IOMICA Forum

Is it wood, balsa sandwich, fibreglass (poliester/epoxy)??? Is it already painted etc??' These factors amongst others will be important. I find that the weight of my bare wood hulls, sanded down but without epoxy/varnish finish don't seem to bare any relationship to the near finished item - they seem to absorb epoxy resin (which I use for waterproofing and protection inside and out) at extremely variable rates.

Roy,

It's a wood hull with a coat of epoxy. I was just curious how I was doing so far as I think it will be heavy for sure. Any weight will help me to see if I am at least on track.

Thanks!

Greg,
I have to say I'm not an expert and I've only made 4 complete hulls and 3 others which never got to be completely finished for variuos reasons.

After my first wood hull I started to note down weights at various stages of construction with the same paranoia that you are probably experiencing and from my notes the bare hull wt with transom rubbed down, without any epoxy coat depended on two main factors - the type of wood (balsa, cedar, other 'soft woods' etc) and the epoxy resin mix I used for glueing the planks together (with a lot of fibres added or not, and with other additives such as colloidal silica added for thickening etc.) These two factors seemed to affect resin absorbtion and the result was anywhere between 175 grams and 400 grams. That's not a lot of help is it?

I have also tried using cyano acrylate glues for plank bonding, thinking that the two coats of epoxy inside and out later on will also hold the planks together and I don't need the added wt and bother of mixing up small quantities to epoxy glue 2 planks each side at a time and then having to wait at least 8 hours for the epoxy to bond enough to glue the next ones. I had trouble with the planks seperating during sanding down even though I left the hull on the frames. I guess the cyano was absorbed to much and didn't stick the planks enough. I have had one hull in which I had to add about 120grams of wt to get it up to 4kg, and that was with and RMG winch and 120gr battery pack, so it's more than possible to get the hull down to wt woith a little care. I know of others that have had to add even more with wooden hulls. It all depends on so many other factors - deck materials being one of my downfalls - I've tried fibreglass decks and plywood but often they seem to be over engineered and add a lot to the total wt.
Anyway, enough of my ramblings! A wooden hull is incredibly strong and resistant compared to an epoxy hull, and is beautiful to behold.

hi, my fibreglas hull with i built in a form with colourd gelcoat weigts about 320g. the hull build over an positiv without gelcoat so you have some to put fillers an finishcolour on weight without that about 250g.
my hull with wood (3mm planks) weight about 400g. so that ist the limit to get at the end a 4 kg boat. i only take small batteries with 70g weight an the boat has a weight of 4,030g.

i hpoe it helped.
sorry about my english writing

andreas

Hi Greg,

at the moment i´m building a "arrow" with balsawood and a coat of epoxy.



-planks of 3mm extra-light balsa, glued with cyano
-complete transoms and fin box
-the inside complete sealed with epoxy and reinforced with some stripes of fiberglass
-the outside coated with two layers of 105gr fiberglass and epoxy

the actual weight (without filler and varnish) is 415 gr.

Rainer

Thanks all, real good answers. Rainer, super nice job on the Arrow.

Please, keep it coming as I'm currently starved for this knowledge. I've wanted to build a boat for about 15 years now and I finally took the time to start this Monday. Can't wait to get onto the next one!

MORE PLEASE!

Hi Greg,

My experience coincides with Rainer's - a (balsa-planked, one-off) hull, approximately at the finish-level of the Rainer's Arrow (as shown), should weigh in around 400g. If it is more (at that stage) - you have to start worrying.

However, you have a lot of latitude still - the most critical juncture (in my experience) has always been building the support structure (winch, servo tray, deck supports) etc. There's always a temptation for "extra reinforcement" and it adds the weight remarkably quickly.

Great to hear that you're finally building one yourself! Hope to see it in New London in June. (if it's not ready to sail - bring it anywayt to show).

Marko

A completed, painted hull ready for hardware needs to be under about 800 grams to be underweight when ready to sail. There are some places to save weight if you are slighly over, but thats a good # to use as a target.

Steve Landeau wrote:A completed, painted hull ready for hardware needs to be under about 800 grams to be underweight when ready to sail. There are some places to save weight if you are slighly over, but thats a good # to use as a target.

When building my last boat, an Italiko from Sails ETC, i recorded all weights. The results are on my IOM-Info page at:
http://www.helsinki.fi/~awallin/iom/

I will probably do the same for my next boat, a Cockatoo that Jeff Byerley tells me is already on its way to me from aus, so stay tuned...

Anders

Anders, That's a big help. I printed that out and will use it as a guide. I think I’m OK with what I’m doing so far.
Thanks Steve also. Good numbers.
Marko, I will have the boat done as soon as the hardware arrives this week. Boat looks good but I know where I messed up. I can't wait to see how it sails!

Thanks all.

It would be great to have a thread here on home built boats. Photos, problems, tricks, tips. I think that creating a boat with your own hands is something everyone should try. How about it?
We have six members in our club that have been building this winter. Everything from wood to glass to CF and Kevlar. It something that I personally want to become more inept with.

Greg Vasileff wrote: It something that I personally want to become more inept with.

No comment

Ya know Dan, I saw that I wrote that and went to edit it, but I thought again and felt that what I wrote was probably a more accurate statement ..

.... thanks for the good info you gave me here. The boat is finished and has been test sailed. I'm very happy to say that it seems to sail very well!

Boat, ready to sail, came in 8.5 oz light which I was quite happy, and surprised, about.

Some photos .... http://members.tripod.com/ghmyc_1m/3crown.html

Great job, Greg!
Very nice example for the home builder. Victory will be even sweeter knowing how little it costs!
I expect the Triple Crown to be as competitive as anything else on the water. See you in June.