills of coverage when the job is done, protecting the wood in build if you have weather/shelter issues, and so on. I always figure the edges need at least an extra coat or two, so why precoat the surfaces when I'm going to be getting after the edges a bunch of times anyway? -but other smart people precoat, so there must be some merit to it.

I have some raw carbon mast tube weights on another computer, I can look them up tomorrow and maybe that'll give you an idea how yours compares.

Ah OK, so the new frame profiles will not need too much modification to give fair sides? Cool.

Knowing the carbon weights would be helpful - thanks. I've dusted off my copy of principals of yacht design in a (probably vain) attempt to get my head around specifying rigs...

C-Tech tube with track and masthead is 17#, 7.7kg

Thanks for that - I'll check it out.

Dear all

Analog wrote

"With regards to the rig, yeah, it's a bit of an unknown. I know that 49er/16' skiff rigs haven't worked well in the past".

This is the first I have heard of any issues in using a rig form a 16 footer. I would have though that with three big guys on the wire, the 16 foot rig would be plenty strong.

Who has had issues?

Kind regards

I thought that that Baby Faced Assasin had snapped theirs, however, I've probably got 49er and 16' skiff masts confused. I'd imagine the 16' skiff masts would be pretty substantial sorts of things in comparison.

http://forums.sailinganarchy.com/index. ... opic=99461

Is the tenuous discussion I found regarding 49er rig failure.

Looking at the mast support systems for my i14, they've gone to pretty serious lengths to control the mast movement around the step and gooseneck areas (well, most areas really). I think I will need to replicate most of these systems on my i550 to keep the mast happy.

Thanks for clearing that up - it is my strategy to get a hold of a 16 footer and salvage the rig and anything else I can. I thought for a moment that I might need a new strategy.

Kind regards

David