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Old 19-05-2013, 21:50   #16
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Re: bowsprit design

Here's the heel socket through bolted to the deck.
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Old 19-05-2013, 22:08   #17
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Re: bowsprit design

Now I'm having a hard time uploading pics.

The person that put the deck and hull together didn't attach the Sampson posts to the keel beam as called out by the original design. Two huge holes were cut in the bulkhead that the Sampson posts were attached to for easy access forward. A few years of water infiltration at the highly loaded Sampson post and much damage had occured.

The original design had used a load of 38,000 lbs aft on the bowsprit/Sampson posts. Had it been built properly it may have lasted quite a few more years than it did. The loads aft on those posts though are amazing and I could see it all happening again eventually.

I hope I've addressed the issue.
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Old 20-05-2013, 01:10   #18
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Re: bowsprit design

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Originally Posted by Benz View Post
I made my bowsprit out of fiberglass, wrapping layers around a piece of 4" ABS pipe until I had about a half-inch all 'round. Polyester resin, gelcoat finish; could have faired it to perfection, but didn't bother. It is immensely strong, requires no maintenance, and will never rot nor rust. My 15-foot boom is built the same way, and serves wonderfully.
I'd be interested to know what dimensions of ABS (internal wall thickness, type of ABS), you used and how you attached it to the hull, end fittings (cranse and gammon stuff). Did you use polyester glass for cost instead of epoxy? or is epoxy not compatable with the ABS. sounds interesting. thanks for the info.
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Old 20-05-2013, 09:49   #19
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Re: bowsprit design

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Yes wood doesn't last forever but it is straightforward to work with. Here's a bowsprit I built for my old boat, a Cape Dory 30. Nothing fancy, it sounds similar to what you have now, but it is laminated and through-bolted with stainless rod. It was a good anchoring platform too, which was just as important to me.

No reason you cant use other materials, but wood is simple. This is Iroko, not teak.

Yes, I made a similar one for my Seawind, usinag a big teak plank and I also used the Spartan stemhead fitting like you did. I did add some whisker stays on mine though. On another boat I bought a Propellor blank; Clear vertical grain spruce about 5 x 8 x 8 ft long. Lightweight and tough. A little soft for around the anchor handling though so I laminated a tteak top on it with resorcinal.
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Old 20-05-2013, 10:32   #20
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Re: bowsprit design

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Originally Posted by seano View Post
yeah, nice pretty set up on the rob roy; very pretty. Bit exposed for my liking, probably just needs some rails, bit lumpy in Bass Strait for no safetys.
Plank or pole? the plank systems seem simple and seem to get around the side stay issue and an access deck is already there; the bow roller for the anchor, i guess keeps it clear of fouling the bobstay but i worry about the potential heaving load of a boat at anchor or moored in a blow with swell. i think back closer to the stem would be safer and stronger. is the fouling such an issue?
I like the way the rob roy has shaped its side planks; very pretty!
what's the consensus on plank systems v's a pole with overlaid deck of sorts. i tend to think the pole type would be structurally more appropritae if appropriately stayed.
any comments?
On my Rob Roy 23 the rode rides out in the port chock. In most cases I haul the anchor in from the cockpit; I have a retrieval line looped around the rode. The mizzen is close hauled, the main and stay sail loose and luffing. I usually just run over the anchor to break free. This is in normal conditions. In heavy weather the anchor comes up through the bow roller and just hangs out of the way for the time being. OK, to bore you further for lunch I just drop my tiny 5# Danforth. You would be surprised at the holding power of that 'lil anchor. That 5#'r even holds my 23 ton Daedalus for lunch or swimming. Sorry, I drifted off the topic, It seems, I always do...
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Old 20-05-2013, 19:14   #21
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Re: bowsprit design

Hi Seano,
I used 4" ABS, but it doesn't matter--it only serves as a mandrel to form the glass around, and adds no structural element. You could use a cardboard tube or PVC pipe of whatever diameter suits you needs. I used polyester because I had lots left over from building my decks and house, and it's far cheaper and easier to work with than epoxy. And less poisonous. All my attachments are simply through-bolted: the mooring bitts take the heel, and my homemade bronze gammon iron supports it by means of a pin. You could buy a stock cranse iron and make the diameter to suit, or you could use eye bolts with eye nuts on the other side--with fiberglass you are limited only by your imagination. I see no need for a plank or walking platform: why would anyone want to go out to the bowsprit end anyway? All those walkways and pulpits really do is add weight, windage, and water scooping capacity when the water gets rough.
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Old 22-05-2013, 04:18   #22
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Re: Bowsprit Design

thanks to all for input, photos and suggestions. much to consider. shall get back when ive progressed further.
ooroo!
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Old 19-10-2013, 23:06   #23
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Re: Bowsprit Design

Simple and lighter bowsprit design? My first try to ask anything on the forum and not even sure if this bowsprit topic is closed.
Most of the bowsprit arrangements - pole, platform or combination - are laid over the fore deck using sampson post(s) and designed for wooden vessels? For non-wooden yachts why not heel the sprit against the stem at the deck level - assuming that the fore deck is rigid, with hefty transverse under deck battens; the load on the stem spread around the bow (s.steel band); the usual bob and side stays and even inner rigid bob stays (v arrangement) to reduce platform twisting. No need for sampson post(s) and less weight.
I am interested in this topic because I am about to fit such a fabricated bowsprit my 31 ft cutter using a AL boom (cut down to 1.8m) and a light stainless platform frame, both bolted together to increase entire bowsprit rigidity.
Any critical comments welcome. Gandy
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Old 20-10-2013, 06:42   #24
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Re: Bowsprit Design

Greetings and welcome aboard the CF, Gandy.
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Old 20-10-2013, 08:33   #25
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Re: Bowsprit Design

This, or similar, has been asked before. Usually it comes from a desire to impart something of a traditional appearance to a new-ish designed boat. The end result will be the equivalent of a Prias with big tail fins. That aside, if you add a bowsprit to a boat that was not designed for one you may be opening a very expen$ive can of worms. At a minimum, you will be $hifting the CE forward of the CLR. That will impart more lee helm than you will be comfortable with. Then you will have to add $ail area aft to compensate. In so doing you may over canva$s the boat. There are also structural issues others have touched upon. How do you deal with the thrust of the bowsprit heel; hull reinforcement to receive the whisker stays and bob stay; masthead anchorage for the jib stay; added compression on the mast step; running or fixed back stays?

And when time comes to sell the boat you will have $omething that is neither fish nor fowl. IMHO, if you want a boat with a bowsprit, buy one so designed.
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Old 20-10-2013, 12:40   #26
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Re: Bowsprit Design

Quote:
Originally Posted by Sam Plan B View Post
This, or similar, has been asked before. Usually it comes from a desire to impart something of a traditional appearance to a new-ish designed boat. The end result will be the equivalent of a Prias with big tail fins. That aside, if you add a bowsprit to a boat that was not designed for one you may be opening a very expen$ive can of worms. At a minimum, you will be $hifting the CE forward of the CLR. That will impart more lee helm than you will be comfortable with. Then you will have to add $ail area aft to compensate. In so doing you may over canva$s the boat. There are also structural issues others have touched upon. How do you deal with the thrust of the bowsprit heel; hull reinforcement to receive the whisker stays and bob stay; masthead anchorage for the jib stay; added compression on the mast step; running or fixed back stays?

And when time comes to sell the boat you will have $omething that is neither fish nor fowl. IMHO, if you want a boat with a bowsprit, buy one so designed.
Hi Sam Plan B, Of course you know, we will believe want we wanna believe. With all due respect, I can overcome most all if not all your objections above. Toy boats that are just designed for racing are lighter and weaker structurally. The points of the forces are usually beefed up. It's true they cannot be easily modified, because they are one purpose boats. Now for the boat that can be modified for most any configuration. is a full keel heavy displacement hull, especially with a classic shear line and with a cabin that doesn't look like an after thought. Now you have something to work with. I've designed and built the 50' cutter yawl Daedalus, worked on and revised a/o restored from the ground up several boats, cars and houses. BTW certain boats are designed for the sea and they are not toys! I'll post some photos. Also, my 4 albums might be interesting...
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Old 22-10-2013, 21:23   #27
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Re: Bowsprit Design

Simple and lighter b.s. (cont.) All former observations so useful. I should have included a more comprehensive description.
My yacht is (was) a Mariner 31 ketch - heavy, inadequate sail area, long keel, wood deck/GRP hull and traditional bowsprit (120 cm) arrangement (stem bob stay fitting, wood pole with plank and rails attached.) A traditional looking hull form.
Now after rebuilt (just about) its a cutter sloop, but I set the mast too far aft (stepped on deck with hull structural support). Weather helm would be most likely so I extended the b.s. (180 cm) with both foresails (well separated) forward of the stem - something like Cpt. Fred's Rob Roy. The yankee is forward of large genoa - following the Shannon 'scutter' plan. (Sail plan entirely unmentioned).
As above -b.s. to be heeled against the stem at deck level - load spread. A foredeck of well laid-up saturated sandwich (with transverse under-deck battens should present sufficient resistance - equal or more than sampson posts formerly resting on lower stem and supported with wood deck. B.s. also will have rigid parallel twin inner bob stay supporting the light plank frame attached to the stem and bolted to the aluminium boom/b.s. pole.
That arrangement - less weight and without the traditional heavy clutter on a foredeck is a reasonable exchange. Regards to all views, Gandy
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